Add test for glob imported prelude collision trait.

src/test/ui/rust-2021/future-prelude-collision-imported.fixed

@@ -56,4 +56,15 @@ mod c {
     }
 }
 
+mod d {
+    use super::m::*;
+
+    fn main() {
+        // See https://github.com/rust-lang/rust/issues/88471
+        let _: u32 = TryIntoU32::try_into(3u8).unwrap();
+        //~^ WARNING trait method `try_into` will become ambiguous in Rust 2021
+        //~^^ WARNING this is accepted in the current edition
+    }
+}
+
 fn main() {}

src/test/ui/rust-2021/future-prelude-collision-imported.rs

@@ -56,4 +56,15 @@ mod c {
     }
 }
 
+mod d {
+    use super::m::*;
+
+    fn main() {
+        // See https://github.com/rust-lang/rust/issues/88471
+        let _: u32 = 3u8.try_into().unwrap();
+        //~^ WARNING trait method `try_into` will become ambiguous in Rust 2021
+        //~^^ WARNING this is accepted in the current edition
+    }
+}
+
 fn main() {}

src/test/ui/rust-2021/future-prelude-collision-imported.stderr

@@ -30,5 +30,14 @@ LL |         let _: u32 = 3u8.try_into().unwrap();
    = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
    = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/prelude.html>
 
-warning: 3 warnings emitted
+warning: trait method `try_into` will become ambiguous in Rust 2021
+  --> $DIR/future-prelude-collision-imported.rs:64:22
+   |
+LL |         let _: u32 = 3u8.try_into().unwrap();
+   |                      ^^^^^^^^^^^^^^ help: disambiguate the associated function: `TryIntoU32::try_into(3u8)`
+   |
+   = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/prelude.html>
+
+warning: 4 warnings emitted