Auto merge of rust-lang#147196 - LorrensP-2158466:same-res-ambiguity-test, r=petrochenkov

Test: Ambigious bindings in same namespace with the same res

Add a test based on the discussion [here](https://rust-lang.zulipchat.com/#narrow/channel/421156-gsoc/topic/Project.3A.20Parallel.20Macro.20Expansion/near/542316157) and related to rust-lang#145575 (comment).

This is the most reduced form I could create that passes on nightly but fails with rust-lang#145108 (see [#gsoc > Project: Parallel Macro Expansion @ 💬](https://rust-lang.zulipchat.com/#narrow/channel/421156-gsoc/topic/Project.3A.20Parallel.20Macro.20Expansion/near/542335131)).

Also not sure about the test names.

r? `@petrochenkov`

Author: bors

tests/ui/imports/auxiliary/same-res-ambigious-extern-fail.rs

@@ -0,0 +1,16 @@
+//@ edition:2018
+//@ proc-macro: same-res-ambigious-extern-macro.rs
+
+macro_rules! globbing{
+    () => {
+        pub use same_res_ambigious_extern_macro::*;
+    }
+}
+
+#[macro_use] // this imports the `RustEmbed` macro with `pub(crate)` visibility
+extern crate same_res_ambigious_extern_macro;
+globbing! {} // this imports the same `RustEmbed` macro with `pub` visibility
+
+pub trait RustEmbed {}
+
+pub use RustEmbed as Embed;

tests/ui/imports/auxiliary/same-res-ambigious-extern-macro.rs

@@ -0,0 +1,8 @@
+//@ edition: 2018
+extern crate proc_macro;
+use proc_macro::TokenStream;
+
+#[proc_macro_derive(RustEmbed)]
+pub fn rust_embed_derive(_input: TokenStream) -> TokenStream {
+    TokenStream::new()
+}

tests/ui/imports/auxiliary/same-res-ambigious-extern.rs

@@ -0,0 +1,11 @@
+//@ edition:2018
+//@ proc-macro: same-res-ambigious-extern-macro.rs
+
+#[macro_use] // this imports the `RustEmbed` macro with `pub(crate)` visibility
+extern crate same_res_ambigious_extern_macro;
+// this imports the same `RustEmbed` macro with `pub` visibility
+pub use same_res_ambigious_extern_macro::*;
+
+pub trait RustEmbed {}
+
+pub use RustEmbed as Embed;

tests/ui/imports/same-res-ambigious.fail.stderr

@@ -0,0 +1,20 @@
+error[E0603]: derive macro `Embed` is private
+  --> $DIR/same-res-ambigious.rs:8:28
+   |
+LL | #[derive(ambigious_extern::Embed)]
+   |                            ^^^^^ private derive macro
+   |
+note: the derive macro `Embed` is defined here
+  --> $DIR/auxiliary/same-res-ambigious-extern-fail.rs:16:9
+   |
+LL | pub use RustEmbed as Embed;
+   |         ^^^^^^^^^
+help: import `Embed` directly
+   |
+LL - #[derive(ambigious_extern::Embed)]
+LL + #[derive(same_res_ambigious_extern_macro::RustEmbed)]
+   |
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0603`.

tests/ui/imports/same-res-ambigious.nightly-fail.stderr

@@ -0,0 +1,20 @@
+error[E0603]: derive macro `Embed` is private
+  --> $DIR/same-res-ambigious.rs:8:28
+   |
+LL | #[derive(ambigious_extern::Embed)]
+   |                            ^^^^^ private derive macro
+   |
+note: the derive macro `Embed` is defined here
+  --> $DIR/auxiliary/same-res-ambigious-extern-fail.rs:16:9
+   |
+LL | pub use RustEmbed as Embed;
+   |         ^^^^^^^^^
+help: import `Embed` directly
+   |
+LL - #[derive(ambigious_extern::Embed)]
+LL + #[derive(same_res_ambigious_extern_macro::RustEmbed)]
+   |
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0603`.

tests/ui/imports/same-res-ambigious.rs

@@ -0,0 +1,11 @@
+//@ edition: 2018
+//@ revisions: fail pass
+//@[pass] check-pass
+//@[pass] aux-crate: ambigious_extern=same-res-ambigious-extern.rs
+//@[fail] aux-crate: ambigious_extern=same-res-ambigious-extern-fail.rs
+// see https://github.com/rust-lang/rust/pull/147196
+
+#[derive(ambigious_extern::Embed)] //[fail]~ ERROR: derive macro `Embed` is private
+struct Foo{}
+
+fn main(){}