Auto merge of #65324 - Centril:organize-syntax, r=petrochenkov

Split libsyntax apart

In this PR the general idea is to separate the AST, parser, and friends by a more data / logic structure (tho not fully realized!) by separating out the parser and macro expansion code from libsyntax. Specifically have now three crates instead of one (libsyntax):

- libsyntax:

   - concrete syntax tree (`syntax::ast`)

   - definition of tokens and token-streams (`syntax::{token, tokenstream}`) -- used by `syntax::ast`

   - visitors (`syntax::visit`, `syntax::mut_visit`)

   - shared definitions between `libsyntax_expand`

   - feature gating (`syntax::feature_gate`) -- we could possibly move this out to its own crater later.

   - attribute and meta item utilities, including used-marking (`syntax::attr`)

   - pretty printer (`syntax::print`) -- this should possibly be moved out later. For now I've reduced down the dependencies to a single essential one which could be broken via `ParseSess`. This entails that e.g. `Debug` impls for `Path` cannot reference the pretty printer.

   - definition of `ParseSess` (`syntax::sess`) -- this is used by `syntax::{attr, print, feature_gate}` and is a common definition used by the parser and other things like librustc.

   - the `syntax::source_map` -- this includes definitions used by `syntax::ast` and other things but could ostensibly be moved `syntax_pos` since that is more related to this module.

   - a smattering of misc utilities not sufficiently important to itemize -- some of these could be moved to where they are used (often a single place) but I wanted to limit the scope of this PR.

- librustc_parse:

   - parser (`rustc_parse::parser`) -- reading a file and such are defined in the crate root tho.

   - lexer (`rustc_parse::lexer`)

   - validation of meta grammar (post-expansion) in (`rustc_parse::validate_attr`)

- libsyntax_expand -- this defines the infra for macro expansion and conditional compilation but this is not libsyntax_ext; we might want to merge them later but currently libsyntax_expand is depended on by librustc_metadata which libsyntax_ext is not.

   - conditional compilation (`syntax_expand::config`) -- moved from `syntax::config` to here

   - the bulk of this crate is made up of the old `syntax::ext`

r? @estebank

Cargo.lock

@@ -3504,6 +3504,7 @@ dependencies = [
  "rustc_lint",
  "rustc_metadata",
  "rustc_mir",
+ "rustc_parse",
  "rustc_plugin",
  "rustc_plugin_impl",
  "rustc_resolve",
@@ -3572,6 +3573,7 @@ dependencies = [
  "rustc_lint",
  "rustc_metadata",
  "rustc_mir",
+ "rustc_parse",
  "rustc_passes",
  "rustc_plugin_impl",
  "rustc_privacy",
@@ -3649,6 +3651,7 @@ dependencies = [
  "rustc_data_structures",
  "rustc_errors",
  "rustc_index",
+ "rustc_parse",
  "rustc_target",
  "serialize",
  "smallvec 1.0.0",
@@ -3692,6 +3695,21 @@ dependencies = [
  "core",
 ]
 
+[[package]]
+name = "rustc_parse"
+version = "0.0.0"
+dependencies = [
+ "bitflags",
+ "log",
+ "rustc_data_structures",
+ "rustc_errors",
+ "rustc_lexer",
+ "rustc_target",
+ "smallvec 1.0.0",
+ "syntax",
+ "syntax_pos",
+]
+
 [[package]]
 name = "rustc_passes"
 version = "0.0.0"
@@ -3701,6 +3719,7 @@ dependencies = [
  "rustc_data_structures",
  "rustc_errors",
  "rustc_index",
+ "rustc_parse",
  "rustc_target",
  "syntax",
  "syntax_pos",
@@ -3763,6 +3782,7 @@ dependencies = [
  "rustc",
  "rustc_codegen_utils",
  "rustc_data_structures",
+ "rustc_parse",
  "serde_json",
  "syntax",
  "syntax_pos",
@@ -4372,14 +4392,11 @@ dependencies = [
 name = "syntax_expand"
 version = "0.0.0"
 dependencies = [
- "bitflags",
- "lazy_static 1.3.0",
  "log",
  "rustc_data_structures",
  "rustc_errors",
- "rustc_index",
  "rustc_lexer",
- "scoped-tls",
+ "rustc_parse",
  "serialize",
  "smallvec 1.0.0",
  "syntax",
@@ -4394,6 +4411,7 @@ dependencies = [
  "log",
  "rustc_data_structures",
  "rustc_errors",
+ "rustc_parse",
  "rustc_target",
  "smallvec 1.0.0",
  "syntax",

src/librustc/session/mod.rs

@@ -26,7 +26,7 @@ use syntax::expand::allocator::AllocatorKind;
 use syntax::feature_gate::{self, AttributeType};
 use syntax::json::JsonEmitter;
 use syntax::source_map;
-use syntax::sess::ParseSess;
+use syntax::sess::{ParseSess, ProcessCfgMod};
 use syntax::symbol::Symbol;
 use syntax_pos::{MultiSpan, Span};
 use crate::util::profiling::{SelfProfiler, SelfProfilerRef};
@@ -934,6 +934,7 @@ pub fn build_session(
     sopts: config::Options,
     local_crate_source_file: Option<PathBuf>,
     registry: errors::registry::Registry,
+    process_cfg_mod: ProcessCfgMod,
 ) -> Session {
     let file_path_mapping = sopts.file_path_mapping();
 
@@ -944,6 +945,7 @@ pub fn build_session(
         Lrc::new(source_map::SourceMap::new(file_path_mapping)),
         DiagnosticOutput::Default,
         Default::default(),
+        process_cfg_mod,
     )
 }
 
@@ -1022,6 +1024,7 @@ pub fn build_session_with_source_map(
     source_map: Lrc<source_map::SourceMap>,
     diagnostics_output: DiagnosticOutput,
     lint_caps: FxHashMap<lint::LintId, lint::Level>,
+    process_cfg_mod: ProcessCfgMod,
 ) -> Session {
     // FIXME: This is not general enough to make the warning lint completely override
     // normal diagnostic warnings, since the warning lint can also be denied and changed
@@ -1062,7 +1065,14 @@ pub fn build_session_with_source_map(
         },
     );
 
-    build_session_(sopts, local_crate_source_file, diagnostic_handler, source_map, lint_caps)
+    build_session_(
+        sopts,
+        local_crate_source_file,
+        diagnostic_handler,
+        source_map,
+        lint_caps,
+        process_cfg_mod,
+    )
 }
 
 fn build_session_(
@@ -1071,6 +1081,7 @@ fn build_session_(
     span_diagnostic: errors::Handler,
     source_map: Lrc<source_map::SourceMap>,
     driver_lint_caps: FxHashMap<lint::LintId, lint::Level>,
+    process_cfg_mod: ProcessCfgMod,
 ) -> Session {
     let self_profiler =
         if let SwitchWithOptPath::Enabled(ref d) = sopts.debugging_opts.self_profile {
@@ -1109,6 +1120,7 @@ fn build_session_(
     let parse_sess = ParseSess::with_span_handler(
         span_diagnostic,
         source_map,
+        process_cfg_mod,
     );
     let sysroot = match &sopts.maybe_sysroot {
         Some(sysroot) => sysroot.clone(),

src/librustc_driver/Cargo.toml

@@ -21,6 +21,7 @@ rustc_data_structures = { path = "../librustc_data_structures" }
 errors = { path = "../librustc_errors", package = "rustc_errors" }
 rustc_metadata = { path = "../librustc_metadata" }
 rustc_mir = { path = "../librustc_mir" }
+rustc_parse = { path = "../librustc_parse" }
 rustc_plugin = { path = "../librustc_plugin/deprecated" } # To get this in the sysroot
 rustc_plugin_impl = { path = "../librustc_plugin" }
 rustc_save_analysis = { path = "../librustc_save_analysis" }

src/librustc_driver/lib.rs

@@ -63,7 +63,6 @@ use std::time::Instant;
 use syntax::ast;
 use syntax::source_map::FileLoader;
 use syntax::feature_gate::{GatedCfg, UnstableFeatures};
-use syntax::parse;
 use syntax::symbol::sym;
 use syntax_pos::{DUMMY_SP, FileName};
 
@@ -1062,14 +1061,16 @@ pub fn handle_options(args: &[String]) -> Option<getopts::Matches> {
 }
 
 fn parse_crate_attrs<'a>(sess: &'a Session, input: &Input) -> PResult<'a, Vec<ast::Attribute>> {
-    match *input {
+    match input {
-        Input::File(ref ifile) => {
+        Input::File(ifile) => {
-            parse::parse_crate_attrs_from_file(ifile, &sess.parse_sess)
+            rustc_parse::parse_crate_attrs_from_file(ifile, &sess.parse_sess)
         }
-        Input::Str { ref name, ref input } => {
+        Input::Str { name, input } => {
-            parse::parse_crate_attrs_from_source_str(name.clone(),
+            rustc_parse::parse_crate_attrs_from_source_str(
-                                                     input.clone(),
+                name.clone(),
-                                                     &sess.parse_sess)
+                input.clone(),
+                &sess.parse_sess,
+            )
         }
     }
 }

src/librustc_interface/Cargo.toml

@@ -16,6 +16,7 @@ smallvec = { version = "1.0", features = ["union", "may_dangle"] }
 syntax = { path = "../libsyntax" }
 syntax_ext = { path = "../libsyntax_ext" }
 syntax_expand = { path = "../libsyntax_expand" }
+rustc_parse = { path = "../librustc_parse" }
 syntax_pos = { path = "../libsyntax_pos" }
 rustc_serialize = { path = "../libserialize", package = "serialize" }
 rustc = { path = "../librustc" }

src/librustc_interface/interface.rs

@@ -11,14 +11,15 @@ use rustc_codegen_utils::codegen_backend::CodegenBackend;
 use rustc_data_structures::OnDrop;
 use rustc_data_structures::sync::Lrc;
 use rustc_data_structures::fx::{FxHashSet, FxHashMap};
+use rustc_parse::new_parser_from_source_str;
 use std::path::PathBuf;
 use std::result;
 use std::sync::{Arc, Mutex};
-use syntax::{self, parse};
 use syntax::ast::{self, MetaItemKind};
 use syntax::token;
 use syntax::source_map::{FileName, FileLoader, SourceMap};
 use syntax::sess::ParseSess;
+use syntax_expand::config::process_configure_mod;
 use syntax_pos::edition;
 
 pub type Result<T> = result::Result<T, ErrorReported>;
@@ -64,9 +65,9 @@ impl Compiler {
 pub fn parse_cfgspecs(cfgspecs: Vec<String>) -> FxHashSet<(String, Option<String>)> {
     syntax::with_default_globals(move || {
         let cfg = cfgspecs.into_iter().map(|s| {
-            let sess = ParseSess::with_silent_emitter();
+            let sess = ParseSess::with_silent_emitter(process_configure_mod);
             let filename = FileName::cfg_spec_source_code(&s);
-            let mut parser = parse::new_parser_from_source_str(&sess, filename, s.to_string());
+            let mut parser = new_parser_from_source_str(&sess, filename, s.to_string());
 
             macro_rules! error {($reason: expr) => {
                 early_error(ErrorOutputType::default(),

src/librustc_interface/passes.rs

@@ -27,6 +27,7 @@ use rustc_errors::PResult;
 use rustc_incremental;
 use rustc_metadata::cstore;
 use rustc_mir as mir;
+use rustc_parse::{parse_crate_from_file, parse_crate_from_source_str};
 use rustc_passes::{self, ast_validation, hir_stats, layout_test};
 use rustc_plugin as plugin;
 use rustc_plugin::registry::Registry;
@@ -38,7 +39,6 @@ use syntax::{self, ast, visit};
 use syntax::early_buffered_lints::BufferedEarlyLint;
 use syntax_expand::base::{NamedSyntaxExtension, ExtCtxt};
 use syntax::mut_visit::MutVisitor;
-use syntax::parse;
 use syntax::util::node_count::NodeCounter;
 use syntax::symbol::Symbol;
 use syntax_pos::FileName;
@@ -61,12 +61,11 @@ pub fn parse<'a>(sess: &'a Session, input: &Input) -> PResult<'a, ast::Crate> {
     let krate = time(sess, "parsing", || {
         let _prof_timer = sess.prof.generic_activity("parse_crate");
 
-        match *input {
+        match input {
-            Input::File(ref file) => parse::parse_crate_from_file(file, &sess.parse_sess),
+            Input::File(file) => parse_crate_from_file(file, &sess.parse_sess),
-            Input::Str {
+            Input::Str { input, name } => {
-                ref input,
+                parse_crate_from_source_str(name.clone(), input.clone(), &sess.parse_sess)
-                ref name,
+            }
-            } => parse::parse_crate_from_source_str(name.clone(), input.clone(), &sess.parse_sess),
         }
     })?;
 
@@ -182,7 +181,7 @@ pub fn register_plugins<'a>(
         )
     });
 
-    let (krate, features) = syntax::config::features(
+    let (krate, features) = syntax_expand::config::features(
         krate,
         &sess.parse_sess,
         sess.edition(),
@@ -489,7 +488,7 @@ pub fn lower_to_hir(
 ) -> Result<hir::map::Forest> {
     // Lower AST to HIR.
     let hir_forest = time(sess, "lowering AST -> HIR", || {
-        let nt_to_tokenstream = syntax::parse::nt_to_tokenstream;
+        let nt_to_tokenstream = rustc_parse::nt_to_tokenstream;
         let hir_crate = lower_crate(sess, &dep_graph, &krate, resolver, nt_to_tokenstream);
 
         if sess.opts.debugging_opts.hir_stats {

src/librustc_interface/tests.rs

@@ -8,7 +8,7 @@ use rustc::session::config::{build_configuration, build_session_options, to_crat
 use rustc::session::config::{LtoCli, LinkerPluginLto, SwitchWithOptPath, ExternEntry};
 use rustc::session::config::{Externs, OutputType, OutputTypes, SymbolManglingVersion};
 use rustc::session::config::{rustc_optgroups, Options, ErrorOutputType, Passes};
-use rustc::session::build_session;
+use rustc::session::{build_session, Session};
 use rustc::session::search_paths::SearchPath;
 use std::collections::{BTreeMap, BTreeSet};
 use std::iter::FromIterator;
@@ -17,16 +17,23 @@ use rustc_target::spec::{MergeFunctions, PanicStrategy, RelroLevel};
 use syntax::symbol::sym;
 use syntax::edition::{Edition, DEFAULT_EDITION};
 use syntax;
+use syntax_expand::config::process_configure_mod;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::{ColorConfig, emitter::HumanReadableErrorType, registry};
 
-pub fn build_session_options_and_crate_config(
+type CfgSpecs = FxHashSet<(String, Option<String>)>;
-    matches: &getopts::Matches,
+
-) -> (Options, FxHashSet<(String, Option<String>)>) {
+fn build_session_options_and_crate_config(matches: getopts::Matches) -> (Options, CfgSpecs) {
-    (
+    let sessopts = build_session_options(&matches);
-        build_session_options(matches),
+    let cfg = parse_cfgspecs(matches.opt_strs("cfg"));
-        parse_cfgspecs(matches.opt_strs("cfg")),
+    (sessopts, cfg)
-    )
+}
+
+fn mk_session(matches: getopts::Matches) -> (Session, CfgSpecs) {
+    let registry = registry::Registry::new(&[]);
+    let (sessopts, cfg) = build_session_options_and_crate_config(matches);
+    let sess = build_session(sessopts, None, registry, process_configure_mod);
+    (sess, cfg)
 }
 
 fn new_public_extern_entry<S, I>(locations: I) -> ExternEntry
@@ -59,31 +66,19 @@ fn mk_map<K: Ord, V>(entries: Vec<(K, V)>) -> BTreeMap<K, V> {
 #[test]
 fn test_switch_implies_cfg_test() {
     syntax::with_default_globals(|| {
-        let matches = &match optgroups().parse(&["--test".to_string()]) {
+        let matches = optgroups().parse(&["--test".to_string()]).unwrap();
-            Ok(m) => m,
+        let (sess, cfg) = mk_session(matches);
-            Err(f) => panic!("test_switch_implies_cfg_test: {}", f),
-        };
-        let registry = registry::Registry::new(&[]);
-        let (sessopts, cfg) = build_session_options_and_crate_config(matches);
-        let sess = build_session(sessopts, None, registry);
         let cfg = build_configuration(&sess, to_crate_config(cfg));
         assert!(cfg.contains(&(sym::test, None)));
     });
 }
 
-// When the user supplies --test and --cfg test, don't implicitly add
+// When the user supplies --test and --cfg test, don't implicitly add another --cfg test
-// another --cfg test
 #[test]
 fn test_switch_implies_cfg_test_unless_cfg_test() {
     syntax::with_default_globals(|| {
-        let matches = &match optgroups().parse(&["--test".to_string(),
+        let matches = optgroups().parse(&["--test".to_string(), "--cfg=test".to_string()]).unwrap();
-                                                 "--cfg=test".to_string()]) {
+        let (sess, cfg) = mk_session(matches);
-            Ok(m) => m,
-            Err(f) => panic!("test_switch_implies_cfg_test_unless_cfg_test: {}", f),
-        };
-        let registry = registry::Registry::new(&[]);
-        let (sessopts, cfg) = build_session_options_and_crate_config(matches);
-        let sess = build_session(sessopts, None, registry);
         let cfg = build_configuration(&sess, to_crate_config(cfg));
         let mut test_items = cfg.iter().filter(|&&(name, _)| name == sym::test);
         assert!(test_items.next().is_some());
@@ -95,9 +90,7 @@ fn test_switch_implies_cfg_test_unless_cfg_test() {
 fn test_can_print_warnings() {
     syntax::with_default_globals(|| {
         let matches = optgroups().parse(&["-Awarnings".to_string()]).unwrap();
-        let registry = registry::Registry::new(&[]);
+        let (sess, _) = mk_session(matches);
-        let (sessopts, _) = build_session_options_and_crate_config(&matches);
-        let sess = build_session(sessopts, None, registry);
         assert!(!sess.diagnostic().can_emit_warnings());
     });
 
@@ -105,17 +98,13 @@ fn test_can_print_warnings() {
         let matches = optgroups()
             .parse(&["-Awarnings".to_string(), "-Dwarnings".to_string()])
             .unwrap();
-        let registry = registry::Registry::new(&[]);
+        let (sess, _) = mk_session(matches);
-        let (sessopts, _) = build_session_options_and_crate_config(&matches);
-        let sess = build_session(sessopts, None, registry);
         assert!(sess.diagnostic().can_emit_warnings());
     });
 
     syntax::with_default_globals(|| {
         let matches = optgroups().parse(&["-Adead_code".to_string()]).unwrap();
-        let registry = registry::Registry::new(&[]);
+        let (sess, _) = mk_session(matches);
-        let (sessopts, _) = build_session_options_and_crate_config(&matches);
-        let sess = build_session(sessopts, None, registry);
         assert!(sess.diagnostic().can_emit_warnings());
     });
 }
@@ -704,6 +693,6 @@ fn test_edition_parsing() {
     let matches = optgroups()
         .parse(&["--edition=2018".to_string()])
         .unwrap();
-    let (sessopts, _) = build_session_options_and_crate_config(&matches);
+    let (sessopts, _) = build_session_options_and_crate_config(matches);
     assert!(sessopts.edition == Edition::Edition2018)
 }

src/librustc_interface/util.rs

@@ -36,6 +36,7 @@ use syntax::util::lev_distance::find_best_match_for_name;
 use syntax::source_map::{FileLoader, RealFileLoader, SourceMap};
 use syntax::symbol::{Symbol, sym};
 use syntax::{self, ast, attr};
+use syntax_expand::config::process_configure_mod;
 use syntax_pos::edition::Edition;
 #[cfg(not(parallel_compiler))]
 use std::{thread, panic};
@@ -49,6 +50,7 @@ pub fn diagnostics_registry() -> Registry {
     // FIXME: need to figure out a way to get these back in here
     // all_errors.extend_from_slice(get_codegen_backend(sess).diagnostics());
     all_errors.extend_from_slice(&rustc_metadata::error_codes::DIAGNOSTICS);
+    all_errors.extend_from_slice(&rustc_parse::error_codes::DIAGNOSTICS);
     all_errors.extend_from_slice(&rustc_passes::error_codes::DIAGNOSTICS);
     all_errors.extend_from_slice(&rustc_plugin::error_codes::DIAGNOSTICS);
     all_errors.extend_from_slice(&rustc_mir::error_codes::DIAGNOSTICS);
@@ -103,6 +105,7 @@ pub fn create_session(
         source_map.clone(),
         diagnostic_output,
         lint_caps,
+        process_configure_mod,
     );
 
     let codegen_backend = get_codegen_backend(&sess);

src/librustc_lexer/src/lib.rs

@@ -1,7 +1,7 @@
 //! Low-level Rust lexer.
 //!
 //! Tokens produced by this lexer are not yet ready for parsing the Rust syntax,
-//! for that see `libsyntax::parse::lexer`, which converts this basic token stream
+//! for that see `librustc_parse::lexer`, which converts this basic token stream
 //! into wide tokens used by actual parser.
 //!
 //! The purpose of this crate is to convert raw sources into a labeled sequence

src/librustc_metadata/Cargo.toml

@@ -23,4 +23,5 @@ rustc_serialize = { path = "../libserialize", package = "serialize" }
 stable_deref_trait = "1.0.0"
 syntax = { path = "../libsyntax" }
 syntax_expand = { path = "../libsyntax_expand" }
+rustc_parse = { path = "../librustc_parse" }
 syntax_pos = { path = "../libsyntax_pos" }

src/librustc_metadata/rmeta/decoder/cstore_impl.rs

@@ -18,6 +18,8 @@ use rustc::hir::map::{DefKey, DefPath, DefPathHash};
 use rustc::hir::map::definitions::DefPathTable;
 use rustc::util::nodemap::DefIdMap;
 use rustc_data_structures::svh::Svh;
+use rustc_parse::source_file_to_stream;
+use rustc_parse::parser::emit_unclosed_delims;
 
 use smallvec::SmallVec;
 use std::any::Any;
@@ -27,8 +29,6 @@ use std::sync::Arc;
 use syntax::ast;
 use syntax::attr;
 use syntax::source_map;
-use syntax::parse::source_file_to_stream;
-use syntax::parse::parser::emit_unclosed_delims;
 use syntax::source_map::Spanned;
 use syntax::symbol::Symbol;
 use syntax_pos::{Span, FileName};

src/librustc_parse/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+authors = ["The Rust Project Developers"]
+name = "rustc_parse"
+version = "0.0.0"
+edition = "2018"
+
+[lib]
+name = "rustc_parse"
+path = "lib.rs"
+doctest = false
+
+[dependencies]
+bitflags = "1.0"
+log = "0.4"
+syntax_pos = { path = "../libsyntax_pos" }
+syntax = { path = "../libsyntax" }
+errors = { path = "../librustc_errors", package = "rustc_errors" }
+rustc_data_structures = { path = "../librustc_data_structures" }
+rustc_lexer = { path = "../librustc_lexer" }
+rustc_target = { path = "../librustc_target" }
+smallvec = { version = "1.0", features = ["union", "may_dangle"] }

src/librustc_parse/error_codes.rs

@@ -0,0 +1,174 @@
+// Error messages for EXXXX errors.
+// Each message should start and end with a new line, and be wrapped to 80
+// characters.  In vim you can `:set tw=80` and use `gq` to wrap paragraphs. Use
+// `:set tw=0` to disable.
+syntax::register_diagnostics! {
+
+E0178: r##"
+In types, the `+` type operator has low precedence, so it is often necessary
+to use parentheses.
+
+For example:
+
+```compile_fail,E0178
+trait Foo {}
+
+struct Bar<'a> {
+    w: &'a Foo + Copy,   // error, use &'a (Foo + Copy)
+    x: &'a Foo + 'a,     // error, use &'a (Foo + 'a)
+    y: &'a mut Foo + 'a, // error, use &'a mut (Foo + 'a)
+    z: fn() -> Foo + 'a, // error, use fn() -> (Foo + 'a)
+}
+```
+
+More details can be found in [RFC 438].
+
+[RFC 438]: https://github.com/rust-lang/rfcs/pull/438
+"##,
+
+E0583: r##"
+A file wasn't found for an out-of-line module.
+
+Erroneous code example:
+
+```ignore (compile_fail not working here; see Issue #43707)
+mod file_that_doesnt_exist; // error: file not found for module
+
+fn main() {}
+```
+
+Please be sure that a file corresponding to the module exists. If you
+want to use a module named `file_that_doesnt_exist`, you need to have a file
+named `file_that_doesnt_exist.rs` or `file_that_doesnt_exist/mod.rs` in the
+same directory.
+"##,
+
+E0584: r##"
+A doc comment that is not attached to anything has been encountered.
+
+Erroneous code example:
+
+```compile_fail,E0584
+trait Island {
+    fn lost();
+
+    /// I'm lost!
+}
+```
+
+A little reminder: a doc comment has to be placed before the item it's supposed
+to document. So if you want to document the `Island` trait, you need to put a
+doc comment before it, not inside it. Same goes for the `lost` method: the doc
+comment needs to be before it:
+
+```
+/// I'm THE island!
+trait Island {
+    /// I'm lost!
+    fn lost();
+}
+```
+"##,
+
+E0585: r##"
+A documentation comment that doesn't document anything was found.
+
+Erroneous code example:
+
+```compile_fail,E0585
+fn main() {
+    // The following doc comment will fail:
+    /// This is a useless doc comment!
+}
+```
+
+Documentation comments need to be followed by items, including functions,
+types, modules, etc. Examples:
+
+```
+/// I'm documenting the following struct:
+struct Foo;
+
+/// I'm documenting the following function:
+fn foo() {}
+```
+"##,
+
+E0586: r##"
+An inclusive range was used with no end.
+
+Erroneous code example:
+
+```compile_fail,E0586
+fn main() {
+    let tmp = vec![0, 1, 2, 3, 4, 4, 3, 3, 2, 1];
+    let x = &tmp[1..=]; // error: inclusive range was used with no end
+}
+```
+
+An inclusive range needs an end in order to *include* it. If you just need a
+start and no end, use a non-inclusive range (with `..`):
+
+```
+fn main() {
+    let tmp = vec![0, 1, 2, 3, 4, 4, 3, 3, 2, 1];
+    let x = &tmp[1..]; // ok!
+}
+```
+
+Or put an end to your inclusive range:
+
+```
+fn main() {
+    let tmp = vec![0, 1, 2, 3, 4, 4, 3, 3, 2, 1];
+    let x = &tmp[1..=3]; // ok!
+}
+```
+"##,
+
+E0704: r##"
+This error indicates that a incorrect visibility restriction was specified.
+
+Example of erroneous code:
+
+```compile_fail,E0704
+mod foo {
+    pub(foo) struct Bar {
+        x: i32
+    }
+}
+```
+
+To make struct `Bar` only visible in module `foo` the `in` keyword should be
+used:
+```
+mod foo {
+    pub(in crate::foo) struct Bar {
+        x: i32
+    }
+}
+# fn main() {}
+```
+
+For more information see the Rust Reference on [Visibility].
+
+[Visibility]: https://doc.rust-lang.org/reference/visibility-and-privacy.html
+"##,
+
+E0743: r##"
+C-variadic has been used on a non-foreign function.
+
+Erroneous code example:
+
+```compile_fail,E0743
+fn foo2(x: u8, ...) {} // error!
+```
+
+Only foreign functions can use C-variadic (`...`). It is used to give an
+undefined number of parameters to a given function (like `printf` in C). The
+equivalent in Rust would be to use macros directly.
+"##,
+
+;
+
+}

src/librustc_parse/lexer/mod.rs

@@ -1,7 +1,7 @@
-use crate::token::{self, Token, TokenKind};
+use syntax::token::{self, Token, TokenKind};
-use crate::sess::ParseSess;
+use syntax::sess::ParseSess;
-use crate::symbol::{sym, Symbol};
+use syntax::symbol::{sym, Symbol};
-use crate::util::comments;
+use syntax::util::comments;
 
 use errors::{FatalError, DiagnosticBuilder};
 use syntax_pos::{BytePos, Pos, Span};
@@ -13,9 +13,6 @@ use std::convert::TryInto;
 use rustc_data_structures::sync::Lrc;
 use log::debug;
 
-#[cfg(test)]
-mod tests;
-
 mod tokentrees;
 mod unicode_chars;
 mod unescape_error_reporting;
@@ -35,7 +32,8 @@ pub struct StringReader<'a> {
     /// Initial position, read-only.
     start_pos: BytePos,
     /// The absolute offset within the source_map of the current character.
-    pos: BytePos,
+    // FIXME(#64197): `pub` is needed by tests for now.
+    pub pos: BytePos,
     /// Stop reading src at this index.
     end_src_index: usize,
     /// Source text to tokenize.

src/librustc_parse/lexer/tokentrees.rs

@@ -3,9 +3,9 @@ use syntax_pos::Span;
 
 use super::{StringReader, UnmatchedBrace};
 
-use crate::print::pprust::token_to_string;
+use syntax::print::pprust::token_to_string;
-use crate::token::{self, Token};
+use syntax::token::{self, Token};
-use crate::tokenstream::{DelimSpan, IsJoint::{self, *}, TokenStream, TokenTree, TreeAndJoint};
+use syntax::tokenstream::{DelimSpan, IsJoint::{self, *}, TokenStream, TokenTree, TreeAndJoint};
 
 use errors::PResult;
 

src/librustc_parse/lexer/unescape_error_reporting.rs

@@ -6,7 +6,7 @@ use std::iter::once;
 use rustc_lexer::unescape::{EscapeError, Mode};
 use syntax_pos::{Span, BytePos};
 
-use crate::errors::{Handler, Applicability};
+use syntax::errors::{Handler, Applicability};
 
 pub(crate) fn emit_unescape_error(
     handler: &Handler,

src/librustc_parse/lib.rs

@@ -1,11 +1,12 @@
 //! The main parser interface.
 
-use crate::ast;
+#![feature(crate_visibility_modifier)]
-use crate::parse::parser::{Parser, emit_unclosed_delims, make_unclosed_delims_error};
+
-use crate::token::{self, Nonterminal};
+use syntax::ast;
-use crate::tokenstream::{self, TokenStream, TokenTree};
+use syntax::print::pprust;
-use crate::print::pprust;
+use syntax::sess::ParseSess;
-use crate::sess::ParseSess;
+use syntax::token::{self, Nonterminal};
+use syntax::tokenstream::{self, TokenStream, TokenTree};
 
 use errors::{PResult, FatalError, Level, Diagnostic};
 use rustc_data_structures::sync::Lrc;
@@ -17,12 +18,14 @@ use std::str;
 
 use log::info;
 
-#[cfg(test)]
+pub const MACRO_ARGUMENTS: Option<&'static str> = Some("macro arguments");
-mod tests;
 
 #[macro_use]
 pub mod parser;
+use parser::{Parser, emit_unclosed_delims, make_unclosed_delims_error};
 pub mod lexer;
+pub mod validate_attr;
+pub mod error_codes;
 
 #[derive(Clone)]
 pub struct Directory<'a> {

src/librustc_parse/parser/attr.rs

@@ -1,12 +1,10 @@
 use super::{SeqSep, Parser, TokenType, PathStyle};
-use crate::attr;
+use syntax::attr;
-use crate::ast;
+use syntax::ast;
-use crate::util::comments;
+use syntax::util::comments;
-use crate::token::{self, Nonterminal, DelimToken};
+use syntax::token::{self, Nonterminal, DelimToken};
-use crate::tokenstream::{TokenStream, TokenTree};
+use syntax::tokenstream::{TokenStream, TokenTree};
-use crate::source_map::Span;
+use syntax_pos::{Span, Symbol};
-
-use syntax_pos::Symbol;
 use errors::PResult;
 
 use log::debug;
@@ -158,12 +156,7 @@ impl<'a> Parser<'a> {
             }
         };
 
-        Ok(ast::Attribute {
+        Ok(attr::mk_attr_from_item(style, item, span))
-            kind: ast::AttrKind::Normal(item),
-            id: attr::mk_attr_id(),
-            style,
-            span,
-        })
     }
 
     /// Parses an inner part of an attribute (the path and following tokens).
@@ -268,7 +261,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses `cfg_attr(pred, attr_item_list)` where `attr_item_list` is comma-delimited.
-    crate fn parse_cfg_attr(&mut self) -> PResult<'a, (ast::MetaItem, Vec<(ast::AttrItem, Span)>)> {
+    pub fn parse_cfg_attr(&mut self) -> PResult<'a, (ast::MetaItem, Vec<(ast::AttrItem, Span)>)> {
         self.expect(&token::OpenDelim(token::Paren))?;
 
         let cfg_predicate = self.parse_meta_item()?;

src/librustc_parse/parser/diagnostics.rs

@@ -1,14 +1,16 @@
 use super::{BlockMode, PathStyle, SemiColonMode, TokenType, TokenExpectType, SeqSep, Parser};
-use crate::ast::{
+
+use syntax::ast::{
     self, Param, BinOpKind, BindingMode, BlockCheckMode, Expr, ExprKind, Ident, Item, ItemKind,
     Mutability, Pat, PatKind, PathSegment, QSelf, Ty, TyKind,
 };
-use crate::token::{self, TokenKind, token_can_begin_expr};
+use syntax::token::{self, TokenKind, token_can_begin_expr};
-use crate::print::pprust;
+use syntax::print::pprust;
-use crate::ptr::P;
+use syntax::ptr::P;
-use crate::symbol::{kw, sym};
+use syntax::symbol::{kw, sym};
-use crate::ThinVec;
+use syntax::ThinVec;
-use crate::util::parser::AssocOp;
+use syntax::util::parser::AssocOp;
+use syntax::struct_span_err;
 
 use errors::{PResult, Applicability, DiagnosticBuilder, DiagnosticId, pluralize};
 use rustc_data_structures::fx::FxHashSet;

src/librustc_parse/parser/expr.rs

@@ -2,24 +2,23 @@ use super::{Parser, Restrictions, PrevTokenKind, TokenType, PathStyle, BlockMode
 use super::{SemiColonMode, SeqSep, TokenExpectType};
 use super::pat::{GateOr, PARAM_EXPECTED};
 use super::diagnostics::Error;
+use crate::maybe_recover_from_interpolated_ty_qpath;
 
-use crate::ast::{
+use syntax::ast::{
     self, DUMMY_NODE_ID, Attribute, AttrStyle, Ident, CaptureBy, BlockCheckMode,
     Expr, ExprKind, RangeLimits, Label, Movability, IsAsync, Arm, Ty, TyKind,
     FunctionRetTy, Param, FnDecl, BinOpKind, BinOp, UnOp, Mac, AnonConst, Field, Lit,
 };
-use crate::maybe_recover_from_interpolated_ty_qpath;
+use syntax::token::{self, Token, TokenKind};
-use crate::token::{self, Token, TokenKind};
+use syntax::print::pprust;
-use crate::print::pprust;
+use syntax::ptr::P;
-use crate::ptr::P;
+use syntax::source_map::{self, Span};
-use crate::source_map::{self, Span};
+use syntax::util::classify;
-use crate::util::classify;
+use syntax::util::literal::LitError;
-use crate::util::literal::LitError;
+use syntax::util::parser::{AssocOp, Fixity, prec_let_scrutinee_needs_par};
-use crate::util::parser::{AssocOp, Fixity, prec_let_scrutinee_needs_par};
-
-use errors::{PResult, Applicability};
 use syntax_pos::symbol::{kw, sym};
 use syntax_pos::Symbol;
+use errors::{PResult, Applicability};
 use std::mem;
 use rustc_data_structures::thin_vec::ThinVec;
 

src/librustc_parse/parser/generics.rs

@@ -1,9 +1,8 @@
 use super::Parser;
 
-use crate::ast::{self, WhereClause, GenericParam, GenericParamKind, GenericBounds, Attribute};
+use syntax::ast::{self, WhereClause, GenericParam, GenericParamKind, GenericBounds, Attribute};
-use crate::token;
+use syntax::token;
-use crate::source_map::DUMMY_SP;
+use syntax::source_map::DUMMY_SP;
-
 use syntax_pos::symbol::{kw, sym};
 
 use errors::PResult;

src/librustc_parse/parser/item.rs

@@ -2,23 +2,24 @@ use super::{Parser, PathStyle};
 use super::diagnostics::{Error, dummy_arg, ConsumeClosingDelim};
 
 use crate::maybe_whole;
-use crate::ptr::P;
+
-use crate::ast::{self, Abi, DUMMY_NODE_ID, Ident, Attribute, AttrKind, AttrStyle, AnonConst, Item};
+use syntax::ast::{self, Abi, DUMMY_NODE_ID, Ident, Attribute, AttrKind, AttrStyle, AnonConst, Item};
-use crate::ast::{ItemKind, ImplItem, ImplItemKind, TraitItem, TraitItemKind, UseTree, UseTreeKind};
+use syntax::ast::{ItemKind, ImplItem, ImplItemKind, TraitItem, TraitItemKind, UseTree, UseTreeKind};
-use crate::ast::{PathSegment, IsAuto, Constness, IsAsync, Unsafety, Defaultness};
+use syntax::ast::{PathSegment, IsAuto, Constness, IsAsync, Unsafety, Defaultness};
-use crate::ast::{Visibility, VisibilityKind, Mutability, FnHeader, ForeignItem, ForeignItemKind};
+use syntax::ast::{Visibility, VisibilityKind, Mutability, FnHeader, ForeignItem, ForeignItemKind};
-use crate::ast::{Ty, TyKind, Generics, GenericBounds, TraitRef, EnumDef, VariantData, StructField};
+use syntax::ast::{Ty, TyKind, Generics, GenericBounds, TraitRef, EnumDef, VariantData, StructField};
-use crate::ast::{Mac, MacDelimiter, Block, BindingMode, FnDecl, FnSig, SelfKind, Param};
+use syntax::ast::{Mac, MacDelimiter, Block, BindingMode, FnDecl, FnSig, SelfKind, Param};
-use crate::parse::token;
+use syntax::ptr::P;
-use crate::tokenstream::{TokenTree, TokenStream};
+use syntax::ThinVec;
-use crate::symbol::{kw, sym};
+use syntax::token;
-use crate::source_map::{self, respan, Span};
+use syntax::tokenstream::{TokenTree, TokenStream};
-use crate::ThinVec;
+use syntax::source_map::{self, respan, Span};
+use syntax_pos::BytePos;
+use syntax_pos::symbol::{kw, sym};
 
 use log::debug;
 use std::mem;
 use errors::{PResult, Applicability, DiagnosticBuilder, DiagnosticId, StashKey};
-use syntax_pos::BytePos;
 
 /// Whether the type alias or associated type is a concrete type or an opaque type.
 #[derive(Debug)]

src/librustc_parse/parser/mod.rs

@@ -11,24 +11,26 @@ mod generics;
 mod diagnostics;
 use diagnostics::Error;
 
-use crate::ast::{
+use crate::{Directory, DirectoryOwnership};
+use crate::lexer::UnmatchedBrace;
+
+use syntax::ast::{
     self, Abi, DUMMY_NODE_ID, AttrStyle, Attribute, CrateSugar, Ident,
     IsAsync, MacDelimiter, Mutability, StrStyle, Visibility, VisibilityKind, Unsafety,
 };
-use crate::parse::{Directory, DirectoryOwnership};
-use crate::parse::lexer::UnmatchedBrace;
-use crate::util::comments::{doc_comment_style, strip_doc_comment_decoration};
-use crate::token::{self, Token, TokenKind, DelimToken};
-use crate::print::pprust;
-use crate::ptr::P;
-use crate::sess::ParseSess;
-use crate::source_map::respan;
-use crate::symbol::{kw, sym, Symbol};
-use crate::tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint};
-use crate::ThinVec;
 
-use errors::{PResult, Applicability, DiagnosticBuilder, DiagnosticId, FatalError};
+use syntax::print::pprust;
+use syntax::ptr::P;
+use syntax::token::{self, Token, TokenKind, DelimToken};
+use syntax::tokenstream::{self, DelimSpan, TokenTree, TokenStream, TreeAndJoint};
+use syntax::sess::ParseSess;
+use syntax::source_map::respan;
+use syntax::struct_span_err;
+use syntax::util::comments::{doc_comment_style, strip_doc_comment_decoration};
+use syntax_pos::symbol::{kw, sym, Symbol};
 use syntax_pos::{Span, BytePos, DUMMY_SP, FileName};
+use rustc_data_structures::thin_vec::ThinVec;
+use errors::{PResult, Applicability, DiagnosticBuilder, DiagnosticId, FatalError};
 use log::debug;
 
 use std::borrow::Cow;

src/librustc_parse/parser/module.rs

@@ -2,13 +2,14 @@ use super::Parser;
 use super::item::ItemInfo;
 use super::diagnostics::Error;
 
-use crate::attr;
+use crate::{new_sub_parser_from_file, DirectoryOwnership};
-use crate::ast::{self, Ident, Attribute, ItemKind, Mod, Crate};
-use crate::parse::{new_sub_parser_from_file, DirectoryOwnership};
-use crate::token::{self, TokenKind};
-use crate::source_map::{SourceMap, Span, DUMMY_SP, FileName};
-use crate::symbol::sym;
 
+use syntax::attr;
+use syntax::ast::{self, Ident, Attribute, ItemKind, Mod, Crate};
+use syntax::token::{self, TokenKind};
+use syntax::source_map::{SourceMap, Span, DUMMY_SP, FileName};
+
+use syntax_pos::symbol::sym;
 use errors::PResult;
 
 use std::path::{self, Path, PathBuf};
@@ -39,17 +40,12 @@ impl<'a> Parser<'a> {
 
     /// Parses a `mod <foo> { ... }` or `mod <foo>;` item.
     pub(super) fn parse_item_mod(&mut self, outer_attrs: &[Attribute]) -> PResult<'a, ItemInfo> {
-        let (in_cfg, outer_attrs) = {
+        // HACK(Centril): See documentation on `ParseSess::process_cfg_mod`.
-            // FIXME(Centril): This results in a cycle between config and parsing.
+        let (in_cfg, outer_attrs) = (self.sess.process_cfg_mod)(
-            // Consider using dynamic dispatch via `self.sess` to disentangle the knot.
+            self.sess,
-            let mut strip_unconfigured = crate::config::StripUnconfigured {
+            self.cfg_mods,
-                sess: self.sess,
+            outer_attrs,
-                features: None, // Don't perform gated feature checking.
+        );
-            };
-            let mut outer_attrs = outer_attrs.to_owned();
-            strip_unconfigured.process_cfg_attrs(&mut outer_attrs);
-            (!self.cfg_mods || strip_unconfigured.in_cfg(&outer_attrs), outer_attrs)
-        };
 
         let id_span = self.token.span;
         let id = self.parse_ident()?;

src/librustc_parse/parser/pat.rs

@@ -1,14 +1,13 @@
 use super::{Parser, PathStyle};
-
 use crate::{maybe_recover_from_interpolated_ty_qpath, maybe_whole};
-use crate::ptr::P;
+use syntax::ast::{self, Attribute, Pat, PatKind, FieldPat, RangeEnd, RangeSyntax, Mac};
-use crate::ast::{self, Attribute, Pat, PatKind, FieldPat, RangeEnd, RangeSyntax, Mac};
+use syntax::ast::{BindingMode, Ident, Mutability, Path, QSelf, Expr, ExprKind};
-use crate::ast::{BindingMode, Ident, Mutability, Path, QSelf, Expr, ExprKind};
+use syntax::mut_visit::{noop_visit_pat, noop_visit_mac, MutVisitor};
-use crate::mut_visit::{noop_visit_pat, noop_visit_mac, MutVisitor};
+use syntax::ptr::P;
-use crate::token;
+use syntax::print::pprust;
-use crate::print::pprust;
+use syntax::ThinVec;
-use crate::source_map::{respan, Span, Spanned};
+use syntax::token;
-use crate::ThinVec;
+use syntax::source_map::{respan, Span, Spanned};
 use syntax_pos::symbol::{kw, sym};
 use errors::{PResult, Applicability, DiagnosticBuilder};
 

src/librustc_parse/parser/path.rs

@@ -1,10 +1,10 @@
 use super::{Parser, TokenType};
-
+use crate::maybe_whole;
-use crate::{maybe_whole, ThinVec};
+use syntax::ast::{self, QSelf, Path, PathSegment, Ident, ParenthesizedArgs, AngleBracketedArgs};
-use crate::ast::{self, QSelf, Path, PathSegment, Ident, ParenthesizedArgs, AngleBracketedArgs};
+use syntax::ast::{AnonConst, GenericArg, AssocTyConstraint, AssocTyConstraintKind, BlockCheckMode};
-use crate::ast::{AnonConst, GenericArg, AssocTyConstraint, AssocTyConstraintKind, BlockCheckMode};
+use syntax::ThinVec;
-use crate::token::{self, Token};
+use syntax::token::{self, Token};
-use crate::source_map::{Span, BytePos};
+use syntax::source_map::{Span, BytePos};
 use syntax_pos::symbol::{kw, sym};
 
 use std::mem;

src/librustc_parse/parser/stmt.rs

@@ -3,16 +3,18 @@ use super::expr::LhsExpr;
 use super::path::PathStyle;
 use super::pat::GateOr;
 use super::diagnostics::Error;
+use crate::maybe_whole;
+use crate::DirectoryOwnership;
 
-use crate::ptr::P;
+use syntax::ThinVec;
-use crate::{maybe_whole, ThinVec};
+use syntax::ptr::P;
-use crate::ast::{self, DUMMY_NODE_ID, Stmt, StmtKind, Local, Block, BlockCheckMode, Expr, ExprKind};
+use syntax::ast;
-use crate::ast::{Attribute, AttrStyle, VisibilityKind, MacStmtStyle, Mac, MacDelimiter};
+use syntax::ast::{DUMMY_NODE_ID, Stmt, StmtKind, Local, Block, BlockCheckMode, Expr, ExprKind};
-use crate::parse::DirectoryOwnership;
+use syntax::ast::{Attribute, AttrStyle, VisibilityKind, MacStmtStyle, Mac, MacDelimiter};
-use crate::util::classify;
+use syntax::util::classify;
-use crate::token;
+use syntax::token;
-use crate::source_map::{respan, Span};
+use syntax::source_map::{respan, Span};
-use crate::symbol::{kw, sym};
+use syntax::symbol::{kw, sym};
 
 use std::mem;
 use errors::{PResult, Applicability};

src/librustc_parse/parser/ty.rs

@@ -2,13 +2,15 @@ use super::{Parser, PathStyle, PrevTokenKind, TokenType};
 use super::item::ParamCfg;
 
 use crate::{maybe_whole, maybe_recover_from_interpolated_ty_qpath};
-use crate::ptr::P;
+
-use crate::ast::{self, Ty, TyKind, MutTy, BareFnTy, FunctionRetTy, GenericParam, Lifetime, Ident};
+use syntax::ptr::P;
-use crate::ast::{TraitBoundModifier, TraitObjectSyntax, GenericBound, GenericBounds, PolyTraitRef};
+use syntax::ast::{self, Ty, TyKind, MutTy, BareFnTy, FunctionRetTy, GenericParam, Lifetime, Ident};
-use crate::ast::{Mutability, AnonConst, Mac};
+use syntax::ast::{TraitBoundModifier, TraitObjectSyntax, GenericBound, GenericBounds, PolyTraitRef};
-use crate::token::{self, Token};
+use syntax::ast::{Mutability, AnonConst, Mac};
-use crate::source_map::Span;
+use syntax::token::{self, Token};
-use crate::symbol::{kw};
+use syntax::source_map::Span;
+use syntax::struct_span_fatal;
+use syntax_pos::symbol::kw;
 
 use errors::{PResult, Applicability, pluralize};
 

src/librustc_parse/validate_attr.rs

@@ -0,0 +1,111 @@
+//! Meta-syntax validation logic of attributes for post-expansion.
+
+use errors::{PResult, Applicability};
+use syntax::ast::{self, Attribute, AttrKind, Ident, MetaItem};
+use syntax::attr::{AttributeTemplate, mk_name_value_item_str};
+use syntax::early_buffered_lints::BufferedEarlyLintId;
+use syntax::feature_gate::BUILTIN_ATTRIBUTE_MAP;
+use syntax::token;
+use syntax::tokenstream::TokenTree;
+use syntax::sess::ParseSess;
+use syntax_pos::{Symbol, sym};
+
+pub fn check_meta(sess: &ParseSess, attr: &Attribute) {
+    let attr_info =
+        attr.ident().and_then(|ident| BUILTIN_ATTRIBUTE_MAP.get(&ident.name)).map(|a| **a);
+
+    // Check input tokens for built-in and key-value attributes.
+    match attr_info {
+        // `rustc_dummy` doesn't have any restrictions specific to built-in attributes.
+        Some((name, _, template, _)) if name != sym::rustc_dummy =>
+            check_builtin_attribute(sess, attr, name, template),
+        _ => if let Some(TokenTree::Token(token)) = attr.get_normal_item().tokens.trees().next() {
+            if token == token::Eq {
+                // All key-value attributes are restricted to meta-item syntax.
+                parse_meta(sess, attr).map_err(|mut err| err.emit()).ok();
+            }
+        }
+    }
+}
+
+pub fn parse_meta<'a>(sess: &'a ParseSess, attr: &Attribute) -> PResult<'a, MetaItem> {
+    Ok(match attr.kind {
+        AttrKind::Normal(ref item) => MetaItem {
+            path: item.path.clone(),
+            kind: super::parse_in_attr(sess, attr, |p| p.parse_meta_item_kind())?,
+            span: attr.span,
+        },
+        AttrKind::DocComment(comment) => {
+            mk_name_value_item_str(Ident::new(sym::doc, attr.span), comment, attr.span)
+        }
+    })
+}
+
+pub fn check_builtin_attribute(
+    sess: &ParseSess,
+    attr: &Attribute,
+    name: Symbol,
+    template: AttributeTemplate,
+) {
+    // Some special attributes like `cfg` must be checked
+    // before the generic check, so we skip them here.
+    let should_skip = |name| name == sym::cfg;
+    // Some of previously accepted forms were used in practice,
+    // report them as warnings for now.
+    let should_warn = |name| name == sym::doc || name == sym::ignore ||
+                             name == sym::inline || name == sym::link ||
+                             name == sym::test || name == sym::bench;
+
+    match parse_meta(sess, attr) {
+        Ok(meta) => if !should_skip(name) && !template.compatible(&meta.kind) {
+            let error_msg = format!("malformed `{}` attribute input", name);
+            let mut msg = "attribute must be of the form ".to_owned();
+            let mut suggestions = vec![];
+            let mut first = true;
+            if template.word {
+                first = false;
+                let code = format!("#[{}]", name);
+                msg.push_str(&format!("`{}`", &code));
+                suggestions.push(code);
+            }
+            if let Some(descr) = template.list {
+                if !first {
+                    msg.push_str(" or ");
+                }
+                first = false;
+                let code = format!("#[{}({})]", name, descr);
+                msg.push_str(&format!("`{}`", &code));
+                suggestions.push(code);
+            }
+            if let Some(descr) = template.name_value_str {
+                if !first {
+                    msg.push_str(" or ");
+                }
+                let code = format!("#[{} = \"{}\"]", name, descr);
+                msg.push_str(&format!("`{}`", &code));
+                suggestions.push(code);
+            }
+            if should_warn(name) {
+                sess.buffer_lint(
+                    BufferedEarlyLintId::IllFormedAttributeInput,
+                    meta.span,
+                    ast::CRATE_NODE_ID,
+                    &msg,
+                );
+            } else {
+                sess.span_diagnostic.struct_span_err(meta.span, &error_msg)
+                    .span_suggestions(
+                        meta.span,
+                        if suggestions.len() == 1 {
+                            "must be of the form"
+                        } else {
+                            "the following are the possible correct uses"
+                        },
+                        suggestions.into_iter(),
+                        Applicability::HasPlaceholders,
+                    ).emit();
+            }
+        }
+        Err(mut err) => err.emit(),
+    }
+}

src/librustc_passes/Cargo.toml

@@ -12,8 +12,9 @@ path = "lib.rs"
 log = "0.4"
 rustc = { path = "../librustc" }
 rustc_data_structures = { path = "../librustc_data_structures" }
+rustc_index = { path = "../librustc_index" }
+rustc_parse = { path = "../librustc_parse" }
+rustc_target = { path = "../librustc_target" }
 syntax = { path = "../libsyntax" }
 syntax_pos = { path = "../libsyntax_pos" }
 errors = { path = "../librustc_errors", package = "rustc_errors" }
-rustc_target = { path = "../librustc_target" }
-rustc_index = { path = "../librustc_index" }

src/librustc_passes/ast_validation.rs

@@ -7,14 +7,15 @@
 // or type checking or some other kind of complex analysis.
 
 use std::mem;
-use syntax::print::pprust;
 use rustc::lint;
 use rustc::session::Session;
 use rustc_data_structures::fx::FxHashMap;
+use rustc_parse::validate_attr;
 use syntax::ast::*;
 use syntax::attr;
 use syntax::expand::is_proc_macro_attr;
 use syntax::feature_gate::is_builtin_attr;
+use syntax::print::pprust;
 use syntax::source_map::Spanned;
 use syntax::symbol::{kw, sym};
 use syntax::visit::{self, Visitor};
@@ -369,6 +370,10 @@ fn validate_generics_order<'a>(
 }
 
 impl<'a> Visitor<'a> for AstValidator<'a> {
+    fn visit_attribute(&mut self, attr: &Attribute) {
+        validate_attr::check_meta(&self.session.parse_sess, attr);
+    }
+
     fn visit_expr(&mut self, expr: &'a Expr) {
         match &expr.kind {
             ExprKind::Closure(_, _, _, fn_decl, _, _) => {

src/librustc_save_analysis/Cargo.toml

@@ -13,6 +13,7 @@ log = "0.4"
 rustc = { path = "../librustc" }
 rustc_data_structures = { path = "../librustc_data_structures" }
 rustc_codegen_utils = { path = "../librustc_codegen_utils" }
+rustc_parse = { path = "../librustc_parse" }
 serde_json = "1"
 syntax = { path = "../libsyntax" }
 syntax_pos = { path = "../libsyntax_pos" }

src/librustc_save_analysis/span_utils.rs

@@ -1,8 +1,6 @@
-use rustc::session::Session;
-
 use crate::generated_code;
-
+use rustc::session::Session;
-use syntax::parse::lexer::{self, StringReader};
+use rustc_parse::lexer::{self, StringReader};
 use syntax::token::{self, TokenKind};
 use syntax_pos::*;
 

src/librustdoc/html/highlight.rs

@@ -11,11 +11,12 @@ use std::fmt::Display;
 use std::io;
 use std::io::prelude::*;
 
-use syntax::source_map::SourceMap;
+use rustc_parse::lexer;
-use syntax::parse::lexer;
 use syntax::token::{self, Token};
 use syntax::sess::ParseSess;
+use syntax::source_map::SourceMap;
 use syntax::symbol::{kw, sym};
+use syntax_expand::config::process_configure_mod;
 use syntax_pos::{Span, FileName};
 
 /// Highlights `src`, returning the HTML output.
@@ -33,7 +34,7 @@ pub fn render_with_highlighting(
                class, tooltip).unwrap();
     }
 
-    let sess = ParseSess::with_silent_emitter();
+    let sess = ParseSess::with_silent_emitter(process_configure_mod);
     let fm = sess.source_map().new_source_file(
         FileName::Custom(String::from("rustdoc-highlighting")),
         src.to_owned(),

src/librustdoc/lib.rs

@@ -29,6 +29,7 @@ extern crate rustc_resolve;
 extern crate rustc_lint;
 extern crate rustc_interface;
 extern crate rustc_metadata;
+extern crate rustc_parse;
 extern crate rustc_target;
 extern crate rustc_typeck;
 extern crate rustc_lexer;

src/librustdoc/passes/check_code_block_syntax.rs

@@ -1,8 +1,9 @@
 use errors::Applicability;
-use syntax::parse::lexer::{StringReader as Lexer};
+use rustc_parse::lexer::{StringReader as Lexer};
 use syntax::token;
 use syntax::sess::ParseSess;
 use syntax::source_map::FilePathMapping;
+use syntax_expand::config::process_configure_mod;
 use syntax_pos::{InnerSpan, FileName};
 
 use crate::clean;
@@ -27,7 +28,7 @@ struct SyntaxChecker<'a, 'tcx> {
 
 impl<'a, 'tcx> SyntaxChecker<'a, 'tcx> {
     fn check_rust_syntax(&self, item: &clean::Item, dox: &str, code_block: RustCodeBlock) {
-        let sess = ParseSess::new(FilePathMapping::empty());
+        let sess = ParseSess::new(FilePathMapping::empty(), process_configure_mod);
         let source_file = sess.source_map().new_source_file(
             FileName::Custom(String::from("doctest")),
             dox[code_block.code].to_owned(),

src/librustdoc/test.rs

@@ -17,6 +17,7 @@ use std::path::PathBuf;
 use std::process::{self, Command, Stdio};
 use std::str;
 use syntax::symbol::sym;
+use syntax_expand::config::process_configure_mod;
 use syntax_pos::{BytePos, DUMMY_SP, Pos, Span, FileName};
 use tempfile::Builder as TempFileBuilder;
 use testing;
@@ -398,7 +399,8 @@ pub fn make_test(s: &str,
     // Uses libsyntax to parse the doctest and find if there's a main fn and the extern
     // crate already is included.
     let (already_has_main, already_has_extern_crate, found_macro) = with_globals(edition, || {
-        use crate::syntax::{parse, sess::ParseSess, source_map::FilePathMapping};
+        use crate::syntax::{sess::ParseSess, source_map::FilePathMapping};
+        use rustc_parse::maybe_new_parser_from_source_str;
         use errors::emitter::EmitterWriter;
         use errors::Handler;
 
@@ -411,13 +413,13 @@ pub fn make_test(s: &str,
         let emitter = EmitterWriter::new(box io::sink(), None, false, false, false, None, false);
         // FIXME(misdreavus): pass `-Z treat-err-as-bug` to the doctest parser
         let handler = Handler::with_emitter(false, None, box emitter);
-        let sess = ParseSess::with_span_handler(handler, cm);
+        let sess = ParseSess::with_span_handler(handler, cm, process_configure_mod);
 
         let mut found_main = false;
         let mut found_extern_crate = cratename.is_none();
         let mut found_macro = false;
 
-        let mut parser = match parse::maybe_new_parser_from_source_str(&sess, filename, source) {
+        let mut parser = match maybe_new_parser_from_source_str(&sess, filename, source) {
             Ok(p) => p,
             Err(errs) => {
                 for mut err in errs {

src/libsyntax/ast.rs

@@ -537,7 +537,7 @@ pub struct Pat {
 impl Pat {
     /// Attempt reparsing the pattern as a type.
     /// This is intended for use by diagnostics.
-    pub(super) fn to_ty(&self) -> Option<P<Ty>> {
+    pub fn to_ty(&self) -> Option<P<Ty>> {
         let kind = match &self.kind {
             // In a type expression `_` is an inference variable.
             PatKind::Wild => TyKind::Infer,
@@ -1031,7 +1031,7 @@ impl Expr {
         }
     }
 
-    fn to_bound(&self) -> Option<GenericBound> {
+    pub fn to_bound(&self) -> Option<GenericBound> {
         match &self.kind {
             ExprKind::Path(None, path) => Some(GenericBound::Trait(
                 PolyTraitRef::new(Vec::new(), path.clone(), self.span),
@@ -1042,7 +1042,7 @@ impl Expr {
     }
 
     /// Attempts to reparse as `Ty` (for diagnostic purposes).
-    pub(super) fn to_ty(&self) -> Option<P<Ty>> {
+    pub fn to_ty(&self) -> Option<P<Ty>> {
         let kind = match &self.kind {
             // Trivial conversions.
             ExprKind::Path(qself, path) => TyKind::Path(qself.clone(), path.clone()),

src/libsyntax/attr/builtin.rs

@@ -1,7 +1,6 @@
 //! Parsing and validation of builtin attributes
 
 use crate::ast::{self, Attribute, MetaItem, NestedMetaItem};
-use crate::early_buffered_lints::BufferedEarlyLintId;
 use crate::feature_gate::{Features, GatedCfg};
 use crate::print::pprust;
 use crate::sess::ParseSess;
@@ -25,9 +24,9 @@ enum AttrError {
 /// Only top-level shape (`#[attr]` vs `#[attr(...)]` vs `#[attr = ...]`) is considered now.
 #[derive(Clone, Copy)]
 pub struct AttributeTemplate {
-    crate word: bool,
+    pub word: bool,
-    crate list: Option<&'static str>,
+    pub list: Option<&'static str>,
-    crate name_value_str: Option<&'static str>,
+    pub name_value_str: Option<&'static str>,
 }
 
 impl AttributeTemplate {
@@ -36,7 +35,7 @@ impl AttributeTemplate {
     }
 
     /// Checks that the given meta-item is compatible with this template.
-    fn compatible(&self, meta_item_kind: &ast::MetaItemKind) -> bool {
+    pub fn compatible(&self, meta_item_kind: &ast::MetaItemKind) -> bool {
         match meta_item_kind {
             ast::MetaItemKind::Word => self.word,
             ast::MetaItemKind::List(..) => self.list.is_some(),
@@ -938,69 +937,3 @@ pub fn find_transparency(
     let fallback = if is_legacy { Transparency::SemiTransparent } else { Transparency::Opaque };
     (transparency.map_or(fallback, |t| t.0), error)
 }
-
-pub fn check_builtin_attribute(
-    sess: &ParseSess, attr: &ast::Attribute, name: Symbol, template: AttributeTemplate
-) {
-    // Some special attributes like `cfg` must be checked
-    // before the generic check, so we skip them here.
-    let should_skip = |name| name == sym::cfg;
-    // Some of previously accepted forms were used in practice,
-    // report them as warnings for now.
-    let should_warn = |name| name == sym::doc || name == sym::ignore ||
-                             name == sym::inline || name == sym::link ||
-                             name == sym::test || name == sym::bench;
-
-    match attr.parse_meta(sess) {
-        Ok(meta) => if !should_skip(name) && !template.compatible(&meta.kind) {
-            let error_msg = format!("malformed `{}` attribute input", name);
-            let mut msg = "attribute must be of the form ".to_owned();
-            let mut suggestions = vec![];
-            let mut first = true;
-            if template.word {
-                first = false;
-                let code = format!("#[{}]", name);
-                msg.push_str(&format!("`{}`", &code));
-                suggestions.push(code);
-            }
-            if let Some(descr) = template.list {
-                if !first {
-                    msg.push_str(" or ");
-                }
-                first = false;
-                let code = format!("#[{}({})]", name, descr);
-                msg.push_str(&format!("`{}`", &code));
-                suggestions.push(code);
-            }
-            if let Some(descr) = template.name_value_str {
-                if !first {
-                    msg.push_str(" or ");
-                }
-                let code = format!("#[{} = \"{}\"]", name, descr);
-                msg.push_str(&format!("`{}`", &code));
-                suggestions.push(code);
-            }
-            if should_warn(name) {
-                sess.buffer_lint(
-                    BufferedEarlyLintId::IllFormedAttributeInput,
-                    meta.span,
-                    ast::CRATE_NODE_ID,
-                    &msg,
-                );
-            } else {
-                sess.span_diagnostic.struct_span_err(meta.span, &error_msg)
-                    .span_suggestions(
-                        meta.span,
-                        if suggestions.len() == 1 {
-                            "must be of the form"
-                        } else {
-                            "the following are the possible correct uses"
-                        },
-                        suggestions.into_iter(),
-                        Applicability::HasPlaceholders,
-                    ).emit();
-            }
-        }
-        Err(mut err) => err.emit(),
-    }
-}

src/libsyntax/attr/mod.rs

@@ -14,17 +14,13 @@ use crate::ast::{MetaItem, MetaItemKind, NestedMetaItem};
 use crate::ast::{Lit, LitKind, Expr, Item, Local, Stmt, StmtKind, GenericParam};
 use crate::mut_visit::visit_clobber;
 use crate::source_map::{BytePos, Spanned};
-use crate::parse;
 use crate::token::{self, Token};
 use crate::ptr::P;
-use crate::sess::ParseSess;
 use crate::symbol::{sym, Symbol};
 use crate::ThinVec;
 use crate::tokenstream::{DelimSpan, TokenStream, TokenTree, TreeAndJoint};
 use crate::GLOBALS;
 
-use errors::PResult;
-
 use log::debug;
 use syntax_pos::Span;
 
@@ -281,7 +277,7 @@ impl MetaItem {
 }
 
 impl AttrItem {
-    crate fn meta(&self, span: Span) -> Option<MetaItem> {
+    pub fn meta(&self, span: Span) -> Option<MetaItem> {
         let mut tokens = self.tokens.trees().peekable();
         Some(MetaItem {
             path: self.path.clone(),
@@ -328,21 +324,6 @@ impl Attribute {
                 Some(mk_name_value_item_str(Ident::new(sym::doc, self.span), comment, self.span)),
         }
     }
-
-    pub fn parse_meta<'a>(&self, sess: &'a ParseSess) -> PResult<'a, MetaItem> {
-        match self.kind {
-            AttrKind::Normal(ref item) => {
-                Ok(MetaItem {
-                    path: item.path.clone(),
-                    kind: parse::parse_in_attr(sess, self, |parser| parser.parse_meta_item_kind())?,
-                    span: self.span,
-                })
-            }
-            AttrKind::DocComment(comment) => {
-                Ok(mk_name_value_item_str(Ident::new(sym::doc, self.span), comment, self.span))
-            }
-        }
-    }
 }
 
 /* Constructors */
@@ -382,8 +363,12 @@ crate fn mk_attr_id() -> AttrId {
 }
 
 pub fn mk_attr(style: AttrStyle, path: Path, tokens: TokenStream, span: Span) -> Attribute {
+    mk_attr_from_item(style, AttrItem { path, tokens }, span)
+}
+
+pub fn mk_attr_from_item(style: AttrStyle, item: AttrItem, span: Span) -> Attribute {
     Attribute {
-        kind: AttrKind::Normal(AttrItem { path, tokens }),
+        kind: AttrKind::Normal(item),
         id: mk_attr_id(),
         style,
         span,

src/libsyntax/error_codes.rs

@@ -4,28 +4,6 @@
 // `:set tw=0` to disable.
 register_diagnostics! {
 
-E0178: r##"
-In types, the `+` type operator has low precedence, so it is often necessary
-to use parentheses.
-
-For example:
-
-```compile_fail,E0178
-trait Foo {}
-
-struct Bar<'a> {
-    w: &'a Foo + Copy,   // error, use &'a (Foo + Copy)
-    x: &'a Foo + 'a,     // error, use &'a (Foo + 'a)
-    y: &'a mut Foo + 'a, // error, use &'a mut (Foo + 'a)
-    z: fn() -> Foo + 'a, // error, use fn() -> (Foo + 'a)
-}
-```
-
-More details can be found in [RFC 438].
-
-[RFC 438]: https://github.com/rust-lang/rfcs/pull/438
-"##,
-
 E0536: r##"
 The `not` cfg-predicate was malformed.
 
@@ -278,106 +256,6 @@ pub fn something() {}
 ```
 "##,
 
-E0583: r##"
-A file wasn't found for an out-of-line module.
-
-Erroneous code example:
-
-```ignore (compile_fail not working here; see Issue #43707)
-mod file_that_doesnt_exist; // error: file not found for module
-
-fn main() {}
-```
-
-Please be sure that a file corresponding to the module exists. If you
-want to use a module named `file_that_doesnt_exist`, you need to have a file
-named `file_that_doesnt_exist.rs` or `file_that_doesnt_exist/mod.rs` in the
-same directory.
-"##,
-
-E0584: r##"
-A doc comment that is not attached to anything has been encountered.
-
-Erroneous code example:
-
-```compile_fail,E0584
-trait Island {
-    fn lost();
-
-    /// I'm lost!
-}
-```
-
-A little reminder: a doc comment has to be placed before the item it's supposed
-to document. So if you want to document the `Island` trait, you need to put a
-doc comment before it, not inside it. Same goes for the `lost` method: the doc
-comment needs to be before it:
-
-```
-/// I'm THE island!
-trait Island {
-    /// I'm lost!
-    fn lost();
-}
-```
-"##,
-
-E0585: r##"
-A documentation comment that doesn't document anything was found.
-
-Erroneous code example:
-
-```compile_fail,E0585
-fn main() {
-    // The following doc comment will fail:
-    /// This is a useless doc comment!
-}
-```
-
-Documentation comments need to be followed by items, including functions,
-types, modules, etc. Examples:
-
-```
-/// I'm documenting the following struct:
-struct Foo;
-
-/// I'm documenting the following function:
-fn foo() {}
-```
-"##,
-
-E0586: r##"
-An inclusive range was used with no end.
-
-Erroneous code example:
-
-```compile_fail,E0586
-fn main() {
-    let tmp = vec![0, 1, 2, 3, 4, 4, 3, 3, 2, 1];
-    let x = &tmp[1..=]; // error: inclusive range was used with no end
-}
-```
-
-An inclusive range needs an end in order to *include* it. If you just need a
-start and no end, use a non-inclusive range (with `..`):
-
-```
-fn main() {
-    let tmp = vec![0, 1, 2, 3, 4, 4, 3, 3, 2, 1];
-    let x = &tmp[1..]; // ok!
-}
-```
-
-Or put an end to your inclusive range:
-
-```
-fn main() {
-    let tmp = vec![0, 1, 2, 3, 4, 4, 3, 3, 2, 1];
-    let x = &tmp[1..=3]; // ok!
-}
-```
-"##,
-
 E0589: r##"
 The value of `N` that was specified for `repr(align(N))` was not a power
 of two, or was greater than 2^29.
@@ -446,35 +324,6 @@ and likely to change in the future.
 
 "##,
 
-E0704: r##"
-This error indicates that a incorrect visibility restriction was specified.
-
-Example of erroneous code:
-
-```compile_fail,E0704
-mod foo {
-    pub(foo) struct Bar {
-        x: i32
-    }
-}
-```
-
-To make struct `Bar` only visible in module `foo` the `in` keyword should be
-used:
-```
-mod foo {
-    pub(in crate::foo) struct Bar {
-        x: i32
-    }
-}
-# fn main() {}
-```
-
-For more information see the Rust Reference on [Visibility].
-
-[Visibility]: https://doc.rust-lang.org/reference/visibility-and-privacy.html
-"##,
-
 E0705: r##"
 A `#![feature]` attribute was declared for a feature that is stable in
 the current edition, but not in all editions.
@@ -504,20 +353,6 @@ Delete the offending feature attribute, or add it to the list of allowed
 features in the `-Z allow_features` flag.
 "##,
 
-E0743: r##"
-C-variadic has been used on a non-foreign function.
-
-Erroneous code example:
-
-```compile_fail,E0743
-fn foo2(x: u8, ...) {} // error!
-```
-
-Only foreign functions can use C-variadic (`...`). It is used to give an
-undefined number of parameters to a given function (like `printf` in C). The
-equivalent in Rust would be to use macros directly.
-"##,
-
 ;
 
     E0539, // incorrect meta item

src/libsyntax/feature_gate/check.rs

@@ -3,18 +3,14 @@ use super::accepted::ACCEPTED_FEATURES;
 use super::removed::{REMOVED_FEATURES, STABLE_REMOVED_FEATURES};
 use super::builtin_attrs::{AttributeGate, BUILTIN_ATTRIBUTE_MAP};
 
-use crate::ast::{
+use crate::ast::{self, AssocTyConstraint, AssocTyConstraintKind, NodeId};
-    self, AssocTyConstraint, AssocTyConstraintKind, NodeId, GenericParam, GenericParamKind,
+use crate::ast::{GenericParam, GenericParamKind, PatKind, RangeEnd, VariantData};
-    PatKind, RangeEnd, VariantData,
+use crate::attr;
-};
-use crate::attr::{self, check_builtin_attribute};
 use crate::source_map::Spanned;
 use crate::edition::{ALL_EDITIONS, Edition};
 use crate::visit::{self, FnKind, Visitor};
-use crate::token;
 use crate::sess::ParseSess;
 use crate::symbol::{Symbol, sym};
-use crate::tokenstream::TokenTree;
 
 use errors::{Applicability, DiagnosticBuilder, Handler};
 use rustc_data_structures::fx::FxHashMap;
@@ -331,19 +327,6 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
         if let Some((.., AttributeGate::Gated(_, name, descr, has_feature))) = attr_info {
             gate_feature_fn!(self, has_feature, attr.span, name, descr, GateStrength::Hard);
         }
-        // Check input tokens for built-in and key-value attributes.
-        match attr_info {
-            // `rustc_dummy` doesn't have any restrictions specific to built-in attributes.
-            Some((name, _, template, _)) if name != sym::rustc_dummy =>
-                check_builtin_attribute(self.parse_sess, attr, name, template),
-            _ => if let Some(TokenTree::Token(token)) =
-                    attr.get_normal_item().tokens.trees().next() {
-                if token == token::Eq {
-                    // All key-value attributes are restricted to meta-item syntax.
-                    attr.parse_meta(self.parse_sess).map_err(|mut err| err.emit()).ok();
-                }
-            }
-        }
         // Check unstable flavors of the `#[doc]` attribute.
         if attr.check_name(sym::doc) {
             for nested_meta in attr.meta_item_list().unwrap_or_default() {

src/libsyntax/json/tests.rs

@@ -2,7 +2,6 @@ use super::*;
 
 use crate::json::JsonEmitter;
 use crate::source_map::{FilePathMapping, SourceMap};
-use crate::tests::Shared;
 use crate::with_default_globals;
 
 use errors::emitter::{ColorConfig, HumanReadableErrorType};
@@ -27,6 +26,20 @@ struct SpanTestData {
     pub column_end: u32,
 }
 
+struct Shared<T> {
+    data: Arc<Mutex<T>>,
+}
+
+impl<T: Write> Write for Shared<T> {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        self.data.lock().unwrap().write(buf)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        self.data.lock().unwrap().flush()
+    }
+}
+
 /// Test the span yields correct positions in JSON.
 fn test_positions(code: &str, span: (u32, u32), expected_output: SpanTestData) {
     let expected_output = TestData { spans: vec![expected_output] };

src/libsyntax/lib.rs

@@ -26,11 +26,6 @@ pub use rustc_data_structures::thin_vec::ThinVec;
 use ast::AttrId;
 use syntax_pos::edition::Edition;
 
-#[cfg(test)]
-mod tests;
-
-pub const MACRO_ARGUMENTS: Option<&'static str> = Some("macro arguments");
-
 #[macro_export]
 macro_rules! unwrap_or {
     ($opt:expr, $default:expr) => {
@@ -85,10 +80,10 @@ pub mod diagnostics {
 pub mod error_codes;
 
 pub mod util {
-    crate mod classify;
+    pub mod classify;
     pub mod comments;
     pub mod lev_distance;
-    crate mod literal;
+    pub mod literal;
     pub mod node_count;
     pub mod parser;
     pub mod map_in_place;
@@ -100,11 +95,9 @@ pub mod ast;
 pub mod attr;
 pub mod expand;
 pub mod source_map;
-#[macro_use] pub mod config;
 pub mod entry;
 pub mod feature_gate;
 pub mod mut_visit;
-pub mod parse;
 pub mod ptr;
 pub mod show_span;
 pub use syntax_pos::edition;

src/libsyntax/mut_visit.rs

@@ -22,9 +22,6 @@ use rustc_data_structures::sync::Lrc;
 use std::ops::DerefMut;
 use std::{panic, process, ptr};
 
-#[cfg(test)]
-mod tests;
-
 pub trait ExpectOne<A: Array> {
     fn expect_one(self, err: &'static str) -> A::Item;
 }

src/libsyntax/print/pprust.rs

@@ -321,7 +321,7 @@ fn token_to_string_ext(token: &Token, convert_dollar_crate: bool) -> String {
     token_kind_to_string_ext(&token.kind, convert_dollar_crate)
 }
 
-crate fn nonterminal_to_string(nt: &Nonterminal) -> String {
+pub fn nonterminal_to_string(nt: &Nonterminal) -> String {
     match *nt {
         token::NtExpr(ref e)        => expr_to_string(e),
         token::NtMeta(ref e)        => attr_item_to_string(e),
@@ -939,8 +939,11 @@ impl<'a> State<'a> {
         self.commasep_cmnt(b, exprs, |s, e| s.print_expr(e), |e| e.span)
     }
 
-    crate fn print_mod(&mut self, _mod: &ast::Mod,
+    pub fn print_mod(
-                       attrs: &[ast::Attribute]) {
+        &mut self,
+        _mod: &ast::Mod,
+        attrs: &[ast::Attribute],
+    ) {
         self.print_inner_attributes(attrs);
         for item in &_mod.items {
             self.print_item(item);
@@ -955,7 +958,7 @@ impl<'a> State<'a> {
         }
     }
 
-    crate fn print_opt_lifetime(&mut self, lifetime: &Option<ast::Lifetime>) {
+    pub fn print_opt_lifetime(&mut self, lifetime: &Option<ast::Lifetime>) {
         if let Some(lt) = *lifetime {
             self.print_lifetime(lt);
             self.nbsp();
@@ -970,7 +973,7 @@ impl<'a> State<'a> {
         }
     }
 
-    crate fn print_type(&mut self, ty: &ast::Ty) {
+    pub fn print_type(&mut self, ty: &ast::Ty) {
         self.maybe_print_comment(ty.span.lo());
         self.ibox(0);
         match ty.kind {
@@ -1995,7 +1998,7 @@ impl<'a> State<'a> {
         self.print_expr_maybe_paren(expr, parser::PREC_PREFIX)
     }
 
-    crate fn print_expr(&mut self, expr: &ast::Expr) {
+    pub fn print_expr(&mut self, expr: &ast::Expr) {
         self.print_expr_outer_attr_style(expr, true)
     }
 
@@ -2332,7 +2335,7 @@ impl<'a> State<'a> {
         }
     }
 
-    crate fn print_usize(&mut self, i: usize) {
+    pub fn print_usize(&mut self, i: usize) {
         self.s.word(i.to_string())
     }
 
@@ -2601,7 +2604,7 @@ impl<'a> State<'a> {
         }
     }
 
-    crate fn print_type_bounds(&mut self, prefix: &'static str, bounds: &[ast::GenericBound]) {
+    pub fn print_type_bounds(&mut self, prefix: &'static str, bounds: &[ast::GenericBound]) {
         if !bounds.is_empty() {
             self.s.word(prefix);
             let mut first = true;
@@ -2760,7 +2763,7 @@ impl<'a> State<'a> {
         }
     }
 
-    crate fn print_mutability(&mut self, mutbl: ast::Mutability) {
+    pub fn print_mutability(&mut self, mutbl: ast::Mutability) {
         match mutbl {
             ast::Mutability::Mutable => self.word_nbsp("mut"),
             ast::Mutability::Immutable => {},

src/libsyntax/sess.rs

@@ -1,7 +1,7 @@
 //! Contains `ParseSess` which holds state living beyond what one `Parser` might.
 //! It also serves as an input to the parser itself.
 
-use crate::ast::{CrateConfig, NodeId};
+use crate::ast::{CrateConfig, NodeId, Attribute};
 use crate::early_buffered_lints::{BufferedEarlyLint, BufferedEarlyLintId};
 use crate::source_map::{SourceMap, FilePathMapping};
 use crate::feature_gate::UnstableFeatures;
@@ -71,14 +71,14 @@ impl GatedSpans {
 /// Info about a parsing session.
 pub struct ParseSess {
     pub span_diagnostic: Handler,
-    crate unstable_features: UnstableFeatures,
+    pub unstable_features: UnstableFeatures,
     pub config: CrateConfig,
     pub edition: Edition,
     pub missing_fragment_specifiers: Lock<FxHashSet<Span>>,
     /// Places where raw identifiers were used. This is used for feature-gating raw identifiers.
     pub raw_identifier_spans: Lock<Vec<Span>>,
     /// Used to determine and report recursive module inclusions.
-    pub(super) included_mod_stack: Lock<Vec<PathBuf>>,
+    pub included_mod_stack: Lock<Vec<PathBuf>>,
     source_map: Lrc<SourceMap>,
     pub buffered_lints: Lock<Vec<BufferedEarlyLint>>,
     /// Contains the spans of block expressions that could have been incomplete based on the
@@ -89,10 +89,22 @@ pub struct ParseSess {
     pub gated_spans: GatedSpans,
     /// The parser has reached `Eof` due to an unclosed brace. Used to silence unnecessary errors.
     pub reached_eof: Lock<bool>,
+    /// Process the potential `cfg` attributes on a module.
+    /// Also determine if the module should be included in this configuration.
+    ///
+    /// HACK(Centril): This is used to break a cyclic dependency between
+    /// the parser and cfg-stripping as defined in `syntax_expand::config`.
+    /// The dependency edge from the parser comes from `parse_item_mod`.
+    /// A principled solution to this hack would be to implement [#64197].
+    ///
+    /// [#64197]: https://github.com/rust-lang/rust/issues/64197
+    pub process_cfg_mod: ProcessCfgMod,
 }
 
+pub type ProcessCfgMod = fn(&ParseSess, bool, &[Attribute]) -> (bool, Vec<Attribute>);
+
 impl ParseSess {
-    pub fn new(file_path_mapping: FilePathMapping) -> Self {
+    pub fn new(file_path_mapping: FilePathMapping, process_cfg_mod: ProcessCfgMod) -> Self {
         let cm = Lrc::new(SourceMap::new(file_path_mapping));
         let handler = Handler::with_tty_emitter(
             ColorConfig::Auto,
@@ -100,12 +112,17 @@ impl ParseSess {
             None,
             Some(cm.clone()),
         );
-        ParseSess::with_span_handler(handler, cm)
+        ParseSess::with_span_handler(handler, cm, process_cfg_mod)
     }
 
-    pub fn with_span_handler(handler: Handler, source_map: Lrc<SourceMap>) -> Self {
+    pub fn with_span_handler(
+        handler: Handler,
+        source_map: Lrc<SourceMap>,
+        process_cfg_mod: ProcessCfgMod,
+    ) -> Self {
         Self {
             span_diagnostic: handler,
+            process_cfg_mod,
             unstable_features: UnstableFeatures::from_environment(),
             config: FxHashSet::default(),
             edition: ExpnId::root().expn_data().edition,
@@ -121,10 +138,10 @@ impl ParseSess {
         }
     }
 
-    pub fn with_silent_emitter() -> Self {
+    pub fn with_silent_emitter(process_cfg_mod: ProcessCfgMod) -> Self {
         let cm = Lrc::new(SourceMap::new(FilePathMapping::empty()));
         let handler = Handler::with_emitter(false, None, Box::new(SilentEmitter));
-        ParseSess::with_span_handler(handler, cm)
+        ParseSess::with_span_handler(handler, cm, process_cfg_mod)
     }
 
     #[inline]

src/libsyntax/token.rs

@@ -107,14 +107,14 @@ impl fmt::Display for Lit {
 
 impl LitKind {
     /// An English article for the literal token kind.
-    crate fn article(self) -> &'static str {
+    pub fn article(self) -> &'static str {
         match self {
             Integer | Err => "an",
             _ => "a",
         }
     }
 
-    crate fn descr(self) -> &'static str {
+    pub fn descr(self) -> &'static str {
         match self {
             Bool => panic!("literal token contains `Lit::Bool`"),
             Byte => "byte",
@@ -141,12 +141,12 @@ impl Lit {
     }
 }
 
-pub(crate) fn ident_can_begin_expr(name: ast::Name, span: Span, is_raw: bool) -> bool {
+pub fn ident_can_begin_expr(name: ast::Name, span: Span, is_raw: bool) -> bool {
     let ident_token = Token::new(Ident(name, is_raw), span);
     token_can_begin_expr(&ident_token)
 }
 
-pub(crate) fn token_can_begin_expr(ident_token: &Token) -> bool {
+pub fn token_can_begin_expr(ident_token: &Token) -> bool {
     !ident_token.is_reserved_ident() ||
     ident_token.is_path_segment_keyword() ||
     match ident_token.kind {
@@ -276,7 +276,7 @@ impl TokenKind {
 
     /// Returns tokens that are likely to be typed accidentally instead of the current token.
     /// Enables better error recovery when the wrong token is found.
-    crate fn similar_tokens(&self) -> Option<Vec<TokenKind>> {
+    pub fn similar_tokens(&self) -> Option<Vec<TokenKind>> {
         match *self {
             Comma => Some(vec![Dot, Lt, Semi]),
             Semi => Some(vec![Colon, Comma]),
@@ -291,7 +291,7 @@ impl Token {
     }
 
     /// Some token that will be thrown away later.
-    crate fn dummy() -> Self {
+    pub fn dummy() -> Self {
         Token::new(TokenKind::Whitespace, DUMMY_SP)
     }
 
@@ -305,7 +305,7 @@ impl Token {
         mem::replace(self, Token::dummy())
     }
 
-    crate fn is_op(&self) -> bool {
+    pub fn is_op(&self) -> bool {
         match self.kind {
             OpenDelim(..) | CloseDelim(..) | Literal(..) | DocComment(..) |
             Ident(..) | Lifetime(..) | Interpolated(..) |
@@ -314,7 +314,7 @@ impl Token {
         }
     }
 
-    crate fn is_like_plus(&self) -> bool {
+    pub fn is_like_plus(&self) -> bool {
         match self.kind {
             BinOp(Plus) | BinOpEq(Plus) => true,
             _ => false,
@@ -377,7 +377,7 @@ impl Token {
     }
 
     /// Returns `true` if the token can appear at the start of a const param.
-    crate fn can_begin_const_arg(&self) -> bool {
+    pub fn can_begin_const_arg(&self) -> bool {
         match self.kind {
             OpenDelim(Brace) => true,
             Interpolated(ref nt) => match **nt {
@@ -389,7 +389,7 @@ impl Token {
     }
 
     /// Returns `true` if the token can appear at the start of a generic bound.
-    crate fn can_begin_bound(&self) -> bool {
+    pub fn can_begin_bound(&self) -> bool {
         self.is_path_start() || self.is_lifetime() || self.is_keyword(kw::For) ||
         self == &Question || self == &OpenDelim(Paren)
     }
@@ -446,13 +446,13 @@ impl Token {
     }
 
     /// Returns `true` if the token is a lifetime.
-    crate fn is_lifetime(&self) -> bool {
+    pub fn is_lifetime(&self) -> bool {
         self.lifetime().is_some()
     }
 
     /// Returns `true` if the token is a identifier whose name is the given
     /// string slice.
-    crate fn is_ident_named(&self, name: Symbol) -> bool {
+    pub fn is_ident_named(&self, name: Symbol) -> bool {
         self.ident().map_or(false, |(ident, _)| ident.name == name)
     }
 
@@ -469,7 +469,7 @@ impl Token {
     /// Would `maybe_whole_expr` in `parser.rs` return `Ok(..)`?
     /// That is, is this a pre-parsed expression dropped into the token stream
     /// (which happens while parsing the result of macro expansion)?
-    crate fn is_whole_expr(&self) -> bool {
+    pub fn is_whole_expr(&self) -> bool {
         if let Interpolated(ref nt) = self.kind {
             if let NtExpr(_) | NtLiteral(_) | NtPath(_) | NtIdent(..) | NtBlock(_) = **nt {
                 return true;
@@ -480,16 +480,16 @@ impl Token {
     }
 
     /// Returns `true` if the token is either the `mut` or `const` keyword.
-    crate fn is_mutability(&self) -> bool {
+    pub fn is_mutability(&self) -> bool {
         self.is_keyword(kw::Mut) ||
         self.is_keyword(kw::Const)
     }
 
-    crate fn is_qpath_start(&self) -> bool {
+    pub fn is_qpath_start(&self) -> bool {
         self == &Lt || self == &BinOp(Shl)
     }
 
-    crate fn is_path_start(&self) -> bool {
+    pub fn is_path_start(&self) -> bool {
         self == &ModSep || self.is_qpath_start() || self.is_path() ||
         self.is_path_segment_keyword() || self.is_ident() && !self.is_reserved_ident()
     }
@@ -499,23 +499,23 @@ impl Token {
         self.is_non_raw_ident_where(|id| id.name == kw)
     }
 
-    crate fn is_path_segment_keyword(&self) -> bool {
+    pub fn is_path_segment_keyword(&self) -> bool {
         self.is_non_raw_ident_where(ast::Ident::is_path_segment_keyword)
     }
 
     // Returns true for reserved identifiers used internally for elided lifetimes,
     // unnamed method parameters, crate root module, error recovery etc.
-    crate fn is_special_ident(&self) -> bool {
+    pub fn is_special_ident(&self) -> bool {
         self.is_non_raw_ident_where(ast::Ident::is_special)
     }
 
     /// Returns `true` if the token is a keyword used in the language.
-    crate fn is_used_keyword(&self) -> bool {
+    pub fn is_used_keyword(&self) -> bool {
         self.is_non_raw_ident_where(ast::Ident::is_used_keyword)
     }
 
     /// Returns `true` if the token is a keyword reserved for possible future use.
-    crate fn is_unused_keyword(&self) -> bool {
+    pub fn is_unused_keyword(&self) -> bool {
         self.is_non_raw_ident_where(ast::Ident::is_unused_keyword)
     }
 
@@ -525,7 +525,7 @@ impl Token {
     }
 
     /// Returns `true` if the token is the identifier `true` or `false`.
-    crate fn is_bool_lit(&self) -> bool {
+    pub fn is_bool_lit(&self) -> bool {
         self.is_non_raw_ident_where(|id| id.name.is_bool_lit())
     }
 
@@ -537,7 +537,7 @@ impl Token {
         }
     }
 
-    crate fn glue(&self, joint: &Token) -> Option<Token> {
+    pub fn glue(&self, joint: &Token) -> Option<Token> {
         let kind = match self.kind {
             Eq => match joint.kind {
                 Eq => EqEq,

src/libsyntax/tokenstream.rs

@@ -23,9 +23,6 @@ use smallvec::{SmallVec, smallvec};
 
 use std::{iter, mem};
 
-#[cfg(test)]
-mod tests;
-
 /// When the main rust parser encounters a syntax-extension invocation, it
 /// parses the arguments to the invocation as a token-tree. This is a very
 /// loose structure, such that all sorts of different AST-fragments can
@@ -218,7 +215,7 @@ impl TokenStream {
         self.0.len()
     }
 
-    pub(crate) fn from_streams(mut streams: SmallVec<[TokenStream; 2]>) -> TokenStream {
+    pub fn from_streams(mut streams: SmallVec<[TokenStream; 2]>) -> TokenStream {
         match streams.len() {
             0 => TokenStream::default(),
             1 => streams.pop().unwrap(),

src/libsyntax/util/comments.rs

@@ -32,14 +32,14 @@ pub struct Comment {
     pub pos: BytePos,
 }
 
-crate fn is_line_doc_comment(s: &str) -> bool {
+pub fn is_line_doc_comment(s: &str) -> bool {
     let res = (s.starts_with("///") && *s.as_bytes().get(3).unwrap_or(&b' ') != b'/') ||
               s.starts_with("//!");
     debug!("is {:?} a doc comment? {}", s, res);
     res
 }
 
-crate fn is_block_doc_comment(s: &str) -> bool {
+pub fn is_block_doc_comment(s: &str) -> bool {
     // Prevent `/**/` from being parsed as a doc comment
     let res = ((s.starts_with("/**") && *s.as_bytes().get(3).unwrap_or(&b' ') != b'*') ||
                s.starts_with("/*!")) && s.len() >= 5;
@@ -47,7 +47,8 @@ crate fn is_block_doc_comment(s: &str) -> bool {
     res
 }
 
-crate fn is_doc_comment(s: &str) -> bool {
+// FIXME(#64197): Try to privatize this again.
+pub fn is_doc_comment(s: &str) -> bool {
     (s.starts_with("///") && is_line_doc_comment(s)) || s.starts_with("//!") ||
     (s.starts_with("/**") && is_block_doc_comment(s)) || s.starts_with("/*!")
 }

src/libsyntax/util/literal.rs

@@ -14,7 +14,7 @@ use rustc_lexer::unescape::{unescape_raw_str, unescape_raw_byte_str};
 
 use std::ascii;
 
-crate enum LitError {
+pub enum LitError {
     NotLiteral,
     LexerError,
     InvalidSuffix,
@@ -185,12 +185,12 @@ impl LitKind {
 
 impl Lit {
     /// Converts literal token into an AST literal.
-    crate fn from_lit_token(token: token::Lit, span: Span) -> Result<Lit, LitError> {
+    pub fn from_lit_token(token: token::Lit, span: Span) -> Result<Lit, LitError> {
         Ok(Lit { token, kind: LitKind::from_lit_token(token)?, span })
     }
 
     /// Converts arbitrary token into an AST literal.
-    crate fn from_token(token: &Token) -> Result<Lit, LitError> {
+    pub fn from_token(token: &Token) -> Result<Lit, LitError> {
         let lit = match token.kind {
             token::Ident(name, false) if name.is_bool_lit() =>
                 token::Lit::new(token::Bool, name, None),
@@ -217,8 +217,8 @@ impl Lit {
         Lit { token: kind.to_lit_token(), kind, span }
     }
 
-    /// Losslessly convert an AST literal into a token tree.
+    /// Losslessly convert an AST literal into a token stream.
-    crate fn token_tree(&self) -> TokenTree {
+    pub fn token_tree(&self) -> TokenTree {
         let token = match self.token.kind {
             token::Bool => token::Ident(self.token.symbol, false),
             _ => token::Literal(self.token),

src/libsyntax/util/parser.rs

@@ -69,7 +69,7 @@ pub enum Fixity {
 
 impl AssocOp {
     /// Creates a new AssocOP from a token
-    crate fn from_token(t: &Token) -> Option<AssocOp> {
+    pub fn from_token(t: &Token) -> Option<AssocOp> {
         use AssocOp::*;
         match t.kind {
             token::BinOpEq(k) => Some(AssignOp(k)),
@@ -358,7 +358,7 @@ impl ExprPrecedence {
 }
 
 /// In `let p = e`, operators with precedence `<=` this one requires parenthesis in `e`.
-crate fn prec_let_scrutinee_needs_par() -> usize {
+pub fn prec_let_scrutinee_needs_par() -> usize {
     AssocOp::LAnd.precedence()
 }
 

src/libsyntax_expand/Cargo.toml

@@ -11,15 +11,12 @@ path = "lib.rs"
 doctest = false
 
 [dependencies]
-bitflags = "1.0"
 rustc_serialize = { path = "../libserialize", package = "serialize" }
 log = "0.4"
-scoped-tls = "1.0"
-lazy_static = "1.0.0"
 syntax_pos = { path = "../libsyntax_pos" }
 errors = { path = "../librustc_errors", package = "rustc_errors" }
 rustc_data_structures = { path = "../librustc_data_structures" }
-rustc_index = { path = "../librustc_index" }
 rustc_lexer = { path = "../librustc_lexer" }
+rustc_parse = { path = "../librustc_parse" }
 smallvec = { version = "1.0", features = ["union", "may_dangle"] }
 syntax = { path = "../libsyntax" }

src/libsyntax_expand/base.rs

@@ -1,15 +1,15 @@
 use crate::expand::{self, AstFragment, Invocation};
 
+use rustc_parse::{self, parser, DirectoryOwnership, MACRO_ARGUMENTS};
 use syntax::ast::{self, NodeId, Attribute, Name, PatKind};
 use syntax::attr::{self, HasAttrs, Stability, Deprecation};
 use syntax::source_map::SourceMap;
 use syntax::edition::Edition;
 use syntax::mut_visit::{self, MutVisitor};
-use syntax::parse::{self, parser, DirectoryOwnership};
 use syntax::ptr::P;
 use syntax::sess::ParseSess;
 use syntax::symbol::{kw, sym, Ident, Symbol};
-use syntax::{ThinVec, MACRO_ARGUMENTS};
+use syntax::ThinVec;
 use syntax::token;
 use syntax::tokenstream::{self, TokenStream};
 use syntax::visit::Visitor;
@@ -18,9 +18,9 @@ use errors::{DiagnosticBuilder, DiagnosticId};
 use smallvec::{smallvec, SmallVec};
 use syntax_pos::{FileName, Span, MultiSpan, DUMMY_SP};
 use syntax_pos::hygiene::{AstPass, ExpnId, ExpnData, ExpnKind};
-
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::{self, Lrc};
+
 use std::iter;
 use std::path::PathBuf;
 use std::rc::Rc;
@@ -922,7 +922,7 @@ impl<'a> ExtCtxt<'a> {
         expand::MacroExpander::new(self, true)
     }
     pub fn new_parser_from_tts(&self, stream: TokenStream) -> parser::Parser<'a> {
-        parse::stream_to_parser(self.parse_sess, stream, MACRO_ARGUMENTS)
+        rustc_parse::stream_to_parser(self.parse_sess, stream, MACRO_ARGUMENTS)
     }
     pub fn source_map(&self) -> &'a SourceMap { self.parse_sess.source_map() }
     pub fn parse_sess(&self) -> &'a ParseSess { self.parse_sess }

src/libsyntax_expand/config.rs

@@ -1,20 +1,20 @@
-use crate::attr::HasAttrs;
+use rustc_parse::validate_attr;
-use crate::feature_gate::{
+use syntax::attr::HasAttrs;
+use syntax::feature_gate::{
     feature_err,
     EXPLAIN_STMT_ATTR_SYNTAX,
     Features,
     get_features,
     GateIssue,
 };
-use crate::attr;
+use syntax::attr;
-use crate::ast;
+use syntax::ast;
-use crate::edition::Edition;
+use syntax::edition::Edition;
-use crate::mut_visit::*;
+use syntax::mut_visit::*;
-use crate::parse;
+use syntax::ptr::P;
-use crate::ptr::P;
+use syntax::sess::ParseSess;
-use crate::sess::ParseSess;
+use syntax::util::map_in_place::MapInPlace;
-use crate::symbol::sym;
+use syntax_pos::symbol::sym;
-use crate::util::map_in_place::MapInPlace;
 
 use errors::Applicability;
 use smallvec::SmallVec;
@@ -113,7 +113,7 @@ impl<'a> StripUnconfigured<'a> {
             return vec![];
         }
 
-        let res = parse::parse_in_attr(self.sess, &attr, |p| p.parse_cfg_attr());
+        let res = rustc_parse::parse_in_attr(self.sess, &attr, |p| p.parse_cfg_attr());
         let (cfg_predicate, expanded_attrs) = match res {
             Ok(result) => result,
             Err(mut e) => {
@@ -135,12 +135,11 @@ impl<'a> StripUnconfigured<'a> {
             // `cfg_attr` inside of another `cfg_attr`. E.g.
             //  `#[cfg_attr(false, cfg_attr(true, some_attr))]`.
             expanded_attrs.into_iter()
-            .flat_map(|(item, span)| self.process_cfg_attr(ast::Attribute {
+            .flat_map(|(item, span)| self.process_cfg_attr(attr::mk_attr_from_item(
-                kind: ast::AttrKind::Normal(item),
+                attr.style,
-                id: attr::mk_attr_id(),
+                item,
-                style: attr.style,
                 span,
-            }))
+            )))
             .collect()
         } else {
             vec![]
@@ -148,7 +147,7 @@ impl<'a> StripUnconfigured<'a> {
     }
 
     /// Determines if a node with the given attributes should be included in this configuration.
-    pub fn in_cfg(&mut self, attrs: &[ast::Attribute]) -> bool {
+    pub fn in_cfg(&self, attrs: &[ast::Attribute]) -> bool {
         attrs.iter().all(|attr| {
             if !is_cfg(attr) {
                 return true;
@@ -168,7 +167,7 @@ impl<'a> StripUnconfigured<'a> {
                 true
             };
 
-            let meta_item = match attr.parse_meta(self.sess) {
+            let meta_item = match validate_attr::parse_meta(self.sess, attr) {
                 Ok(meta_item) => meta_item,
                 Err(mut err) => { err.emit(); return true; }
             };
@@ -350,3 +349,17 @@ impl<'a> MutVisitor for StripUnconfigured<'a> {
 fn is_cfg(attr: &ast::Attribute) -> bool {
     attr.check_name(sym::cfg)
 }
+
+/// Process the potential `cfg` attributes on a module.
+/// Also determine if the module should be included in this configuration.
+pub fn process_configure_mod(
+    sess: &ParseSess,
+    cfg_mods: bool,
+    attrs: &[ast::Attribute],
+) -> (bool, Vec<ast::Attribute>) {
+    // Don't perform gated feature checking.
+    let mut strip_unconfigured = StripUnconfigured { sess, features: None };
+    let mut attrs = attrs.to_owned();
+    strip_unconfigured.process_cfg_attrs(&mut attrs);
+    (!cfg_mods || strip_unconfigured.in_cfg(&attrs), attrs)
+}

src/libsyntax_expand/expand.rs

@@ -3,17 +3,18 @@ use crate::proc_macro::{collect_derives, MarkAttrs};
 use crate::hygiene::{ExpnId, SyntaxContext, ExpnData, ExpnKind};
 use crate::mbe::macro_rules::annotate_err_with_kind;
 use crate::placeholders::{placeholder, PlaceholderExpander};
+use crate::config::StripUnconfigured;
+use crate::configure;
 
+use rustc_parse::DirectoryOwnership;
+use rustc_parse::parser::Parser;
+use rustc_parse::validate_attr;
 use syntax::ast::{self, AttrItem, Block, Ident, LitKind, NodeId, PatKind, Path};
 use syntax::ast::{MacStmtStyle, StmtKind, ItemKind};
 use syntax::attr::{self, HasAttrs};
 use syntax::source_map::respan;
-use syntax::configure;
-use syntax::config::StripUnconfigured;
 use syntax::feature_gate::{self, Features, GateIssue, is_builtin_attr, emit_feature_err};
 use syntax::mut_visit::*;
-use syntax::parse::DirectoryOwnership;
-use syntax::parse::parser::Parser;
 use syntax::print::pprust;
 use syntax::ptr::P;
 use syntax::sess::ParseSess;
@@ -640,7 +641,7 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                     self.parse_ast_fragment(tok_result, fragment_kind, &item.path, span)
                 }
                 SyntaxExtensionKind::LegacyAttr(expander) => {
-                    match attr.parse_meta(self.cx.parse_sess) {
+                    match validate_attr::parse_meta(self.cx.parse_sess, &attr) {
                         Ok(meta) => {
                             let item = expander.expand(self.cx, span, &meta, item);
                             fragment_kind.expect_from_annotatables(item)
@@ -1031,6 +1032,7 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
         let features = self.cx.ecfg.features.unwrap();
         for attr in attrs.iter() {
             feature_gate::check_attribute(attr, self.cx.parse_sess, features);
+            validate_attr::check_meta(self.cx.parse_sess, attr);
 
             // macros are expanded before any lint passes so this warning has to be hardcoded
             if attr.has_name(sym::derive) {

src/libsyntax_expand/lib.rs

@@ -33,6 +33,35 @@ pub use mbe::macro_rules::compile_declarative_macro;
 pub mod base;
 pub mod build;
 pub mod expand;
+#[macro_use] pub mod config;
 pub mod proc_macro;
 
 crate mod mbe;
+
+// HACK(Centril, #64197): These shouldn't really be here.
+// Rather, they should be with their respective modules which are defined in other crates.
+// However, since for now constructing a `ParseSess` sorta requires `config` from this crate,
+// these tests will need to live here in the iterim.
+
+#[cfg(test)]
+mod tests;
+#[cfg(test)]
+mod parse {
+    #[cfg(test)]
+    mod tests;
+    #[cfg(test)]
+    mod lexer {
+        #[cfg(test)]
+        mod tests;
+    }
+}
+#[cfg(test)]
+mod tokenstream {
+    #[cfg(test)]
+    mod tests;
+}
+#[cfg(test)]
+mod mut_visit {
+    #[cfg(test)]
+    mod tests;
+}

src/libsyntax_expand/mbe/macro_parser.rs

@@ -76,9 +76,9 @@ use TokenTreeOrTokenTreeSlice::*;
 
 use crate::mbe::{self, TokenTree};
 
+use rustc_parse::Directory;
+use rustc_parse::parser::{Parser, PathStyle};
 use syntax::ast::{Ident, Name};
-use syntax::parse::Directory;
-use syntax::parse::parser::{Parser, PathStyle};
 use syntax::print::pprust;
 use syntax::sess::ParseSess;
 use syntax::symbol::{kw, sym, Symbol};
@@ -652,7 +652,7 @@ pub(super) fn parse(
         directory,
         recurse_into_modules,
         true,
-        syntax::MACRO_ARGUMENTS,
+        rustc_parse::MACRO_ARGUMENTS,
     );
 
     // A queue of possible matcher positions. We initialize it with the matcher position in which

src/libsyntax_expand/mbe/macro_rules.rs

@@ -8,30 +8,30 @@ use crate::mbe::macro_parser::{Error, Failure, Success};
 use crate::mbe::macro_parser::{MatchedNonterminal, MatchedSeq, NamedParseResult};
 use crate::mbe::transcribe::transcribe;
 
+use rustc_parse::parser::Parser;
+use rustc_parse::Directory;
 use syntax::ast;
 use syntax::attr::{self, TransparencyError};
 use syntax::edition::Edition;
 use syntax::feature_gate::Features;
-use syntax::parse::parser::Parser;
-use syntax::parse::Directory;
 use syntax::print::pprust;
 use syntax::sess::ParseSess;
 use syntax::symbol::{kw, sym, Symbol};
 use syntax::token::{self, NtTT, Token, TokenKind::*};
 use syntax::tokenstream::{DelimSpan, TokenStream};
-
-use errors::{DiagnosticBuilder, FatalError};
-use log::debug;
 use syntax_pos::hygiene::Transparency;
 use syntax_pos::Span;
 
+use errors::{DiagnosticBuilder, FatalError};
+use log::debug;
+
 use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::sync::Lrc;
 use std::borrow::Cow;
 use std::collections::hash_map::Entry;
 use std::{mem, slice};
 
 use errors::Applicability;
-use rustc_data_structures::sync::Lrc;
 
 const VALID_FRAGMENT_NAMES_MSG: &str = "valid fragment specifiers are \
                                         `ident`, `block`, `stmt`, `expr`, `pat`, `ty`, `lifetime`, \

src/libsyntax_expand/mut_visit/tests.rs

@@ -1,10 +1,9 @@
-use super::*;
-
-use crate::ast::{self, Ident};
 use crate::tests::{string_to_crate, matches_codepattern};
-use crate::print::pprust;
+
-use crate::mut_visit;
+use syntax::ast::{self, Ident};
-use crate::with_default_globals;
+use syntax::print::pprust;
+use syntax::mut_visit::{self, MutVisitor};
+use syntax::with_default_globals;
 
 // This version doesn't care about getting comments or doc-strings in.
 fn fake_print_crate(s: &mut pprust::State<'_>,

src/libsyntax_expand/parse/lexer/tests.rs

@@ -1,15 +1,18 @@
-use super::*;
+use crate::config::process_configure_mod;
 
-use crate::symbol::Symbol;
+use rustc_data_structures::sync::Lrc;
-use crate::source_map::{SourceMap, FilePathMapping};
+use rustc_parse::lexer::StringReader;
-use crate::token;
+use syntax::token::{self, Token, TokenKind};
-use crate::util::comments::is_doc_comment;
+use syntax::sess::ParseSess;
-use crate::with_default_globals;
+use syntax::source_map::{SourceMap, FilePathMapping};
+use syntax::util::comments::is_doc_comment;
+use syntax::with_default_globals;
+use syntax_pos::symbol::Symbol;
+use syntax_pos::{BytePos, Span};
 
 use errors::{Handler, emitter::EmitterWriter};
 use std::io;
 use std::path::PathBuf;
-use syntax_pos::{BytePos, Span};
 
 fn mk_sess(sm: Lrc<SourceMap>) -> ParseSess {
     let emitter = EmitterWriter::new(
@@ -21,7 +24,11 @@ fn mk_sess(sm: Lrc<SourceMap>) -> ParseSess {
         None,
         false,
     );
-    ParseSess::with_span_handler(Handler::with_emitter(true, None, Box::new(emitter)), sm)
+    ParseSess::with_span_handler(
+        Handler::with_emitter(true, None, Box::new(emitter)),
+        sm,
+        process_configure_mod,
+    )
 }
 
 // Creates a string reader for the given string.

src/libsyntax_expand/parse/tests.rs

@@ -1,21 +1,27 @@
-use super::*;
+use crate::config::process_configure_mod;
-
-use crate::ast::{self, Name, PatKind};
-use crate::attr::first_attr_value_str_by_name;
-use crate::sess::ParseSess;
-use crate::parse::{PResult, new_parser_from_source_str};
-use crate::token::Token;
-use crate::print::pprust::item_to_string;
-use crate::ptr::P;
-use crate::source_map::FilePathMapping;
-use crate::symbol::{kw, sym};
 use crate::tests::{matches_codepattern, string_to_stream, with_error_checking_parse};
-use crate::tokenstream::{DelimSpan, TokenTree, TokenStream};
+
-use crate::with_default_globals;
+use rustc_parse::new_parser_from_source_str;
-use syntax_pos::{Span, BytePos, Pos};
+use syntax::ast::{self, Name, PatKind};
+use syntax::attr::first_attr_value_str_by_name;
+use syntax::sess::ParseSess;
+use syntax::token::{self, Token};
+use syntax::print::pprust::item_to_string;
+use syntax::ptr::P;
+use syntax::source_map::FilePathMapping;
+use syntax::symbol::{kw, sym};
+use syntax::tokenstream::{DelimSpan, TokenTree, TokenStream};
+use syntax::visit;
+use syntax::with_default_globals;
+use syntax_pos::{Span, BytePos, Pos, FileName};
+use errors::PResult;
 
 use std::path::PathBuf;
 
+fn sess() -> ParseSess {
+    ParseSess::new(FilePathMapping::empty(), process_configure_mod)
+}
+
 /// Parses an item.
 ///
 /// Returns `Ok(Some(item))` when successful, `Ok(None)` when no item was found, and `Err`
@@ -32,18 +38,12 @@ fn sp(a: u32, b: u32) -> Span {
 
 /// Parses a string, return an expression.
 fn string_to_expr(source_str : String) -> P<ast::Expr> {
-    let ps = ParseSess::new(FilePathMapping::empty());
+    with_error_checking_parse(source_str, &sess(), |p| p.parse_expr())
-    with_error_checking_parse(source_str, &ps, |p| {
-        p.parse_expr()
-    })
 }
 
 /// Parses a string, returns an item.
 fn string_to_item(source_str : String) -> Option<P<ast::Item>> {
-    let ps = ParseSess::new(FilePathMapping::empty());
+    with_error_checking_parse(source_str, &sess(), |p| p.parse_item())
-    with_error_checking_parse(source_str, &ps, |p| {
-        p.parse_item()
-    })
 }
 
 #[should_panic]
@@ -169,20 +169,20 @@ fn get_spans_of_pat_idents(src: &str) -> Vec<Span> {
     struct PatIdentVisitor {
         spans: Vec<Span>
     }
-    impl<'a> crate::visit::Visitor<'a> for PatIdentVisitor {
+    impl<'a> visit::Visitor<'a> for PatIdentVisitor {
         fn visit_pat(&mut self, p: &'a ast::Pat) {
             match p.kind {
                 PatKind::Ident(_ , ref ident, _) => {
                     self.spans.push(ident.span.clone());
                 }
                 _ => {
-                    crate::visit::walk_pat(self, p);
+                    visit::walk_pat(self, p);
                 }
             }
         }
     }
     let mut v = PatIdentVisitor { spans: Vec::new() };
-    crate::visit::walk_item(&mut v, &item);
+    visit::walk_item(&mut v, &item);
     return v.spans;
 }
 
@@ -233,7 +233,7 @@ let mut fflags: c_int = wb();
 
 #[test] fn crlf_doc_comments() {
     with_default_globals(|| {
-        let sess = ParseSess::new(FilePathMapping::empty());
+        let sess = sess();
 
         let name_1 = FileName::Custom("crlf_source_1".to_string());
         let source = "/// doc comment\r\nfn foo() {}".to_string();
@@ -268,7 +268,7 @@ fn ttdelim_span() {
     }
 
     with_default_globals(|| {
-        let sess = ParseSess::new(FilePathMapping::empty());
+        let sess = sess();
         let expr = parse_expr_from_source_str(PathBuf::from("foo").into(),
             "foo!( fn main() { body } )".to_string(), &sess).unwrap();
 
@@ -292,11 +292,10 @@ fn ttdelim_span() {
 #[test]
 fn out_of_line_mod() {
     with_default_globals(|| {
-        let sess = ParseSess::new(FilePathMapping::empty());
         let item = parse_item_from_source_str(
             PathBuf::from("foo").into(),
             "mod foo { struct S; mod this_does_not_exist; }".to_owned(),
-            &sess,
+            &sess(),
         ).unwrap().unwrap();
 
         if let ast::ItemKind::Mod(ref m) = item.kind {

src/libsyntax_expand/proc_macro.rs

@@ -4,7 +4,6 @@ use crate::proc_macro_server;
 use syntax::ast::{self, ItemKind, Attribute, Mac};
 use syntax::attr::{mark_used, mark_known};
 use syntax::errors::{Applicability, FatalError};
-use syntax::parse;
 use syntax::symbol::sym;
 use syntax::token;
 use syntax::tokenstream::{self, TokenStream};
@@ -135,7 +134,11 @@ impl MultiItemModifier for ProcMacroDerive {
         let error_count_before = ecx.parse_sess.span_diagnostic.err_count();
         let msg = "proc-macro derive produced unparseable tokens";
 
-        let mut parser = parse::stream_to_parser(ecx.parse_sess, stream, Some("proc-macro derive"));
+        let mut parser = rustc_parse::stream_to_parser(
+            ecx.parse_sess,
+            stream,
+            Some("proc-macro derive"),
+        );
         let mut items = vec![];
 
         loop {
@@ -200,7 +203,7 @@ crate fn collect_derives(cx: &mut ExtCtxt<'_>, attrs: &mut Vec<ast::Attribute>)
             if attr.get_normal_item().tokens.is_empty() {
                 return Ok(Vec::new());
             }
-            parse::parse_in_attr(cx.parse_sess, attr, |p| p.parse_derive_paths())
+            rustc_parse::parse_in_attr(cx.parse_sess, attr, |p| p.parse_derive_paths())
         };
 
         match parse_derive_paths(attr) {

src/libsyntax_expand/proc_macro_server.rs

@@ -1,17 +1,17 @@
 use crate::base::ExtCtxt;
 
+use rustc_parse::{parse_stream_from_source_str, nt_to_tokenstream};
 use syntax::ast;
-use syntax::parse;
 use syntax::util::comments;
 use syntax::print::pprust;
 use syntax::sess::ParseSess;
 use syntax::token;
 use syntax::tokenstream::{self, DelimSpan, IsJoint::*, TokenStream, TreeAndJoint};
+use syntax_pos::{BytePos, FileName, MultiSpan, Pos, SourceFile, Span};
+use syntax_pos::symbol::{kw, sym, Symbol};
 
 use errors::Diagnostic;
 use rustc_data_structures::sync::Lrc;
-use syntax_pos::{BytePos, FileName, MultiSpan, Pos, SourceFile, Span};
-use syntax_pos::symbol::{kw, sym, Symbol};
 
 use pm::{Delimiter, Level, LineColumn, Spacing};
 use pm::bridge::{server, TokenTree};
@@ -178,7 +178,7 @@ impl FromInternal<(TreeAndJoint, &'_ ParseSess, &'_ mut Vec<Self>)>
             }
 
             Interpolated(nt) => {
-                let stream = parse::nt_to_tokenstream(&nt, sess, span);
+                let stream = nt_to_tokenstream(&nt, sess, span);
                 TokenTree::Group(Group {
                     delimiter: Delimiter::None,
                     stream,
@@ -402,7 +402,7 @@ impl server::TokenStream for Rustc<'_> {
         stream.is_empty()
     }
     fn from_str(&mut self, src: &str) -> Self::TokenStream {
-        parse::parse_stream_from_source_str(
+        parse_stream_from_source_str(
             FileName::proc_macro_source_code(src),
             src.to_string(),
             self.sess,

src/libsyntax_expand/tests.rs

@@ -1,16 +1,15 @@
-use crate::ast;
+use crate::config::process_configure_mod;
-use crate::parse::source_file_to_stream;
+use rustc_parse::{source_file_to_stream, new_parser_from_source_str, parser::Parser};
-use crate::parse::new_parser_from_source_str;
+use syntax::ast;
-use crate::parse::parser::Parser;
+use syntax::tokenstream::TokenStream;
-use crate::sess::ParseSess;
+use syntax::sess::ParseSess;
-use crate::source_map::{SourceMap, FilePathMapping};
+use syntax::source_map::{SourceMap, FilePathMapping};
-use crate::tokenstream::TokenStream;
+use syntax::with_default_globals;
-use crate::with_default_globals;
+use syntax_pos::{BytePos, Span, MultiSpan};
 
 use errors::emitter::EmitterWriter;
 use errors::{PResult, Handler};
 use rustc_data_structures::sync::Lrc;
-use syntax_pos::{BytePos, Span, MultiSpan};
 
 use std::io;
 use std::io::prelude::*;
@@ -35,7 +34,7 @@ crate fn with_error_checking_parse<'a, T, F>(s: String, ps: &'a ParseSess, f: F)
 
 /// Maps a string to tts, using a made-up filename.
 crate fn string_to_stream(source_str: String) -> TokenStream {
-    let ps = ParseSess::new(FilePathMapping::empty());
+    let ps = ParseSess::new(FilePathMapping::empty(), process_configure_mod);
     source_file_to_stream(
         &ps,
         ps.source_map().new_source_file(PathBuf::from("bogofile").into(),
@@ -45,7 +44,7 @@ crate fn string_to_stream(source_str: String) -> TokenStream {
 
 /// Parses a string, returns a crate.
 crate fn string_to_crate(source_str : String) -> ast::Crate {
-    let ps = ParseSess::new(FilePathMapping::empty());
+    let ps = ParseSess::new(FilePathMapping::empty(), process_configure_mod);
     with_error_checking_parse(source_str, &ps, |p| {
         p.parse_crate_mod()
     })

src/libsyntax_expand/tokenstream/tests.rs

@@ -1,9 +1,11 @@
-use super::*;
-
-use crate::ast::Name;
-use crate::with_default_globals;
 use crate::tests::string_to_stream;
+
+use syntax::ast::Name;
+use syntax::token;
+use syntax::tokenstream::{TokenStream, TokenStreamBuilder, TokenTree};
+use syntax::with_default_globals;
 use syntax_pos::{Span, BytePos};
+use smallvec::smallvec;
 
 fn string_to_ts(string: &str) -> TokenStream {
     string_to_stream(string.to_owned())

src/libsyntax_ext/Cargo.toml

@@ -14,6 +14,7 @@ errors = { path = "../librustc_errors", package = "rustc_errors" }
 fmt_macros = { path = "../libfmt_macros" }
 log = "0.4"
 rustc_data_structures = { path = "../librustc_data_structures" }
+rustc_parse = { path = "../librustc_parse" }
 rustc_target = { path = "../librustc_target" }
 smallvec = { version = "1.0", features = ["union", "may_dangle"] }
 syntax = { path = "../libsyntax" }

src/libsyntax_ext/assert.rs

@@ -1,13 +1,13 @@
 use errors::{Applicability, DiagnosticBuilder};
 
+use rustc_parse::parser::Parser;
 use syntax::ast::{self, *};
-use syntax_expand::base::*;
 use syntax::token::{self, TokenKind};
-use syntax::parse::parser::Parser;
 use syntax::print::pprust;
 use syntax::ptr::P;
 use syntax::symbol::{sym, Symbol};
 use syntax::tokenstream::{TokenStream, TokenTree};
+use syntax_expand::base::*;
 use syntax_pos::{Span, DUMMY_SP};
 
 pub fn expand_assert<'cx>(

src/libsyntax_ext/cmdline_attrs.rs

@@ -2,7 +2,6 @@
 
 use syntax::ast::{self, AttrItem, AttrStyle};
 use syntax::attr::mk_attr;
-use syntax::parse;
 use syntax::token;
 use syntax::sess::ParseSess;
 use syntax_expand::panictry;
@@ -10,7 +9,7 @@ use syntax_pos::FileName;
 
 pub fn inject(mut krate: ast::Crate, parse_sess: &ParseSess, attrs: &[String]) -> ast::Crate {
     for raw_attr in attrs {
-        let mut parser = parse::new_parser_from_source_str(
+        let mut parser = rustc_parse::new_parser_from_source_str(
             parse_sess,
             FileName::cli_crate_attr_source_code(&raw_attr),
             raw_attr.clone(),

src/libsyntax_ext/source_util.rs

@@ -1,13 +1,13 @@
-use syntax_expand::panictry;
+use rustc_parse::{self, DirectoryOwnership, new_sub_parser_from_file, parser::Parser};
-use syntax_expand::base::{self, *};
 use syntax::ast;
-use syntax::parse::{self, DirectoryOwnership};
 use syntax::print::pprust;
 use syntax::ptr::P;
 use syntax::symbol::Symbol;
 use syntax::token;
 use syntax::tokenstream::TokenStream;
 use syntax::early_buffered_lints::BufferedEarlyLintId;
+use syntax_expand::panictry;
+use syntax_expand::base::{self, *};
 
 use smallvec::SmallVec;
 use syntax_pos::{self, Pos, Span};
@@ -85,10 +85,10 @@ pub fn expand_include<'cx>(cx: &'cx mut ExtCtxt<'_>, sp: Span, tts: TokenStream)
         },
     };
     let directory_ownership = DirectoryOwnership::Owned { relative: None };
-    let p = parse::new_sub_parser_from_file(cx.parse_sess(), &file, directory_ownership, None, sp);
+    let p = new_sub_parser_from_file(cx.parse_sess(), &file, directory_ownership, None, sp);
 
     struct ExpandResult<'a> {
-        p: parse::parser::Parser<'a>,
+        p: Parser<'a>,
     }
     impl<'a> base::MacResult for ExpandResult<'a> {
         fn make_expr(mut self: Box<ExpandResult<'a>>) -> Option<P<ast::Expr>> {

src/libsyntax_ext/util.rs

@@ -1,11 +1,12 @@
+use rustc_parse::validate_attr;
 use syntax_pos::Symbol;
 use syntax::ast::MetaItem;
-use syntax::attr::{check_builtin_attribute, AttributeTemplate};
+use syntax::attr::AttributeTemplate;
 use syntax_expand::base::ExtCtxt;
 
 pub fn check_builtin_macro_attribute(ecx: &ExtCtxt<'_>, meta_item: &MetaItem, name: Symbol) {
     // All the built-in macro attributes are "words" at the moment.
     let template = AttributeTemplate::only_word();
     let attr = ecx.attribute(meta_item.clone());
-    check_builtin_attribute(ecx.parse_sess, &attr, name, template);
+    validate_attr::check_builtin_attribute(ecx.parse_sess, &attr, name, template);
 }

src/test/ui-fulldeps/ast_stmt_expr_attr.rs

@@ -6,21 +6,23 @@
 #![feature(rustc_private)]
 
 extern crate syntax;
+extern crate syntax_expand;
+extern crate rustc_parse;
 extern crate rustc_errors;
 
 use rustc_errors::PResult;
+use rustc_parse::parser::attr::*;
+use rustc_parse::new_parser_from_source_str;
+use rustc_parse::parser::Parser;
 use syntax::ast::*;
 use syntax::attr::*;
 use syntax::ast;
 use syntax::sess::ParseSess;
 use syntax::source_map::{FilePathMapping, FileName};
-use syntax::parse;
-use syntax::parse::new_parser_from_source_str;
-use syntax::parse::parser::Parser;
-use syntax::token;
 use syntax::ptr::P;
-use syntax::parse::parser::attr::*;
 use syntax::print::pprust;
+use syntax::token;
+use syntax_expand::config::process_configure_mod;
 use std::fmt;
 
 // Copied out of syntax::util::parser_testing
@@ -72,8 +74,12 @@ fn str_compare<T, F: Fn(&T) -> String>(e: &str, expected: &[T], actual: &[T], f:
     }
 }
 
+fn sess() -> ParseSess {
+    ParseSess::new(FilePathMapping::empty(), process_configure_mod)
+}
+
 fn check_expr_attrs(es: &str, expected: &[&str]) {
-    let ps = ParseSess::new(FilePathMapping::empty());
+    let ps = sess();
     let e = expr(es, &ps).expect("parse error");
     let actual = &e.attrs;
     str_compare(es,
@@ -83,7 +89,7 @@ fn check_expr_attrs(es: &str, expected: &[&str]) {
 }
 
 fn check_stmt_attrs(es: &str, expected: &[&str]) {
-    let ps = ParseSess::new(FilePathMapping::empty());
+    let ps = sess();
     let e = stmt(es, &ps).expect("parse error");
     let actual = e.kind.attrs();
     str_compare(es,
@@ -93,7 +99,7 @@ fn check_stmt_attrs(es: &str, expected: &[&str]) {
 }
 
 fn reject_expr_parse(es: &str) {
-    let ps = ParseSess::new(FilePathMapping::empty());
+    let ps = sess();
     match expr(es, &ps) {
         Ok(_) => panic!("parser did not reject `{}`", es),
         Err(mut e) => e.cancel(),
@@ -101,7 +107,7 @@ fn reject_expr_parse(es: &str) {
 }
 
 fn reject_stmt_parse(es: &str) {
-    let ps = ParseSess::new(FilePathMapping::empty());
+    let ps = sess();
     match stmt(es, &ps) {
         Ok(_) => panic!("parser did not reject `{}`", es),
         Err(mut e) => e.cancel(),

src/test/ui-fulldeps/mod_dir_path_canonicalized.rs

@@ -5,11 +5,14 @@
 #![feature(rustc_private)]
 
 extern crate syntax;
+extern crate syntax_expand;
+extern crate rustc_parse;
 
+use rustc_parse::new_parser_from_file;
 use std::path::Path;
 use syntax::sess::ParseSess;
 use syntax::source_map::FilePathMapping;
-use syntax::parse;
+use syntax_expand::config::process_configure_mod;
 
 #[path = "mod_dir_simple/test.rs"]
 mod gravy;
@@ -21,10 +24,10 @@ pub fn main() {
 }
 
 fn parse() {
-    let parse_session = ParseSess::new(FilePathMapping::empty());
+    let parse_session = ParseSess::new(FilePathMapping::empty(), process_configure_mod);
 
     let path = Path::new(file!());
     let path = path.canonicalize().unwrap();
-    let mut parser = parse::new_parser_from_file(&parse_session, &path);
+    let mut parser = new_parser_from_file(&parse_session, &path);
     let _ = parser.parse_crate_mod();
 }

src/test/ui-fulldeps/pprust-expr-roundtrip.rs

@@ -21,21 +21,24 @@
 
 extern crate rustc_data_structures;
 extern crate syntax;
+extern crate syntax_expand;
+extern crate rustc_parse;
 
 use rustc_data_structures::thin_vec::ThinVec;
+use rustc_parse::new_parser_from_source_str;
 use syntax::ast::*;
 use syntax::sess::ParseSess;
 use syntax::source_map::{Spanned, DUMMY_SP, FileName};
 use syntax::source_map::FilePathMapping;
 use syntax::mut_visit::{self, MutVisitor, visit_clobber};
-use syntax::parse;
 use syntax::print::pprust;
 use syntax::ptr::P;
+use syntax_expand::config::process_configure_mod;
 
 fn parse_expr(ps: &ParseSess, src: &str) -> Option<P<Expr>> {
     let src_as_string = src.to_string();
 
-    let mut p = parse::new_parser_from_source_str(
+    let mut p = new_parser_from_source_str(
         ps,
         FileName::Custom(src_as_string.clone()),
         src_as_string,
@@ -202,7 +205,7 @@ fn main() {
 }
 
 fn run() {
-    let ps = ParseSess::new(FilePathMapping::empty());
+    let ps = ParseSess::new(FilePathMapping::empty(), process_configure_mod);
 
     iter_exprs(2, &mut |mut e| {
         // If the pretty printer is correct, then `parse(print(e))` should be identical to `e`,

src/test/ui/proc-macro/attribute.stderr

@@ -1,3 +1,15 @@
+error: malformed `proc_macro_derive` attribute input
+  --> $DIR/attribute.rs:9:1
+   |
+LL | #[proc_macro_derive]
+   | ^^^^^^^^^^^^^^^^^^^^ help: must be of the form: `#[proc_macro_derive(TraitName, /*opt*/ attributes(name1, name2, ...))]`
+
+error: malformed `proc_macro_derive` attribute input
+  --> $DIR/attribute.rs:12:1
+   |
+LL | #[proc_macro_derive = ""]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^ help: must be of the form: `#[proc_macro_derive(TraitName, /*opt*/ attributes(name1, name2, ...))]`
+
 error: attribute must have either one or two arguments
   --> $DIR/attribute.rs:15:1
    |
@@ -88,17 +100,5 @@ error: `self` cannot be a name of derive helper attribute
 LL | #[proc_macro_derive(d17, attributes(self))]
    |                                     ^^^^
 
-error: malformed `proc_macro_derive` attribute input
-  --> $DIR/attribute.rs:9:1
-   |
-LL | #[proc_macro_derive]
-   | ^^^^^^^^^^^^^^^^^^^^ help: must be of the form: `#[proc_macro_derive(TraitName, /*opt*/ attributes(name1, name2, ...))]`
-
-error: malformed `proc_macro_derive` attribute input
-  --> $DIR/attribute.rs:12:1
-   |
-LL | #[proc_macro_derive = ""]
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^ help: must be of the form: `#[proc_macro_derive(TraitName, /*opt*/ attributes(name1, name2, ...))]`
-
 error: aborting due to 17 previous errors