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 a4c35ea1.

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:

src/include/parser/parse_node.h

@@ -55,6 +55,7 @@ typedef enum ParseExprKind
 	EXPR_KIND_OFFSET,			/* OFFSET */
 	EXPR_KIND_RETURNING,		/* RETURNING */
 	EXPR_KIND_VALUES,			/* VALUES */
+	EXPR_KIND_VALUES_SINGLE,	/* single-row VALUES (in INSERT only) */
 	EXPR_KIND_CHECK_CONSTRAINT, /* CHECK constraint for a table */
 	EXPR_KIND_DOMAIN_CHECK,		/* CHECK constraint for a domain */
 	EXPR_KIND_COLUMN_DEFAULT,	/* default value for a table column */

src/test/regress/expected/tsrf.out

@@ -374,7 +374,9 @@ LINE 1: INSERT INTO fewmore VALUES(1) RETURNING generate_series(1,3)...
                                                 ^
 -- nor standalone VALUES (but surely this is a bug?)
 VALUES(1, generate_series(1,2));
-ERROR:  set-valued function called in context that cannot accept a set
+ERROR:  set-returning functions are not allowed in VALUES
+LINE 1: VALUES(1, generate_series(1,2));
+                  ^
 -- We allow tSRFs that are not at top level
 SELECT int4mul(generate_series(1,2), 10);
  int4mul