Auto merge of #63823 - petrochenkov:noapply2, r=matthewjasper

Audit uses of `apply_mark` in built-in macros + Remove default macro transparencies

Every use of `apply_mark` in a built-in or procedural macro is supposed to look like this
```rust
location.with_ctxt(SyntaxContext::root().apply_mark(ecx.current_expansion.id))
```
where `SyntaxContext::root()` means that the built-in/procedural macro is defined directly, rather than expanded from some other macro.

However, few people understood what `apply_mark` does, so we had a lot of copy-pasted uses of it looking e.g. like
```rust
span = span.apply_mark(ecx.current_expansion.id);
```
, which doesn't really make sense for procedural macros, but at the same time is not too harmful, if the macros use the traditional `macro_rules` hygiene.

So, to fight this, we stop using `apply_mark` directly in built-in macro implementations, and follow the example of regular proc macros instead and use analogues of `Span::def_site()` and `Span::call_site()`, which are much more intuitive and less error-prone.
- `ecx.with_def_site_ctxt(span)` takes the `span`'s location and combines it with a def-site context.
- `ecx.with_call_site_ctxt(span)` takes the `span`'s location and combines it with a call-site context.

Even if called multiple times (which sometimes happens due to some historical messiness of the built-in macro code) these functions will produce the same result, unlike `apply_mark` which will grow  the mark chain further in this case.

---

After `apply_mark`s in built-in macros are eliminated, the remaining `apply_mark`s are very few in number, so we can start passing the previously implicit `Transparency` argument to them explicitly, thus eliminating the need in `default_transparency` fields in hygiene structures and `#[rustc_macro_transparency]` annotations on built-in macros.

So, the task of making built-in macros opaque can now be formulated as "eliminate `with_legacy_ctxt` in favor of `with_def_site_ctxt`" rather than "replace `#[rustc_macro_transparency = "semitransparent"]` with `#[rustc_macro_transparency = "opaque"]`".

r? @matthewjasper

src/libcore/macros.rs

@@ -734,7 +734,6 @@ pub(crate) mod builtin {
     #[allow_internal_unstable(fmt_internals)]
     #[rustc_builtin_macro]
     #[macro_export]
-    #[rustc_macro_transparency = "opaque"]
     macro_rules! format_args {
         ($fmt:expr) => ({ /* compiler built-in */ });
         ($fmt:expr, $($args:tt)*) => ({ /* compiler built-in */ })
@@ -747,7 +746,6 @@ pub(crate) mod builtin {
     #[allow_internal_unstable(fmt_internals)]
     #[rustc_builtin_macro]
     #[macro_export]
-    #[rustc_macro_transparency = "opaque"]
     macro_rules! format_args_nl {
         ($fmt:expr) => ({ /* compiler built-in */ });
         ($fmt:expr, $($args:tt)*) => ({ /* compiler built-in */ })
@@ -1235,7 +1233,6 @@ pub(crate) mod builtin {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[allow_internal_unstable(test, rustc_attrs)]
     #[rustc_builtin_macro]
-    #[rustc_macro_transparency = "semitransparent"]
     pub macro test($item:item) { /* compiler built-in */ }
 
     /// Attribute macro applied to a function to turn it into a benchmark test.
@@ -1243,7 +1240,6 @@ pub(crate) mod builtin {
                reason = "`bench` is a part of custom test frameworks which are unstable")]
     #[allow_internal_unstable(test, rustc_attrs)]
     #[rustc_builtin_macro]
-    #[rustc_macro_transparency = "semitransparent"]
     pub macro bench($item:item) { /* compiler built-in */ }
 
     /// An implementation detail of the `#[test]` and `#[bench]` macros.
@@ -1251,26 +1247,22 @@ pub(crate) mod builtin {
                reason = "custom test frameworks are an unstable feature")]
     #[allow_internal_unstable(test, rustc_attrs)]
     #[rustc_builtin_macro]
-    #[rustc_macro_transparency = "semitransparent"]
     pub macro test_case($item:item) { /* compiler built-in */ }
 
     /// Attribute macro applied to a static to register it as a global allocator.
     #[stable(feature = "global_allocator", since = "1.28.0")]
     #[allow_internal_unstable(rustc_attrs)]
     #[rustc_builtin_macro]
-    #[rustc_macro_transparency = "semitransparent"]
     pub macro global_allocator($item:item) { /* compiler built-in */ }
 
     /// Unstable implementation detail of the `rustc` compiler, do not use.
     #[rustc_builtin_macro]
-    #[cfg_attr(boostrap_stdarch_ignore_this, rustc_macro_transparency = "semitransparent")]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[allow_internal_unstable(core_intrinsics, libstd_sys_internals)]
     pub macro RustcDecodable($item:item) { /* compiler built-in */ }
 
     /// Unstable implementation detail of the `rustc` compiler, do not use.
     #[rustc_builtin_macro]
-    #[cfg_attr(boostrap_stdarch_ignore_this, rustc_macro_transparency = "semitransparent")]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[allow_internal_unstable(core_intrinsics)]
     pub macro RustcEncodable($item:item) { /* compiler built-in */ }

src/librustc/ich/impls_syntax.rs

@@ -402,7 +402,6 @@ impl_stable_hash_for!(struct ::syntax_pos::hygiene::ExpnData {
     parent -> _,
     call_site,
     def_site,
-    default_transparency,
     allow_internal_unstable,
     allow_internal_unsafe,
     local_inner_macros,

src/librustc/ty/query/on_disk_cache.rs

@@ -23,7 +23,7 @@ use std::mem;
 use syntax::ast::NodeId;
 use syntax::source_map::{SourceMap, StableSourceFileId};
 use syntax_pos::{BytePos, Span, DUMMY_SP, SourceFile};
-use syntax_pos::hygiene::{ExpnId, SyntaxContext, ExpnData};
+use syntax_pos::hygiene::{ExpnId, SyntaxContext};
 
 const TAG_FILE_FOOTER: u128 = 0xC0FFEE_C0FFEE_C0FFEE_C0FFEE_C0FFEE;
 
@@ -593,8 +593,8 @@ impl<'a, 'tcx> SpecializedDecoder<Span> for CacheDecoder<'a, 'tcx> {
         // don't seem to be used after HIR lowering, so everything should be fine
         // as long as incremental compilation does not kick in before that.
         let location = || Span::with_root_ctxt(lo, hi);
-        let recover_from_expn_data = |this: &Self, expn_data, pos| {
+        let recover_from_expn_data = |this: &Self, expn_data, transparency, pos| {
-            let span = location().fresh_expansion(expn_data);
+            let span = location().fresh_expansion_with_transparency(expn_data, transparency);
             this.synthetic_syntax_contexts.borrow_mut().insert(pos, span.ctxt());
             span
         };
@@ -603,9 +603,9 @@ impl<'a, 'tcx> SpecializedDecoder<Span> for CacheDecoder<'a, 'tcx> {
                 location()
             }
             TAG_EXPN_DATA_INLINE => {
-                let expn_data = Decodable::decode(self)?;
+                let (expn_data, transparency) = Decodable::decode(self)?;
                 recover_from_expn_data(
-                    self, expn_data, AbsoluteBytePos::new(self.opaque.position())
+                    self, expn_data, transparency, AbsoluteBytePos::new(self.opaque.position())
                 )
             }
             TAG_EXPN_DATA_SHORTHAND => {
@@ -614,9 +614,9 @@ impl<'a, 'tcx> SpecializedDecoder<Span> for CacheDecoder<'a, 'tcx> {
                 if let Some(ctxt) = cached_ctxt {
                     Span::new(lo, hi, ctxt)
                 } else {
-                    let expn_data =
+                    let (expn_data, transparency) =
-                        self.with_position(pos.to_usize(), |this| ExpnData::decode(this))?;
+                        self.with_position(pos.to_usize(), |this| Decodable::decode(this))?;
-                    recover_from_expn_data(self, expn_data, pos)
+                    recover_from_expn_data(self, expn_data, transparency, pos)
                 }
             }
             _ => {
@@ -819,7 +819,7 @@ where
         if span_data.ctxt == SyntaxContext::root() {
             TAG_NO_EXPN_DATA.encode(self)
         } else {
-            let (expn_id, expn_data) = span_data.ctxt.outer_expn_with_data();
+            let (expn_id, transparency, expn_data) = span_data.ctxt.outer_mark_with_data();
             if let Some(pos) = self.expn_data_shorthands.get(&expn_id).cloned() {
                 TAG_EXPN_DATA_SHORTHAND.encode(self)?;
                 pos.encode(self)
@@ -827,7 +827,7 @@ where
                 TAG_EXPN_DATA_INLINE.encode(self)?;
                 let pos = AbsoluteBytePos::new(self.position());
                 self.expn_data_shorthands.insert(expn_id, pos);
-                expn_data.encode(self)
+                (expn_data, transparency).encode(self)
             }
         }
     }

src/librustc_resolve/build_reduced_graph.rs

@@ -145,7 +145,7 @@ impl<'a> Resolver<'a> {
         }
     }
 
-    fn get_macro_by_def_id(&mut self, def_id: DefId) -> Option<Lrc<SyntaxExtension>> {
+    crate fn get_macro_by_def_id(&mut self, def_id: DefId) -> Option<Lrc<SyntaxExtension>> {
         if let Some(ext) = self.macro_map.get(&def_id) {
             return Some(ext.clone());
         }

src/librustc_resolve/lib.rs

@@ -1647,10 +1647,14 @@ impl<'a> Resolver<'a> {
             if module.expansion != parent.expansion &&
             module.expansion.is_descendant_of(parent.expansion) {
                 // The macro is a proc macro derive
-                if module.expansion.looks_like_proc_macro_derive() {
+                if let Some(&def_id) = self.macro_defs.get(&module.expansion) {
-                    if parent.expansion.outer_expn_is_descendant_of(span.ctxt()) {
+                    if let Some(ext) = self.get_macro_by_def_id(def_id) {
-                        *poisoned = Some(node_id);
+                        if !ext.is_builtin && ext.macro_kind() == MacroKind::Derive {
-                        return module.parent;
+                            if parent.expansion.outer_expn_is_descendant_of(span.ctxt()) {
+                                *poisoned = Some(node_id);
+                                return module.parent;
+                            }
+                        }
                     }
                 }
             }

src/libsyntax/ext/base.rs

@@ -3,7 +3,7 @@ use crate::attr::{HasAttrs, Stability, Deprecation};
 use crate::source_map::SourceMap;
 use crate::edition::Edition;
 use crate::ext::expand::{self, AstFragment, Invocation};
-use crate::ext::hygiene::{ExpnId, SyntaxContext, Transparency};
+use crate::ext::hygiene::{ExpnId, Transparency};
 use crate::mut_visit::{self, MutVisitor};
 use crate::parse::{self, parser, DirectoryOwnership};
 use crate::parse::token;
@@ -549,8 +549,6 @@ pub struct SyntaxExtension {
     pub kind: SyntaxExtensionKind,
     /// Span of the macro definition.
     pub span: Span,
-    /// Hygienic properties of spans produced by this macro by default.
-    pub default_transparency: Transparency,
     /// Whitelist of unstable features that are treated as stable inside this macro.
     pub allow_internal_unstable: Option<Lrc<[Symbol]>>,
     /// Suppresses the `unsafe_code` lint for code produced by this macro.
@@ -572,22 +570,6 @@ pub struct SyntaxExtension {
     pub is_derive_copy: bool,
 }
 
-impl SyntaxExtensionKind {
-    /// When a syntax extension is constructed,
-    /// its transparency can often be inferred from its kind.
-    fn default_transparency(&self) -> Transparency {
-        match self {
-            SyntaxExtensionKind::Bang(..) |
-            SyntaxExtensionKind::Attr(..) |
-            SyntaxExtensionKind::Derive(..) |
-            SyntaxExtensionKind::NonMacroAttr { .. } => Transparency::Opaque,
-            SyntaxExtensionKind::LegacyBang(..) |
-            SyntaxExtensionKind::LegacyAttr(..) |
-            SyntaxExtensionKind::LegacyDerive(..) => Transparency::SemiTransparent,
-        }
-    }
-}
-
 impl SyntaxExtension {
     /// Returns which kind of macro calls this syntax extension.
     pub fn macro_kind(&self) -> MacroKind {
@@ -606,7 +588,6 @@ impl SyntaxExtension {
     pub fn default(kind: SyntaxExtensionKind, edition: Edition) -> SyntaxExtension {
         SyntaxExtension {
             span: DUMMY_SP,
-            default_transparency: kind.default_transparency(),
             allow_internal_unstable: None,
             allow_internal_unsafe: false,
             local_inner_macros: false,
@@ -646,7 +627,6 @@ impl SyntaxExtension {
             parent,
             call_site,
             def_site: self.span,
-            default_transparency: self.default_transparency,
             allow_internal_unstable: self.allow_internal_unstable.clone(),
             allow_internal_unsafe: self.allow_internal_unsafe,
             local_inner_macros: self.local_inner_macros,
@@ -760,23 +740,39 @@ impl<'a> ExtCtxt<'a> {
     pub fn call_site(&self) -> Span {
         self.current_expansion.id.expn_data().call_site
     }
-    pub fn backtrace(&self) -> SyntaxContext {
+
-        SyntaxContext::root().apply_mark(self.current_expansion.id)
+    /// Equivalent of `Span::def_site` from the proc macro API,
+    /// except that the location is taken from the span passed as an argument.
+    pub fn with_def_site_ctxt(&self, span: Span) -> Span {
+        span.with_ctxt_from_mark(self.current_expansion.id, Transparency::Opaque)
+    }
+
+    /// Equivalent of `Span::call_site` from the proc macro API,
+    /// except that the location is taken from the span passed as an argument.
+    pub fn with_call_site_ctxt(&self, span: Span) -> Span {
+        span.with_ctxt_from_mark(self.current_expansion.id, Transparency::Transparent)
+    }
+
+    /// Span with a context reproducing `macro_rules` hygiene (hygienic locals, unhygienic items).
+    /// FIXME: This should be eventually replaced either with `with_def_site_ctxt` (preferably),
+    /// or with `with_call_site_ctxt` (where necessary).
+    pub fn with_legacy_ctxt(&self, span: Span) -> Span {
+        span.with_ctxt_from_mark(self.current_expansion.id, Transparency::SemiTransparent)
     }
 
     /// Returns span for the macro which originally caused the current expansion to happen.
     ///
     /// Stops backtracing at include! boundary.
     pub fn expansion_cause(&self) -> Option<Span> {
-        let mut ctxt = self.backtrace();
+        let mut expn_id = self.current_expansion.id;
         let mut last_macro = None;
         loop {
-            let expn_data = ctxt.outer_expn_data();
+            let expn_data = expn_id.expn_data();
             // Stop going up the backtrace once include! is encountered
             if expn_data.is_root() || expn_data.kind.descr() == sym::include {
                 break;
             }
-            ctxt = expn_data.call_site.ctxt();
+            expn_id = expn_data.call_site.ctxt().outer_expn();
             last_macro = Some(expn_data.call_site);
         }
         last_macro
@@ -865,7 +861,7 @@ impl<'a> ExtCtxt<'a> {
         ast::Ident::from_str(st)
     }
     pub fn std_path(&self, components: &[Symbol]) -> Vec<ast::Ident> {
-        let def_site = DUMMY_SP.apply_mark(self.current_expansion.id);
+        let def_site = self.with_def_site_ctxt(DUMMY_SP);
         iter::once(Ident::new(kw::DollarCrate, def_site))
             .chain(components.iter().map(|&s| Ident::with_dummy_span(s)))
             .collect()

src/libsyntax/ext/expand.rs

@@ -565,7 +565,6 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
                         return fragment_kind.dummy(span);
                     }
                     let meta = ast::MetaItem { node: ast::MetaItemKind::Word, span, path };
-                    let span = span.with_ctxt(self.cx.backtrace());
                     let items = expander.expand(self.cx, span, &meta, item);
                     fragment_kind.expect_from_annotatables(items)
                 }
@@ -1389,17 +1388,3 @@ impl<'feat> ExpansionConfig<'feat> {
         self.features.map_or(false, |features| features.custom_inner_attributes)
     }
 }
-
-// A Marker adds the given mark to the syntax context.
-#[derive(Debug)]
-pub struct Marker(pub ExpnId);
-
-impl MutVisitor for Marker {
-    fn visit_span(&mut self, span: &mut Span) {
-        *span = span.apply_mark(self.0)
-    }
-
-    fn visit_mac(&mut self, mac: &mut ast::Mac) {
-        noop_visit_mac(mac, self)
-    }
-}

src/libsyntax/ext/proc_macro_server.rs

@@ -7,7 +7,6 @@ use crate::tokenstream::{self, DelimSpan, IsJoint::*, TokenStream, TreeAndJoint}
 use errors::{Diagnostic, DiagnosticBuilder};
 use rustc_data_structures::sync::Lrc;
 use syntax_pos::{BytePos, FileName, MultiSpan, Pos, SourceFile, Span};
-use syntax_pos::hygiene::{SyntaxContext, Transparency};
 use syntax_pos::symbol::{kw, sym, Symbol};
 
 use proc_macro::{Delimiter, Level, LineColumn, Spacing};
@@ -363,16 +362,10 @@ impl<'a> Rustc<'a> {
     pub fn new(cx: &'a ExtCtxt<'_>) -> Self {
         // No way to determine def location for a proc macro right now, so use call location.
         let location = cx.current_expansion.id.expn_data().call_site;
-        let to_span = |transparency| {
-            location.with_ctxt(
-                SyntaxContext::root()
-                    .apply_mark_with_transparency(cx.current_expansion.id, transparency),
-            )
-        };
         Rustc {
             sess: cx.parse_sess,
-            def_site: to_span(Transparency::Opaque),
+            def_site: cx.with_def_site_ctxt(location),
-            call_site: to_span(Transparency::Transparent),
+            call_site: cx.with_call_site_ctxt(location),
         }
     }
 

src/libsyntax/ext/tt/macro_rules.rs

@@ -19,6 +19,7 @@ use crate::{ast, attr, attr::TransparencyError};
 
 use errors::{DiagnosticBuilder, FatalError};
 use log::debug;
+use syntax_pos::hygiene::Transparency;
 use syntax_pos::Span;
 
 use rustc_data_structures::fx::FxHashMap;
@@ -128,6 +129,7 @@ impl<'a> ParserAnyMacro<'a> {
 struct MacroRulesMacroExpander {
     name: ast::Ident,
     span: Span,
+    transparency: Transparency,
     lhses: Vec<quoted::TokenTree>,
     rhses: Vec<quoted::TokenTree>,
     valid: bool,
@@ -143,7 +145,9 @@ impl TTMacroExpander for MacroRulesMacroExpander {
         if !self.valid {
             return DummyResult::any(sp);
         }
-        generic_extension(cx, sp, self.span, self.name, input, &self.lhses, &self.rhses)
+        generic_extension(
+            cx, sp, self.span, self.name, self.transparency, input, &self.lhses, &self.rhses
+        )
     }
 }
 
@@ -158,6 +162,7 @@ fn generic_extension<'cx>(
     sp: Span,
     def_span: Span,
     name: ast::Ident,
+    transparency: Transparency,
     arg: TokenStream,
     lhses: &[quoted::TokenTree],
     rhses: &[quoted::TokenTree],
@@ -187,7 +192,7 @@ fn generic_extension<'cx>(
 
                 let rhs_spans = rhs.iter().map(|t| t.span()).collect::<Vec<_>>();
                 // rhs has holes ( `$id` and `$(...)` that need filled)
-                let mut tts = transcribe(cx, &named_matches, rhs);
+                let mut tts = transcribe(cx, &named_matches, rhs, transparency);
 
                 // Replace all the tokens for the corresponding positions in the macro, to maintain
                 // proper positions in error reporting, while maintaining the macro_backtrace.
@@ -415,11 +420,7 @@ pub fn compile(
     // that is not lint-checked and trigger the "failed to process buffered lint here" bug.
     valid &= macro_check::check_meta_variables(sess, ast::CRATE_NODE_ID, def.span, &lhses, &rhses);
 
-    let expander: Box<_> =
+    let (transparency, transparency_error) = attr::find_transparency(&def.attrs, body.legacy);
-        Box::new(MacroRulesMacroExpander { name: def.ident, span: def.span, lhses, rhses, valid });
-
-    let (default_transparency, transparency_error) =
-        attr::find_transparency(&def.attrs, body.legacy);
     match transparency_error {
         Some(TransparencyError::UnknownTransparency(value, span)) =>
             sess.span_diagnostic.span_err(
@@ -432,6 +433,10 @@ pub fn compile(
         None => {}
     }
 
+    let expander: Box<_> = Box::new(MacroRulesMacroExpander {
+        name: def.ident, span: def.span, transparency, lhses, rhses, valid
+    });
+
     let allow_internal_unstable =
         attr::find_by_name(&def.attrs, sym::allow_internal_unstable).map(|attr| {
             attr.meta_item_list()
@@ -473,7 +478,6 @@ pub fn compile(
     SyntaxExtension {
         kind: SyntaxExtensionKind::LegacyBang(expander),
         span: def.span,
-        default_transparency,
         allow_internal_unstable,
         allow_internal_unsafe: attr::contains_name(&def.attrs, sym::allow_internal_unsafe),
         local_inner_macros,

src/libsyntax/ext/tt/transcribe.rs

@@ -1,9 +1,8 @@
-use crate::ast::Ident;
+use crate::ast::{Ident, Mac};
 use crate::ext::base::ExtCtxt;
-use crate::ext::expand::Marker;
 use crate::ext::tt::macro_parser::{MatchedNonterminal, MatchedSeq, NamedMatch};
 use crate::ext::tt::quoted;
-use crate::mut_visit::noop_visit_tt;
+use crate::mut_visit::{self, MutVisitor};
 use crate::parse::token::{self, NtTT, Token};
 use crate::tokenstream::{DelimSpan, TokenStream, TokenTree, TreeAndJoint};
 
@@ -11,8 +10,31 @@ use smallvec::{smallvec, SmallVec};
 
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::Lrc;
+use syntax_pos::hygiene::{ExpnId, Transparency};
+use syntax_pos::Span;
+
 use std::mem;
 
+// A Marker adds the given mark to the syntax context.
+struct Marker(ExpnId, Transparency);
+
+impl MutVisitor for Marker {
+    fn visit_span(&mut self, span: &mut Span) {
+        *span = span.apply_mark(self.0, self.1)
+    }
+
+    fn visit_mac(&mut self, mac: &mut Mac) {
+        mut_visit::noop_visit_mac(mac, self)
+    }
+}
+
+impl Marker {
+    fn visit_delim_span(&mut self, dspan: &mut DelimSpan) {
+        self.visit_span(&mut dspan.open);
+        self.visit_span(&mut dspan.close);
+    }
+}
+
 /// An iterator over the token trees in a delimited token tree (`{ ... }`) or a sequence (`$(...)`).
 enum Frame {
     Delimited { forest: Lrc<quoted::Delimited>, idx: usize, span: DelimSpan },
@@ -68,6 +90,7 @@ pub(super) fn transcribe(
     cx: &ExtCtxt<'_>,
     interp: &FxHashMap<Ident, NamedMatch>,
     src: Vec<quoted::TokenTree>,
+    transparency: Transparency,
 ) -> TokenStream {
     // Nothing for us to transcribe...
     if src.is_empty() {
@@ -96,6 +119,7 @@ pub(super) fn transcribe(
     // again, and we are done transcribing.
     let mut result: Vec<TreeAndJoint> = Vec::new();
     let mut result_stack = Vec::new();
+    let mut marker = Marker(cx.current_expansion.id, transparency);
 
     loop {
         // Look at the last frame on the stack.
@@ -207,7 +231,7 @@ pub(super) fn transcribe(
             }
 
             // Replace the meta-var with the matched token tree from the invocation.
-            quoted::TokenTree::MetaVar(mut sp, ident) => {
+            quoted::TokenTree::MetaVar(mut sp, mut ident) => {
                 // Find the matched nonterminal from the macro invocation, and use it to replace
                 // the meta-var.
                 if let Some(cur_matched) = lookup_cur_matched(ident, interp, &repeats) {
@@ -218,7 +242,7 @@ pub(super) fn transcribe(
                         if let NtTT(ref tt) = **nt {
                             result.push(tt.clone().into());
                         } else {
-                            sp = sp.apply_mark(cx.current_expansion.id);
+                            marker.visit_span(&mut sp);
                             let token = TokenTree::token(token::Interpolated(nt.clone()), sp);
                             result.push(token.into());
                         }
@@ -232,9 +256,8 @@ pub(super) fn transcribe(
                 } else {
                     // If we aren't able to match the meta-var, we push it back into the result but
                     // with modified syntax context. (I believe this supports nested macros).
-                    let ident =
+                    marker.visit_span(&mut sp);
-                        Ident::new(ident.name, ident.span.apply_mark(cx.current_expansion.id));
+                    marker.visit_ident(&mut ident);
-                    sp = sp.apply_mark(cx.current_expansion.id);
                     result.push(TokenTree::token(token::Dollar, sp).into());
                     result.push(TokenTree::Token(Token::from_ast_ident(ident)).into());
                 }
@@ -246,7 +269,7 @@ pub(super) fn transcribe(
             // jump back out of the Delimited, pop the result_stack and add the new results back to
             // the previous results (from outside the Delimited).
             quoted::TokenTree::Delimited(mut span, delimited) => {
-                span = span.apply_mark(cx.current_expansion.id);
+                marker.visit_delim_span(&mut span);
                 stack.push(Frame::Delimited { forest: delimited, idx: 0, span });
                 result_stack.push(mem::take(&mut result));
             }
@@ -254,9 +277,8 @@ pub(super) fn transcribe(
             // Nothing much to do here. Just push the token to the result, being careful to
             // preserve syntax context.
             quoted::TokenTree::Token(token) => {
-                let mut marker = Marker(cx.current_expansion.id);
                 let mut tt = TokenTree::Token(token);
-                noop_visit_tt(&mut tt, &mut marker);
+                marker.visit_tt(&mut tt);
                 result.push(tt.into());
             }
 

src/libsyntax/tokenstream.rs

@@ -19,7 +19,7 @@ use crate::parse::Directory;
 use crate::parse::token::{self, DelimToken, Token, TokenKind};
 use crate::print::pprust;
 
-use syntax_pos::{BytePos, ExpnId, Span, DUMMY_SP};
+use syntax_pos::{BytePos, Span, DUMMY_SP};
 #[cfg(target_arch = "x86_64")]
 use rustc_data_structures::static_assert_size;
 use rustc_data_structures::sync::Lrc;
@@ -547,11 +547,4 @@ impl DelimSpan {
     pub fn entire(self) -> Span {
         self.open.with_hi(self.close.hi())
     }
-
-    pub fn apply_mark(self, expn_id: ExpnId) -> Self {
-        DelimSpan {
-            open: self.open.apply_mark(expn_id),
-            close: self.close.apply_mark(expn_id),
-        }
-    }
 }

src/libsyntax_ext/asm.rs

@@ -63,7 +63,7 @@ pub fn expand_asm<'cx>(cx: &'cx mut ExtCtxt<'_>,
     MacEager::expr(P(ast::Expr {
         id: ast::DUMMY_NODE_ID,
         node: ast::ExprKind::InlineAsm(P(inline_asm)),
-        span: sp.with_ctxt(cx.backtrace()),
+        span: cx.with_legacy_ctxt(sp),
         attrs: ThinVec::new(),
     }))
 }

src/libsyntax_ext/assert.rs

@@ -23,7 +23,7 @@ pub fn expand_assert<'cx>(
         }
     };
 
-    let sp = sp.apply_mark(cx.current_expansion.id);
+    let sp = cx.with_legacy_ctxt(sp);
     let panic_call = Mac {
         path: Path::from_ident(Ident::new(sym::panic, sp)),
         tts: custom_message.unwrap_or_else(|| {

src/libsyntax_ext/cfg.rs

@@ -16,7 +16,7 @@ pub fn expand_cfg(
     sp: Span,
     tts: &[tokenstream::TokenTree],
 ) -> Box<dyn base::MacResult + 'static> {
-    let sp = sp.apply_mark(cx.current_expansion.id);
+    let sp = cx.with_legacy_ctxt(sp);
 
     match parse_cfg(cx, sp, tts) {
         Ok(cfg) => {

src/libsyntax_ext/concat.rs

@@ -59,6 +59,6 @@ pub fn expand_syntax_ext(
     } else if has_errors {
         return DummyResult::any(sp);
     }
-    let sp = sp.apply_mark(cx.current_expansion.id);
+    let sp = cx.with_legacy_ctxt(sp);
     base::MacEager::expr(cx.expr_str(sp, Symbol::intern(&accumulator)))
 }

src/libsyntax_ext/concat_idents.rs

@@ -39,7 +39,7 @@ pub fn expand_syntax_ext<'cx>(cx: &'cx mut ExtCtxt<'_>,
         }
     }
 
-    let ident = ast::Ident::new(Symbol::intern(&res_str), sp.apply_mark(cx.current_expansion.id));
+    let ident = ast::Ident::new(Symbol::intern(&res_str), cx.with_legacy_ctxt(sp));
 
     struct ConcatIdentsResult { ident: ast::Ident }
 

src/libsyntax_ext/deriving/clone.rs

@@ -112,7 +112,7 @@ fn cs_clone_shallow(name: &str,
                         ty: P<ast::Ty>, span: Span, helper_name: &str) {
         // Generate statement `let _: helper_name<ty>;`,
         // set the expn ID so we can use the unstable struct.
-        let span = span.with_ctxt(cx.backtrace());
+        let span = cx.with_def_site_ctxt(span);
         let assert_path = cx.path_all(span, true,
                                         cx.std_path(&[sym::clone, Symbol::intern(helper_name)]),
                                         vec![GenericArg::Type(ty)], vec![]);

src/libsyntax_ext/deriving/cmp/eq.rs

@@ -53,7 +53,7 @@ fn cs_total_eq_assert(cx: &mut ExtCtxt<'_>,
                         ty: P<ast::Ty>, span: Span, helper_name: &str) {
         // Generate statement `let _: helper_name<ty>;`,
         // set the expn ID so we can use the unstable struct.
-        let span = span.with_ctxt(cx.backtrace());
+        let span = cx.with_def_site_ctxt(span);
         let assert_path = cx.path_all(span, true,
                                         cx.std_path(&[sym::cmp, Symbol::intern(helper_name)]),
                                         vec![GenericArg::Type(ty)], vec![]);

src/libsyntax_ext/deriving/debug.rs

@@ -60,7 +60,7 @@ fn show_substructure(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>
     };
 
     // We want to make sure we have the ctxt set so that we can use unstable methods
-    let span = span.with_ctxt(cx.backtrace());
+    let span = cx.with_def_site_ctxt(span);
     let name = cx.expr_lit(span, ast::LitKind::Str(ident.name, ast::StrStyle::Cooked));
     let builder = Ident::from_str_and_span("debug_trait_builder", span);
     let builder_expr = cx.expr_ident(span, builder.clone());

src/libsyntax_ext/deriving/generic/ty.rs

@@ -85,7 +85,7 @@ impl<'a> Path<'a> {
             PathKind::Global => cx.path_all(span, true, idents, params, Vec::new()),
             PathKind::Local => cx.path_all(span, false, idents, params, Vec::new()),
             PathKind::Std => {
-                let def_site = DUMMY_SP.apply_mark(cx.current_expansion.id);
+                let def_site = cx.with_def_site_ctxt(DUMMY_SP);
                 idents.insert(0, Ident::new(kw::DollarCrate, def_site));
                 cx.path_all(span, false, idents, params, Vec::new())
             }

src/libsyntax_ext/deriving/mod.rs

@@ -48,6 +48,9 @@ impl MultiItemModifier for BuiltinDerive {
               meta_item: &MetaItem,
               item: Annotatable)
               -> Vec<Annotatable> {
+        // FIXME: Built-in derives often forget to give spans contexts,
+        // so we are doing it here in a centralized way.
+        let span = ecx.with_def_site_ctxt(span);
         let mut items = Vec::new();
         (self.0)(ecx, span, meta_item, &item, &mut |a| items.push(a));
         items
@@ -60,7 +63,7 @@ fn call_intrinsic(cx: &ExtCtxt<'_>,
                   intrinsic: &str,
                   args: Vec<P<ast::Expr>>)
                   -> P<ast::Expr> {
-    let span = span.with_ctxt(cx.backtrace());
+    let span = cx.with_def_site_ctxt(span);
     let path = cx.std_path(&[sym::intrinsics, Symbol::intern(intrinsic)]);
     let call = cx.expr_call_global(span, path, args);
 

src/libsyntax_ext/env.rs

@@ -20,7 +20,7 @@ pub fn expand_option_env<'cx>(cx: &'cx mut ExtCtxt<'_>,
         Some(v) => v,
     };
 
-    let sp = sp.apply_mark(cx.current_expansion.id);
+    let sp = cx.with_legacy_ctxt(sp);
     let e = match env::var(&*var.as_str()) {
         Err(..) => {
             let lt = cx.lifetime(sp, Ident::with_dummy_span(kw::StaticLifetime));

src/libsyntax_ext/format.rs

@@ -12,7 +12,7 @@ use syntax::parse::token;
 use syntax::ptr::P;
 use syntax::symbol::{Symbol, sym};
 use syntax::tokenstream;
-use syntax_pos::{MultiSpan, Span, DUMMY_SP};
+use syntax_pos::{MultiSpan, Span};
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use std::borrow::Cow;
@@ -666,8 +666,7 @@ impl<'a, 'b> Context<'a, 'b> {
         // passed to this function.
         for (i, e) in self.args.into_iter().enumerate() {
             let name = names_pos[i];
-            let span =
+            let span = self.ecx.with_def_site_ctxt(e.span);
-                DUMMY_SP.with_ctxt(e.span.ctxt().apply_mark(self.ecx.current_expansion.id));
             pats.push(self.ecx.pat_ident(span, name));
             for ref arg_ty in self.arg_unique_types[i].iter() {
                 locals.push(Context::format_arg(self.ecx, self.macsp, e.span, arg_ty, name));
@@ -745,7 +744,7 @@ impl<'a, 'b> Context<'a, 'b> {
         ty: &ArgumentType,
         arg: ast::Ident,
     ) -> P<ast::Expr> {
-        sp = sp.apply_mark(ecx.current_expansion.id);
+        sp = ecx.with_def_site_ctxt(sp);
         let arg = ecx.expr_ident(sp, arg);
         let trait_ = match *ty {
             Placeholder(ref tyname) => {
@@ -798,7 +797,7 @@ fn expand_format_args_impl<'cx>(
     tts: &[tokenstream::TokenTree],
     nl: bool,
 ) -> Box<dyn base::MacResult + 'cx> {
-    sp = sp.apply_mark(ecx.current_expansion.id);
+    sp = ecx.with_def_site_ctxt(sp);
     match parse_args(ecx, sp, tts) {
         Ok((efmt, args, names)) => {
             MacEager::expr(expand_preparsed_format_args(ecx, sp, efmt, args, names, nl))
@@ -842,7 +841,7 @@ pub fn expand_preparsed_format_args(
     let arg_unique_types: Vec<_> = (0..args.len()).map(|_| Vec::new()).collect();
 
     let mut macsp = ecx.call_site();
-    macsp = macsp.with_ctxt(ecx.backtrace());
+    macsp = ecx.with_def_site_ctxt(macsp);
 
     let msg = "format argument must be a string literal";
     let fmt_sp = efmt.span;

src/libsyntax_ext/global_allocator.rs

@@ -3,7 +3,6 @@ use syntax::ast::{self, Arg, Attribute, Expr, FnHeader, Generics, Ident};
 use syntax::attr::check_builtin_macro_attribute;
 use syntax::ext::allocator::{AllocatorKind, AllocatorMethod, AllocatorTy, ALLOCATOR_METHODS};
 use syntax::ext::base::{Annotatable, ExtCtxt};
-use syntax::ext::hygiene::SyntaxContext;
 use syntax::ptr::P;
 use syntax::symbol::{kw, sym, Symbol};
 use syntax_pos::Span;
@@ -29,7 +28,7 @@ pub fn expand(
     };
 
     // Generate a bunch of new items using the AllocFnFactory
-    let span = item.span.with_ctxt(SyntaxContext::root().apply_mark(ecx.current_expansion.id));
+    let span = ecx.with_legacy_ctxt(item.span);
     let f = AllocFnFactory {
         span,
         kind: AllocatorKind::Global,

src/libsyntax_ext/global_asm.rs

@@ -30,7 +30,7 @@ pub fn expand_global_asm<'cx>(cx: &'cx mut ExtCtxt<'_>,
                 id: ast::DUMMY_NODE_ID,
                 node: ast::ItemKind::GlobalAsm(P(global_asm)),
                 vis: respan(sp.shrink_to_lo(), ast::VisibilityKind::Inherited),
-                span: sp.with_ctxt(cx.backtrace()),
+                span: cx.with_legacy_ctxt(sp),
                 tokens: None,
             })])
         }

src/libsyntax_ext/test.rs

@@ -4,7 +4,6 @@
 use syntax::ast;
 use syntax::attr::{self, check_builtin_macro_attribute};
 use syntax::ext::base::*;
-use syntax::ext::hygiene::SyntaxContext;
 use syntax::print::pprust;
 use syntax::source_map::respan;
 use syntax::symbol::{Symbol, sym};
@@ -29,7 +28,7 @@ pub fn expand_test_case(
 
     if !ecx.ecfg.should_test { return vec![]; }
 
-    let sp = attr_sp.with_ctxt(SyntaxContext::root().apply_mark(ecx.current_expansion.id));
+    let sp = ecx.with_legacy_ctxt(attr_sp);
     let mut item = anno_item.expect_item();
     item = item.map(|mut item| {
         item.vis = respan(item.vis.span, ast::VisibilityKind::Public);
@@ -93,8 +92,7 @@ pub fn expand_test_or_bench(
         return vec![Annotatable::Item(item)];
     }
 
-    let ctxt = SyntaxContext::root().apply_mark(cx.current_expansion.id);
+    let (sp, attr_sp) = (cx.with_legacy_ctxt(item.span), cx.with_legacy_ctxt(attr_sp));
-    let (sp, attr_sp) = (item.span.with_ctxt(ctxt), attr_sp.with_ctxt(ctxt));
 
     // Gensym "test" so we can extern crate without conflicting with any local names
     let test_id = cx.ident_of("test").gensym();

src/libsyntax_pos/hygiene.rs

@@ -119,18 +119,6 @@ impl ExpnId {
     pub fn outer_expn_is_descendant_of(self, ctxt: SyntaxContext) -> bool {
         HygieneData::with(|data| data.is_descendant_of(self, data.outer_expn(ctxt)))
     }
-
-    // Used for enabling some compatibility fallback in resolve.
-    #[inline]
-    pub fn looks_like_proc_macro_derive(self) -> bool {
-        HygieneData::with(|data| {
-            let expn_data = data.expn_data(self);
-            if let ExpnKind::Macro(MacroKind::Derive, _) = expn_data.kind {
-                return expn_data.default_transparency == Transparency::Opaque;
-            }
-            false
-        })
-    }
 }
 
 #[derive(Debug)]
@@ -195,24 +183,25 @@ impl HygieneData {
         self.syntax_context_data[ctxt.0 as usize].outer_expn
     }
 
-    fn outer_transparency(&self, ctxt: SyntaxContext) -> Transparency {
+    fn outer_mark(&self, ctxt: SyntaxContext) -> (ExpnId, Transparency) {
-        self.syntax_context_data[ctxt.0 as usize].outer_transparency
+        let data = &self.syntax_context_data[ctxt.0 as usize];
+        (data.outer_expn, data.outer_transparency)
     }
 
     fn parent_ctxt(&self, ctxt: SyntaxContext) -> SyntaxContext {
         self.syntax_context_data[ctxt.0 as usize].parent
     }
 
-    fn remove_mark(&self, ctxt: &mut SyntaxContext) -> ExpnId {
+    fn remove_mark(&self, ctxt: &mut SyntaxContext) -> (ExpnId, Transparency) {
-        let outer_expn = self.outer_expn(*ctxt);
+        let outer_mark = self.outer_mark(*ctxt);
         *ctxt = self.parent_ctxt(*ctxt);
-        outer_expn
+        outer_mark
     }
 
     fn marks(&self, mut ctxt: SyntaxContext) -> Vec<(ExpnId, Transparency)> {
         let mut marks = Vec::new();
         while ctxt != SyntaxContext::root() {
-            marks.push((self.outer_expn(ctxt), self.outer_transparency(ctxt)));
+            marks.push(self.outer_mark(ctxt));
             ctxt = self.parent_ctxt(ctxt);
         }
         marks.reverse();
@@ -229,20 +218,14 @@ impl HygieneData {
     fn adjust(&self, ctxt: &mut SyntaxContext, expn_id: ExpnId) -> Option<ExpnId> {
         let mut scope = None;
         while !self.is_descendant_of(expn_id, self.outer_expn(*ctxt)) {
-            scope = Some(self.remove_mark(ctxt));
+            scope = Some(self.remove_mark(ctxt).0);
         }
         scope
     }
 
-    fn apply_mark(&mut self, ctxt: SyntaxContext, expn_id: ExpnId) -> SyntaxContext {
+    fn apply_mark(
-        assert_ne!(expn_id, ExpnId::root());
+        &mut self, ctxt: SyntaxContext, expn_id: ExpnId, transparency: Transparency
-        self.apply_mark_with_transparency(
+    ) -> SyntaxContext {
-            ctxt, expn_id, self.expn_data(expn_id).default_transparency
-        )
-    }
-
-    fn apply_mark_with_transparency(&mut self, ctxt: SyntaxContext, expn_id: ExpnId,
-                                    transparency: Transparency) -> SyntaxContext {
         assert_ne!(expn_id, ExpnId::root());
         if transparency == Transparency::Opaque {
             return self.apply_mark_internal(ctxt, expn_id, transparency);
@@ -376,15 +359,9 @@ impl SyntaxContext {
         SyntaxContext(raw)
     }
 
-    /// Extend a syntax context with a given expansion and default transparency for that expansion.
-    pub fn apply_mark(self, expn_id: ExpnId) -> SyntaxContext {
-        HygieneData::with(|data| data.apply_mark(self, expn_id))
-    }
-
     /// Extend a syntax context with a given expansion and transparency.
-    pub fn apply_mark_with_transparency(self, expn_id: ExpnId, transparency: Transparency)
+    pub fn apply_mark(self, expn_id: ExpnId, transparency: Transparency) -> SyntaxContext {
-                                        -> SyntaxContext {
+        HygieneData::with(|data| data.apply_mark(self, expn_id, transparency))
-        HygieneData::with(|data| data.apply_mark_with_transparency(self, expn_id, transparency))
     }
 
     /// Pulls a single mark off of the syntax context. This effectively moves the
@@ -404,7 +381,7 @@ impl SyntaxContext {
     /// invocation of f that created g1.
     /// Returns the mark that was removed.
     pub fn remove_mark(&mut self) -> ExpnId {
-        HygieneData::with(|data| data.remove_mark(self))
+        HygieneData::with(|data| data.remove_mark(self).0)
     }
 
     pub fn marks(self) -> Vec<(ExpnId, Transparency)> {
@@ -477,8 +454,8 @@ impl SyntaxContext {
             let mut scope = None;
             let mut glob_ctxt = data.modern(glob_span.ctxt());
             while !data.is_descendant_of(expn_id, data.outer_expn(glob_ctxt)) {
-                scope = Some(data.remove_mark(&mut glob_ctxt));
+                scope = Some(data.remove_mark(&mut glob_ctxt).0);
-                if data.remove_mark(self) != scope.unwrap() {
+                if data.remove_mark(self).0 != scope.unwrap() {
                     return None;
                 }
             }
@@ -509,9 +486,9 @@ impl SyntaxContext {
                 marks.push(data.remove_mark(&mut glob_ctxt));
             }
 
-            let scope = marks.last().cloned();
+            let scope = marks.last().map(|mark| mark.0);
-            while let Some(mark) = marks.pop() {
+            while let Some((expn_id, transparency)) = marks.pop() {
-                *self = data.apply_mark(*self, mark);
+                *self = data.apply_mark(*self, expn_id, transparency);
             }
             Some(scope)
         })
@@ -547,13 +524,11 @@ impl SyntaxContext {
         HygieneData::with(|data| data.expn_data(data.outer_expn(self)).clone())
     }
 
-    /// `ctxt.outer_expn_with_data()` is equivalent to but faster than
-    /// `{ let outer = ctxt.outer_expn(); (outer, outer.expn_data()) }`.
     #[inline]
-    pub fn outer_expn_with_data(self) -> (ExpnId, ExpnData) {
+    pub fn outer_mark_with_data(self) -> (ExpnId, Transparency, ExpnData) {
         HygieneData::with(|data| {
-            let outer = data.outer_expn(self);
+            let (expn_id, transparency) = data.outer_mark(self);
-            (outer, data.expn_data(outer).clone())
+            (expn_id, transparency, data.expn_data(expn_id).clone())
         })
     }
 
@@ -575,9 +550,15 @@ impl Span {
     /// The returned span belongs to the created expansion and has the new properties,
     /// but its location is inherited from the current span.
     pub fn fresh_expansion(self, expn_data: ExpnData) -> Span {
+        self.fresh_expansion_with_transparency(expn_data, Transparency::SemiTransparent)
+    }
+
+    pub fn fresh_expansion_with_transparency(
+        self, expn_data: ExpnData, transparency: Transparency
+    ) -> Span {
         HygieneData::with(|data| {
             let expn_id = data.fresh_expn(Some(expn_data));
-            self.with_ctxt(data.apply_mark(SyntaxContext::root(), expn_id))
+            self.with_ctxt(data.apply_mark(SyntaxContext::root(), expn_id, transparency))
         })
     }
 }
@@ -609,8 +590,6 @@ pub struct ExpnData {
     /// The span of the macro definition (possibly dummy).
     /// This span serves only informational purpose and is not used for resolution.
     pub def_site: Span,
-    /// Transparency used by `apply_mark` for the expansion with this expansion data by default.
-    pub default_transparency: Transparency,
     /// List of #[unstable]/feature-gated features that the macro is allowed to use
     /// internally without forcing the whole crate to opt-in
     /// to them.
@@ -633,7 +612,6 @@ impl ExpnData {
             parent: ExpnId::root(),
             call_site,
             def_site: DUMMY_SP,
-            default_transparency: Transparency::SemiTransparent,
             allow_internal_unstable: None,
             allow_internal_unsafe: false,
             local_inner_macros: false,

src/libsyntax_pos/lib.rs

@@ -22,6 +22,7 @@ pub mod edition;
 use edition::Edition;
 pub mod hygiene;
 pub use hygiene::{ExpnId, SyntaxContext, ExpnData, ExpnKind, MacroKind, DesugaringKind};
+use hygiene::Transparency;
 
 mod span_encoding;
 pub use span_encoding::{Span, DUMMY_SP};
@@ -512,10 +513,17 @@ impl Span {
                   span.ctxt)
     }
 
+    /// Produces a span with the same location as `self` and context produced by a macro with the
+    /// given ID and transparency, assuming that macro was defined directly and not produced by
+    /// some other macro (which is the case for built-in and procedural macros).
+    pub fn with_ctxt_from_mark(self, expn_id: ExpnId, transparency: Transparency) -> Span {
+        self.with_ctxt(SyntaxContext::root().apply_mark(expn_id, transparency))
+    }
+
     #[inline]
-    pub fn apply_mark(self, mark: ExpnId) -> Span {
+    pub fn apply_mark(self, expn_id: ExpnId, transparency: Transparency) -> Span {
         let span = self.data();
-        span.with_ctxt(span.ctxt.apply_mark(mark))
+        span.with_ctxt(span.ctxt.apply_mark(expn_id, transparency))
     }
 
     #[inline]