// If typ is a type parameter, underIs returns the result of typ.underIs(f).
// Otherwise, underIs returns the result of f(under(typ)).
func underIs(typ Type, f func(Type) bool) bool {
	typ = Unalias(typ)
	if tpar, _ := typ.(*TypeParam); tpar != nil {
		return tpar.underIs(f)
	}
	return f(under(typ))
}

// The unary expression e may be nil. It's passed in for better error messages only.

// If typ is a type parameter, underIs returns the result of typ.underIs(f).
// Otherwise, underIs returns the result of f(under(typ)).
func underIs(typ Type, f func(Type) bool) bool {
	typ = Unalias(typ)
	if tpar, _ := typ.(*TypeParam); tpar != nil {
		return tpar.underIs(f)
	}
	return f(under(typ))
}

func (check *Checker) unary(x *operand, e *syntax.Operation) {
	check.expr(nil, x, e.X)
	if x.mode == invalid {
		return
	}