case *ast.SelectorExpr:
		return p.isVariable(x.X)
	case *ast.IndexExpr:
		return true
	}
	return false
}

// rewriteUnsafe returns a version of t with references to unsafe.Pointer
// rewritten to use _cgo_unsafe.Pointer instead.
func (p *Package) rewriteUnsafe(t ast.Expr) ast.Expr {
	switch t := t.(type) {
	case *ast.Ident:
		// We don't see a SelectorExpr for unsafe.Pointer;