parser: fix byacc regression related to hash-semi.

The "byacc_fool" rule needed a small update when
in November 2016 it became involved in newly introduced #;
(hash semicolon) syntax for commenting out.

The problem is that when a top-level nested list expression
is followed by #; then a byacc-generated parser throws
a syntax error.

This is because the byacc_fool production only generates
a n_expr, or empty. Thus only those symbols are allowed
which may begin a n_expr. The hash-semicolon token isn't
one of them.

* parser.y (byacc_fool): Add a production rule which generates
a HASH_SEMI. Thus HASH_SEMI is now one of the terminals
that may legally follow any sentential form that matches
a byacc_fool rule after it.

1 files changed, 1 insertions, 0 deletions

diff --git a/parser.y b/parser.y
index 92f223d4..95c8969b 100644
--- a/parser.y
+++ b/parser.y
@@ -221,6 +221,7 @@ hash_semi_or_i_expr : HASH_SEMI                 { parser->circ_suppress = 1; }
 
 /* Hack needed for Berkeley Yacc */
 byacc_fool : n_expr { internal_error("notreached"); }
+           | HASH_SEMI { internal_error("notreached"); }
            | { internal_error("notreached"); }
            ;