Clean up plpgsql grammar to make sure that check_assignable() is applied

consistently.  This is mostly cosmetic right at the moment because
check_assignable() does nothing for ROW or RECORD datums, but that might
not always be so.  This also syncs several different places that read
INTO target lists.  They're just enough different that it seems
impractical to factor them into a single routine, but they surely
should be the same as much as possible.

src/pl/plpgsql/src/gram.y

@@ -4,7 +4,7 @@
  *						  procedural language
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.82 2005/10/13 15:34:19 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/pl/plpgsql/src/gram.y,v 1.83 2006/02/12 04:59:32 tgl Exp $
  *
  *	  This software is copyrighted by Jan Wieck - Hamburg.
  *
@@ -881,9 +881,15 @@ for_control		:
 							new->cmd_type = PLPGSQL_STMT_DYNFORS;
 							new->lineno   = $1;
 							if ($2.rec)
+							{
 								new->rec = $2.rec;
+								check_assignable((PLpgSQL_datum *) new->rec);
+							}
 							else if ($2.row)
+							{
 								new->row = $2.row;
+								check_assignable((PLpgSQL_datum *) new->row);
+							}
 							else
 							{
 								plpgsql_error_lineno = $1;
@@ -942,6 +948,7 @@ for_control		:
 
 								expr2 = plpgsql_read_expression(K_LOOP, "LOOP");
 
+								/* create loop's private variable */
 								fvar = (PLpgSQL_var *)
 									plpgsql_build_variable($2.name,
 														   $2.lineno,
@@ -986,9 +993,15 @@ for_control		:
 								new->cmd_type = PLPGSQL_STMT_FORS;
 								new->lineno   = $1;
 								if ($2.rec)
+								{
 									new->rec = $2.rec;
+									check_assignable((PLpgSQL_datum *) new->rec);
+								}
 								else if ($2.row)
+								{
 									new->row = $2.row;
+									check_assignable((PLpgSQL_datum *) new->row);
+								}
 								else
 								{
 									plpgsql_error_lineno = $1;
@@ -1002,6 +1015,17 @@ for_control		:
 					}
 				;
 
+/*
+ * Processing the for_variable is tricky because we don't yet know if the
+ * FOR is an integer FOR loop or a loop over query results.  In the former
+ * case, the variable is just a name that we must instantiate as a loop
+ * local variable, regardless of any other definition it might have.
+ * Therefore, we always save the actual identifier into $$.name where it
+ * can be used for that case.  We also save the outer-variable definition,
+ * if any, because that's what we need for the loop-over-query case.  Note
+ * that we must NOT apply check_assignable() or any other semantic check
+ * until we know what's what.
+ */
 for_variable	: T_SCALAR
 					{
 						char		*name;
@@ -1304,13 +1328,13 @@ stmt_dynexecute : K_EXECUTE lno
 							switch (yylex())
 							{
 								case T_ROW:
-									check_assignable((PLpgSQL_datum *) yylval.row);
 									new->row = yylval.row;
+									check_assignable((PLpgSQL_datum *) new->row);
 									break;
 
 								case T_RECORD:
-									check_assignable((PLpgSQL_datum *) yylval.row);
 									new->rec = yylval.rec;
+									check_assignable((PLpgSQL_datum *) new->rec);
 									break;
 
 								case T_SCALAR:
@@ -1917,11 +1941,13 @@ make_select_stmt(void)
 			{
 				case T_ROW:
 					row = yylval.row;
+					check_assignable((PLpgSQL_datum *) row);
 					have_into = true;
 					break;
 
 				case T_RECORD:
 					rec = yylval.rec;
+					check_assignable((PLpgSQL_datum *) rec);
 					have_into = true;
 					break;
 
@@ -2028,10 +2054,12 @@ make_fetch_stmt(void)
 	{
 		case T_ROW:
 			row = yylval.row;
+			check_assignable((PLpgSQL_datum *) row);
 			break;
 
 		case T_RECORD:
 			rec = yylval.rec;
+			check_assignable((PLpgSQL_datum *) rec);
 			break;
 
 		case T_SCALAR:
@@ -2039,7 +2067,12 @@ make_fetch_stmt(void)
 			break;
 
 		default:
-			yyerror("syntax error");
+			plpgsql_error_lineno = plpgsql_scanner_lineno();
+			ereport(ERROR,
+					(errcode(ERRCODE_SYNTAX_ERROR),
+					 errmsg("syntax error at \"%s\"", yytext),
+					 errdetail("Expected record variable, row variable, "
+							   "or list of scalar variables.")));
 	}
 
 	tok = yylex();
@@ -2136,13 +2169,13 @@ read_into_scalar_list(const char *initial_name,
 				plpgsql_error_lineno = plpgsql_scanner_lineno();
 				ereport(ERROR,
 						(errcode(ERRCODE_SYNTAX_ERROR),
-						 errmsg("\"%s\" is not a variable",
+						 errmsg("\"%s\" is not a scalar variable",
 								yytext)));
 		}
 	}
 
 	/*
-	 * We read an extra, non-comma character from yylex(), so push it
+	 * We read an extra, non-comma token from yylex(), so push it
 	 * back onto the input stream
 	 */
 	plpgsql_push_back_token(tok);