// dirs are the directories to look for *.go files in.
	// TODO(bradfitz): just use all directories?
	dirs = []string{".", "ken", "chan", "interface", "syntax", "dwarf", "fixedbugs", "codegen", "runtime", "abi", "typeparam", "typeparam/mdempsky", "arenas"}
)

// Test is the main entrypoint that runs tests in the GOROOT/test directory.
//
// Each .go file test case in GOROOT/test is registered as a subtest with a

// 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
	}