make parser disambiguate fn~ at top level correctly

1 files changed, 12 insertions, 1 deletions

diff --git a/src/comp/syntax/parse/parser.rs b/src/comp/syntax/parse/parser.rs
index 13396d68227..4e5620efed6 100644
--- a/src/comp/syntax/parse/parser.rs
+++ b/src/comp/syntax/parse/parser.rs
@@ -2166,13 +2166,24 @@ fn parse_fn_ty_proto(p: parser) -> ast::proto {
     }
 }
 
+fn fn_expr_lookahead(tok: token::token) -> bool {
+    alt tok {
+      token::LPAREN. | token::AT. | token::TILDE. | token::BINOP(_) {
+        true
+      }
+      _ {
+        false
+      }
+    }
+}
+
 fn parse_item(p: parser, attrs: [ast::attribute]) -> option::t<@ast::item> {
     if eat_word(p, "const") {
         ret some(parse_item_const(p, attrs));
     } else if eat_word(p, "inline") {
         expect_word(p, "fn");
         ret some(parse_item_fn(p, ast::impure_fn, attrs));
-    } else if is_word(p, "fn") && p.look_ahead(1u) != token::LPAREN {
+    } else if is_word(p, "fn") && !fn_expr_lookahead(p.look_ahead(1u)) {
         p.bump();
         ret some(parse_item_fn(p, ast::impure_fn, attrs));
     } else if eat_word(p, "pure") {