implement leading bar and ampersand in types

Ast/src/Parser.cpp

@@ -1523,7 +1523,11 @@ AstType* Parser::parseFunctionTypeTail(const Lexeme& begin, AstArray<AstGenericT
 AstType* Parser::parseTypeSuffix(AstType* type, const Location& begin)
 {
     TempVector<AstType*> parts(scratchType);
-    parts.push_back(type);
+
+    if (type != nullptr)
+    {
+        parts.push_back(type);
+    }
 
     incrementRecursionCounter("type annotation");
 
@@ -1622,11 +1626,17 @@ AstTypeOrPack Parser::parseTypeOrPack()
 
 AstType* Parser::parseType(bool inDeclarationContext)
 {
+    Location begin = lexer.current().location;
+
+    Lexeme::Type c = lexer.current().type;
+    if (c == '|' || c == '&')
+    {
+        return parseTypeSuffix(nullptr, begin);
+    }
+
     unsigned int oldRecursionCount = recursionCounter;
     // recursion counter is incremented in parseSimpleType
 
-    Location begin = lexer.current().location;
-
     AstType* type = parseSimpleType(/* allowPack= */ false, /* in declaration context */ inDeclarationContext).type;
 
     recursionCounter = oldRecursionCount;

tests/Parser.test.cpp

@@ -3167,4 +3167,14 @@ TEST_CASE_FIXTURE(Fixture, "read_write_table_properties")
     LUAU_ASSERT(pr.errors.size() == 0);
 }
 
+TEST_CASE_FIXTURE(Fixture, "can_parse_leading_bar_unions_successfully")
+{
+    parse(R"(type A = | "Hello" | "World")");
+}
+
+TEST_CASE_FIXTURE(Fixture, "can_parse_leading_ampersand_intersections_successfully")
+{
+    parse(R"(type A = & { string } & { number })");
+}
+
 TEST_SUITE_END();