proc_macro: move the rustc server to syntax_ext.

Cargo.lock

@@ -1599,12 +1599,6 @@ dependencies = [
 [[package]]
 name = "proc_macro"
 version = "0.0.0"
-dependencies = [
- "rustc_data_structures 0.0.0",
- "rustc_errors 0.0.0",
- "syntax 0.0.0",
- "syntax_pos 0.0.0",
-]
 
 [[package]]
 name = "profiler_builtins"

src/libproc_macro/Cargo.toml

@@ -7,8 +7,3 @@ version = "0.0.0"
 path = "lib.rs"
 crate-type = ["dylib"]
 
-[dependencies]
-syntax = { path = "../libsyntax" }
-syntax_pos = { path = "../libsyntax_pos" }
-rustc_errors = { path = "../librustc_errors" }
-rustc_data_structures = { path = "../librustc_data_structures" }

src/libproc_macro/lib.rs

@@ -28,7 +28,6 @@
        test(attr(allow(dead_code, deprecated, unused_variables, unused_mut))))]
 
 #![feature(nll)]
-#![feature(rustc_private)]
 #![feature(staged_api)]
 #![feature(const_fn)]
 #![feature(extern_types)]
@@ -39,19 +38,10 @@
 
 #![recursion_limit="256"]
 
-extern crate syntax;
-extern crate syntax_pos;
-extern crate rustc_errors;
-extern crate rustc_data_structures;
-
 #[unstable(feature = "proc_macro_internals", issue = "27812")]
 #[doc(hidden)]
 pub mod bridge;
 
-#[unstable(feature = "proc_macro_internals", issue = "27812")]
-#[doc(hidden)]
-pub mod rustc;
-
 mod diagnostic;
 
 #[unstable(feature = "proc_macro_diagnostic", issue = "54140")]

src/libsyntax_ext/deriving/custom.rs

@@ -78,7 +78,7 @@ impl MultiItemModifier for ProcMacroDerive {
         let token = Token::interpolated(token::NtItem(item));
         let input = tokenstream::TokenTree::Token(DUMMY_SP, token).into();
 
-        let server = ::proc_macro::rustc::Rustc::new(ecx);
+        let server = ::proc_macro_server::Rustc::new(ecx);
         let stream = match self.client.run(&EXEC_STRATEGY, server, input) {
             Ok(stream) => stream,
             Err(e) => {

src/libsyntax_ext/lib.rs

@@ -14,7 +14,10 @@
        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
        html_root_url = "https://doc.rust-lang.org/nightly/")]
 
+#![feature(in_band_lifetimes)]
+#![feature(proc_macro_diagnostic)]
 #![feature(proc_macro_internals)]
+#![feature(proc_macro_span)]
 #![feature(decl_macro)]
 #![feature(nll)]
 #![feature(str_escape)]
@@ -57,6 +60,7 @@ mod test_case;
 
 pub mod proc_macro_decls;
 pub mod proc_macro_impl;
+mod proc_macro_server;
 
 use rustc_data_structures::sync::Lrc;
 use syntax::ast;

src/libsyntax_ext/proc_macro_impl.rs

@@ -32,7 +32,7 @@ impl base::AttrProcMacro for AttrProcMacro {
                    annotation: TokenStream,
                    annotated: TokenStream)
                    -> TokenStream {
-        let server = ::proc_macro::rustc::Rustc::new(ecx);
+        let server = ::proc_macro_server::Rustc::new(ecx);
         match self.client.run(&EXEC_STRATEGY, server, annotation, annotated) {
             Ok(stream) => stream,
             Err(e) => {
@@ -61,7 +61,7 @@ impl base::ProcMacro for BangProcMacro {
                    span: Span,
                    input: TokenStream)
                    -> TokenStream {
-        let server = ::proc_macro::rustc::Rustc::new(ecx);
+        let server = ::proc_macro_server::Rustc::new(ecx);
         match self.client.run(&EXEC_STRATEGY, server, input) {
             Ok(stream) => stream,
             Err(e) => {

src/libsyntax_ext/proc_macro_server.rs

@@ -8,11 +8,13 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use bridge::{server, TokenTree};
+use errors::{self, Diagnostic, DiagnosticBuilder};
-use {Delimiter, Level, LineColumn, Spacing};
+use std::panic;
+
+use proc_macro::bridge::{server, TokenTree};
+use proc_macro::{Delimiter, Level, LineColumn, Spacing};
 
 use rustc_data_structures::sync::Lrc;
-use rustc_errors::{self as errors, Diagnostic, DiagnosticBuilder};
 use std::ascii;
 use std::ops::Bound;
 use syntax::ast;
@@ -24,7 +26,15 @@ use syntax_pos::hygiene::{SyntaxContext, Transparency};
 use syntax_pos::symbol::{keywords, Symbol};
 use syntax_pos::{BytePos, FileName, MultiSpan, Pos, SourceFile, Span};
 
-impl Delimiter {
+trait FromInternal<T> {
+    fn from_internal(x: T) -> Self;
+}
+
+trait ToInternal<T> {
+    fn to_internal(self) -> T;
+}
+
+impl FromInternal<token::DelimToken> for Delimiter {
     fn from_internal(delim: token::DelimToken) -> Delimiter {
         match delim {
             token::Paren => Delimiter::Parenthesis,
@@ -33,7 +43,9 @@ impl Delimiter {
             token::NoDelim => Delimiter::None,
         }
     }
+}
 
+impl ToInternal<token::DelimToken> for Delimiter {
     fn to_internal(self) -> token::DelimToken {
         match self {
             Delimiter::Parenthesis => token::Paren,
@@ -44,8 +56,10 @@ impl Delimiter {
     }
 }
 
-impl TokenTree<Group, Punct, Ident, Literal> {
+impl FromInternal<(TokenStream, &'_ ParseSess, &'_ mut Vec<Self>)>
-    fn from_internal(stream: TokenStream, sess: &ParseSess, stack: &mut Vec<Self>) -> Self {
+    for TokenTree<Group, Punct, Ident, Literal>
+{
+    fn from_internal((stream, sess, stack): (TokenStream, &ParseSess, &mut Vec<Self>)) -> Self {
         use syntax::parse::token::*;
 
         let (tree, joint) = stream.as_tree();
@@ -204,7 +218,9 @@ impl TokenTree<Group, Punct, Ident, Literal> {
             Whitespace | Comment | Shebang(..) | Eof => unreachable!(),
         }
     }
+}
 
+impl ToInternal<TokenStream> for TokenTree<Group, Punct, Ident, Literal> {
     fn to_internal(self) -> TokenStream {
         use syntax::parse::token::*;
 
@@ -292,13 +308,14 @@ impl TokenTree<Group, Punct, Ident, Literal> {
     }
 }
 
-impl Level {
+impl ToInternal<errors::Level> for Level {
     fn to_internal(self) -> errors::Level {
         match self {
             Level::Error => errors::Level::Error,
             Level::Warning => errors::Level::Warning,
             Level::Note => errors::Level::Note,
             Level::Help => errors::Level::Help,
+            _ => unreachable!("unknown proc_macro::Level variant: {:?}", self),
         }
     }
 }
@@ -339,7 +356,7 @@ pub struct Literal {
     span: Span,
 }
 
-pub struct Rustc<'a> {
+pub(crate) struct Rustc<'a> {
     sess: &'a ParseSess,
     def_site: Span,
     call_site: Span,
@@ -429,7 +446,7 @@ impl server::TokenStreamIter for Rustc<'_> {
         loop {
             let tree = iter.stack.pop().or_else(|| {
                 let next = iter.cursor.next_as_stream()?;
-                Some(TokenTree::from_internal(next, self.sess, &mut iter.stack))
+                Some(TokenTree::from_internal((next, self.sess, &mut iter.stack)))
             })?;
             // HACK: The condition "dummy span + group with empty delimiter" represents an AST
             // fragment approximately converted into a token stream. This may happen, for