fix(resolve): update shadowed_glob more precision

Author: bvanjoi

compiler/rustc_resolve/src/imports.rs

@@ -338,7 +338,21 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                         } else {
                             resolution.binding = Some(nonglob_binding);
                         }
-                        resolution.shadowed_glob = Some(glob_binding);
+
+                        if let Some(old_binding) = resolution.shadowed_glob {
+                            assert!(old_binding.is_glob_import());
+                            if glob_binding.res() != old_binding.res() {
+                                resolution.shadowed_glob = Some(this.ambiguity(
+                                    AmbiguityKind::GlobVsGlob,
+                                    old_binding,
+                                    glob_binding,
+                                ));
+                            } else if !old_binding.vis.is_at_least(binding.vis, this.tcx) {
+                                resolution.shadowed_glob = Some(glob_binding);
+                            }
+                        } else {
+                            resolution.shadowed_glob = Some(glob_binding);
+                        }
                     }
                     (false, false) => {
                         return Err(old_binding);

tests/ui/resolve/issue-105069.stderr

@@ -4,17 +4,19 @@ error[E0659]: `V` is ambiguous
 LL | use V;
    |     ^ ambiguous name
    |
-   = note: ambiguous because of multiple potential import sources
+   = note: ambiguous because of multiple glob imports of a name in the same module
 note: `V` could refer to the variant imported here
   --> $DIR/issue-105069.rs:1:5
    |
 LL | use self::A::*;
    |     ^^^^^^^^^^
+   = help: consider adding an explicit import of `V` to disambiguate
 note: `V` could also refer to the variant imported here
   --> $DIR/issue-105069.rs:3:5
    |
 LL | use self::B::*;
    |     ^^^^^^^^^^
+   = help: consider adding an explicit import of `V` to disambiguate
 
 error: aborting due to previous error
 

tests/ui/resolve/issue-109153.rs

@@ -0,0 +1,14 @@
+use foo::*;
+
+mod foo {
+    pub mod bar {
+        pub mod bar {
+            pub mod bar {}
+        }
+    }
+}
+
+use bar::bar; //~ ERROR `bar` is ambiguous
+use bar::*;
+
+fn main() { }

tests/ui/resolve/issue-109153.stderr

@@ -0,0 +1,23 @@
+error[E0659]: `bar` is ambiguous
+  --> $DIR/issue-109153.rs:11:5
+   |
+LL | use bar::bar;
+   |     ^^^ ambiguous name
+   |
+   = note: ambiguous because of multiple glob imports of a name in the same module
+note: `bar` could refer to the module imported here
+  --> $DIR/issue-109153.rs:1:5
+   |
+LL | use foo::*;
+   |     ^^^^^^
+   = help: consider adding an explicit import of `bar` to disambiguate
+note: `bar` could also refer to the module imported here
+  --> $DIR/issue-109153.rs:12:5
+   |
+LL | use bar::*;
+   |     ^^^^^^
+   = help: consider adding an explicit import of `bar` to disambiguate
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0659`.