Fix check_srf_call_placement() to handle VALUES cases correctly.

INSERT ... VALUES with a single VALUES row is implemented quite differently
from the general VALUES case.  A user-visible implication of that is that
we accept SRFs in the single-row case, but not in the multi-row case.
That's a historical artifact no doubt, but in view of the lack of field
complaints, I'm not excited about fixing it right now.

However, check_srf_call_placement() needs to know about this, first because
it should throw an error in the unsupported case, and second because it
should set p_hasTargetSRFs in the single-row case (because we treat that
like a SELECT tlist).  That's an oversight in commit a4c35ea1c.

To fix, split EXPR_KIND_VALUES into two values.  So far as I can see,
this is the only place where we need to distinguish the two cases at
present; but there might be more later.

Patch by me, per report from Andres Freund.

Discussion: https://postgr.es/m/20170116081548.zg63zltblwimpfgp@alap3.anarazel.de

src/backend/parser/analyze.c

@@ -790,7 +790,7 @@ transformInsertStmt(ParseState *pstate, InsertStmt *stmt)
 		 */
 		exprList = transformExpressionList(pstate,
 										   (List *) linitial(valuesLists),
-										   EXPR_KIND_VALUES,
+										   EXPR_KIND_VALUES_SINGLE,
 										   true);
 
 		/* Prepare row for assignment to target table */

src/backend/parser/parse_agg.c

@@ -447,6 +447,7 @@ check_agglevels_and_constraints(ParseState *pstate, Node *expr)
 			errkind = true;
 			break;
 		case EXPR_KIND_VALUES:
+		case EXPR_KIND_VALUES_SINGLE:
 			errkind = true;
 			break;
 		case EXPR_KIND_CHECK_CONSTRAINT:
@@ -840,6 +841,7 @@ transformWindowFuncCall(ParseState *pstate, WindowFunc *wfunc,
 			errkind = true;
 			break;
 		case EXPR_KIND_VALUES:
+		case EXPR_KIND_VALUES_SINGLE:
 			errkind = true;
 			break;
 		case EXPR_KIND_CHECK_CONSTRAINT:

src/backend/parser/parse_expr.c

@@ -1797,6 +1797,7 @@ transformSubLink(ParseState *pstate, SubLink *sublink)
 		case EXPR_KIND_OFFSET:
 		case EXPR_KIND_RETURNING:
 		case EXPR_KIND_VALUES:
+		case EXPR_KIND_VALUES_SINGLE:
 			/* okay */
 			break;
 		case EXPR_KIND_CHECK_CONSTRAINT:
@@ -3410,6 +3411,7 @@ ParseExprKindName(ParseExprKind exprKind)
 		case EXPR_KIND_RETURNING:
 			return "RETURNING";
 		case EXPR_KIND_VALUES:
+		case EXPR_KIND_VALUES_SINGLE:
 			return "VALUES";
 		case EXPR_KIND_CHECK_CONSTRAINT:
 		case EXPR_KIND_DOMAIN_CHECK:

src/backend/parser/parse_func.c

@@ -2141,7 +2141,12 @@ check_srf_call_placement(ParseState *pstate, int location)
 			errkind = true;
 			break;
 		case EXPR_KIND_VALUES:
-			/* okay */
+			/* SRFs are presently not supported by nodeValuesscan.c */
+			errkind = true;
+			break;
+		case EXPR_KIND_VALUES_SINGLE:
+			/* okay, since we process this like a SELECT tlist */
+			pstate->p_hasTargetSRFs = true;
 			break;
 		case EXPR_KIND_CHECK_CONSTRAINT:
 		case EXPR_KIND_DOMAIN_CHECK: