DateFunctionReturnTypeHelper: prevent unnecessary TypeCombinator::union() (#5629)

Author: staabm

src/Type/Php/DateFunctionReturnTypeHelper.php

@@ -30,13 +30,13 @@ public function getTypeFromFormatType(Type $formatType, bool $useMicrosec): Type
 		}
 
 		if (count($types) === 0) {
-			$types[] = $formatType->isNonEmptyString()->yes()
+			$type = $formatType->isNonEmptyString()->yes()
 				? new IntersectionType([new StringType(), new AccessoryNonEmptyStringType()])
 				: new StringType();
+		} else {
+			$type = TypeCombinator::union(...$types);
 		}
 
-		$type = TypeCombinator::union(...$types);
-
 		if ($type->isNumericString()->no() && $formatType->isNonEmptyString()->yes()) {
 			$type = TypeCombinator::union($type, new IntersectionType([
 				new StringType(), new AccessoryNonEmptyStringType(),