Fix ICE when parsing token trees after an error.

Author: jseyfried

src/libsyntax/parse/parser.rs

@@ -813,6 +813,10 @@ impl<'a> Parser<'a> {
         let mut first: bool = true;
         let mut v = vec![];
         while !kets.contains(&&self.token) {
+            match self.token {
+                token::CloseDelim(..) | token::Eof => break,
+                _ => {}
+            };
             match sep.sep {
                 Some(ref t) => {
                     if first {
@@ -2606,9 +2610,12 @@ impl<'a> Parser<'a> {
             return Ok((None, kleene_op));
         }
 
-        let separator = self.bump_and_get();
+        let separator = match self.token {
+            token::CloseDelim(..) => None,
+            _ => Some(self.bump_and_get()),
+        };
         match parse_kleene_op(self)? {
-            Some(zerok) => Ok((Some(separator), zerok)),
+            Some(zerok) => Ok((separator, zerok)),
             None => return Err(self.fatal("expected `*` or `+`"))
         }
     }
@@ -2645,7 +2652,7 @@ impl<'a> Parser<'a> {
                     tts: tts,
                 })))
             },
-            token::CloseDelim(_) | token::Eof => unreachable!(),
+            token::CloseDelim(..) | token::Eof => Ok(TokenTree::Token(self.span, token::Eof)),
             token::Dollar | token::SubstNt(..) if self.quote_depth > 0 => self.parse_unquoted(),
             _ => Ok(TokenTree::Token(self.span, self.bump_and_get())),
         }

src/test/compile-fail/issue-39388.rs

@@ -0,0 +1,17 @@
+// Copyright 2017 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.
+
+macro_rules! assign {
+    (($($a:tt)*) = ($($b:tt))*) => { //~ ERROR expected `*` or `+`
+        $($a)* = $($b)*
+    }
+}
+
+fn main() {}

src/test/compile-fail/issue-39616.rs

@@ -0,0 +1,15 @@
+// Copyright 2017 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.
+
+fn foo(a: [0; 1]) {} //~ ERROR expected type, found `0`
+//~| ERROR expected one of `->`, `where`, or `{`, found `]`
+// FIXME(jseyfried): avoid emitting the second error (preexisting)
+
+fn main() {}