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

// Optional parameters allow initializers only in implementation signatures

function foo(x = 1) { }
var f = function foo(x = 1) { }
var f2 = (x: number, y = 1) => { }

foo(1);
foo();
f(1);
f();
f2(1);
f2(1, 2);

class C {
    foo(x = 1) { }
}

var c: C;
c.foo();
c.foo(1);

// these are errors
interface I {
    (x = 1);
    foo(x: number, y = 1);
}

var i: I;
i();
i(1);
i.foo(1);
i.foo(1, 2);

// these are errors
var a: {
    (x = 1);
    foo(x = 1);
}

a();
a(1);
a.foo();
a.foo(1);

var b = {
    foo(x = 1) { },
    a: function foo(x: number, y = 1) { },
    b: (x = 1) => { }
}

b.foo();
b.foo(1);
b.a(1);
b.a(1, 2);
b.b();
b.b(1);