luau/tests/TypeInfer.functions.test.cpp

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

#include "Luau/AstQuery.h"
#include "Luau/BuiltinDefinitions.h"
#include "Luau/Scope.h"
#include "Luau/TypeInfer.h"
#include "Luau/TypeVar.h"
#include "Luau/VisitTypeVar.h"

#include "Fixture.h"

#include "doctest.h"

using namespace Luau;

TEST_SUITE_BEGIN("TypeInferFunctions");

TEST_CASE_FIXTURE(Fixture, "tc_function")
{
    CheckResult result = check("function five() return 5 end");
    LUAU_REQUIRE_NO_ERRORS(result);

    const FunctionTypeVar* fiveType = get<FunctionTypeVar>(requireType("five"));
    REQUIRE(fiveType != nullptr);
}

TEST_CASE_FIXTURE(Fixture, "check_function_bodies")
{
    CheckResult result = check("function myFunction()    local a = 0    a = true    end");
    LUAU_REQUIRE_ERROR_COUNT(1, result);

    CHECK_EQ(result.errors[0], (TypeError{Location{Position{0, 44}, Position{0, 48}}, TypeMismatch{
                                                                                          typeChecker.numberType,
                                                                                          typeChecker.booleanType,
                                                                                      }}));
}

TEST_CASE_FIXTURE(Fixture, "infer_return_type")
{
    CheckResult result = check("function take_five() return 5 end");
    LUAU_REQUIRE_NO_ERRORS(result);

    const FunctionTypeVar* takeFiveType = get<FunctionTypeVar>(requireType("take_five"));
    REQUIRE(takeFiveType != nullptr);

    std::vector<TypeId> retVec = flatten(takeFiveType->retType).first;
    REQUIRE(!retVec.empty());

    REQUIRE_EQ(*follow(retVec[0]), *typeChecker.numberType);
}

TEST_CASE_FIXTURE(Fixture, "infer_from_function_return_type")
{
    CheckResult result = check("function take_five() return 5 end    local five = take_five()");
    LUAU_REQUIRE_NO_ERRORS(result);

    CHECK_EQ(*typeChecker.numberType, *follow(requireType("five")));
}

TEST_CASE_FIXTURE(Fixture, "infer_that_function_does_not_return_a_table")
{
    CheckResult result = check(R"(
        function take_five()
            return 5
        end

        take_five().prop = 888
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
    CHECK_EQ(result.errors[0], (TypeError{Location{Position{5, 8}, Position{5, 24}}, NotATable{typeChecker.numberType}}));
}

TEST_CASE_FIXTURE(Fixture, "vararg_functions_should_allow_calls_of_any_types_and_size")
{
    CheckResult result = check(R"(
        function f(...) end

        f(1)
        f("foo", 2)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "vararg_function_is_quantified")
{
    CheckResult result = check(R"(
        local T = {}
        function T.f(...)
            local result = {}

            for i = 1, select("#", ...) do
                local dictionary = select(i, ...)
                for key, value in pairs(dictionary) do
                    result[key] = value
                end
            end

            return result
         end

        return T
    )");

    auto r = first(getMainModule()->getModuleScope()->returnType);
    REQUIRE(r);

    TableTypeVar* ttv = getMutable<TableTypeVar>(*r);
    REQUIRE(ttv);

    TypeId k = ttv->props["f"].type;
    REQUIRE(k);

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "list_only_alternative_overloads_that_match_argument_count")
{
    CheckResult result = check(R"(
        local multiply: ((number)->number) & ((number)->string) & ((number, number)->number)
        multiply("")
    )");

    LUAU_REQUIRE_ERROR_COUNT(2, result);

    TypeMismatch* tm = get<TypeMismatch>(result.errors[0]);
    REQUIRE(tm);
    CHECK_EQ(typeChecker.numberType, tm->wantedType);
    CHECK_EQ(typeChecker.stringType, tm->givenType);

    ExtraInformation* ei = get<ExtraInformation>(result.errors[1]);
    REQUIRE(ei);
    CHECK_EQ("Other overloads are also not viable: (number) -> string", ei->message);
}

TEST_CASE_FIXTURE(Fixture, "list_all_overloads_if_no_overload_takes_given_argument_count")
{
    CheckResult result = check(R"(
        local multiply: ((number)->number) & ((number)->string) & ((number, number)->number)
        multiply()
    )");

    LUAU_REQUIRE_ERROR_COUNT(2, result);

    GenericError* ge = get<GenericError>(result.errors[0]);
    REQUIRE(ge);
    CHECK_EQ("No overload for function accepts 0 arguments.", ge->message);

    ExtraInformation* ei = get<ExtraInformation>(result.errors[1]);
    REQUIRE(ei);
    CHECK_EQ("Available overloads: (number) -> number; (number) -> string; and (number, number) -> number", ei->message);
}

TEST_CASE_FIXTURE(Fixture, "dont_give_other_overloads_message_if_only_one_argument_matching_overload_exists")
{
    CheckResult result = check(R"(
        local multiply: ((number)->number) & ((number)->string) & ((number, number)->number)
        multiply(1, "")
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);

    TypeMismatch* tm = get<TypeMismatch>(result.errors[0]);
    REQUIRE(tm);
    CHECK_EQ(typeChecker.numberType, tm->wantedType);
    CHECK_EQ(typeChecker.stringType, tm->givenType);
}

TEST_CASE_FIXTURE(Fixture, "infer_return_type_from_selected_overload")
{
    CheckResult result = check(R"(
        type T = {method: ((T, number) -> number) & ((number) -> string)}
        local T: T

        local a = T.method(T, 4)
        local b = T.method(5)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
    CHECK_EQ("number", toString(requireType("a")));
    CHECK_EQ("string", toString(requireType("b")));
}

TEST_CASE_FIXTURE(Fixture, "too_many_arguments")
{
    CheckResult result = check(R"(
        --!nonstrict

        function g(a: number) end

        g()

    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);

    auto err = result.errors[0];
    auto acm = get<CountMismatch>(err);
    REQUIRE(acm);

    CHECK_EQ(1, acm->expected);
    CHECK_EQ(0, acm->actual);
}

TEST_CASE_FIXTURE(Fixture, "recursive_function")
{
    CheckResult result = check(R"(
        function count(n: number)
            if n == 0 then
                return 0
            else
                return count(n - 1)
            end
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "lambda_form_of_local_function_cannot_be_recursive")
{
    CheckResult result = check(R"(
        local f = function() return f() end
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
}

TEST_CASE_FIXTURE(Fixture, "recursive_local_function")
{
    CheckResult result = check(R"(
        local function count(n: number)
            if n == 0 then
                return 0
            else
                return count(n - 1)
            end
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

// FIXME: This and the above case get handled very differently.  It's pretty dumb.
// We really should unify the two code paths, probably by deleting AstStatFunction.
TEST_CASE_FIXTURE(Fixture, "another_recursive_local_function")
{
    CheckResult result = check(R"(
        local count
        function count(n: number)
            if n == 0 then
                return 0
            else
                return count(n - 1)
            end
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "cyclic_function_type_in_rets")
{
    CheckResult result = check(R"(
        function f()
            return f
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
    CHECK_EQ("t1 where t1 = () -> t1", toString(requireType("f")));
}

TEST_CASE_FIXTURE(Fixture, "cyclic_function_type_in_args")
{
    CheckResult result = check(R"(
        function f(g)
            return f(f)
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
    CHECK_EQ("t1 where t1 = (t1) -> ()", toString(requireType("f")));
}

TEST_CASE_FIXTURE(Fixture, "another_higher_order_function")
{
    CheckResult result = check(R"(
        local Get_des
        function Get_des(func)
            Get_des(func)
        end

        local function f(d)
            d:IsA("BasePart")
            d.Parent:FindFirstChild("Humanoid")
            d:IsA("Decal")
        end
        Get_des(f)

    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

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

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "local_function")
{
    CheckResult result = check(R"(
        function f()
            return 8
        end

        function g()
            local function f()
                return 'hello'
            end
            return f
        end

        local h = g()
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    TypeId h = follow(requireType("h"));

    const FunctionTypeVar* ftv = get<FunctionTypeVar>(h);
    REQUIRE(ftv != nullptr);

    std::optional<TypeId> rt = first(ftv->retType);
    REQUIRE(bool(rt));

    TypeId retType = follow(*rt);
    CHECK_EQ(PrimitiveTypeVar::String, getPrimitiveType(retType));
}

TEST_CASE_FIXTURE(Fixture, "func_expr_doesnt_leak_free")
{
    CheckResult result = check(R"(
        local p = function(x) return x end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
    const Luau::FunctionTypeVar* fn = get<FunctionTypeVar>(requireType("p"));
    REQUIRE(fn);
    auto ret = first(fn->retType);
    REQUIRE(ret);
    REQUIRE(get<GenericTypeVar>(follow(*ret)));
}

TEST_CASE_FIXTURE(Fixture, "first_argument_can_be_optional")
{
    CheckResult result = check(R"(
        local T = {}
        function T.new(a: number?, b: number?, c: number?) return 5 end
        local m = T.new()
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
    dumpErrors(result);
}

TEST_CASE_FIXTURE(Fixture, "it_is_ok_not_to_supply_enough_retvals")
{
    CheckResult result = check(R"(
        function get_two() return 5, 6 end

        local a = get_two()
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
    dumpErrors(result);
}

TEST_CASE_FIXTURE(Fixture, "duplicate_functions2")
{
    CheckResult result = check(R"(
        function foo() end

        function bar()
            local function foo() end
        end
    )");

    LUAU_REQUIRE_ERROR_COUNT(0, result);
}

TEST_CASE_FIXTURE(Fixture, "duplicate_functions_allowed_in_nonstrict")
{
    CheckResult result = check(R"(
        --!nonstrict
        function foo() end

        function foo() end

        function bar()
            local function foo() end
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "duplicate_functions_with_different_signatures_not_allowed_in_nonstrict")
{
    CheckResult result = check(R"(
        --!nonstrict
        function foo(): number
            return 1
        end
        foo()

        function foo(n: number): number
            return 2
        end
        foo()
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);

    TypeMismatch* tm = get<TypeMismatch>(result.errors[0]);
    REQUIRE(tm);
    CHECK_EQ("() -> number", toString(tm->wantedType));
    CHECK_EQ("(number) -> number", toString(tm->givenType));
}

TEST_CASE_FIXTURE(Fixture, "complicated_return_types_require_an_explicit_annotation")
{
    CheckResult result = check(R"(
        local i = 0
        function most_of_the_natural_numbers(): number?
            if i < 10 then
                i = i + 1
                return i
            else
                return nil
            end
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    const FunctionTypeVar* functionType = get<FunctionTypeVar>(requireType("most_of_the_natural_numbers"));

    std::optional<TypeId> retType = first(functionType->retType);
    REQUIRE(retType);
    CHECK(get<UnionTypeVar>(*retType));
}

TEST_CASE_FIXTURE(Fixture, "infer_higher_order_function")
{
    CheckResult result = check(R"(
        function apply(f, x)
            return f(x)
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    const FunctionTypeVar* ftv = get<FunctionTypeVar>(requireType("apply"));
    REQUIRE(ftv != nullptr);

    std::vector<TypeId> argVec = flatten(ftv->argTypes).first;

    REQUIRE_EQ(2, argVec.size());

    const FunctionTypeVar* fType = get<FunctionTypeVar>(follow(argVec[0]));
    REQUIRE(fType != nullptr);

    std::vector<TypeId> fArgs = flatten(fType->argTypes).first;

    TypeId xType = argVec[1];

    CHECK_EQ(1, fArgs.size());
    CHECK_EQ(xType, fArgs[0]);
}

TEST_CASE_FIXTURE(Fixture, "higher_order_function_2")
{
    CheckResult result = check(R"(
        function bottomupmerge(comp, a, b, left, mid, right)
            local i, j = left, mid
            for k = left, right do
                if i < mid and (j > right or not comp(a[j], a[i])) then
                    b[k] = a[i]
                    i = i + 1
                else
                    b[k] = a[j]
                    j = j + 1
                end
            end
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    const FunctionTypeVar* ftv = get<FunctionTypeVar>(requireType("bottomupmerge"));
    REQUIRE(ftv != nullptr);

    std::vector<TypeId> argVec = flatten(ftv->argTypes).first;

    REQUIRE_EQ(6, argVec.size());

    const FunctionTypeVar* fType = get<FunctionTypeVar>(follow(argVec[0]));
    REQUIRE(fType != nullptr);
}

TEST_CASE_FIXTURE(Fixture, "higher_order_function_3")
{
    CheckResult result = check(R"(
        function swap(p)
            local t = p[0]
            p[0] = p[1]
            p[1] = t
            return nil
        end

        function swapTwice(p)
            swap(p)
            swap(p)
            return p
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    const FunctionTypeVar* ftv = get<FunctionTypeVar>(requireType("swapTwice"));
    REQUIRE(ftv != nullptr);

    std::vector<TypeId> argVec = flatten(ftv->argTypes).first;

    REQUIRE_EQ(1, argVec.size());

    const TableTypeVar* argType = get<TableTypeVar>(follow(argVec[0]));
    REQUIRE(argType != nullptr);

    CHECK(bool(argType->indexer));
}

TEST_CASE_FIXTURE(Fixture, "higher_order_function_4")
{
    CheckResult result = check(R"(
        function bottomupmerge(comp, a, b, left, mid, right)
            local i, j = left, mid
            for k = left, right do
                if i < mid and (j > right or not comp(a[j], a[i])) then
                    b[k] = a[i]
                    i = i + 1
                else
                    b[k] = a[j]
                    j = j + 1
                end
            end
        end

        function mergesort(arr, comp)
            local work = {}
            for i = 1, #arr do
                work[i] = arr[i]
            end
            local width = 1
            while width < #arr do
                for i = 1, #arr, 2*width do
                    bottomupmerge(comp, arr, work, i, math.min(i+width, #arr), math.min(i+2*width-1, #arr))
                end
                local temp = work
                work = arr
                arr = temp
                width = width * 2
            end
            return arr
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
    dumpErrors(result);

    /*
     * mergesort takes two arguments: an array of some type T and a function that takes two Ts.
     * We must assert that these two types are in fact the same type.
     * In other words, comp(arr[x], arr[y]) is well-typed.
     */

    const FunctionTypeVar* ftv = get<FunctionTypeVar>(requireType("mergesort"));
    REQUIRE(ftv != nullptr);

    std::vector<TypeId> argVec = flatten(ftv->argTypes).first;

    REQUIRE_EQ(2, argVec.size());

    const TableTypeVar* arg0 = get<TableTypeVar>(follow(argVec[0]));
    REQUIRE(arg0 != nullptr);
    REQUIRE(bool(arg0->indexer));

    const FunctionTypeVar* arg1 = get<FunctionTypeVar>(follow(argVec[1]));
    REQUIRE(arg1 != nullptr);
    REQUIRE_EQ(2, size(arg1->argTypes));

    std::vector<TypeId> arg1Args = flatten(arg1->argTypes).first;

    CHECK_EQ(*arg0->indexer->indexResultType, *arg1Args[0]);
    CHECK_EQ(*arg0->indexer->indexResultType, *arg1Args[1]);
}

TEST_CASE_FIXTURE(Fixture, "mutual_recursion")
{
    CheckResult result = check(R"(
        --!strict

        function newPlayerCharacter()
            startGui() -- Unknown symbol 'startGui'
        end

        local characterAddedConnection: any
        function startGui()
            characterAddedConnection = game:GetService("Players").LocalPlayer.CharacterAdded:connect(newPlayerCharacter)
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
    dumpErrors(result);
}

TEST_CASE_FIXTURE(Fixture, "toposort_doesnt_break_mutual_recursion")
{
    CheckResult result = check(R"(
        --!strict
        local x = nil
        function f() g() end
        -- make sure print(x) doesn't get toposorted here, breaking the mutual block
        function g() x = f end
        print(x)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
    dumpErrors(result);
}

TEST_CASE_FIXTURE(Fixture, "check_function_before_lambda_that_uses_it")
{
    CheckResult result = check(R"(
        --!nonstrict

        function f()
            return 114
        end

        return function()
            return f():andThen()
        end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "it_is_ok_to_oversaturate_a_higher_order_function_argument")
{
    CheckResult result = check(R"(
        function onerror() end
        function foo() end
        xpcall(foo, onerror)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "another_indirect_function_case_where_it_is_ok_to_provide_too_many_arguments")
{
    CheckResult result = check(R"(
        local mycb: (number, number) -> ()

        function f() end

        mycb = f
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "report_exiting_without_return_nonstrict")
{
    CheckResult result = check(R"(
        --!nonstrict

        local function f1(v): number?
            if v then
                return 1
            end
        end

        local function f2(v)
            if v then
                return 1
            end
        end

        local function f3(v): ()
            if v then
                return
            end
        end

        local function f4(v)
            if v then
                return
            end
        end
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
    FunctionExitsWithoutReturning* err = get<FunctionExitsWithoutReturning>(result.errors[0]);
    CHECK(err);
}

TEST_CASE_FIXTURE(Fixture, "report_exiting_without_return_strict")
{
    CheckResult result = check(R"(
        --!strict

        local function f1(v): number?
            if v then
                return 1
            end
        end

        local function f2(v)
            if v then
                return 1
            end
        end

        local function f3(v): ()
            if v then
                return
            end
        end

        local function f4(v)
            if v then
                return
            end
        end
    )");

    LUAU_REQUIRE_ERROR_COUNT(2, result);
    FunctionExitsWithoutReturning* annotatedErr = get<FunctionExitsWithoutReturning>(result.errors[0]);
    CHECK(annotatedErr);

    FunctionExitsWithoutReturning* inferredErr = get<FunctionExitsWithoutReturning>(result.errors[1]);
    CHECK(inferredErr);
}

TEST_CASE_FIXTURE(Fixture, "calling_function_with_incorrect_argument_type_yields_errors_spanning_argument")
{
    CheckResult result = check(R"(
        function foo(a: number, b: string) end

        foo("Test", 123)
    )");

    LUAU_REQUIRE_ERROR_COUNT(2, result);

    CHECK_EQ(result.errors[0], (TypeError{Location{Position{3, 12}, Position{3, 18}}, TypeMismatch{
                                                                                          typeChecker.numberType,
                                                                                          typeChecker.stringType,
                                                                                      }}));

    CHECK_EQ(result.errors[1], (TypeError{Location{Position{3, 20}, Position{3, 23}}, TypeMismatch{
                                                                                          typeChecker.stringType,
                                                                                          typeChecker.numberType,
                                                                                      }}));
}

TEST_CASE_FIXTURE(Fixture, "calling_function_with_anytypepack_doesnt_leak_free_types")
{
    CheckResult result = check(R"(
        --!nonstrict

        function Test(a)
            return 1, ""
        end


        local tab = {}
        table.insert(tab, Test(1));
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    ToStringOptions opts;
    opts.exhaustive = true;
    opts.maxTableLength = 0;

    CHECK_EQ("{any}", toString(requireType("tab"), opts));
}

TEST_CASE_FIXTURE(Fixture, "too_many_return_values")
{
    CheckResult result = check(R"(
        --!strict

        function f()
            return 55
        end

        local a, b = f()
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);

    CountMismatch* acm = get<CountMismatch>(result.errors[0]);
    REQUIRE(acm);
    CHECK_EQ(acm->context, CountMismatch::Result);
    CHECK_EQ(acm->expected, 1);
    CHECK_EQ(acm->actual, 2);
}

TEST_CASE_FIXTURE(Fixture, "ignored_return_values")
{
    CheckResult result = check(R"(
        --!strict

        function f()
            return 55, ""
        end

        local a = f()
    )");

    LUAU_REQUIRE_ERROR_COUNT(0, result);
}

TEST_CASE_FIXTURE(Fixture, "function_does_not_return_enough_values")
{
    CheckResult result = check(R"(
        --!strict

        function f(): (number, string)
            return 55
        end
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);

    CountMismatch* acm = get<CountMismatch>(result.errors[0]);
    REQUIRE(acm);
    CHECK_EQ(acm->context, CountMismatch::Return);
    CHECK_EQ(acm->expected, 2);
    CHECK_EQ(acm->actual, 1);
}

TEST_CASE_FIXTURE(Fixture, "function_cast_error_uses_correct_language")
{
    CheckResult result = check(R"(
        function foo(a, b): number
            return 0
        end

        local a: (string)->number = foo
        local b: (number, number)->(number, number) = foo

        local c: (string, number)->number = foo -- no error
    )");

    LUAU_REQUIRE_ERROR_COUNT(2, result);

    auto tm1 = get<TypeMismatch>(result.errors[0]);
    REQUIRE(tm1);

    CHECK_EQ("(string) -> number", toString(tm1->wantedType));
    CHECK_EQ("(string, *unknown*) -> number", toString(tm1->givenType));

    auto tm2 = get<TypeMismatch>(result.errors[1]);
    REQUIRE(tm2);

    CHECK_EQ("(number, number) -> (number, number)", toString(tm2->wantedType));
    CHECK_EQ("(string, *unknown*) -> number", toString(tm2->givenType));
}

TEST_CASE_FIXTURE(Fixture, "no_lossy_function_type")
{
    CheckResult result = check(R"(
        --!strict
        local tbl = {}
        function tbl:abc(a: number, b: number)
            return a
        end
        tbl:abc(1, 2) -- Line 6
        --   | Column 14
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
    TypeId type = requireTypeAtPosition(Position(6, 14));
    CHECK_EQ("(tbl, number, number) -> number", toString(type));
    auto ftv = get<FunctionTypeVar>(type);
    REQUIRE(ftv);
    CHECK(ftv->hasSelf);
}

TEST_CASE_FIXTURE(Fixture, "record_matching_overload")
{
    CheckResult result = check(R"(
        type Overload = ((string) -> string) & ((number) -> number)
        local abc: Overload
        abc(1)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    // AstExprCall is the node that has the overload stored on it.
    // findTypeAtPosition will look at the AstExprLocal, but this is not what
    // we want to look at.
    std::vector<AstNode*> ancestry = findAstAncestryOfPosition(*getMainSourceModule(), Position(3, 10));
    REQUIRE_GE(ancestry.size(), 2);
    AstExpr* parentExpr = ancestry[ancestry.size() - 2]->asExpr();
    REQUIRE(bool(parentExpr));
    REQUIRE(parentExpr->is<AstExprCall>());

    ModulePtr module = getMainModule();
    auto it = module->astOverloadResolvedTypes.find(parentExpr);
    REQUIRE(it);
    CHECK_EQ(toString(*it), "(number) -> number");
}

TEST_CASE_FIXTURE(Fixture, "return_type_by_overload")
{
    ScopedFastFlag sff{"LuauErrorRecoveryType", true};

    CheckResult result = check(R"(
        type Overload = ((string) -> string) & ((number, number) -> number)
        local abc: Overload
        local x = abc(true)
        local y = abc(true,true)
        local z = abc(true,true,true)
    )");

    LUAU_REQUIRE_ERRORS(result);
    CHECK_EQ("string", toString(requireType("x")));
    CHECK_EQ("number", toString(requireType("y")));
    // Should this be string|number?
    CHECK_EQ("string", toString(requireType("z")));
}

TEST_CASE_FIXTURE(Fixture, "infer_anonymous_function_arguments")
{
    // Simple direct arg to arg propagation
    CheckResult result = check(R"(
type Table = { x: number, y: number }
local function f(a: (Table) -> number) return a({x = 1, y = 2}) end
f(function(a) return a.x + a.y end)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    // An optional function is accepted, but since we already provide a function, nil can be ignored
    result = check(R"(
type Table = { x: number, y: number }
local function f(a: ((Table) -> number)?) if a then return a({x = 1, y = 2}) else return 0 end end
f(function(a) return a.x + a.y end)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    // Make sure self calls match correct index
    result = check(R"(
type Table = { x: number, y: number }
local x = {}
x.b = {x = 1, y = 2}
function x:f(a: (Table) -> number) return a(self.b) end
x:f(function(a) return a.x + a.y end)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    // Mix inferred and explicit argument types
    result = check(R"(
function f(a: (a: number, b: number, c: boolean) -> number) return a(1, 2, true) end
f(function(a: number, b, c) return c and a + b or b - a end)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    // Anonymous function has a variadic pack
    result = check(R"(
type Table = { x: number, y: number }
local function f(a: (Table) -> number) return a({x = 1, y = 2}) end
f(function(...) return select(1, ...).z end)
    )");

    LUAU_REQUIRE_ERRORS(result);
    CHECK_EQ("Key 'z' not found in table 'Table'", toString(result.errors[0]));

    // Can't accept more arguments than provided
    result = check(R"(
function f(a: (a: number, b: number) -> number) return a(1, 2) end
f(function(a, b, c, ...) return a + b end)
    )");

    LUAU_REQUIRE_ERRORS(result);

    CHECK_EQ(R"(Type '(number, number, a) -> number' could not be converted into '(number, number) -> number'
caused by:
  Argument count mismatch. Function expects 3 arguments, but only 2 are specified)",
        toString(result.errors[0]));

    // Infer from variadic packs into elements
    result = check(R"(
function f(a: (...number) -> number) return a(1, 2) end
f(function(a, b) return a + b end)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    // Infer from variadic packs into variadic packs
    result = check(R"(
type Table = { x: number, y: number }
function f(a: (...Table) -> number) return a({x = 1, y = 2}, {x = 3, y = 4}) end
f(function(a, ...) local b = ... return b.z end)
    )");

    LUAU_REQUIRE_ERRORS(result);
    CHECK_EQ("Key 'z' not found in table 'Table'", toString(result.errors[0]));

    // Return type inference
    result = check(R"(
type Table = { x: number, y: number }
function f(a: (number) -> Table) return a(4) end
f(function(x) return x * 2 end)
    )");

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

    // Return type doesn't inference 'nil'
    result = check(R"(
function f(a: (number) -> nil) return a(4) end
f(function(x) print(x) end)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "infer_anonymous_function_arguments")
{
    // Simple direct arg to arg propagation
    CheckResult result = check(R"(
type Table = { x: number, y: number }
local function f(a: (Table) -> number) return a({x = 1, y = 2}) end
f(function(a) return a.x + a.y end)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    // An optional function is accepted, but since we already provide a function, nil can be ignored
    result = check(R"(
type Table = { x: number, y: number }
local function f(a: ((Table) -> number)?) if a then return a({x = 1, y = 2}) else return 0 end end
f(function(a) return a.x + a.y end)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    // Make sure self calls match correct index
    result = check(R"(
type Table = { x: number, y: number }
local x = {}
x.b = {x = 1, y = 2}
function x:f(a: (Table) -> number) return a(self.b) end
x:f(function(a) return a.x + a.y end)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    // Mix inferred and explicit argument types
    result = check(R"(
function f(a: (a: number, b: number, c: boolean) -> number) return a(1, 2, true) end
f(function(a: number, b, c) return c and a + b or b - a end)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    // Anonymous function has a variadic pack
    result = check(R"(
type Table = { x: number, y: number }
local function f(a: (Table) -> number) return a({x = 1, y = 2}) end
f(function(...) return select(1, ...).z end)
    )");

    LUAU_REQUIRE_ERRORS(result);
    CHECK_EQ("Key 'z' not found in table 'Table'", toString(result.errors[0]));

    // Can't accept more arguments than provided
    result = check(R"(
function f(a: (a: number, b: number) -> number) return a(1, 2) end
f(function(a, b, c, ...) return a + b end)
    )");

    LUAU_REQUIRE_ERRORS(result);

    CHECK_EQ(R"(Type '(number, number, a) -> number' could not be converted into '(number, number) -> number'
caused by:
  Argument count mismatch. Function expects 3 arguments, but only 2 are specified)",
        toString(result.errors[0]));

    // Infer from variadic packs into elements
    result = check(R"(
function f(a: (...number) -> number) return a(1, 2) end
f(function(a, b) return a + b end)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    // Infer from variadic packs into variadic packs
    result = check(R"(
type Table = { x: number, y: number }
function f(a: (...Table) -> number) return a({x = 1, y = 2}, {x = 3, y = 4}) end
f(function(a, ...) local b = ... return b.z end)
    )");

    LUAU_REQUIRE_ERRORS(result);
    CHECK_EQ("Key 'z' not found in table 'Table'", toString(result.errors[0]));

    // Return type inference
    result = check(R"(
type Table = { x: number, y: number }
function f(a: (number) -> Table) return a(4) end
f(function(x) return x * 2 end)
    )");

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

    // Return type doesn't inference 'nil'
    result = check(R"(
function f(a: (number) -> nil) return a(4) end
f(function(x) print(x) end)
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "infer_anonymous_function_arguments_outside_call")
{
    CheckResult result = check(R"(
type Table = { x: number, y: number }
local f: (Table) -> number = function(t) return t.x + t.y end

type TableWithFunc = { x: number, y: number, f: (number, number) -> number }
local a: TableWithFunc = { x = 3, y = 4, f = function(a, b) return a + b end }
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "infer_return_value_type")
{
    CheckResult result = check(R"(
local function f(): {string|number}
    return {1, "b", 3}
end

local function g(): (number, {string|number})
    return 4, {1, "b", 3}
end

local function h(): ...{string|number}
    return {4}, {1, "b", 3}, {"s"}
end

local function i(): ...{string|number}
    return {1, "b", 3}, h()
end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "error_detailed_function_mismatch_arg_count")
{
    CheckResult result = check(R"(
type A = (number, number) -> string
type B = (number) -> string

local a: A
local b: B = a
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
    CHECK_EQ(toString(result.errors[0]), R"(Type '(number, number) -> string' could not be converted into '(number) -> string'
caused by:
  Argument count mismatch. Function expects 2 arguments, but only 1 is specified)");
}

TEST_CASE_FIXTURE(Fixture, "error_detailed_function_mismatch_arg")
{
    CheckResult result = check(R"(
type A = (number, number) -> string
type B = (number, string) -> string

local a: A
local b: B = a
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
    CHECK_EQ(toString(result.errors[0]), R"(Type '(number, number) -> string' could not be converted into '(number, string) -> string'
caused by:
  Argument #2 type is not compatible. Type 'string' could not be converted into 'number')");
}

TEST_CASE_FIXTURE(Fixture, "error_detailed_function_mismatch_ret_count")
{
    CheckResult result = check(R"(
type A = (number, number) -> (number)
type B = (number, number) -> (number, boolean)

local a: A
local b: B = a
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
    CHECK_EQ(toString(result.errors[0]), R"(Type '(number, number) -> number' could not be converted into '(number, number) -> (number, boolean)'
caused by:
  Function only returns 1 value. 2 are required here)");
}

TEST_CASE_FIXTURE(Fixture, "error_detailed_function_mismatch_ret")
{
    CheckResult result = check(R"(
type A = (number, number) -> string
type B = (number, number) -> number

local a: A
local b: B = a
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
    CHECK_EQ(toString(result.errors[0]), R"(Type '(number, number) -> string' could not be converted into '(number, number) -> number'
caused by:
  Return type is not compatible. Type 'string' could not be converted into 'number')");
}

TEST_CASE_FIXTURE(Fixture, "error_detailed_function_mismatch_ret_mult")
{
    CheckResult result = check(R"(
type A = (number, number) -> (number, string)
type B = (number, number) -> (number, boolean)

local a: A
local b: B = a
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
    CHECK_EQ(toString(result.errors[0]),
        R"(Type '(number, number) -> (number, string)' could not be converted into '(number, number) -> (number, boolean)'
caused by:
  Return #2 type is not compatible. Type 'string' could not be converted into 'boolean')");
}

TEST_CASE_FIXTURE(Fixture, "function_decl_quantify_right_type")
{
    ScopedFastFlag statFunctionSimplify{"LuauStatFunctionSimplify4", true};

    fileResolver.source["game/isAMagicMock"] = R"(
--!nonstrict
return function(value)
    return false
end
    )";

    CheckResult result = check(R"(
--!nonstrict
local MagicMock = {}
MagicMock.is = require(game.isAMagicMock)

function MagicMock.is(value)
    return false
end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "function_decl_non_self_sealed_overwrite")
{
    ScopedFastFlag statFunctionSimplify{"LuauStatFunctionSimplify4", true};

    CheckResult result = check(R"(
function string.len(): number
    return 1
end
    )");

    LUAU_REQUIRE_NO_ERRORS(result);

    // if 'string' library property was replaced with an internal module type, it will be freed and the next check will crash
    frontend.clear();

    result = check(R"(
print(string.len('hello'))
    )");

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "function_decl_non_self_sealed_overwrite_2")
{
    ScopedFastFlag statFunctionSimplify{"LuauStatFunctionSimplify4", true};
    ScopedFastFlag inferStatFunction{"LuauInferStatFunction", true};

    CheckResult result = check(R"(
local t: { f: ((x: number) -> number)? } = {}

function t.f(x)
    print(x + 5)
    return x .. "asd" -- 1st error: we know that return type is a number, not a string
end

t.f = function(x)
    print(x + 5)
    return x .. "asd" -- 2nd error: we know that return type is a number, not a string
end
    )");

    LUAU_REQUIRE_ERROR_COUNT(2, result);
    CHECK_EQ(toString(result.errors[0]), R"(Type 'string' could not be converted into 'number')");
    CHECK_EQ(toString(result.errors[1]), R"(Type 'string' could not be converted into 'number')");
}

TEST_CASE_FIXTURE(Fixture, "function_decl_non_self_unsealed_overwrite")
{
    ScopedFastFlag statFunctionSimplify{"LuauStatFunctionSimplify4", true};
    ScopedFastFlag inferStatFunction{"LuauInferStatFunction", true};

    CheckResult result = check(R"(
local t = { f = nil :: ((x: number) -> number)? }

function t.f(x: string): string -- 1st error: new function value type is incompatible
    return x .. "asd"
end

t.f = function(x)
    print(x + 5)
    return x .. "asd" -- 2nd error: we know that return type is a number, not a string
end
    )");

    LUAU_REQUIRE_ERROR_COUNT(2, result);
    CHECK_EQ(toString(result.errors[0]), R"(Type '(string) -> string' could not be converted into '((number) -> number)?'
caused by:
  None of the union options are compatible. For example: Type '(string) -> string' could not be converted into '(number) -> number'
caused by:
  Argument #1 type is not compatible. Type 'number' could not be converted into 'string')");
    CHECK_EQ(toString(result.errors[1]), R"(Type 'string' could not be converted into 'number')");
}

TEST_CASE_FIXTURE(Fixture, "strict_mode_ok_with_missing_arguments")
{
    ScopedFastFlag sff{"LuauAnyInIsOptionalIsOptional", true};

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

    LUAU_REQUIRE_NO_ERRORS(result);
}

TEST_CASE_FIXTURE(Fixture, "function_statement_sealed_table_assignment_through_indexer")
{
    ScopedFastFlag statFunctionSimplify{"LuauStatFunctionSimplify4", true};

    CheckResult result = check(R"(
local t: {[string]: () -> number} = {}

function t.a() return 1 end -- OK
function t:b() return 2 end -- not OK
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);
    CHECK_EQ(R"(Type '(*unknown*) -> number' could not be converted into '() -> number'
caused by:
  Argument count mismatch. Function expects 1 argument, but none are specified)",
        toString(result.errors[0]));
}

TEST_CASE_FIXTURE(Fixture, "too_few_arguments_variadic")
{
    ScopedFastFlag sff{"LuauArgCountMismatchSaysAtLeastWhenVariadic", true};
    CheckResult result = check(R"(
    function test(a: number, b: string, ...)
    end

    test(1)
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);

    auto err = result.errors[0];
    auto acm = get<CountMismatch>(err);
    REQUIRE(acm);

    CHECK_EQ(2, acm->expected);
    CHECK_EQ(1, acm->actual);
    CHECK_EQ(CountMismatch::Context::Arg, acm->context);
    CHECK(acm->isVariadic);
}

TEST_CASE_FIXTURE(Fixture, "too_few_arguments_variadic_generic")
{
    ScopedFastFlag sff1{"LuauArgCountMismatchSaysAtLeastWhenVariadic", true};
    ScopedFastFlag sff2{"LuauFixArgumentCountMismatchAmountWithGenericTypes", true};
    CheckResult result = check(R"(
function test(a: number, b: string, ...)
    return 1
end

function wrapper<A...>(f: (A...) -> number, ...: A...)
end

wrapper(test)
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);

    auto err = result.errors[0];
    auto acm = get<CountMismatch>(err);
    REQUIRE(acm);

    CHECK_EQ(3, acm->expected);
    CHECK_EQ(1, acm->actual);
    CHECK_EQ(CountMismatch::Context::Arg, acm->context);
    CHECK(acm->isVariadic);
}

TEST_CASE_FIXTURE(Fixture, "too_few_arguments_variadic_generic2")
{
    ScopedFastFlag sff1{"LuauArgCountMismatchSaysAtLeastWhenVariadic", true};
    ScopedFastFlag sff2{"LuauFixArgumentCountMismatchAmountWithGenericTypes", true};
    CheckResult result = check(R"(
function test(a: number, b: string, ...)
    return 1
end

function wrapper<A...>(f: (A...) -> number, ...: A...)
end

pcall(wrapper, test)
    )");

    LUAU_REQUIRE_ERROR_COUNT(1, result);

    auto err = result.errors[0];
    auto acm = get<CountMismatch>(err);
    REQUIRE(acm);

    CHECK_EQ(4, acm->expected);
    CHECK_EQ(2, acm->actual);
    CHECK_EQ(CountMismatch::Context::Arg, acm->context);
    CHECK(acm->isVariadic);
}

TEST_SUITE_END();