Add hook for overriding compiler builtin macros

Cargo.lock

@@ -4222,6 +4222,7 @@ dependencies = [
  "rustc_data_structures",
  "rustc_error_messages",
  "rustc_errors",
+ "rustc_expand",
  "rustc_feature",
  "rustc_fluent_macro",
  "rustc_graphviz",

compiler/rustc_const_eval/src/lib.rs

@@ -40,6 +40,7 @@ pub fn provide(providers: &mut Providers) {
     providers.eval_to_allocation_raw = const_eval::eval_to_allocation_raw_provider;
     providers.eval_static_initializer = const_eval::eval_static_initializer_provider;
     providers.hooks.const_caller_location = util::caller_location::const_caller_location_provider;
+    providers.hooks.after_register_builtin_macros = |_, _| {};
     providers.eval_to_valtree = |tcx, ty::PseudoCanonicalInput { typing_env, value }| {
         const_eval::eval_to_valtree(tcx, typing_env, value)
     };

compiler/rustc_expand/src/base.rs

@@ -1,5 +1,6 @@
 use std::any::Any;
 use std::default::Default;
+use std::fmt::Debug;
 use std::iter;
 use std::path::Component::Prefix;
 use std::path::{Path, PathBuf};
@@ -1090,7 +1091,7 @@ pub struct DeriveResolution {
     pub is_const: bool,
 }
 
-pub trait ResolverExpand {
+pub trait ResolverExpand: Debug {
     fn next_node_id(&mut self) -> NodeId;
     fn invocation_parent(&self, id: LocalExpnId) -> LocalDefId;
 
@@ -1101,6 +1102,7 @@ pub trait ResolverExpand {
         fragment: &AstFragment,
     );
     fn register_builtin_macro(&mut self, name: Symbol, ext: SyntaxExtensionKind);
+    fn override_builtin_macro(&mut self, name: Symbol, ext: SyntaxExtensionKind);
 
     fn expansion_for_ast_pass(
         &mut self,

compiler/rustc_interface/src/passes.rs

@@ -140,6 +140,7 @@ fn configure_and_expand(
         crate_name,
     );
     rustc_builtin_macros::register_builtin_macros(resolver);
+    tcx.after_register_builtin_macros(resolver);
 
     let num_standard_library_imports = sess.time("crate_injection", || {
         rustc_builtin_macros::standard_library_imports::inject(

compiler/rustc_middle/Cargo.toml

@@ -17,6 +17,7 @@ rustc_ast_ir = { path = "../rustc_ast_ir" }
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_error_messages = { path = "../rustc_error_messages" } # Used for intra-doc links
 rustc_errors = { path = "../rustc_errors" }
+rustc_expand = { path = "../rustc_expand" }
 rustc_feature = { path = "../rustc_feature" }
 rustc_fluent_macro = { path = "../rustc_fluent_macro" }
 rustc_graphviz = { path = "../rustc_graphviz" }

compiler/rustc_middle/src/hooks/mod.rs

@@ -88,6 +88,8 @@ declare_hooks! {
 
     hook alloc_self_profile_query_strings() -> ();
 
+    hook after_register_builtin_macros(resolver: &mut dyn rustc_expand::base::ResolverExpand) -> ();
+
     /// Saves and writes the DepGraph to the file system.
     ///
     /// This function saves both the dep-graph and the query result cache,

compiler/rustc_resolve/src/lib.rs

@@ -1280,6 +1280,12 @@ pub struct Resolver<'ra, 'tcx> {
     impl_trait_names: FxHashMap<NodeId, Symbol>,
 }
 
+impl std::fmt::Debug for Resolver<'_, '_> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("Resolver").finish_non_exhaustive()
+    }
+}
+
 /// This provides memory for the rest of the crate. The `'ra` lifetime that is
 /// used by many types in this crate is an abbreviation of `ResolverArenas`.
 #[derive(Default)]

compiler/rustc_resolve/src/macros.rs

@@ -203,6 +203,10 @@ impl<'ra, 'tcx> ResolverExpand for Resolver<'ra, 'tcx> {
         }
     }
 
+    fn override_builtin_macro(&mut self, name: Symbol, ext: SyntaxExtensionKind) {
+        self.builtin_macros.insert(name, ext);
+    }
+
     // Create a new Expansion with a definition site of the provided module, or
     // a fake empty `#[no_implicit_prelude]` module if no module is provided.
     fn expansion_for_ast_pass(