argument types inference breaks for specific object literal method syntax #26629

TypeScript Version: 3.1.0-dev.20180823

Search Terms: object literal method argument

Code

function goofus <ARGS extends any[]> (f: (...args: ARGS) => any ) {}

goofus((a: string) => ({ dog() { return a; } }));
goofus((a: string) => ({ dog: function() { return a; } }));

Expected behavior:
infers ARGS === [string]

Actual behavior:
[ts] Argument of type '(a: string) => { dog(): string; }' is not assignable to parameter of type '() => any'.

Note that everything works correctly if you do any of the below:

1. infer a single argument: function gallant <ARG extends any> (f: (arg: ARG) => any ) {}
2. use arrow syntax in the object literal: goofus((a: string) => ({ dog: () => a }));
3. use method syntax to return the object literal: goofus(function (a: string) { return { dog() { return a; } } });

Playground Link: link

Related Issues: couldn't find any