Add test for issue rust-lang#56175

Author: da-x

src/test/ui/issues/auxiliary/reexported-trait.rs

@@ -0,0 +1,17 @@
+mod private {
+    pub trait Trait {
+        fn trait_method(&self) {
+        }
+    }
+    pub trait TraitB {
+        fn trait_method_b(&self) {
+        }
+    }
+}
+
+pub struct FooStruct;
+pub use crate::private::Trait;
+impl crate::private::Trait for FooStruct {}
+
+pub use crate::private::TraitB as TraitBRename;
+impl crate::private::TraitB for FooStruct {}

src/test/ui/issues/issue-56175.rs

@@ -0,0 +1,9 @@
+// edition:2018
+// aux-crate:reexported_trait=reexported-trait.rs
+
+fn main() {
+    reexported_trait::FooStruct.trait_method();
+    //~^ ERROR
+    reexported_trait::FooStruct.trait_method_b();
+    //~^ ERROR
+}

src/test/ui/issues/issue-56175.stderr

@@ -0,0 +1,27 @@
+error[E0599]: no method named `trait_method` found for struct `reexported_trait::FooStruct` in the current scope
+  --> $DIR/issue-56175.rs:5:33
+   |
+LL |     reexported_trait::FooStruct.trait_method();
+   |                                 ^^^^^^^^^^^^ method not found in `reexported_trait::FooStruct`
+   |
+   = help: items from traits can only be used if the trait is in scope
+help: the following trait is implemented but not in scope; perhaps add a `use` for it:
+   |
+LL | use reexported_trait::private::Trait;
+   |
+
+error[E0599]: no method named `trait_method_b` found for struct `reexported_trait::FooStruct` in the current scope
+  --> $DIR/issue-56175.rs:7:33
+   |
+LL |     reexported_trait::FooStruct.trait_method_b();
+   |                                 ^^^^^^^^^^^^^^ method not found in `reexported_trait::FooStruct`
+   |
+   = help: items from traits can only be used if the trait is in scope
+help: the following trait is implemented but not in scope; perhaps add a `use` for it:
+   |
+LL | use reexported_trait::private::TraitB;
+   |
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0599`.