// 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;
		// this is created by code in this file.
		if t.Name == "unsafe.Pointer" {
			return ast.NewIdent("_cgo_unsafe.Pointer")
		}
	case *ast.ArrayType: