Auto merge of #113099 - bvanjoi:fix-112713-2, r=petrochenkov

fix(resolve): update the ambiguity glob binding as warning recursively

Fixes #47525
Fixes #56593, but `issue-56593-2.rs` is not fixed to ensure backward compatibility.
Fixes #98467
Fixes #105235
Fixes #112713

This PR had added a field called `warn_ambiguous` in `NameBinding` which is only for back compatibly reason and used for lint.

More details: https://github.com/rust-lang/rust/pull/112743

r? `@petrochenkov`

9 files changed, 256 insertions, 46 deletions

diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index aa213cd0720..2181bd526eb 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -1871,6 +1871,22 @@ pub fn add_elided_lifetime_in_path_suggestion(
     });
 }
 
+pub fn report_ambiguity_error<'a, G: EmissionGuarantee>(
+    db: &mut DiagnosticBuilder<'a, G>,
+    ambiguity: rustc_lint_defs::AmbiguityErrorDiag,
+) {
+    db.span_label(ambiguity.label_span, ambiguity.label_msg);
+    db.note(ambiguity.note_msg);
+    db.span_note(ambiguity.b1_span, ambiguity.b1_note_msg);
+    for help_msg in ambiguity.b1_help_msgs {
+        db.help(help_msg);
+    }
+    db.span_note(ambiguity.b2_span, ambiguity.b2_note_msg);
+    for help_msg in ambiguity.b2_help_msgs {
+        db.help(help_msg);
+    }
+}
+
 #[derive(Clone, Copy, PartialEq, Hash, Debug)]
 pub enum TerminalUrl {
     No,
diff --git a/compiler/rustc_lint/src/context.rs b/compiler/rustc_lint/src/context.rs
index 65c56bff841..f7e56b30553 100644
--- a/compiler/rustc_lint/src/context.rs
+++ b/compiler/rustc_lint/src/context.rs
@@ -946,6 +946,9 @@ pub trait LintContext: Sized {
                         Applicability::MachineApplicable,
                     );
                 }
+                BuiltinLintDiagnostics::AmbiguousGlobImports { diag } => {
+                    rustc_errors::report_ambiguity_error(db, diag);
+                }
                 BuiltinLintDiagnostics::AmbiguousGlobReexports { name, namespace, first_reexport_span, duplicate_reexport_span } => {
                     db.span_label(first_reexport_span, format!("the name `{name}` in the {namespace} namespace is first re-exported here"));
                     db.span_label(duplicate_reexport_span, format!("but the name `{name}` in the {namespace} namespace is also re-exported here"));
diff --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs
index f1765d653b0..7e3b6e9e218 100644
--- a/compiler/rustc_lint_defs/src/builtin.rs
+++ b/compiler/rustc_lint_defs/src/builtin.rs
@@ -3316,6 +3316,7 @@ declare_lint_pass! {
         // tidy-alphabetical-start
         ABSOLUTE_PATHS_NOT_STARTING_WITH_CRATE,
         AMBIGUOUS_ASSOCIATED_ITEMS,
+        AMBIGUOUS_GLOB_IMPORTS,
         AMBIGUOUS_GLOB_REEXPORTS,
         ARITHMETIC_OVERFLOW,
         ASM_SUB_REGISTER,
@@ -4405,3 +4406,46 @@ declare_lint! {
     Warn,
     "unrecognized diagnostic attribute"
 }
+
+declare_lint! {
+    /// The `ambiguous_glob_imports` lint detects glob imports that should report ambiguity
+    /// errors, but previously didn't do that due to rustc bugs.
+    ///
+    /// ### Example
+    ///
+    /// ```rust,compile_fail
+    ///
+    /// #![deny(ambiguous_glob_imports)]
+    /// pub fn foo() -> u32 {
+    ///     use sub::*;
+    ///     C
+    /// }
+    ///
+    /// mod sub {
+    ///     mod mod1 { pub const C: u32 = 1; }
+    ///     mod mod2 { pub const C: u32 = 2; }
+    ///
+    ///     pub use mod1::*;
+    ///     pub use mod2::*;
+    /// }
+    /// ```
+    ///
+    /// {{produces}}
+    ///
+    /// ### Explanation
+    ///
+    /// Previous versions of Rust compile it successfully because it
+    /// had lost the ambiguity error when resolve `use sub::mod2::*`.
+    ///
+    /// This is a [future-incompatible] lint to transition this to a
+    /// hard error in the future.
+    ///
+    /// [future-incompatible]: ../index.md#future-incompatible-lints
+    pub AMBIGUOUS_GLOB_IMPORTS,
+    Warn,
+    "detects certain glob imports that require reporting an ambiguity error",
+    @future_incompatible = FutureIncompatibleInfo {
+        reason: FutureIncompatibilityReason::FutureReleaseError,
+        reference: "issue #114095 <https://github.com/rust-lang/rust/issues/114095>",
+    };
+}
diff --git a/compiler/rustc_lint_defs/src/lib.rs b/compiler/rustc_lint_defs/src/lib.rs
index 10ebe29dfce..f350957f72f 100644
--- a/compiler/rustc_lint_defs/src/lib.rs
+++ b/compiler/rustc_lint_defs/src/lib.rs
@@ -467,6 +467,21 @@ impl<HCX> ToStableHashKey<HCX> for LintId {
     }
 }
 
+#[derive(Debug)]
+pub struct AmbiguityErrorDiag {
+    pub msg: String,
+    pub span: Span,
+    pub label_span: Span,
+    pub label_msg: String,
+    pub note_msg: String,
+    pub b1_span: Span,
+    pub b1_note_msg: String,
+    pub b1_help_msgs: Vec<String>,
+    pub b2_span: Span,
+    pub b2_note_msg: String,
+    pub b2_help_msgs: Vec<String>,
+}
+
 // This could be a closure, but then implementing derive trait
 // becomes hacky (and it gets allocated).
 #[derive(Debug)]
@@ -530,6 +545,9 @@ pub enum BuiltinLintDiagnostics {
         vis_span: Span,
         ident_span: Span,
     },
+    AmbiguousGlobImports {
+        diag: AmbiguityErrorDiag,
+    },
     AmbiguousGlobReexports {
         /// The name for which collision(s) have occurred.
         name: String,
diff --git a/compiler/rustc_resolve/src/build_reduced_graph.rs b/compiler/rustc_resolve/src/build_reduced_graph.rs
index ff63e4e33cb..5814e3d6c13 100644
--- a/compiler/rustc_resolve/src/build_reduced_graph.rs
+++ b/compiler/rustc_resolve/src/build_reduced_graph.rs
@@ -41,6 +41,7 @@ impl<'a, Id: Into<DefId>> ToNameBinding<'a>
         arenas.alloc_name_binding(NameBindingData {
             kind: NameBindingKind::Module(self.0),
             ambiguity: None,
+            warn_ambiguity: false,
             vis: self.1.to_def_id(),
             span: self.2,
             expansion: self.3,
@@ -53,6 +54,7 @@ impl<'a, Id: Into<DefId>> ToNameBinding<'a> for (Res, ty::Visibility<Id>, Span,
         arenas.alloc_name_binding(NameBindingData {
             kind: NameBindingKind::Res(self.0),
             ambiguity: None,
+            warn_ambiguity: false,
             vis: self.1.to_def_id(),
             span: self.2,
             expansion: self.3,
@@ -69,7 +71,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
     {
         let binding = def.to_name_binding(self.arenas);
         let key = self.new_disambiguated_key(ident, ns);
-        if let Err(old_binding) = self.try_define(parent, key, binding) {
+        if let Err(old_binding) = self.try_define(parent, key, binding, false) {
             self.report_conflict(parent, ident, ns, old_binding, binding);
         }
     }
diff --git a/compiler/rustc_resolve/src/diagnostics.rs b/compiler/rustc_resolve/src/diagnostics.rs
index 73cd596c076..97ac6891d82 100644
--- a/compiler/rustc_resolve/src/diagnostics.rs
+++ b/compiler/rustc_resolve/src/diagnostics.rs
@@ -5,10 +5,8 @@ use rustc_ast::{self as ast, Crate, ItemKind, ModKind, NodeId, Path, CRATE_NODE_
 use rustc_ast::{MetaItemKind, NestedMetaItem};
 use rustc_ast_pretty::pprust;
 use rustc_data_structures::fx::FxHashSet;
-use rustc_errors::{
-    pluralize, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan,
-};
-use rustc_errors::{struct_span_err, SuggestionStyle};
+use rustc_errors::{pluralize, report_ambiguity_error, struct_span_err, SuggestionStyle};
+use rustc_errors::{Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed, MultiSpan};
 use rustc_feature::BUILTIN_ATTRIBUTES;
 use rustc_hir::def::Namespace::{self, *};
 use rustc_hir::def::{self, CtorKind, CtorOf, DefKind, NonMacroAttrKind, PerNS};
@@ -17,8 +15,9 @@ use rustc_hir::PrimTy;
 use rustc_middle::bug;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::lint::builtin::ABSOLUTE_PATHS_NOT_STARTING_WITH_CRATE;
+use rustc_session::lint::builtin::AMBIGUOUS_GLOB_IMPORTS;
 use rustc_session::lint::builtin::MACRO_EXPANDED_MACRO_EXPORTS_ACCESSED_BY_ABSOLUTE_PATHS;
-use rustc_session::lint::BuiltinLintDiagnostics;
+use rustc_session::lint::{AmbiguityErrorDiag, BuiltinLintDiagnostics};
 use rustc_session::Session;
 use rustc_span::edit_distance::find_best_match_for_name;
 use rustc_span::edition::Edition;
@@ -135,7 +134,23 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         }
 
         for ambiguity_error in &self.ambiguity_errors {
-            self.report_ambiguity_error(ambiguity_error);
+            let diag = self.ambiguity_diagnostics(ambiguity_error);
+            if ambiguity_error.warning {
+                let NameBindingKind::Import { import, .. } = ambiguity_error.b1.0.kind else {
+                    unreachable!()
+                };
+                self.lint_buffer.buffer_lint_with_diagnostic(
+                    AMBIGUOUS_GLOB_IMPORTS,
+                    import.root_id,
+                    ambiguity_error.ident.span,
+                    diag.msg.to_string(),
+                    BuiltinLintDiagnostics::AmbiguousGlobImports { diag },
+                );
+            } else {
+                let mut err = struct_span_err!(self.tcx.sess, diag.span, E0659, "{}", &diag.msg);
+                report_ambiguity_error(&mut err, diag);
+                err.emit();
+            }
         }
 
         let mut reported_spans = FxHashSet::default();
@@ -1540,20 +1555,15 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         }
     }
 
-    fn report_ambiguity_error(&self, ambiguity_error: &AmbiguityError<'_>) {
-        let AmbiguityError { kind, ident, b1, b2, misc1, misc2 } = *ambiguity_error;
+    fn ambiguity_diagnostics(&self, ambiguity_error: &AmbiguityError<'_>) -> AmbiguityErrorDiag {
+        let AmbiguityError { kind, ident, b1, b2, misc1, misc2, .. } = *ambiguity_error;
         let (b1, b2, misc1, misc2, swapped) = if b2.span.is_dummy() && !b1.span.is_dummy() {
             // We have to print the span-less alternative first, otherwise formatting looks bad.
             (b2, b1, misc2, misc1, true)
         } else {
             (b1, b2, misc1, misc2, false)
         };
-
-        let mut err = struct_span_err!(self.tcx.sess, ident.span, E0659, "`{ident}` is ambiguous");
-        err.span_label(ident.span, "ambiguous name");
-        err.note(format!("ambiguous because of {}", kind.descr()));
-
-        let mut could_refer_to = |b: NameBinding<'_>, misc: AmbiguityErrorMisc, also: &str| {
+        let could_refer_to = |b: NameBinding<'_>, misc: AmbiguityErrorMisc, also: &str| {
             let what = self.binding_description(b, ident, misc == AmbiguityErrorMisc::FromPrelude);
             let note_msg = format!("`{ident}` could{also} refer to {what}");
 
@@ -1579,16 +1589,35 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 AmbiguityErrorMisc::FromPrelude | AmbiguityErrorMisc::None => {}
             }
 
-            err.span_note(b.span, note_msg);
-            for (i, help_msg) in help_msgs.iter().enumerate() {
-                let or = if i == 0 { "" } else { "or " };
-                err.help(format!("{}{}", or, help_msg));
-            }
+            (
+                b.span,
+                note_msg,
+                help_msgs
+                    .iter()
+                    .enumerate()
+                    .map(|(i, help_msg)| {
+                        let or = if i == 0 { "" } else { "or " };
+                        format!("{}{}", or, help_msg)
+                    })
+                    .collect::<Vec<_>>(),
+            )
         };
-
-        could_refer_to(b1, misc1, "");
-        could_refer_to(b2, misc2, " also");
-        err.emit();
+        let (b1_span, b1_note_msg, b1_help_msgs) = could_refer_to(b1, misc1, "");
+        let (b2_span, b2_note_msg, b2_help_msgs) = could_refer_to(b2, misc2, " also");
+
+        AmbiguityErrorDiag {
+            msg: format!("`{ident}` is ambiguous"),
+            span: ident.span,
+            label_span: ident.span,
+            label_msg: "ambiguous name".to_string(),
+            note_msg: format!("ambiguous because of {}", kind.descr()),
+            b1_span,
+            b1_note_msg,
+            b1_help_msgs,
+            b2_span,
+            b2_note_msg,
+            b2_help_msgs,
+        }
     }
 
     /// If the binding refers to a tuple struct constructor with fields,
diff --git a/compiler/rustc_resolve/src/ident.rs b/compiler/rustc_resolve/src/ident.rs
index de431444769..00282df700b 100644
--- a/compiler/rustc_resolve/src/ident.rs
+++ b/compiler/rustc_resolve/src/ident.rs
@@ -677,6 +677,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                                         ident: orig_ident,
                                         b1: innermost_binding,
                                         b2: binding,
+                                        warning: false,
                                         misc1: misc(innermost_flags),
                                         misc2: misc(flags),
                                     });
@@ -905,6 +906,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     ident,
                     b1: binding,
                     b2: shadowed_glob,
+                    warning: false,
                     misc1: AmbiguityErrorMisc::None,
                     misc2: AmbiguityErrorMisc::None,
                 });
diff --git a/compiler/rustc_resolve/src/imports.rs b/compiler/rustc_resolve/src/imports.rs
index f3cf61c5b93..e1dae57d34f 100644
--- a/compiler/rustc_resolve/src/imports.rs
+++ b/compiler/rustc_resolve/src/imports.rs
@@ -284,6 +284,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         self.arenas.alloc_name_binding(NameBindingData {
             kind: NameBindingKind::Import { binding, import, used: Cell::new(false) },
             ambiguity: None,
+            warn_ambiguity: false,
             span: import.span,
             vis,
             expansion: import.parent_scope.expansion,
@@ -291,16 +292,18 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
     }
 
     /// Define the name or return the existing binding if there is a collision.
+    /// `update` indicates if the definition is a redefinition of an existing binding.
     pub(crate) fn try_define(
         &mut self,
         module: Module<'a>,
         key: BindingKey,
         binding: NameBinding<'a>,
+        warn_ambiguity: bool,
     ) -> Result<(), NameBinding<'a>> {
         let res = binding.res();
         self.check_reserved_macro_name(key.ident, res);
         self.set_binding_parent_module(binding, module);
-        self.update_resolution(module, key, |this, resolution| {
+        self.update_resolution(module, key, warn_ambiguity, |this, resolution| {
             if let Some(old_binding) = resolution.binding {
                 if res == Res::Err && old_binding.res() != Res::Err {
                     // Do not override real bindings with `Res::Err`s from error recovery.
@@ -308,15 +311,42 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 }
                 match (old_binding.is_glob_import(), binding.is_glob_import()) {
                     (true, true) => {
-                        if res != old_binding.res() {
-                            resolution.binding = Some(this.ambiguity(
-                                AmbiguityKind::GlobVsGlob,
-                                old_binding,
-                                binding,
-                            ));
+                        // FIXME: remove `!binding.is_ambiguity()` after delete the warning ambiguity.
+                        if !binding.is_ambiguity()
+                            && let NameBindingKind::Import { import: old_import, .. } = old_binding.kind
+                            && let NameBindingKind::Import { import, .. } = binding.kind
+                            && old_import == import {
+                            // We should replace the `old_binding` with `binding` regardless
+                            // of whether they has same resolution or not when they are
+                            // imported from the same glob-import statement.
+                            // However we currently using `Some(old_binding)` for back compact
+                            // purposes.
+                            // This case can be removed after once `Undetermined` is prepared
+                            // for glob-imports.
+                        } else if res != old_binding.res() {
+                            let binding = if warn_ambiguity {
+                                this.warn_ambiguity(
+                                    AmbiguityKind::GlobVsGlob,
+                                    old_binding,
+                                    binding,
+                                )
+                            } else {
+                                this.ambiguity(
+                                    AmbiguityKind::GlobVsGlob,
+                                    old_binding,
+                                    binding,
+                                )
+                            };
+                            resolution.binding = Some(binding);
                         } else if !old_binding.vis.is_at_least(binding.vis, this.tcx) {
                             // We are glob-importing the same item but with greater visibility.
                             resolution.binding = Some(binding);
+                        } else if binding.is_ambiguity() {
+                            resolution.binding =
+                                Some(self.arenas.alloc_name_binding(NameBindingData {
+                                    warn_ambiguity: true,
+                                    ..(*binding).clone()
+                                }));
                         }
                     }
                     (old_glob @ true, false) | (old_glob @ false, true) => {
@@ -374,29 +404,52 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
         })
     }
 
+    fn warn_ambiguity(
+        &self,
+        kind: AmbiguityKind,
+        primary_binding: NameBinding<'a>,
+        secondary_binding: NameBinding<'a>,
+    ) -> NameBinding<'a> {
+        self.arenas.alloc_name_binding(NameBindingData {
+            ambiguity: Some((secondary_binding, kind)),
+            warn_ambiguity: true,
+            ..(*primary_binding).clone()
+        })
+    }
+
     // Use `f` to mutate the resolution of the name in the module.
     // If the resolution becomes a success, define it in the module's glob importers.
-    fn update_resolution<T, F>(&mut self, module: Module<'a>, key: BindingKey, f: F) -> T
+    fn update_resolution<T, F>(
+        &mut self,
+        module: Module<'a>,
+        key: BindingKey,
+        warn_ambiguity: bool,
+        f: F,
+    ) -> T
     where
         F: FnOnce(&mut Resolver<'a, 'tcx>, &mut NameResolution<'a>) -> T,
     {
         // Ensure that `resolution` isn't borrowed when defining in the module's glob importers,
         // during which the resolution might end up getting re-defined via a glob cycle.
-        let (binding, t) = {
+        let (binding, t, warn_ambiguity) = {
             let resolution = &mut *self.resolution(module, key).borrow_mut();
             let old_binding = resolution.binding();
 
             let t = f(self, resolution);
 
-            if old_binding.is_none() && let Some(binding) = resolution.binding() {
-                (binding, t)
+            if let Some(binding) = resolution.binding() && old_binding != Some(binding) {
+                (binding, t, warn_ambiguity || old_binding.is_some())
             } else {
                 return t;
             }
         };
 
-        // Define `binding` in `module`s glob importers.
-        for import in module.glob_importers.borrow_mut().iter() {
+        let Ok(glob_importers) = module.glob_importers.try_borrow_mut() else {
+            return t;
+        };
+
+        // Define or update `binding` in `module`s glob importers.
+        for import in glob_importers.iter() {
             let mut ident = key.ident;
             let scope = match ident.span.reverse_glob_adjust(module.expansion, import.span) {
                 Some(Some(def)) => self.expn_def_scope(def),
@@ -406,7 +459,12 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             if self.is_accessible_from(binding.vis, scope) {
                 let imported_binding = self.import(binding, *import);
                 let key = BindingKey { ident, ..key };
-                let _ = self.try_define(import.parent_scope.module, key, imported_binding);
+                let _ = self.try_define(
+                    import.parent_scope.module,
+                    key,
+                    imported_binding,
+                    warn_ambiguity,
+                );
             }
         }
 
@@ -425,7 +483,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             let dummy_binding = self.import(dummy_binding, import);
             self.per_ns(|this, ns| {
                 let key = BindingKey::new(target, ns);
-                let _ = this.try_define(import.parent_scope.module, key, dummy_binding);
+                let _ = this.try_define(import.parent_scope.module, key, dummy_binding, false);
             });
             self.record_use(target, dummy_binding, false);
         } else if import.imported_module.get().is_none() {
@@ -700,7 +758,6 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             Segment::names_to_string(&import.module_path),
             module_to_string(import.parent_scope.module).unwrap_or_else(|| "???".to_string()),
         );
-
         let module = if let Some(module) = import.imported_module.get() {
             module
         } else {
@@ -773,7 +830,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                                 .emit();
                         }
                         let key = BindingKey::new(target, ns);
-                        this.update_resolution(parent, key, |_, resolution| {
+                        this.update_resolution(parent, key, false, |_, resolution| {
                             resolution.single_imports.remove(&import);
                         });
                     }
@@ -989,7 +1046,13 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                             initial_binding.res()
                         });
                         let res = binding.res();
-                        if res == Res::Err || !this.ambiguity_errors.is_empty() {
+                        let has_ambiguity_error = this
+                            .ambiguity_errors
+                            .iter()
+                            .filter(|error| !error.warning)
+                            .next()
+                            .is_some();
+                        if res == Res::Err || has_ambiguity_error {
                             this.tcx
                                 .sess
                                 .delay_span_bug(import.span, "some error happened for an import");
@@ -1338,7 +1401,17 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             };
             if self.is_accessible_from(binding.vis, scope) {
                 let imported_binding = self.import(binding, import);
-                let _ = self.try_define(import.parent_scope.module, key, imported_binding);
+                let warn_ambiguity = self
+                    .resolution(import.parent_scope.module, key)
+                    .borrow()
+                    .binding()
+                    .is_some_and(|binding| binding.is_warn_ambiguity());
+                let _ = self.try_define(
+                    import.parent_scope.module,
+                    key,
+                    imported_binding,
+                    warn_ambiguity,
+                );
             }
         }
 
@@ -1357,7 +1430,8 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
 
             module.for_each_child(self, |this, ident, _, binding| {
                 let res = binding.res().expect_non_local();
-                if res != def::Res::Err && !binding.is_ambiguity() {
+                let error_ambiguity = binding.is_ambiguity() && !binding.warn_ambiguity;
+                if res != def::Res::Err && !error_ambiguity {
                     let mut reexport_chain = SmallVec::new();
                     let mut next_binding = binding;
                     while let NameBindingKind::Import { binding, import, .. } = next_binding.kind {
diff --git a/compiler/rustc_resolve/src/lib.rs b/compiler/rustc_resolve/src/lib.rs
index faa672db59c..91d89f44dbf 100644
--- a/compiler/rustc_resolve/src/lib.rs
+++ b/compiler/rustc_resolve/src/lib.rs
@@ -658,6 +658,7 @@ impl<'a> fmt::Debug for Module<'a> {
 struct NameBindingData<'a> {
     kind: NameBindingKind<'a>,
     ambiguity: Option<(NameBinding<'a>, AmbiguityKind)>,
+    warn_ambiguity: bool,
     expansion: LocalExpnId,
     span: Span,
     vis: ty::Visibility<DefId>,
@@ -767,6 +768,7 @@ struct AmbiguityError<'a> {
     b2: NameBinding<'a>,
     misc1: AmbiguityErrorMisc,
     misc2: AmbiguityErrorMisc,
+    warning: bool,
 }
 
 impl<'a> NameBindingData<'a> {
@@ -794,6 +796,14 @@ impl<'a> NameBindingData<'a> {
             }
     }
 
+    fn is_warn_ambiguity(&self) -> bool {
+        self.warn_ambiguity
+            || match self.kind {
+                NameBindingKind::Import { binding, .. } => binding.is_warn_ambiguity(),
+                _ => false,
+            }
+    }
+
     fn is_possibly_imported_variant(&self) -> bool {
         match self.kind {
             NameBindingKind::Import { binding, .. } => binding.is_possibly_imported_variant(),
@@ -1322,6 +1332,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             dummy_binding: arenas.alloc_name_binding(NameBindingData {
                 kind: NameBindingKind::Res(Res::Err),
                 ambiguity: None,
+                warn_ambiguity: false,
                 expansion: LocalExpnId::ROOT,
                 span: DUMMY_SP,
                 vis: ty::Visibility::Public,
@@ -1685,6 +1696,16 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
     }
 
     fn record_use(&mut self, ident: Ident, used_binding: NameBinding<'a>, is_lexical_scope: bool) {
+        self.record_use_inner(ident, used_binding, is_lexical_scope, used_binding.warn_ambiguity);
+    }
+
+    fn record_use_inner(
+        &mut self,
+        ident: Ident,
+        used_binding: NameBinding<'a>,
+        is_lexical_scope: bool,
+        warn_ambiguity: bool,
+    ) {
         if let Some((b2, kind)) = used_binding.ambiguity {
             let ambiguity_error = AmbiguityError {
                 kind,
@@ -1693,9 +1714,10 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 b2,
                 misc1: AmbiguityErrorMisc::None,
                 misc2: AmbiguityErrorMisc::None,
+                warning: warn_ambiguity,
             };
             if !self.matches_previous_ambiguity_error(&ambiguity_error) {
-                // avoid duplicated span information to be emitt out
+                // avoid duplicated span information to be emit out
                 self.ambiguity_errors.push(ambiguity_error);
             }
         }
@@ -1715,7 +1737,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                 self.used_imports.insert(id);
             }
             self.add_to_glob_map(import, ident);
-            self.record_use(ident, binding, false);
+            self.record_use_inner(ident, binding, false, warn_ambiguity || binding.warn_ambiguity);
         }
     }