luau/tests/TypeInfer.singletons.test.cpp

// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details

#include "Fixture.h"

#include "doctest.h"

using namespace Luau;

LUAU_FASTFLAG(DebugLuauDeferredConstraintResolution);

TEST_SUITE_BEGIN("TypeSingletons");

TEST_CASE_FIXTURE(Fixture, "function_args_infer_singletons")
{
    CheckResult result = check(R"(
--!strict
type Phase = "A" | "B" | "C"
local function f(e : Phase) : number
    return 0
end
local e = f("B")
)");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "bool_singletons")
{
    CheckResult result = check(R"(
        local a: true = true
        local b: false = false
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "string_singletons")
{
    CheckResult result = check(R"(
        local a: "foo" = "foo"
        local b: "bar" = "bar"
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "string_singleton_function_call")
{
    if (!FFlag::DebugLuauDeferredConstraintResolution)
        return;

    CheckResult result = check(R"(
        local x = "a"
        function f(x: "a") end
        f(x)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "bool_singletons_mismatch")
{
    CheckResult result = check(R"(
        local a: true = false
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
    CHECK_EQ("Type 'false' could not be converted into 'true'", toString(result.errors[0]));
}

TEST_CASE_FIXTURE(Fixture, "string_singletons_mismatch")
{
    CheckResult result = check(R"(
        local a: "foo" = "bar"
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
    CHECK_EQ("Type '\"bar\"' could not be converted into '\"foo\"'", toString(result.errors[0]));
}

TEST_CASE_FIXTURE(Fixture, "string_singletons_escape_chars")
{
    CheckResult result = check(R"(
        local a: "\n" = "\000\r"
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
    CHECK_EQ(R"(Type '"\000\r"' could not be converted into '"\n"')", toString(result.errors[0]));
}

TEST_CASE_FIXTURE(Fixture, "bool_singleton_subtype")
{
    CheckResult result = check(R"(
        local a: true = true
        local b: boolean = a
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "string_singleton_subtype")
{
    CheckResult result = check(R"(
        local a: "foo" = "foo"
        local b: string = a
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "string_singleton_subtype_multi_assignment")
{
    CheckResult result = check(R"(
        local a: "foo" = "foo"
        local b: string, c: number = a, 10
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "function_call_with_singletons")
{
    CheckResult result = check(R"(
        function f(a: true, b: "foo") end
        f(true, "foo")
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "function_call_with_singletons_mismatch")
{
    CheckResult result = check(R"(
        function f(a: true, b: "foo") end
        f(true, "bar")
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
    CHECK_EQ("Type '\"bar\"' could not be converted into '\"foo\"'", toString(result.errors[0]));
}

TEST_CASE_FIXTURE(Fixture, "overloaded_function_call_with_singletons")
{
    CheckResult result = check(R"(
        function f(a, b) end
        local g : ((true, string) -> ()) & ((false, number) -> ()) = (f::any)
        g(true, "foo")
        g(false, 37)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "overloaded_function_call_with_singletons_mismatch")
{
    CheckResult result = check(R"(
        function f(g: ((true, string) -> ()) & ((false, number) -> ()))
            g(true, 37)
        end
    )");

    LUAU_REQUIRE_ERROR_COUNT(2, result);
    if (FFlag::DebugLuauDeferredConstraintResolution)
    {
        CHECK_EQ("None of the overloads for function that accept 2 arguments are compatible.", toString(result.errors[0]));
        CHECK_EQ("Available overloads: (true, string) -> (); and (false, number) -> ()", toString(result.errors[1]));
    }
    else
    {
        CHECK_EQ("Type 'number' could not be converted into 'string'", toString(result.errors[0]));
        CHECK_EQ("Other overloads are also not viable: (false, number) -> ()", toString(result.errors[1]));
    }
}

TEST_CASE_FIXTURE(Fixture, "enums_using_singletons")
{
    CheckResult result = check(R"(
        type MyEnum = "foo" | "bar" | "baz"
        local a : MyEnum = "foo"
        local b : MyEnum = "bar"
        local c : MyEnum = "baz"
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "enums_using_singletons_mismatch")
{
    CheckResult result = check(R"(
        type MyEnum = "foo" | "bar" | "baz"
        local a : MyEnum = "bang"
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
    CHECK_EQ("Type '\"bang\"' could not be converted into '\"bar\" | \"baz\" | \"foo\"'; none of the union options are compatible",
        toString(result.errors[0]));
}

TEST_CASE_FIXTURE(Fixture, "enums_using_singletons_subtyping")
{
    CheckResult result = check(R"(
        type MyEnum1 = "foo" | "bar"
        type MyEnum2 = MyEnum1 | "baz"
        local a : MyEnum1 = "foo"
        local b : MyEnum2 = a
        local c : string = b
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "tagged_unions_using_singletons")
{
    CheckResult result = check(R"(
        type Dog = { tag: "Dog", howls: boolean }
        type Cat = { tag: "Cat", meows: boolean }
        type Animal = Dog | Cat
        local a : Dog = { tag = "Dog", howls = true }
        local b : Animal = { tag = "Cat", meows = true }
        local c : Animal = a
        c = b
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "tagged_unions_using_singletons_mismatch")
{
    CheckResult result = check(R"(
        type Dog = { tag: "Dog", howls: boolean }
        type Cat = { tag: "Cat", meows: boolean }
        type Animal = Dog | Cat
        local a : Animal = { tag = "Cat", howls = true }
    )");

    LUAU_REQUIRE_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "tagged_unions_immutable_tag")
{
    CheckResult result = check(R"(
        type Dog = { tag: "Dog", howls: boolean }
        type Cat = { tag: "Cat", meows: boolean }
        type Animal = Dog | Cat
        local a: Animal = { tag = "Cat", meows = true }
        a.tag = "Dog"
    )");

    LUAU_REQUIRE_ERRORS(result);

    if (FFlag::DebugLuauDeferredConstraintResolution)
    {
        CannotAssignToNever* tm = get<CannotAssignToNever>(result.errors[0]);
        REQUIRE(tm);

        CHECK(builtinTypes->stringType == tm->rhsType);
        CHECK(CannotAssignToNever::Reason::PropertyNarrowed == tm->reason);
        REQUIRE(tm->cause.size() == 2);
        CHECK("\"Dog\"" == toString(tm->cause[0]));
        CHECK("\"Cat\"" == toString(tm->cause[1]));
    }
}

TEST_CASE_FIXTURE(Fixture, "table_has_a_boolean")
{
    CheckResult result = check(R"(
        local t={a=1,b=false}
    )");

    CHECK("{ a: number, b: boolean }" == toString(requireType("t"), {true}));
}

TEST_CASE_FIXTURE(Fixture, "table_properties_singleton_strings")
{
    CheckResult result = check(R"(
        --!strict
        type T = {
            ["foo"] : number,
            ["$$bar"] : string,
            baz : boolean
        }
        local t: T =  {
            ["foo"] = 37,
            ["$$bar"] = "hi",
            baz = true
        }
        local a: number = t.foo
        local b: string = t["$$bar"]
        local c: boolean = t.baz
        t.foo = 5
        t["$$bar"] = "lo"
        t.baz = false
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}
TEST_CASE_FIXTURE(Fixture, "table_properties_singleton_strings_mismatch")
{
    CheckResult result = check(R"(
        --!strict
        type T = {
            ["$$bar"] : string,
        }
        local t: T =  {
            ["$$bar"] = "hi",
        }
        t["$$bar"] = 5
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
    CHECK_EQ("Type 'number' could not be converted into 'string'", toString(result.errors[0]));
}

TEST_CASE_FIXTURE(Fixture, "table_properties_alias_or_parens_is_indexer")
{
    CheckResult result = check(R"(
        --!strict
        type S = "bar"
        type T = {
            [("foo")] : number,
            [S] : string,
        }
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
    CHECK_EQ("Cannot have more than one table indexer", toString(result.errors[0]));
}

TEST_CASE_FIXTURE(Fixture, "table_properties_type_error_escapes")
{
    CheckResult result = check(R"(
        --!strict
        local x: { ["<>"] : number }
        x = { ["\n"] = 5 }
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
    CHECK_EQ(R"(Table type '{ ["\n"]: number }' not compatible with type '{| ["<>"]: number |}' because the former is missing field '<>')",
        toString(result.errors[0]));
}

TEST_CASE_FIXTURE(Fixture, "error_detailed_tagged_union_mismatch_string")
{
    CheckResult result = check(R"(
type Cat = { tag: 'cat', catfood: string }
type Dog = { tag: 'dog', dogfood: string }
type Animal = Cat | Dog

local a: Animal = { tag = 'cat', cafood = 'something' }
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
    const std::string expected = R"(Type 'a' could not be converted into 'Cat | Dog'
caused by:
  None of the union options are compatible. For example:
Table type 'a' not compatible with type 'Cat' because the former is missing field 'catfood')";
    CHECK_EQ(expected, toString(result.errors[0]));
}

TEST_CASE_FIXTURE(Fixture, "error_detailed_tagged_union_mismatch_bool")
{
    CheckResult result = check(R"(
type Good = { success: true, result: string }
type Bad = { success: false, error: string }
type Result = Good | Bad

local a: Result = { success = false, result = 'something' }
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
    const std::string expected = R"(Type 'a' could not be converted into 'Bad | Good'
caused by:
  None of the union options are compatible. For example:
Table type 'a' not compatible with type 'Bad' because the former is missing field 'error')";
    CHECK_EQ(expected, toString(result.errors[0]));
}

TEST_CASE_FIXTURE(Fixture, "parametric_tagged_union_alias")
{
    ScopedFastFlag sff[] = {
        {FFlag::DebugLuauDeferredConstraintResolution, true},
    };
    CheckResult result = check(R"(
        type Ok<T> = {success: true, result: T}
        type Err<T> = {success: false, error: T}
        type Result<O, E> = Ok<O> | Err<E>

        local a : Result<string, number> = {success = false, result = "hotdogs"}
        -- local b : Result<string, number> = {success = true, result = "hotdogs"}
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);

    const std::string expectedError = R"(Type
    '{ result: string, success: boolean }'
could not be converted into
    'Err<number> | Ok<string>')";

    CHECK(toString(result.errors[0]) == expectedError);
}

TEST_CASE_FIXTURE(Fixture, "if_then_else_expression_singleton_options")
{
    CheckResult result = check(R"(
type Cat = { tag: 'cat', catfood: string }
type Dog = { tag: 'dog', dogfood: string }
type Animal = Cat | Dog

local a: Animal = if true then { tag = 'cat', catfood = 'something' } else { tag = 'dog', dogfood = 'other' }
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "widen_the_supertype_if_it_is_free_and_subtype_has_singleton")
{
    CheckResult result = check(R"(
        local function foo(f, x)
            if x == "hi" then
                f(x)
                f("foo")
            end
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    CHECK_EQ(R"("hi")", toString(requireTypeAtPosition({3, 18})));
    // should be <a...>((string) -> a..., string) -> () but needs lower bounds calculation
    CHECK_EQ("<a, b...>((string) -> (b...), a) -> ()", toString(requireType("foo")));
}

TEST_CASE_FIXTURE(Fixture, "return_type_of_f_is_not_widened")
{
    CheckResult result = check(R"(
        local function foo(f, x): "hello"? -- anyone there?
            return if x == "hi"
                then f(x)
                else nil
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    CHECK_EQ(R"("hi")", toString(requireTypeAtPosition({3, 23})));
    CHECK_EQ(R"(<a, b, c...>((string) -> (a, c...), b) -> "hello"?)", toString(requireType("foo")));
    // CHECK_EQ(R"(<a, b...>((string) -> ("hello"?, b...), a) -> "hello"?)", toString(requireType("foo")));
}

TEST_CASE_FIXTURE(Fixture, "widening_happens_almost_everywhere")
{
    CheckResult result = check(R"(
        local foo: "foo" = "foo"
        local copy = foo
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    if (FFlag::DebugLuauDeferredConstraintResolution)
        CHECK_EQ(R"("foo")", toString(requireType("copy")));
    else
        CHECK_EQ("string", toString(requireType("copy")));
}

TEST_CASE_FIXTURE(Fixture, "widening_happens_almost_everywhere_except_for_tables")
{
    CheckResult result = check(R"(
        type Cat = {tag: "Cat", meows: boolean}
        type Dog = {tag: "Dog", barks: boolean}
        type Animal = Cat | Dog

        local function f(tag: "Cat" | "Dog"): Animal?
            if tag == "Cat" then
                local result = {tag = tag, meows = true}
                return result
            elseif tag == "Dog" then
                local result = {tag = tag, barks = true}
                return result
            else
                return nil
            end
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "functions_are_not_to_be_widened")
{
    CheckResult result = check(R"(
        local function foo(my_enum: "A" | "B") end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    CHECK_EQ(R"(("A" | "B") -> ())", toString(requireType("foo")));
}

TEST_CASE_FIXTURE(Fixture, "indexing_on_string_singletons")
{
    CheckResult result = check(R"(
        local a: string = "hi"
        if a == "hi" then
            local x = a:byte()
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    CHECK_EQ(R"("hi")", toString(requireTypeAtPosition({3, 22})));
}

TEST_CASE_FIXTURE(Fixture, "indexing_on_union_of_string_singletons")
{
    CheckResult result = check(R"(
        local a: string = "hi"
        if a == "hi" or a == "bye" then
            local x = a:byte()
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    CHECK_EQ(R"("bye" | "hi")", toString(requireTypeAtPosition({3, 22})));
}

TEST_CASE_FIXTURE(Fixture, "taking_the_length_of_string_singleton")
{
    CheckResult result = check(R"(
        local a: string = "hi"
        if a == "hi" then
            local x = #a
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    CHECK_EQ(R"("hi")", toString(requireTypeAtPosition({3, 23})));
}

TEST_CASE_FIXTURE(Fixture, "taking_the_length_of_union_of_string_singleton")
{
    CheckResult result = check(R"(
        local a: string = "hi"
        if a == "hi" or a == "bye" then
            local x = #a
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    CHECK_EQ(R"("bye" | "hi")", toString(requireTypeAtPosition({3, 23})));
}

TEST_CASE_FIXTURE(Fixture, "no_widening_from_callsites")
{
    CheckResult result = check(R"(
        type Direction = "North" | "East" | "West" | "South"

        local function direction(): Direction
            return "North"
        end

        local d: Direction = direction()
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(BuiltinsFixture, "singletons_stick_around_under_assignment")
{
    CheckResult result = check(R"(
        type Foo = {
            kind: "Foo",
        }

        local foo = (nil :: any) :: Foo

        print(foo.kind == "Bar") -- type of equality refines to `false`
        local kind = foo.kind
        print(kind == "Bar") -- type of equality refines to `false`
    )");

    if (FFlag::DebugLuauDeferredConstraintResolution)
        LUAU_REQUIRE_NO_ERRORS(result);
    else
        LUAU_REQUIRE_ERROR_COUNT(1, result);
}

TEST_SUITE_END();