Fix handling of polymorphic output arguments for procedures.

Most of the infrastructure for procedure arguments was already
okay with polymorphic output arguments, but it turns out that
CallStmtResultDesc() was a few bricks shy of a load here.  It thought
all it needed to do was call build_function_result_tupdesc_t, but
that function specifically disclaims responsibility for resolving
polymorphic arguments.  Failing to handle that doesn't seem to be
a problem for CALL in plpgsql, but CALL from plain SQL would get
errors like "cannot display a value of type anyelement", or even
crash outright.

In v14 and later we can simply examine the exposed types of the
CallStmt.outargs nodes to get the right type OIDs.  But it's a lot
more complicated to fix in v12/v13, because those versions don't
have CallStmt.outargs, nor do they do expand_function_arguments
until ExecuteCallStmt runs.  We have to duplicatively run
expand_function_arguments, and then re-determine which elements
of the args list are output arguments.

Per bug #18463 from Drew Kimball.  Back-patch to all supported
versions, since it's busted in all of them.

Discussion: https://postgr.es/m/18463-f8cd77e12564d8a2@postgresql.org

src/backend/commands/functioncmds.c

@@ -54,6 +54,7 @@
 #include "executor/executor.h"
 #include "funcapi.h"
 #include "miscadmin.h"
+#include "nodes/nodeFuncs.h"
 #include "optimizer/optimizer.h"
 #include "parser/parse_coerce.h"
 #include "parser/parse_collate.h"
@@ -2506,6 +2507,78 @@ CallStmtResultDesc(CallStmt *stmt)
 
 	tupdesc = build_function_result_tupdesc_t(tuple);
 
+	/*
+	 * The result of build_function_result_tupdesc_t has the right column
+	 * names, but it just has the declared output argument types, which is the
+	 * wrong thing in polymorphic cases.  Get the correct types by examining
+	 * the procedure's resolved argument expressions.  We intentionally keep
+	 * the atttypmod as -1 and the attcollation as the type's default, since
+	 * that's always the appropriate thing for function outputs; there's no
+	 * point in considering any additional info available from outargs.  Note
+	 * that tupdesc is null if there are no outargs.
+	 */
+	if (tupdesc)
+	{
+		Datum		proargmodes;
+		bool		isnull;
+		ArrayType  *arr;
+		char	   *argmodes;
+		int			nargs,
+					noutargs;
+		ListCell   *lc;
+
+		/*
+		 * Expand named arguments, defaults, etc.  We do not want to scribble
+		 * on the passed-in CallStmt parse tree, so first flat-copy fexpr,
+		 * allowing us to replace its args field.  (Note that
+		 * expand_function_arguments will not modify any of the passed-in data
+		 * structure.)
+		 */
+		{
+			FuncExpr   *nexpr = makeNode(FuncExpr);
+
+			memcpy(nexpr, fexpr, sizeof(FuncExpr));
+			fexpr = nexpr;
+		}
+
+		fexpr->args = expand_function_arguments(fexpr->args,
+												fexpr->funcresulttype,
+												tuple);
+
+		/*
+		 * If we're here, build_function_result_tupdesc_t already validated
+		 * that the procedure has non-null proargmodes that is the right kind
+		 * of array, so it seems unnecessary to check again.
+		 */
+		proargmodes = SysCacheGetAttr(PROCOID, tuple,
+									  Anum_pg_proc_proargmodes,
+									  &isnull);
+		Assert(!isnull);
+		arr = DatumGetArrayTypeP(proargmodes);	/* ensure not toasted */
+		argmodes = (char *) ARR_DATA_PTR(arr);
+
+		nargs = noutargs = 0;
+		foreach(lc, fexpr->args)
+		{
+			Node	   *arg = (Node *) lfirst(lc);
+			Form_pg_attribute att = TupleDescAttr(tupdesc, noutargs);
+			char		argmode = argmodes[nargs++];
+
+			/* ignore non-out arguments */
+			if (argmode == PROARGMODE_IN ||
+				argmode == PROARGMODE_VARIADIC)
+				continue;
+
+			TupleDescInitEntry(tupdesc,
+							   ++noutargs,
+							   NameStr(att->attname),
+							   exprType(arg),
+							   -1,
+							   0);
+		}
+		Assert(tupdesc->natts == noutargs);
+	}
+
 	ReleaseSysCache(tuple);
 
 	return tupdesc;

src/pl/plpgsql/src/expected/plpgsql_call.out

@@ -302,6 +302,40 @@ END
 $$;
 ERROR:  procedure parameter "c" is an output parameter but corresponding argument is not writable
 CONTEXT:  PL/pgSQL function inline_code_block line 5 at CALL
+-- polymorphic OUT arguments
+CREATE PROCEDURE test_proc12(a anyelement, INOUT b anyelement, INOUT c anyarray)
+LANGUAGE plpgsql
+AS $$
+BEGIN
+  RAISE NOTICE 'a: %', a;
+  b := a;
+  c := array[a];
+END;
+$$;
+DO $$
+DECLARE _a int; _b int; _c int[];
+BEGIN
+  _a := 10;
+  CALL test_proc12(_a, _b, _c);
+  RAISE NOTICE '_a: %, _b: %, _c: %', _a, _b, _c;
+END
+$$;
+NOTICE:  a: 10
+NOTICE:  _a: 10, _b: 10, _c: {10}
+DO $$
+DECLARE _a int; _b int; _c text[];
+BEGIN
+  _a := 10;
+  CALL test_proc12(_a, _b, _c);  -- error
+  RAISE NOTICE '_a: %, _b: %, _c: %', _a, _b, _c;
+END
+$$;
+ERROR:  procedure test_proc12(integer, integer, text[]) does not exist
+LINE 1: CALL test_proc12(_a, _b, _c)
+             ^
+HINT:  No procedure matches the given name and argument types. You might need to add explicit type casts.
+QUERY:  CALL test_proc12(_a, _b, _c)
+CONTEXT:  PL/pgSQL function inline_code_block line 5 at CALL
 -- transition variable assignment
 TRUNCATE test1;
 CREATE FUNCTION triggerfunc1() RETURNS trigger

src/pl/plpgsql/src/sql/plpgsql_call.sql

@@ -278,6 +278,36 @@ BEGIN
 END
 $$;
 
+-- polymorphic OUT arguments
+
+CREATE PROCEDURE test_proc12(a anyelement, INOUT b anyelement, INOUT c anyarray)
+LANGUAGE plpgsql
+AS $$
+BEGIN
+  RAISE NOTICE 'a: %', a;
+  b := a;
+  c := array[a];
+END;
+$$;
+
+DO $$
+DECLARE _a int; _b int; _c int[];
+BEGIN
+  _a := 10;
+  CALL test_proc12(_a, _b, _c);
+  RAISE NOTICE '_a: %, _b: %, _c: %', _a, _b, _c;
+END
+$$;
+
+DO $$
+DECLARE _a int; _b int; _c text[];
+BEGIN
+  _a := 10;
+  CALL test_proc12(_a, _b, _c);  -- error
+  RAISE NOTICE '_a: %, _b: %, _c: %', _a, _b, _c;
+END
+$$;
+
 
 -- transition variable assignment
 

src/test/regress/expected/create_procedure.out

@@ -151,6 +151,40 @@ AS $$
 SELECT NULL::int;
 $$;
 CALL ptest6(1, 2);
+CREATE PROCEDURE ptest6a(inout a anyelement, inout b anyelement)
+LANGUAGE SQL
+AS $$
+SELECT $1, $1;
+$$;
+CALL ptest6a(1, null);
+ a | b 
+---+---
+ 1 | 1
+(1 row)
+
+CALL ptest6a(1.1, null);
+  a  |  b  
+-----+-----
+ 1.1 | 1.1
+(1 row)
+
+CREATE PROCEDURE ptest6b(a anyelement, inout b anyelement, inout c anyarray)
+LANGUAGE SQL
+AS $$
+SELECT $1, array[$1];
+$$;
+CALL ptest6b(1, null, null);
+ b |  c  
+---+-----
+ 1 | {1}
+(1 row)
+
+CALL ptest6b(1.1, null, null);
+  b  |   c   
+-----+-------
+ 1.1 | {1.1}
+(1 row)
+
 -- collation assignment
 CREATE PROCEDURE ptest7(a text, b text)
 LANGUAGE SQL

src/test/regress/sql/create_procedure.sql

@@ -109,6 +109,24 @@ $$;
 
 CALL ptest6(1, 2);
 
+CREATE PROCEDURE ptest6a(inout a anyelement, inout b anyelement)
+LANGUAGE SQL
+AS $$
+SELECT $1, $1;
+$$;
+
+CALL ptest6a(1, null);
+CALL ptest6a(1.1, null);
+
+CREATE PROCEDURE ptest6b(a anyelement, inout b anyelement, inout c anyarray)
+LANGUAGE SQL
+AS $$
+SELECT $1, array[$1];
+$$;
+
+CALL ptest6b(1, null, null);
+CALL ptest6b(1.1, null, null);
+
 
 -- collation assignment