From 026baa1c6fb397e9bd2c171d750c939232c13a58 Mon Sep 17 00:00:00 2001
From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date: Tue, 27 May 2025 10:30:47 +0000
Subject: [PATCH] Do not get proc_macro from the sysroot in rustc

With the stage0 refactor the proc_macro version found in the sysroot
will no longer always match the proc_macro version that proc-macros get
compiled with by the rustc executable that uses this proc_macro. This
will cause problems as soon as the ABI of the bridge gets changed to
implement new features or change the way existing features work.

To fix this, this commit changes rustc crates to depend directly on the
local version of proc_macro which will also be used in the sysroot that
rustc will build.
---
 Cargo.lock                                    | 10 +++++++++
 compiler/rustc_builtin_macros/Cargo.toml      |  3 +++
 compiler/rustc_builtin_macros/src/lib.rs      |  4 +---
 compiler/rustc_expand/Cargo.toml              |  3 +++
 compiler/rustc_expand/src/lib.rs              |  2 --
 compiler/rustc_expand/src/proc_macro.rs       |  2 +-
 .../rustc_expand/src/proc_macro_server.rs     | 16 +++++++-------
 compiler/rustc_metadata/Cargo.toml            |  3 +++
 compiler/rustc_metadata/src/creader.rs        |  2 +-
 compiler/rustc_metadata/src/lib.rs            |  2 --
 compiler/rustc_metadata/src/rmeta/decoder.rs  |  2 +-
 compiler/rustc_proc_macro/Cargo.toml          | 21 +++++++++++++++++++
 library/proc_macro/Cargo.toml                 |  4 ++++
 library/proc_macro/src/lib.rs                 |  3 ++-
 src/bootstrap/src/core/build_steps/dist.rs    |  3 ++-
 15 files changed, 60 insertions(+), 20 deletions(-)
 create mode 100644 compiler/rustc_proc_macro/Cargo.toml

diff --git a/Cargo.lock b/Cargo.lock
index 177ff6594e244..67bfcff5f5571 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3444,6 +3444,7 @@ dependencies = [
  "rustc_macros",
  "rustc_parse",
  "rustc_parse_format",
+ "rustc_proc_macro",
  "rustc_session",
  "rustc_span",
  "rustc_target",
@@ -3733,6 +3734,7 @@ dependencies = [
  "rustc_lint_defs",
  "rustc_macros",
  "rustc_parse",
+ "rustc_proc_macro",
  "rustc_serialize",
  "rustc_session",
  "rustc_span",
@@ -4081,6 +4083,7 @@ dependencies = [
  "rustc_index",
  "rustc_macros",
  "rustc_middle",
+ "rustc_proc_macro",
  "rustc_serialize",
  "rustc_session",
  "rustc_span",
@@ -4337,6 +4340,13 @@ dependencies = [
  "tracing",
 ]
 
+[[package]]
+name = "rustc_proc_macro"
+version = "0.0.0"
+dependencies = [
+ "rustc-literal-escaper",
+]
+
 [[package]]
 name = "rustc_query_impl"
 version = "0.0.0"
diff --git a/compiler/rustc_builtin_macros/Cargo.toml b/compiler/rustc_builtin_macros/Cargo.toml
index 5c1ae90f7298f..4c1264c6f1ce1 100644
--- a/compiler/rustc_builtin_macros/Cargo.toml
+++ b/compiler/rustc_builtin_macros/Cargo.toml
@@ -24,6 +24,9 @@ rustc_lint_defs = { path = "../rustc_lint_defs" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_parse = { path = "../rustc_parse" }
 rustc_parse_format = { path = "../rustc_parse_format" }
+# We must use the proc_macro version that we will compile proc-macros against,
+# not the one from our own sysroot.
+rustc_proc_macro = { path = "../rustc_proc_macro" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
 rustc_target = { path = "../rustc_target" }
diff --git a/compiler/rustc_builtin_macros/src/lib.rs b/compiler/rustc_builtin_macros/src/lib.rs
index 9cd4d17059a0f..cd87376fc1ca5 100644
--- a/compiler/rustc_builtin_macros/src/lib.rs
+++ b/compiler/rustc_builtin_macros/src/lib.rs
@@ -20,8 +20,6 @@
 #![recursion_limit = "256"]
 // tidy-alphabetical-end
 
-extern crate proc_macro;
-
 use std::sync::Arc;
 
 use rustc_expand::base::{MacroExpanderFn, ResolverExpand, SyntaxExtensionKind};
@@ -139,7 +137,7 @@ pub fn register_builtin_macros(resolver: &mut dyn ResolverExpand) {
         CoercePointee: coerce_pointee::expand_deriving_coerce_pointee,
     }
 
-    let client = proc_macro::bridge::client::Client::expand1(proc_macro::quote);
+    let client = rustc_proc_macro::bridge::client::Client::expand1(rustc_proc_macro::quote);
     register(sym::quote, SyntaxExtensionKind::Bang(Arc::new(BangProcMacro { client })));
     let requires = SyntaxExtensionKind::Attr(Arc::new(contracts::ExpandRequires));
     register(sym::contracts_requires, requires);
diff --git a/compiler/rustc_expand/Cargo.toml b/compiler/rustc_expand/Cargo.toml
index e8fd2f54d76cb..57dd3a3128df5 100644
--- a/compiler/rustc_expand/Cargo.toml
+++ b/compiler/rustc_expand/Cargo.toml
@@ -23,6 +23,9 @@ rustc_lexer = { path = "../rustc_lexer" }
 rustc_lint_defs = { path = "../rustc_lint_defs" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_parse = { path = "../rustc_parse" }
+# We must use the proc_macro version that we will compile proc-macros against,
+# not the one from our own sysroot.
+rustc_proc_macro = { path = "../rustc_proc_macro" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
diff --git a/compiler/rustc_expand/src/lib.rs b/compiler/rustc_expand/src/lib.rs
index cd744977bb323..35b38d99c7034 100644
--- a/compiler/rustc_expand/src/lib.rs
+++ b/compiler/rustc_expand/src/lib.rs
@@ -14,8 +14,6 @@
 #![feature(yeet_expr)]
 // tidy-alphabetical-end
 
-extern crate proc_macro as pm;
-
 mod build;
 mod errors;
 // FIXME(Nilstrieb) Translate macro_rules diagnostics
diff --git a/compiler/rustc_expand/src/proc_macro.rs b/compiler/rustc_expand/src/proc_macro.rs
index d5af9849e759f..84fbbbef061e3 100644
--- a/compiler/rustc_expand/src/proc_macro.rs
+++ b/compiler/rustc_expand/src/proc_macro.rs
@@ -1,4 +1,3 @@
-use rustc_ast as ast;
 use rustc_ast::ptr::P;
 use rustc_ast::tokenstream::TokenStream;
 use rustc_errors::ErrorGuaranteed;
@@ -6,6 +5,7 @@ use rustc_parse::parser::{ForceCollect, Parser};
 use rustc_session::config::ProcMacroExecutionStrategy;
 use rustc_span::Span;
 use rustc_span::profiling::SpannedEventArgRecorder;
+use {rustc_ast as ast, rustc_proc_macro as pm};
 
 use crate::base::{self, *};
 use crate::{errors, proc_macro_server};
diff --git a/compiler/rustc_expand/src/proc_macro_server.rs b/compiler/rustc_expand/src/proc_macro_server.rs
index f00201ad202af..fb5abaefb570b 100644
--- a/compiler/rustc_expand/src/proc_macro_server.rs
+++ b/compiler/rustc_expand/src/proc_macro_server.rs
@@ -1,10 +1,6 @@
 use std::ops::{Bound, Range};
 
 use ast::token::IdentIsRaw;
-use pm::bridge::{
-    DelimSpan, Diagnostic, ExpnGlobals, Group, Ident, LitKind, Literal, Punct, TokenTree, server,
-};
-use pm::{Delimiter, Level};
 use rustc_ast as ast;
 use rustc_ast::token;
 use rustc_ast::tokenstream::{self, DelimSpacing, Spacing, TokenStream};
@@ -15,6 +11,10 @@ use rustc_errors::{Diag, ErrorGuaranteed, MultiSpan, PResult};
 use rustc_parse::lexer::nfc_normalize;
 use rustc_parse::parser::Parser;
 use rustc_parse::{exp, new_parser_from_source_str, source_str_to_stream, unwrap_or_emit_fatal};
+use rustc_proc_macro::bridge::{
+    DelimSpan, Diagnostic, ExpnGlobals, Group, Ident, LitKind, Literal, Punct, TokenTree, server,
+};
+use rustc_proc_macro::{Delimiter, Level};
 use rustc_session::parse::ParseSess;
 use rustc_span::def_id::CrateNum;
 use rustc_span::{BytePos, FileName, Pos, Span, Symbol, sym};
@@ -66,7 +66,7 @@ impl FromInternal<token::LitKind> for LitKind {
             token::CStr => LitKind::CStr,
             token::CStrRaw(n) => LitKind::CStrRaw(n),
             token::Err(_guar) => {
-                // This is the only place a `pm::bridge::LitKind::ErrWithGuar`
+                // This is the only place a `rustc_proc_macro::bridge::LitKind::ErrWithGuar`
                 // is constructed. Note that an `ErrorGuaranteed` is available,
                 // as required. See the comment in `to_internal`.
                 LitKind::ErrWithGuar
@@ -149,7 +149,7 @@ impl FromInternal<(TokenStream, &mut Rustc<'_, '_>)> for Vec<TokenTree<TokenStre
                     }
 
                     trees.push(TokenTree::Group(Group {
-                        delimiter: pm::Delimiter::from_internal(delim),
+                        delimiter: rustc_proc_macro::Delimiter::from_internal(delim),
                         stream: Some(stream),
                         span: DelimSpan {
                             open: span.open,
@@ -270,7 +270,7 @@ impl FromInternal<(TokenStream, &mut Rustc<'_, '_>)> for Vec<TokenTree<TokenStre
                     let stream =
                         TokenStream::token_alone(token::Lifetime(ident.name, is_raw), ident.span);
                     trees.push(TokenTree::Group(Group {
-                        delimiter: pm::Delimiter::None,
+                        delimiter: rustc_proc_macro::Delimiter::None,
                         stream: Some(stream),
                         span: DelimSpan::from_single(span),
                     }))
@@ -302,7 +302,7 @@ impl FromInternal<(TokenStream, &mut Rustc<'_, '_>)> for Vec<TokenTree<TokenStre
                         trees.push(TokenTree::Punct(Punct { ch: b'!', joint: false, span }));
                     }
                     trees.push(TokenTree::Group(Group {
-                        delimiter: pm::Delimiter::Bracket,
+                        delimiter: rustc_proc_macro::Delimiter::Bracket,
                         stream: Some(stream),
                         span: DelimSpan::from_single(span),
                     }));
diff --git a/compiler/rustc_metadata/Cargo.toml b/compiler/rustc_metadata/Cargo.toml
index cfe412e99d8d5..a163518fd1952 100644
--- a/compiler/rustc_metadata/Cargo.toml
+++ b/compiler/rustc_metadata/Cargo.toml
@@ -23,6 +23,9 @@ rustc_hir_pretty = { path = "../rustc_hir_pretty" }
 rustc_index = { path = "../rustc_index" }
 rustc_macros = { path = "../rustc_macros" }
 rustc_middle = { path = "../rustc_middle" }
+# We must use the proc_macro version that we will compile proc-macros against,
+# not the one from our own sysroot.
+rustc_proc_macro = { path = "../rustc_proc_macro" }
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_session = { path = "../rustc_session" }
 rustc_span = { path = "../rustc_span" }
diff --git a/compiler/rustc_metadata/src/creader.rs b/compiler/rustc_metadata/src/creader.rs
index c7e9a2936f5dd..802d75241dee7 100644
--- a/compiler/rustc_metadata/src/creader.rs
+++ b/compiler/rustc_metadata/src/creader.rs
@@ -7,7 +7,6 @@ use std::str::FromStr;
 use std::time::Duration;
 use std::{cmp, env, iter};
 
-use proc_macro::bridge::client::ProcMacro;
 use rustc_ast::expand::allocator::{AllocatorKind, alloc_error_handler_name, global_fn_name};
 use rustc_ast::{self as ast, *};
 use rustc_data_structures::fx::FxHashSet;
@@ -23,6 +22,7 @@ use rustc_hir::definitions::Definitions;
 use rustc_index::IndexVec;
 use rustc_middle::bug;
 use rustc_middle::ty::{TyCtxt, TyCtxtFeed};
+use rustc_proc_macro::bridge::client::ProcMacro;
 use rustc_session::config::{
     self, CrateType, ExtendedTargetModifierInfo, ExternLocation, OptionsTargetModifiers,
     TargetModifier,
diff --git a/compiler/rustc_metadata/src/lib.rs b/compiler/rustc_metadata/src/lib.rs
index 97b67140fa2d4..389a4ab746625 100644
--- a/compiler/rustc_metadata/src/lib.rs
+++ b/compiler/rustc_metadata/src/lib.rs
@@ -16,8 +16,6 @@
 #![feature(trusted_len)]
 // tidy-alphabetical-end
 
-extern crate proc_macro;
-
 pub use rmeta::provide;
 
 mod dependency_format;
diff --git a/compiler/rustc_metadata/src/rmeta/decoder.rs b/compiler/rustc_metadata/src/rmeta/decoder.rs
index 2e4352ca532aa..1dae858b7ef1a 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder.rs
@@ -6,7 +6,6 @@ use std::sync::{Arc, OnceLock};
 use std::{io, iter, mem};
 
 pub(super) use cstore_impl::provide;
-use proc_macro::bridge::client::ProcMacro;
 use rustc_ast as ast;
 use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::fx::FxIndexMap;
@@ -26,6 +25,7 @@ use rustc_middle::mir::interpret::{AllocDecodingSession, AllocDecodingState};
 use rustc_middle::ty::Visibility;
 use rustc_middle::ty::codec::TyDecoder;
 use rustc_middle::{bug, implement_ty_decoder};
+use rustc_proc_macro::bridge::client::ProcMacro;
 use rustc_serialize::opaque::MemDecoder;
 use rustc_serialize::{Decodable, Decoder};
 use rustc_session::Session;
diff --git a/compiler/rustc_proc_macro/Cargo.toml b/compiler/rustc_proc_macro/Cargo.toml
new file mode 100644
index 0000000000000..4a7c0d78ede81
--- /dev/null
+++ b/compiler/rustc_proc_macro/Cargo.toml
@@ -0,0 +1,21 @@
+# We need to use a separate crate including library/proc_macro as opposed to a
+# direct path dependency on library/proc_macro because doing the latter will
+# cause two copies of libproc_macro.rlib to end up in the sysroot, breaking
+# proc-macro crates. In addition it confuses the workspace_members function of
+# bootstrap.
+
+[package]
+name = "rustc_proc_macro"
+version = "0.0.0"
+edition = "2024"
+
+[lib]
+path = "../../library/proc_macro/src/lib.rs"
+test = false
+doctest = false
+
+[dependencies]
+rustc-literal-escaper = "0.0.2"
+
+[features]
+rustc-dep-of-std = []
diff --git a/library/proc_macro/Cargo.toml b/library/proc_macro/Cargo.toml
index b8bc2a3af4cd4..1d79246356a35 100644
--- a/library/proc_macro/Cargo.toml
+++ b/library/proc_macro/Cargo.toml
@@ -10,3 +10,7 @@ std = { path = "../std" }
 # loaded from sysroot causing duplicate lang items and other similar errors.
 core = { path = "../core" }
 rustc-literal-escaper = { version = "0.0.2", features = ["rustc-dep-of-std"] }
+
+[features]
+default = ["rustc-dep-of-std"]
+rustc-dep-of-std = []
diff --git a/library/proc_macro/src/lib.rs b/library/proc_macro/src/lib.rs
index b4fd20c0c176a..32c306be94ecd 100644
--- a/library/proc_macro/src/lib.rs
+++ b/library/proc_macro/src/lib.rs
@@ -32,6 +32,7 @@
 #![recursion_limit = "256"]
 #![allow(internal_features)]
 #![deny(ffi_unwind_calls)]
+#![allow(rustc::internal)] // Can't use FxHashMap when compiled as part of the standard library
 #![warn(rustdoc::unescaped_backticks)]
 #![warn(unreachable_pub)]
 #![deny(unsafe_op_in_unsafe_fn)]
@@ -95,7 +96,7 @@ pub fn is_available() -> bool {
 ///
 /// This is both the input and output of `#[proc_macro]`, `#[proc_macro_attribute]`
 /// and `#[proc_macro_derive]` definitions.
-#[rustc_diagnostic_item = "TokenStream"]
+#[cfg_attr(feature = "rustc-dep-of-std", rustc_diagnostic_item = "TokenStream")]
 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 #[derive(Clone)]
 pub struct TokenStream(Option<bridge::client::TokenStream>);
diff --git a/src/bootstrap/src/core/build_steps/dist.rs b/src/bootstrap/src/core/build_steps/dist.rs
index 253fa224152cc..bbc0b4df9dfb5 100644
--- a/src/bootstrap/src/core/build_steps/dist.rs
+++ b/src/bootstrap/src/core/build_steps/dist.rs
@@ -776,7 +776,8 @@ impl Step for RustcDev {
         copy_src_dirs(
             builder,
             &builder.src,
-            &["compiler"],
+            // The compiler has a path dependency on proc_macro, so make sure to include it.
+            &["compiler", "library/proc_macro"],
             &[],
             &tarball.image_dir().join("lib/rustlib/rustc-src/rust"),
         );