luau/tests/TypeInfer.classes.test.cpp

// This file is part of the Luau programming language and is licensed under MIT License; see LICENSE.txt for details
#include "Luau/BuiltinDefinitions.h"
#include "Luau/Parser.h"
#include "Luau/TypeInfer.h"
#include "Luau/TypeVar.h"

#include "Fixture.h"

#include "doctest.h"

using namespace Luau;
using std::nullopt;

struct ClassFixture : Fixture
{
    ClassFixture()
    {
        TypeArena& arena = typeChecker.globalTypes;
        TypeId numberType = typeChecker.numberType;

        unfreeze(arena);

        TypeId baseClassInstanceType = arena.addType(ClassTypeVar{"BaseClass", {}, nullopt, nullopt, {}, {}});
        getMutable<ClassTypeVar>(baseClassInstanceType)->props = {
            {"BaseMethod", {makeFunction(arena, baseClassInstanceType, {numberType}, {})}},
            {"BaseField", {numberType}},
        };

        TypeId baseClassType = arena.addType(ClassTypeVar{"BaseClass", {}, nullopt, nullopt, {}, {}});
        getMutable<ClassTypeVar>(baseClassType)->props = {
            {"StaticMethod", {makeFunction(arena, nullopt, {}, {numberType})}},
            {"Clone", {makeFunction(arena, nullopt, {baseClassInstanceType}, {baseClassInstanceType})}},
            {"New", {makeFunction(arena, nullopt, {}, {baseClassInstanceType})}},
        };
        typeChecker.globalScope->exportedTypeBindings["BaseClass"] = TypeFun{{}, baseClassInstanceType};
        addGlobalBinding(typeChecker, "BaseClass", baseClassType, "@test");

        TypeId childClassInstanceType = arena.addType(ClassTypeVar{"ChildClass", {}, baseClassInstanceType, nullopt, {}, {}});

        getMutable<ClassTypeVar>(childClassInstanceType)->props = {
            {"Method", {makeFunction(arena, childClassInstanceType, {}, {typeChecker.stringType})}},
        };

        TypeId childClassType = arena.addType(ClassTypeVar{"ChildClass", {}, baseClassType, nullopt, {}, {}});
        getMutable<ClassTypeVar>(childClassType)->props = {
            {"New", {makeFunction(arena, nullopt, {}, {childClassInstanceType})}},
        };
        typeChecker.globalScope->exportedTypeBindings["ChildClass"] = TypeFun{{}, childClassInstanceType};
        addGlobalBinding(typeChecker, "ChildClass", childClassType, "@test");

        TypeId grandChildInstanceType = arena.addType(ClassTypeVar{"GrandChild", {}, childClassInstanceType, nullopt, {}, {}});

        getMutable<ClassTypeVar>(grandChildInstanceType)->props = {
            {"Method", {makeFunction(arena, grandChildInstanceType, {}, {typeChecker.stringType})}},
        };

        TypeId grandChildType = arena.addType(ClassTypeVar{"GrandChild", {}, baseClassType, nullopt, {}, {}});
        getMutable<ClassTypeVar>(grandChildType)->props = {
            {"New", {makeFunction(arena, nullopt, {}, {grandChildInstanceType})}},
        };
        typeChecker.globalScope->exportedTypeBindings["GrandChild"] = TypeFun{{}, grandChildInstanceType};
        addGlobalBinding(typeChecker, "GrandChild", childClassType, "@test");

        TypeId anotherChildInstanceType = arena.addType(ClassTypeVar{"AnotherChild", {}, baseClassInstanceType, nullopt, {}, {}});

        getMutable<ClassTypeVar>(anotherChildInstanceType)->props = {
            {"Method", {makeFunction(arena, anotherChildInstanceType, {}, {typeChecker.stringType})}},
        };

        TypeId anotherChildType = arena.addType(ClassTypeVar{"AnotherChild", {}, baseClassType, nullopt, {}, {}});
        getMutable<ClassTypeVar>(anotherChildType)->props = {
            {"New", {makeFunction(arena, nullopt, {}, {anotherChildInstanceType})}},
        };
        typeChecker.globalScope->exportedTypeBindings["AnotherChild"] = TypeFun{{}, anotherChildInstanceType};
        addGlobalBinding(typeChecker, "AnotherChild", childClassType, "@test");

        TypeId vector2MetaType = arena.addType(TableTypeVar{});

        TypeId vector2InstanceType = arena.addType(ClassTypeVar{"Vector2", {}, nullopt, vector2MetaType, {}, {}});
        getMutable<ClassTypeVar>(vector2InstanceType)->props = {
            {"X", {numberType}},
            {"Y", {numberType}},
        };

        TypeId vector2Type = arena.addType(ClassTypeVar{"Vector2", {}, nullopt, nullopt, {}, {}});
        getMutable<ClassTypeVar>(vector2Type)->props = {
            {"New", {makeFunction(arena, nullopt, {numberType, numberType}, {vector2InstanceType})}},
        };
        getMutable<TableTypeVar>(vector2MetaType)->props = {
            {"__add", {makeFunction(arena, nullopt, {vector2InstanceType, vector2InstanceType}, {vector2InstanceType})}},
        };
        typeChecker.globalScope->exportedTypeBindings["Vector2"] = TypeFun{{}, vector2InstanceType};
        addGlobalBinding(typeChecker, "Vector2", vector2Type, "@test");

        freeze(arena);
    }
};

TEST_SUITE_BEGIN("TypeInferClasses");

TEST_CASE_FIXTURE(ClassFixture, "call_method_of_a_class")
{
    CheckResult result = check(R"(
        local m = BaseClass.StaticMethod()
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    REQUIRE_EQ("number", toString(requireType("m")));
}

TEST_CASE_FIXTURE(ClassFixture, "call_method_of_a_child_class")
{
    CheckResult result = check(R"(
        local m = ChildClass.StaticMethod()
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    REQUIRE_EQ("number", toString(requireType("m")));
}

TEST_CASE_FIXTURE(ClassFixture, "call_instance_method")
{
    CheckResult result = check(R"(
        local i = ChildClass.New()
        local result = i:Method()
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    CHECK_EQ("string", toString(requireType("result")));
}

TEST_CASE_FIXTURE(ClassFixture, "call_base_method")
{
    CheckResult result = check(R"(
        local i = ChildClass.New()
        i:BaseMethod(41)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(ClassFixture, "cannot_call_unknown_method_of_a_class")
{
    CheckResult result = check(R"(
        local m = BaseClass.Nope()
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
}

TEST_CASE_FIXTURE(ClassFixture, "cannot_call_method_of_child_on_base_instance")
{
    CheckResult result = check(R"(
        local i = BaseClass.New()
        i:Method()
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
}

TEST_CASE_FIXTURE(ClassFixture, "we_can_infer_that_a_parameter_must_be_a_particular_class")
{
    CheckResult result = check(R"(
        function makeClone(o)
            return BaseClass.Clone(o)
        end

        local a = makeClone(ChildClass.New())
    )");

    CHECK_EQ("BaseClass", toString(requireType("a")));
}

TEST_CASE_FIXTURE(ClassFixture, "we_can_report_when_someone_is_trying_to_use_a_table_rather_than_a_class")
{
    CheckResult result = check(R"(
        function makeClone(o)
            return BaseClass.Clone(o)
        end

        type Oopsies = { BaseMethod: (Oopsies, number) -> ()}

        local oopsies: Oopsies = {
            BaseMethod = function (self: Oopsies, i: number)
                print('gadzooks!')
            end
        }

        makeClone(oopsies)
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
    TypeMismatch* tm = get<TypeMismatch>(result.errors[0]);
    REQUIRE(tm != nullptr);

    CHECK_EQ("Oopsies", toString(tm->givenType));
    CHECK_EQ("BaseClass", toString(tm->wantedType));
}

TEST_CASE_FIXTURE(ClassFixture, "assign_to_prop_of_class")
{
    CheckResult result = check(R"(
        local v = Vector2.New(0, 5)
        v.X = 55
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(ClassFixture, "can_read_prop_of_base_class")
{
    CheckResult result = check(R"(
        local c = ChildClass.New()
        local x = 1 + c.BaseField
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(ClassFixture, "can_assign_to_prop_of_base_class")
{
    CheckResult result = check(R"(
        local c = ChildClass.New()
        c.BaseField = 444
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(ClassFixture, "can_read_prop_of_base_class_using_string")
{
    ScopedFastFlag luauClassPropertyAccessAsString("LuauClassPropertyAccessAsString", true);

    CheckResult result = check(R"(
        local c = ChildClass.New()
        local x = 1 + c["BaseField"]
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(ClassFixture, "can_assign_to_prop_of_base_class_using_string")
{
    ScopedFastFlag luauClassPropertyAccessAsString("LuauClassPropertyAccessAsString", true);

    CheckResult result = check(R"(
        local c = ChildClass.New()
        c["BaseField"] = 444
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(ClassFixture, "cannot_unify_class_instance_with_primitive")
{
    CheckResult result = check(R"(
        local v = Vector2.New(0, 5)
        v = 444
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
}

TEST_CASE_FIXTURE(ClassFixture, "warn_when_prop_almost_matches")
{
    CheckResult result = check(R"(
        Vector2.new(0, 0)
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);

    auto err = get<UnknownPropButFoundLikeProp>(result.errors[0]);
    REQUIRE(err != nullptr);

    REQUIRE_EQ(1, err->candidates.size());
    CHECK_EQ("New", *err->candidates.begin());
}

TEST_CASE_FIXTURE(ClassFixture, "classes_can_have_overloaded_operators")
{
    CheckResult result = check(R"(
        local a = Vector2.New(1, 2)
        local b = Vector2.New(3, 4)
        local c = a + b
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    CHECK_EQ("Vector2", toString(requireType("c")));
}

TEST_CASE_FIXTURE(ClassFixture, "classes_without_overloaded_operators_cannot_be_added")
{
    CheckResult result = check(R"(
        local a = BaseClass.New()
        local b = BaseClass.New()
        local c = a + b
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
}

TEST_CASE_FIXTURE(ClassFixture, "function_arguments_are_covariant")
{
    CheckResult result = check(R"(
        function f(b: BaseClass) end

        f(ChildClass.New())
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(ClassFixture, "higher_order_function_arguments_are_contravariant")
{
    CheckResult result = check(R"(
        function apply(f: (BaseClass) -> ())
            f(ChildClass.New()) -- 2
        end

        apply(function (c: ChildClass) end) -- 5
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
}

TEST_CASE_FIXTURE(ClassFixture, "higher_order_function_return_values_are_covariant")
{
    CheckResult result = check(R"(
        function apply(f: () -> BaseClass)
            return f()
        end

        apply(function ()
            return ChildClass.New()
        end)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(ClassFixture, "higher_order_function_return_type_is_not_contravariant")
{
    CheckResult result = check(R"(
        function apply(f: () -> BaseClass)
            return f()
        end

        apply(function ()
            return ChildClass.New()
        end)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(ClassFixture, "table_properties_are_invariant")
{
    CheckResult result = check(R"(
        function f(a: {foo: BaseClass})
            a.foo = AnotherChild.New()
        end

        local t: {foo: ChildClass}
        f(t) -- line 6.  Breaks soundness.

        function g(t: {foo: ChildClass})
        end

        local t2: {foo: BaseClass} = {foo=BaseClass.New()}
        t2.foo = AnotherChild.New()
        g(t2) -- line 13.  Breaks soundness
    )");

    LUAU_REQUIRE_ERROR_COUNT(2, result);
    CHECK_EQ(6, result.errors[0].location.begin.line);
    CHECK_EQ(13, result.errors[1].location.begin.line);
}

TEST_CASE_FIXTURE(ClassFixture, "table_indexers_are_invariant")
{
    CheckResult result = check(R"(
        function f(a: {[number]: BaseClass})
            a[1] = AnotherChild.New()
        end

        local t: {[number]: ChildClass}
        f(t) -- line 6.  Breaks soundness.

        function g(t: {[number]: ChildClass})
        end

        local t2: {[number]: BaseClass} = {BaseClass.New()}
        t2[1] = AnotherChild.New()
        g(t2) -- line 13.  Breaks soundness
    )");

    LUAU_REQUIRE_ERROR_COUNT(2, result);
    CHECK_EQ(6, result.errors[0].location.begin.line);
    CHECK_EQ(13, result.errors[1].location.begin.line);
}

TEST_CASE_FIXTURE(ClassFixture, "table_class_unification_reports_sane_errors_for_missing_properties")
{
    CheckResult result = check(R"(
        function foo(bar)
            bar.Y = 1 -- valid
            bar.x = 2 -- invalid, wanted 'X'
            bar.w = 2 -- invalid
        end

        local a: Vector2
        foo(a)
    )");

    LUAU_REQUIRE_ERROR_COUNT(2, result);
    REQUIRE_EQ("Key 'w' not found in class 'Vector2'", toString(result.errors[0]));
    REQUIRE_EQ("Key 'x' not found in class 'Vector2'.  Did you mean 'X'?", toString(result.errors[1]));
}

TEST_CASE_FIXTURE(ClassFixture, "class_unification_type_mismatch_is_correct_order")
{
    CheckResult result = check(R"(
        local p: BaseClass
        local foo: number = p
        local foo2: BaseClass = 1
    )");

    LUAU_REQUIRE_ERROR_COUNT(2, result);

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

TEST_CASE_FIXTURE(ClassFixture, "optional_class_field_access_error")
{
    CheckResult result = check(R"(
local b: Vector2? = nil
local a = b.X + b.Z

b.X = 2 -- real Vector2.X is also read-only
    )");

    LUAU_REQUIRE_ERROR_COUNT(4, result);
    CHECK_EQ("Value of type 'Vector2?' could be nil", toString(result.errors[0]));
    CHECK_EQ("Value of type 'Vector2?' could be nil", toString(result.errors[1]));
    CHECK_EQ("Key 'Z' not found in class 'Vector2'", toString(result.errors[2]));
    CHECK_EQ("Value of type 'Vector2?' could be nil", toString(result.errors[3]));
}

TEST_SUITE_END();