Handle glob import in redundancy check

Author: fdrinck

src/librustc_resolve/resolve_imports.rs

@@ -1294,7 +1294,10 @@ impl<'a, 'b:'a> ImportResolver<'a, 'b> {
                 directive.span,
             ) {
                 Ok(other_binding) => {
-                    is_redundant[ns] = Some(binding.def() == other_binding.def());
+                    is_redundant[ns] = Some(
+                        binding.def() == other_binding.def()
+                        && !other_binding.is_ambiguity()
+                    );
                     redundant_span[ns] =
                         Some((other_binding.span, other_binding.is_import()));
                 }

src/test/ui/lint/use-redundant.stderr

@@ -25,12 +25,3 @@ LL | use crate::foo::Bar;
 LL |     use crate::foo::Bar;
    |         ^^^^^^^^^^^^^^^
 
-warning: the item `S` is imported redundantly
-  --> $DIR/use-redundant.rs:25:9
-   |
-LL | use m1::*;
-   |     ----- the item `S` is already imported here
-...
-LL |     use m1::S;
-   |         ^^^^^
-