swc/crates/swc_ecma_parser/tests/tsc/spreadObjectOrFalsy.ts

// @strict: true
// @declaration: true

function f1<T>(a: T & undefined) {
    return { ...a };  // Error
}

function f2<T>(a: T | T & undefined) {
    return { ...a };
}

function f3<T extends undefined>(a: T) {
    return { ...a };  // Error
}

function f4<T extends undefined>(a: object | T) {
    return { ...a };
}

function f5<S, T extends undefined>(a: S | T) {
    return { ...a };
}

function f6<T extends object | undefined>(a: T) {
    return { ...a };
}

// Repro from #46976

function g1<T extends {}, A extends { z: (T | undefined) & T }>(a: A) {
    const { z } = a;
    return {
        ...z
    };
}

// Repro from #47028

interface DatafulFoo<T> {
    data: T;
}

class Foo<T extends string> {
    data: T | undefined;
    bar() {
        if (this.hasData()) {
            this.data.toLocaleLowerCase();
        }
    }
    hasData(): this is DatafulFoo<T> {
        return true;
    }
}