Ignore non-semantic tokens for 'probably_eq' streams.

src/libsyntax/parse/token.rs

@@ -570,8 +570,9 @@ impl Token {
         //
         // Instead the "probably equal" check here is "does each token
         // recursively have the same discriminant?" We basically don't look at
-        // the token values here and assume that such fine grained modifications
-        // of token streams doesn't happen.
+        // the token values here and assume that such fine grained token stream
+        // modifications, including adding/removing typically non-semantic
+        // tokens such as extra braces and commas, don't happen.
         if let Some(tokens) = tokens {
             if tokens.probably_equal_for_proc_macro(&tokens_for_real) {
                 return tokens