Address review comments

- Factor `define_extern` into a closure
- Add a test for cross-crate GlobVsExpanded ambiguity

Author: petrochenkov

compiler/rustc_resolve/src/build_reduced_graph.rs

@@ -290,7 +290,11 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
             };
             (self.arenas.new_res_binding(res, vis, span, expansion), ambig_kind)
         });
+
         // Record primary definitions.
+        let define_extern = |ns| {
+            self.define_extern(parent, ident, ns, child_index, res, vis, span, expansion, ambig)
+        };
         match res {
             Res::Def(
                 DefKind::Mod
@@ -307,17 +311,7 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 _,
             )
             | Res::PrimTy(..)
-            | Res::ToolMod => self.define_extern(
-                parent,
-                ident,
-                TypeNS,
-                child_index,
-                res,
-                vis,
-                span,
-                expansion,
-                ambig,
-            ),
+            | Res::ToolMod => define_extern(TypeNS),
             Res::Def(
                 DefKind::Fn
                 | DefKind::AssocFn
@@ -326,28 +320,8 @@ impl<'ra, 'tcx> Resolver<'ra, 'tcx> {
                 | DefKind::AssocConst
                 | DefKind::Ctor(..),
                 _,
-            ) => self.define_extern(
-                parent,
-                ident,
-                ValueNS,
-                child_index,
-                res,
-                vis,
-                span,
-                expansion,
-                ambig,
-            ),
-            Res::Def(DefKind::Macro(..), _) | Res::NonMacroAttr(..) => self.define_extern(
-                parent,
-                ident,
-                MacroNS,
-                child_index,
-                res,
-                vis,
-                span,
-                expansion,
-                ambig,
-            ),
+            ) => define_extern(ValueNS),
+            Res::Def(DefKind::Macro(..), _) | Res::NonMacroAttr(..) => define_extern(MacroNS),
             Res::Def(
                 DefKind::TyParam
                 | DefKind::ConstParam

tests/ui/imports/ambiguous-glob-vs-expanded-extern.rs

@@ -0,0 +1,6 @@
+//@ aux-crate: glob_vs_expanded=glob-vs-expanded.rs
+
+fn main() {
+  glob_vs_expanded::mac!(); //~ ERROR `mac` is ambiguous
+                            //~| WARN this was previously accepted
+}

tests/ui/imports/ambiguous-glob-vs-expanded-extern.stderr

@@ -0,0 +1,45 @@
+error: `mac` is ambiguous
+  --> $DIR/ambiguous-glob-vs-expanded-extern.rs:4:21
+   |
+LL |   glob_vs_expanded::mac!();
+   |                     ^^^ ambiguous name
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #114095 <https://github.com/rust-lang/rust/issues/114095>
+   = note: ambiguous because of multiple glob imports of a name in the same module
+note: `mac` could refer to the macro defined here
+  --> $DIR/auxiliary/glob-vs-expanded.rs:18:9
+   |
+LL | pub use m::*;
+   |         ^
+note: `mac` could also refer to the macro defined here
+  --> $DIR/auxiliary/glob-vs-expanded.rs:18:9
+   |
+LL | pub use m::*;
+   |         ^
+   = note: `#[deny(ambiguous_glob_imports)]` (part of `#[deny(future_incompatible)]`) on by default
+
+error: aborting due to 1 previous error
+
+Future incompatibility report: Future breakage diagnostic:
+error: `mac` is ambiguous
+  --> $DIR/ambiguous-glob-vs-expanded-extern.rs:4:21
+   |
+LL |   glob_vs_expanded::mac!();
+   |                     ^^^ ambiguous name
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #114095 <https://github.com/rust-lang/rust/issues/114095>
+   = note: ambiguous because of multiple glob imports of a name in the same module
+note: `mac` could refer to the macro defined here
+  --> $DIR/auxiliary/glob-vs-expanded.rs:18:9
+   |
+LL | pub use m::*;
+   |         ^
+note: `mac` could also refer to the macro defined here
+  --> $DIR/auxiliary/glob-vs-expanded.rs:18:9
+   |
+LL | pub use m::*;
+   |         ^
+   = note: `#[deny(ambiguous_glob_imports)]` (part of `#[deny(future_incompatible)]`) on by default
+

tests/ui/imports/auxiliary/glob-vs-expanded.rs

@@ -0,0 +1,18 @@
+//@ edition:2018..
+
+#![feature(decl_macro)]
+
+mod m {
+    // Glob import in macro namespace
+    mod inner { pub macro mac() {} }
+    pub use inner::*;
+
+    // Macro-expanded single import in macro namespace
+    macro_rules! define_mac {
+        () => { pub macro mac() {} }
+    }
+    define_mac!();
+}
+
+// Ambiguous reexport
+pub use m::*;