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// Copyright 2021 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build typeparams
// +build typeparams
package typeparams
import (
"fmt"
"go/ast"
)
const Enabled = true
func PackExpr(list []ast.Expr) ast.Expr {
switch len(list) {
case 0:
// Return an empty ListExpr here, rather than nil, as IndexExpr.Index must
// never be nil.
// TODO(rFindley) would a BadExpr be more appropriate here?
return &ast.ListExpr{}
case 1:
return list[0]
default:
return &ast.ListExpr{ElemList: list}
}
}
// TODO(gri) Should find a more efficient solution that doesn't
// require introduction of a new slice for simple
// expressions.
func UnpackExpr(x ast.Expr) []ast.Expr {
if x, _ := x.(*ast.ListExpr); x != nil {
return x.ElemList
}
if x != nil {
return []ast.Expr{x}
}
return nil
}
func IsListExpr(n ast.Node) bool {
_, ok := n.(*ast.ListExpr)
return ok
}
func Get(n ast.Node) *ast.FieldList {
switch n := n.(type) {
case *ast.TypeSpec:
return n.TParams
case *ast.FuncType:
return n.TParams
default:
panic(fmt.Sprintf("node type %T has no type parameters", n))
}
}
func Set(n ast.Node, params *ast.FieldList) {
switch n := n.(type) {
case *ast.TypeSpec:
n.TParams = params
case *ast.FuncType:
n.TParams = params
default:
panic(fmt.Sprintf("node type %T has no type parameters", n))
}
}
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