release-22.2: sql: fix ambigious udf overload with null arguments

This change backports a small change from a larger PR (#98162) that
prevents short-circuiting type checking for UDF function overloads. This
allows us to do more precise type checking even if inputs are NULL.

Epic: none
Fixes: #88374

Release note (bug fix): Fixes ambiguous calls to UDFs with NULL
arguments.

pkg/sql/logictest/testdata/logic_test/enums

@@ -1751,7 +1751,7 @@ $$;
 query TT
 SELECT "🙏"('😊'), "🙏"(NULL:::"Emoji 😉")
 ----
-NULL  NULL
+NULL  mixed
 
 statement ok
 CREATE DATABASE "DB➕➕";

pkg/sql/logictest/testdata/logic_test/udf

@@ -2839,3 +2839,35 @@ statement error unknown function: public\.LOWERCASE_HINT_ERROR_EXPLICIT_SCHEMA_F
 SELECT public."LOWERCASE_HINT_ERROR_EXPLICIT_SCHEMA_FN"();
 
 subtest end
+
+subtest r88374
+
+statement ok
+CREATE FUNCTION f88374(i INT2) RETURNS INT STRICT LANGUAGE SQL AS 'SELECT 2';
+
+statement ok
+CREATE FUNCTION f88374(i TEXT) RETURNS INT STRICT LANGUAGE SQL AS 'SELECT 2';
+
+statement error pgcode 42725 ambiguous call
+SELECT f88374(NULL);
+
+statement ok
+CREATE TABLE t88374 (a INT, b INT);
+
+statement ok
+INSERT INTO t88374 VALUES (1, NULL);
+
+statement ok
+CREATE FUNCTION g88374 (i INT) RETURNS INT CALLED ON NULL INPUT LANGUAGE SQL AS $$ SELECT a FROM t88374 WHERE b IS NOT DISTINCT FROM i $$;
+
+query I
+SELECT g88374(NULL);
+----
+1
+
+query I
+SELECT g88374(NULL::INT);
+----
+1
+
+subtest end

pkg/sql/sem/tree/type_check.go

@@ -1076,6 +1076,7 @@ func (expr *FuncExpr) TypeCheck(
 		return nil, pgerror.Wrapf(err, pgcode.InvalidParameterValue, "%s()", def.Name)
 	}
 
+	var hasUDFOverload bool
 	var calledOnNullInputFns []overloadImpl
 	var notCalledOnNullInputFns []overloadImpl
 	for _, f := range fns {
@@ -1084,6 +1085,9 @@ func (expr *FuncExpr) TypeCheck(
 		} else {
 			notCalledOnNullInputFns = append(notCalledOnNullInputFns, f)
 		}
+		if f.(QualifiedOverload).IsUDF {
+			hasUDFOverload = true
+		}
 	}
 
 	// If the function is an aggregate that does not accept null arguments and we
@@ -1126,7 +1130,7 @@ func (expr *FuncExpr) TypeCheck(
 	// NULL arguments, the function isn't a generator or aggregate builtin, and
 	// NULL is given as an argument.
 	if len(fns) > 0 && len(calledOnNullInputFns) == 0 && funcCls != GeneratorClass &&
-		funcCls != AggregateClass {
+		funcCls != AggregateClass && !hasUDFOverload {
 		for _, expr := range typedSubExprs {
 			if expr.ResolvedType().Family() == types.UnknownFamily {
 				return DNull, nil