resolve: Preserve ambiguous glob reexports in crate metadata

So in cross-crate scenarios they can work in the same way as in crate-local scenarios.

Author: petrochenkov

compiler/rustc_metadata/src/lib.rs

@@ -11,6 +11,7 @@
 #![feature(min_specialization)]
 #![feature(never_type)]
 #![feature(proc_macro_internals)]
+#![feature(result_option_map_or_default)]
 #![feature(rustdoc_internals)]
 #![feature(trusted_len)]
 // tidy-alphabetical-end

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -1308,6 +1308,21 @@ impl<'a> CrateMetadataRef<'a> {
         }
     }
 
+    fn get_ambig_module_children(
+        self,
+        id: DefIndex,
+        sess: &Session,
+    ) -> impl Iterator<Item = AmbigModChild> {
+        gen move {
+            let children = self.root.tables.ambig_module_children.get(self, id);
+            if !children.is_default() {
+                for child in children.decode((self, sess)) {
+                    yield child;
+                }
+            }
+        }
+    }
+
     fn is_ctfe_mir_available(self, id: DefIndex) -> bool {
         self.root.tables.mir_for_ctfe.get(self, id).is_some()
     }

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -8,7 +8,7 @@ use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, LOCAL_CRATE};
 use rustc_hir::definitions::{DefKey, DefPath, DefPathHash};
 use rustc_middle::arena::ArenaAllocatable;
 use rustc_middle::bug;
-use rustc_middle::metadata::ModChild;
+use rustc_middle::metadata::{AmbigModChild, ModChild};
 use rustc_middle::middle::exported_symbols::ExportedSymbol;
 use rustc_middle::middle::stability::DeprecationEntry;
 use rustc_middle::query::{ExternProviders, LocalCrate};
@@ -582,6 +582,14 @@ impl CStore {
         self.get_crate_data(def_id.krate).get_expn_that_defined(def_id.index, sess)
     }
 
+    pub fn ambig_module_children_untracked(
+        &self,
+        def_id: DefId,
+        sess: &Session,
+    ) -> impl Iterator<Item = AmbigModChild> {
+        self.get_crate_data(def_id.krate).get_ambig_module_children(def_id.index, sess)
+    }
+
     /// Only public-facing way to traverse all the definitions in a non-local crate.
     /// Critically useful for this third-party project: <https://github.com/hacspec/hacspec>.
     /// See <https://github.com/rust-lang/rust/pull/85889> for context.

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1705,6 +1705,14 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
 
             record_defaulted_array!(self.tables.module_children_reexports[def_id] <-
                 module_children.iter().filter(|child| !child.reexport_chain.is_empty()));
+
+            let ambig_module_children = tcx
+                .resolutions(())
+                .ambig_module_children
+                .get(&local_def_id)
+                .map_or_default(|v| &v[..]);
+            record_defaulted_array!(self.tables.ambig_module_children[def_id] <-
+                ambig_module_children);
         }
     }
 

compiler/rustc_metadata/src/rmeta/mod.rs

@@ -21,7 +21,7 @@ use rustc_index::bit_set::DenseBitSet;
 use rustc_macros::{
     Decodable, Encodable, MetadataDecodable, MetadataEncodable, TyDecodable, TyEncodable,
 };
-use rustc_middle::metadata::ModChild;
+use rustc_middle::metadata::{AmbigModChild, ModChild};
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs;
 use rustc_middle::middle::debugger_visualizer::DebuggerVisualizerFile;
 use rustc_middle::middle::deduced_param_attrs::DeducedParamAttrs;
@@ -398,6 +398,7 @@ define_tables! {
     // That's why the encoded list needs to contain `ModChild` structures describing all the names
     // individually instead of `DefId`s.
     module_children_reexports: Table<DefIndex, LazyArray<ModChild>>,
+    ambig_module_children: Table<DefIndex, LazyArray<AmbigModChild>>,
     cross_crate_inlinable: Table<DefIndex, bool>,
 
 - optional:

compiler/rustc_metadata/src/rmeta/parameterized.rs

@@ -94,6 +94,7 @@ trivially_parameterized_over_tcx! {
     rustc_hir::def_id::DefIndex,
     rustc_hir::definitions::DefKey,
     rustc_index::bit_set::DenseBitSet<u32>,
+    rustc_middle::metadata::AmbigModChild,
     rustc_middle::metadata::ModChild,
     rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs,
     rustc_middle::middle::debugger_visualizer::DebuggerVisualizerFile,

compiler/rustc_middle/src/metadata.rs

@@ -44,3 +44,18 @@ pub struct ModChild {
     /// Empty if the module child is a proper item.
     pub reexport_chain: SmallVec<[Reexport; 2]>,
 }
+
+#[derive(Debug, TyEncodable, TyDecodable, HashStable)]
+pub enum AmbigModChildKind {
+    GlobVsGlob,
+    GlobVsExpanded,
+}
+
+/// Same as `ModChild`, however, it includes ambiguity error.
+#[derive(Debug, TyEncodable, TyDecodable, HashStable)]
+pub struct AmbigModChild {
+    pub main: ModChild,
+    pub second: ModChild,
+    pub kind: AmbigModChildKind,
+    pub warn_ambiguity: bool,
+}

compiler/rustc_middle/src/ty/mod.rs

@@ -110,7 +110,7 @@ pub use self::typeck_results::{
     Rust2024IncompatiblePatInfo, TypeckResults, UserType, UserTypeAnnotationIndex, UserTypeKind,
 };
 use crate::error::{OpaqueHiddenTypeMismatch, TypeMismatchReason};
-use crate::metadata::ModChild;
+use crate::metadata::{AmbigModChild, ModChild};
 use crate::middle::privacy::EffectiveVisibilities;
 use crate::mir::{Body, CoroutineLayout, CoroutineSavedLocal, SourceInfo};
 use crate::query::{IntoQueryParam, Providers};
@@ -175,6 +175,7 @@ pub struct ResolverGlobalCtxt {
     pub extern_crate_map: UnordMap<LocalDefId, CrateNum>,
     pub maybe_unused_trait_imports: FxIndexSet<LocalDefId>,
     pub module_children: LocalDefIdMap<Vec<ModChild>>,
+    pub ambig_module_children: LocalDefIdMap<Vec<AmbigModChild>>,
     pub glob_map: FxIndexMap<LocalDefId, FxIndexSet<Symbol>>,
     pub main_def: Option<MainDefinition>,
     pub trait_impls: FxIndexMap<DefId, Vec<LocalDefId>>,

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -22,7 +22,7 @@ use rustc_hir::def::{self, *};
 use rustc_hir::def_id::{CRATE_DEF_ID, DefId, LocalDefId};
 use rustc_index::bit_set::DenseBitSet;
 use rustc_metadata::creader::LoadedMacro;
-use rustc_middle::metadata::ModChild;
+use rustc_middle::metadata::{AmbigModChildKind, ModChild};
 use rustc_middle::ty::{Feed, Visibility};
 use rustc_middle::{bug, span_bug};
 use rustc_span::hygiene::{ExpnId, LocalExpnId, MacroKind};
@@ -36,9 +36,9 @@ use crate::imports::{ImportData, ImportKind};
 use crate::macros::{MacroRulesBinding, MacroRulesScope, MacroRulesScopeRef};
 use crate::ref_mut::CmCell;
 use crate::{
-    BindingKey, ExternPreludeEntry, Finalize, MacroData, Module, ModuleKind, ModuleOrUniformRoot,
-    NameBinding, ParentScope, PathResult, ResolutionError, Resolver, Segment, Used,
-    VisResolutionError, errors,
+    AmbiguityKind, BindingKey, ExternPreludeEntry, Finalize, MacroData, Module, ModuleKind,
+    ModuleOrUniformRoot, NameBinding, NameBindingData, NameBindingKind, ParentScope, PathResult,
+    ResolutionError, Resolver, Segment, Used, VisResolutionError, errors,
 };
 
 type Res = def::Res<NodeId>;
@@ -81,9 +81,18 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         res: Res,
         vis: Visibility<DefId>,
         span: Span,
-        expn_id: LocalExpnId,
+        expansion: LocalExpnId,
+        ambiguity: Option<(NameBinding<'ra>, AmbiguityKind)>,
+        warn_ambiguity: bool,
     ) {
-        let binding = self.arenas.new_res_binding(res, vis, span, expn_id);
+        let binding = self.arenas.alloc_name_binding(NameBindingData {
+            kind: NameBindingKind::Res(res),
+            ambiguity,
+            warn_ambiguity,
+            vis,
+            span,
+            expansion,
+        });
         // Even if underscore names cannot be looked up, we still need to add them to modules,
         // because they can be fetched by glob imports from those modules, and bring traits
         // into scope both directly and through glob imports.
@@ -232,9 +241,22 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
     }
 
     pub(crate) fn build_reduced_graph_external(&self, module: Module<'ra>) {
-        for (i, child) in self.tcx.module_children(module.def_id()).into_iter().enumerate() {
-            let parent_scope = ParentScope::module(module, self.arenas);
-            self.build_reduced_graph_for_external_crate_res(child, parent_scope, i)
+        let def_id = module.def_id();
+        let children = self.tcx.module_children(def_id);
+        let parent_scope = ParentScope::module(module, self.arenas);
+        for (i, child) in self.tcx.module_children(def_id).iter().enumerate() {
+            self.build_reduced_graph_for_external_crate_res(child, parent_scope, i, None, false)
+        }
+        for (i, child) in
+            self.cstore().ambig_module_children_untracked(def_id, self.tcx.sess).enumerate()
+        {
+            self.build_reduced_graph_for_external_crate_res(
+                &child.main,
+                parent_scope,
+                children.len() + i,
+                Some((&child.second, child.kind)),
+                child.warn_ambiguity,
+            )
         }
     }
 
@@ -244,6 +266,8 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         child: &ModChild,
         parent_scope: ParentScope<'ra>,
         child_index: usize,
+        ambig_child: Option<(&ModChild, AmbigModChildKind)>,
+        warn_ambiguity: bool,
     ) {
         let parent = parent_scope.module;
         let ModChild { ident, res, vis, ref reexport_chain } = *child;
@@ -255,6 +279,21 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         );
         let res = res.expect_non_local();
         let expansion = parent_scope.expansion;
+        let ambig = ambig_child.map(|(ambig_child, ambig_kind)| {
+            let ModChild { ident: _, res, vis, ref reexport_chain } = *ambig_child;
+            let span = self.def_span(
+                reexport_chain
+                    .first()
+                    .and_then(|reexport| reexport.id())
+                    .unwrap_or_else(|| res.def_id()),
+            );
+            let res = res.expect_non_local();
+            let ambig_kind = match ambig_kind {
+                AmbigModChildKind::GlobVsGlob => AmbiguityKind::GlobVsGlob,
+                AmbigModChildKind::GlobVsExpanded => AmbiguityKind::GlobVsExpanded,
+            };
+            (self.arenas.new_res_binding(res, vis, span, expansion), ambig_kind)
+        });
         // Record primary definitions.
         match res {
             Res::Def(
@@ -272,9 +311,18 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 _,
             )
             | Res::PrimTy(..)
-            | Res::ToolMod => {
-                self.define_extern(parent, ident, TypeNS, child_index, res, vis, span, expansion)
-            }
+            | Res::ToolMod => self.define_extern(
+                parent,
+                ident,
+                TypeNS,
+                child_index,
+                res,
+                vis,
+                span,
+                expansion,
+                ambig,
+                warn_ambiguity,
+            ),
             Res::Def(
                 DefKind::Fn
                 | DefKind::AssocFn
@@ -283,10 +331,30 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 | DefKind::AssocConst
                 | DefKind::Ctor(..),
                 _,
-            ) => self.define_extern(parent, ident, ValueNS, child_index, res, vis, span, expansion),
-            Res::Def(DefKind::Macro(..), _) | Res::NonMacroAttr(..) => {
-                self.define_extern(parent, ident, MacroNS, child_index, res, vis, span, expansion)
-            }
+            ) => self.define_extern(
+                parent,
+                ident,
+                ValueNS,
+                child_index,
+                res,
+                vis,
+                span,
+                expansion,
+                ambig,
+                warn_ambiguity,
+            ),
+            Res::Def(DefKind::Macro(..), _) | Res::NonMacroAttr(..) => self.define_extern(
+                parent,
+                ident,
+                MacroNS,
+                child_index,
+                res,
+                vis,
+                span,
+                expansion,
+                ambig,
+                warn_ambiguity,
+            ),
             Res::Def(
                 DefKind::TyParam
                 | DefKind::ConstParam

compiler/rustc_resolve/src/diagnostics.rs

@@ -145,12 +145,13 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
         for ambiguity_error in &self.ambiguity_errors {
             let diag = self.ambiguity_diagnostics(ambiguity_error);
             if ambiguity_error.warning {
-                let NameBindingKind::Import { import, .. } = ambiguity_error.b1.0.kind else {
-                    unreachable!()
+                let node_id = match ambiguity_error.b1.0.kind {
+                    NameBindingKind::Import { import, .. } => import.root_id,
+                    NameBindingKind::Res(_) => CRATE_NODE_ID,
                 };
                 self.lint_buffer.buffer_lint(
                     AMBIGUOUS_GLOB_IMPORTS,
-                    import.root_id,
+                    node_id,
                     ambiguity_error.ident.span,
                     BuiltinLintDiag::AmbiguousGlobImports { diag },
                 );