Note that chan x(y) is a legal type conversion (chan x)(y). Even though we are expecting a type here, for the parser make(chan X(int)) looks like an ordinary function call (it doesn't know anything about make being special) and so it expects a (non-type) expression as argument. By that logic, that expression must be a conversion. Hence you need the extra parentheses. If the parser knew to expect a type, the parentheses wouldn't be needed.

I suppose the type-checker could re-associate the expression once it knows we're dealing with the built-in make call, but that seems a bit iffy (to me).

Closing as working as intended.