resolve: Relax some asserts in glob overwriting and add tests

compiler/rustc_resolve/src/imports.rs

@@ -300,13 +300,13 @@ fn remove_same_import<'ra>(d1: Decl<'ra>, d2: Decl<'ra>) -> (Decl<'ra>, Decl<'ra
     if let DeclKind::Import { import: import1, source_decl: d1_next } = d1.kind
         && let DeclKind::Import { import: import2, source_decl: d2_next } = d2.kind
         && import1 == import2
-        && d1.warn_ambiguity.get() == d2.warn_ambiguity.get()
     {
         assert_eq!(d1.ambiguity.get(), d2.ambiguity.get());
-        assert!(!d1.warn_ambiguity.get());
         assert_eq!(d1.expansion, d2.expansion);
         assert_eq!(d1.span, d2.span);
-        assert_eq!(d1.vis(), d2.vis());
+        // Visibility of the new import declaration may be different,
+        // because it already incorporates the visibility of the source binding.
+        // `warn_ambiguity` of a re-fetched glob can also change in both directions.
         remove_same_import(d1_next, d2_next)
     } else {
         (d1, d2)

tests/ui/imports/overwrite-deep-glob.rs

@@ -0,0 +1,22 @@
+//@ check-pass
+
+mod openssl {
+    pub use self::handwritten::*;
+
+    mod handwritten {
+        mod m1 {
+            pub struct S {}
+        }
+        mod m2 {
+            #[derive(Default)]
+            pub struct S {}
+        }
+
+        pub use self::m1::*; //~ WARN ambiguous glob re-exports
+        pub use self::m2::*;
+    }
+}
+
+pub use openssl::*;
+
+fn main() {}

tests/ui/imports/overwrite-deep-glob.stderr

@@ -0,0 +1,12 @@
+warning: ambiguous glob re-exports
+  --> $DIR/overwrite-deep-glob.rs:15:17
+   |
+LL |         pub use self::m1::*;
+   |                 ^^^^^^^^^^^ the name `S` in the type namespace is first re-exported here
+LL |         pub use self::m2::*;
+   |                 ----------- but the name `S` in the type namespace is also re-exported here
+   |
+   = note: `#[warn(ambiguous_glob_reexports)]` on by default
+
+warning: 1 warning emitted
+

tests/ui/imports/overwrite-different-ambig.rs

@@ -0,0 +1,25 @@
+//@ check-pass
+//@ edition:2024
+
+mod a {
+    mod b {
+        mod c {
+            pub struct E;
+        }
+        mod d {
+            mod c {
+                pub struct E;
+            }
+            mod d {
+                #[derive(Debug)]
+                pub struct E;
+            }
+            pub use c::*;
+            use d::*;
+        }
+        use c::*;
+        use d::*;
+    }
+}
+
+fn main() {}

tests/ui/imports/overwrite-different-vis.rs

@@ -0,0 +1,21 @@
+//@ check-pass
+
+mod b {
+    pub mod http {
+        pub struct HeaderMap;
+    }
+
+    pub(crate) use self::http::*;
+    #[derive(Debug)]
+    pub struct HeaderMap;
+}
+
+mod a {
+    pub use crate::b::*;
+
+    fn check_type() {
+        let _: HeaderMap = crate::b::HeaderMap;
+    }
+}
+
+fn main() {}