// package name, as defined by the import environment of file.
func TypeExpr(f *ast.File, pkg *types.Package, typ types.Type) ast.Expr {
	switch t := typ.(type) {
	case *types.Basic:
		switch t.Kind() {
		case types.UnsafePointer:
			return &ast.SelectorExpr{X: ast.NewIdent("unsafe"), Sel: ast.NewIdent("Pointer")}
		default:
			return ast.NewIdent(t.Name())
		}
	case *types.Pointer:
		x := TypeExpr(f, pkg, t.Elem())
		if x == nil {