Fix YA unwanted behavioral difference with operator_precedence_warning.

Jeff Janes noted that the error cursor position shown for some errors
would vary when operator_precedence_warning is turned on.  We'd prefer
that option to have no undocumented effects, so this isn't desirable.
To fix, make sure that an AEXPR_PAREN node has the same exprLocation
as its child node.

(Note: it would be a little cheaper to use @2 here instead of an
exprLocation call, but there are cases where that wouldn't produce
the identical answer, so don't do it like that.)

Back-patch to 9.5 where this feature was introduced.

Discussion: https://postgr.es/m/CAMkU=1ykK+VhhcQ4Ky8KBo9FoaUJH3f3rDQB8TkTXi-ZsBRUkQ@mail.gmail.com

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 080d4445423dadbbbf9c4b1d1f62f3f3df652128..ab189a3df2f972974819a4d1bb28753e490ec0c3 100644 (file)
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -12096,7 +12096,10 @@ c_expr:                columnref                                                               { $$ = $1; }
                                                 * AEXPR_PAREN nodes wrapping all explicitly
                                                 * parenthesized subexpressions; this prevents bogus
                                                 * warnings from being issued when the ordering has
-                                                * been forced by parentheses.
+                                                * been forced by parentheses.  Take care that an
+                                                * AEXPR_PAREN node has the same exprLocation as its
+                                                * child, so as not to cause surprising changes in
+                                                * error cursor positioning.
                                                 *
                                                 * In principle we should not be relying on a GUC to
                                                 * decide whether to insert AEXPR_PAREN nodes.
@@ -12105,7 +12108,8 @@ c_expr:         columnref                                                               { $$ = $1; }
                                                 * we'd just as soon not waste cycles on dummy parse
                                                 * nodes if we don't have to.
                                                 */
-                                               $$ = (Node *) makeA_Expr(AEXPR_PAREN, NIL, $2, NULL, @1);
+                                               $$ = (Node *) makeA_Expr(AEXPR_PAREN, NIL, $2, NULL,
+                                                                                                exprLocation($2));
                                        }
                                        else
                                                $$ = $2;