Add a couple more tests

src/test/ui/imports/extern-prelude-extern-crate-restricted-shadowing.rs

@@ -14,4 +14,13 @@ mod m {
  }
 }
 
+macro_rules! define_other_core {
+ () => {
+ extern crate std as core;
+ //~^ ERROR macro-expanded `extern crate` items cannot shadow names passed with `--extern`
+ }
+}
+
+define_other_core!();
+
 fn main() {}

src/test/ui/imports/extern-prelude-extern-crate-restricted-shadowing.stderr

@@ -1,19 +1,28 @@
+error: macro-expanded `extern crate` items cannot shadow names passed with `--extern`
+ --> $DIR/extern-prelude-extern-crate-restricted-shadowing.rs:19:9
+ |
+LL | extern crate std as core;
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^
+...
+LL | define_other_core!();
+ | --------------------- in this macro invocation
+
 error[E0659]: `Vec` is ambiguous (macro-expanded name vs less macro-expanded name from outer scope during import/macro resolution)
- --> $DIR/extern-prelude-extern-crate-restricted-shadowing.rs:15:9
+ --> $DIR/extern-prelude-extern-crate-restricted-shadowing.rs:13:9
  |
 LL | Vec::panic!(); //~ ERROR `Vec` is ambiguous
  | ^^^ ambiguous name
  |
  = note: `Vec` could refer to a struct from prelude
 note: `Vec` could also refer to the extern crate imported here
- --> $DIR/extern-prelude-extern-crate-restricted-shadowing.rs:7:9
+ --> $DIR/extern-prelude-extern-crate-restricted-shadowing.rs:5:9
  |
 LL | extern crate std as Vec;
  | ^^^^^^^^^^^^^^^^^^^^^^^^
 ...
 LL | define_vec!();
  | -------------- in this macro invocation
 
-error: aborting due to previous error
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0659`.

src/test/ui/imports/extern-prelude-extern-crate-shadowing.rs

@@ -0,0 +1,12 @@
+// compile-pass
+// aux-build:two_macros.rs
+
+extern crate two_macros as core;
+
+mod m {
+ fn check() {
+ core::m!(); // OK
+ }
+}
+
+fn main() {}