Rollup merge of #48441 - petrochenkov:exty, r=estebank

Fix parsing of extern paths in types and poly-traits

Fixes #48262

Author: Manishearth

src/libsyntax/parse/parser.rs

@@ -1321,7 +1321,7 @@ impl<'a> Parser<'a> {
     pub fn token_is_bare_fn_keyword(&mut self) -> bool {
         self.check_keyword(keywords::Fn) ||
             self.check_keyword(keywords::Unsafe) ||
-            self.check_keyword(keywords::Extern)
+            self.check_keyword(keywords::Extern) && self.is_extern_non_path()
     }
 
     fn eat_label(&mut self) -> Option<Label> {

src/test/run-pass/rfc-2126-extern-absolute-paths/auxiliary/xcrate.rs

@@ -8,8 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#[derive(Debug)]
+#[derive(Debug, PartialEq)]
 pub struct S;
 
 #[derive(Debug)]
 pub struct Z;
+
+pub trait Tr<'a> {}

src/test/run-pass/rfc-2126-extern-absolute-paths/extern.rs

@@ -14,6 +14,9 @@
 
 use extern::xcrate::Z;
 
+type A = extern::xcrate::S;
+type B = for<'a> extern::xcrate::Tr<'a>;
+
 fn f() {
     use extern::xcrate;
     use extern::xcrate as ycrate;
@@ -28,4 +31,5 @@ fn main() {
     assert_eq!(format!("{:?}", s), "S");
     let z = Z;
     assert_eq!(format!("{:?}", z), "Z");
+    assert_eq!(A {}, extern::xcrate::S {});
 }