tree: don't match variadic builtins when arg list is too short

The new processing for variadic builtins is pretty permissive in what it
allows because they underlying implementations are pretty permissive in
what they accept. However, fixed arguments are still fixed arguments and
must match.

Fixes: #144447
Release note: None

Author: mw5h

pkg/sql/logictest/testdata/logic_test/builtin_function

@@ -2718,6 +2718,12 @@ Testing three, two, three
 query error pq: format\(\): error parsing format string: not enough arguments
 SELECT format(E'%2\x24s','foo');
 
+statement error pgcode 42883 pq: unknown signature: format\(\)
+SELECT format();
+
+statement error pgcode 42883 pq: unknown signature: format\(int\)
+SELECT format(42);
+
 subtest pg_is_in_recovery
 
 query B colnames

pkg/sql/sem/tree/overload.go

@@ -917,6 +917,9 @@ func (s *overloadTypeChecker) typeCheckOverloadedExprs(
 	// Process variadic functions with unrestrained wildcards as their variadic
 	// parameter. This special cas short circuits the logic below, most of which
 	// assumes AnyElement behavior for untyped parameters.
+	//
+	// TODO(mw5h): This is an ugly special case. Refactor this to use the logic
+	// below. I'd do it now but it's a bit too high risk this close to 25.2.
 	for i := range s.params {
 		if vt, ok := s.params[i].(VariadicType); ok && vt.VarType == types.Any {
 			if semaCtx.UsePre_25_2VariadicBuiltins {
@@ -926,16 +929,25 @@ func (s *overloadTypeChecker) typeCheckOverloadedExprs(
 			if numOverloads > 1 {
 				return errors.AssertionFailedf(
 					"only one overload can have VariadicType {types.Any} parameters")
+			} else if !vt.MatchLen(len(s.exprs)) {
+				s.overloadIdxs = s.overloadIdxs[:0]
+				return nil
 			}
+			typeCheckOk := true
 			for j := range s.exprs {
 				typedExpr, err := s.exprs[j].TypeCheck(ctx, semaCtx, vt.GetAt(j))
 				if err != nil {
 					return pgerror.Wrapf(err, pgcode.InvalidParameterValue,
 						"error type checking resolved expression:")
+				} else if !vt.MatchAt(typedExpr.ResolvedType(), j) {
+					typeCheckOk = false
 				}
 				s.typedExprs[j] = typedExpr
 			}
-			s.overloadIdxs = append(s.overloadIdxs[:0], uint8(i))
+			s.overloadIdxs = s.overloadIdxs[:0]
+			if typeCheckOk {
+				s.overloadIdxs = append(s.overloadIdxs, uint8(i))
+			}
 			return nil
 		}
 	}