hygiene: Decouple transparencies from expansion IDs

src/test/ui-fulldeps/proc-macro/auxiliary/generate-mod.rs

@@ -0,0 +1,28 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// run-pass
+// no-prefer-dynamic
+
+#![feature(proc_macro)]
+#![crate_type = "proc-macro"]
+
+extern crate proc_macro;
+use proc_macro::*;
+
+#[proc_macro]
+pub fn check(_: TokenStream) -> TokenStream {
+    "
+    struct Outer;
+    mod inner {
+        type Inner = Outer; // `Outer` shouldn't be available from here
+    }
+    ".parse().unwrap()
+}

src/test/ui-fulldeps/proc-macro/generate-mod.rs

@@ -0,0 +1,21 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Modules generated by transparent proc macros still acts as barriers for names (issue #50504).
+
+// aux-build:generate-mod.rs
+
+#![feature(proc_macro, proc_macro_gen)]
+
+extern crate generate_mod;
+
+generate_mod::check!(); //~ ERROR cannot find type `Outer` in this scope
+
+fn main() {}

src/test/ui-fulldeps/proc-macro/generate-mod.stderr

@@ -0,0 +1,9 @@
+error[E0412]: cannot find type `Outer` in this scope
+  --> $DIR/generate-mod.rs:19:1
+   |
+LL | generate_mod::check!(); //~ ERROR cannot find type `Outer` in this scope
+   | ^^^^^^^^^^^^^^^^^^^^^^^ not found in this scope
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0412`.