Auto merge of #45771 - petrochenkov:crate, r=nikomatsakis

Support `::crate` in paths

cc https://github.com/rust-lang/rust/issues/45477
Fixes https://github.com/rust-lang/rust/issues/45229

1 files changed, 14 insertions, 3 deletions

diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index c1819307928..0b03429ea2e 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -3916,6 +3916,10 @@ impl<'a> Parser<'a> {
         self.look_ahead(1, |t| t.is_ident() && !t.is_reserved_ident())
     }
 
+    fn is_crate_vis(&self) -> bool {
+        self.token.is_keyword(keywords::Crate) && self.look_ahead(1, |t| t != &token::ModSep)
+    }
+
     fn eat_auto_trait(&mut self) -> bool {
         if self.token.is_keyword(keywords::Auto)
             && self.look_ahead(1, |t| t.is_keyword(keywords::Trait))
@@ -4026,10 +4030,15 @@ impl<'a> Parser<'a> {
                 node: StmtKind::Item(macro_def),
                 span: lo.to(self.prev_span),
             }
-        // Starts like a simple path, but not a union item.
+        // Starts like a simple path, but not a union item or item with `crate` visibility.
+        // Our goal here is to parse an arbitrary path `a::b::c` but not something that starts
+        // like a path (1 token), but it fact not a path.
+        // `union::b::c` - path, `union U { ... }` - not a path.
+        // `crate::b::c` - path, `crate struct S;` - not a path.
         } else if self.token.is_path_start() &&
                   !self.token.is_qpath_start() &&
-                  !self.is_union_item() {
+                  !self.is_union_item() &&
+                  !self.is_crate_vis() {
             let pth = self.parse_path(PathStyle::Expr)?;
 
             if !self.eat(&token::Not) {
@@ -5399,7 +5408,9 @@ impl<'a> Parser<'a> {
     pub fn parse_visibility(&mut self, can_take_tuple: bool) -> PResult<'a, Visibility> {
         maybe_whole!(self, NtVis, |x| x);
 
-        if self.eat_keyword(keywords::Crate) {
+        self.expected_tokens.push(TokenType::Keyword(keywords::Crate));
+        if self.is_crate_vis() {
+            self.bump(); // `crate`
             return Ok(Visibility::Crate(self.prev_span, CrateSugar::JustCrate));
         }