//
	// To mitigate this, each matched node n is wrapped in a ParenExpr,
	// so we can reliably replace n in-place by assigning ParenExpr.X.
	// It's safe to use ParenExpr here, because typecheck already
	// removed them all.

	var parens []*ir.ParenExpr
	var mark func(ir.Node) ir.Node
	mark = func(n ir.Node) ir.Node {
		if _, ok := n.(*ir.ParenExpr); ok {
			return n // already visited n.X before wrapping
		}

		// case *Name:
		// case *BasicLit:
		case *CompositeLit:
			if n.Type != nil {
				m = n.Type
				continue
			}
			return n.Pos()
		case *KeyValueExpr:
			m = n.Key
		// case *FuncLit:
		// case *ParenExpr:
		case *SelectorExpr:
			m = n.X
		case *IndexExpr:
			m = n.X
		// case *SliceExpr:
		case *AssertExpr:
			m = n.X
		case *TypeSwitchGuard:
			if n.Lhs != nil {
				m = n.Lhs
				continue
			}

		if n == nil {
			return
		}
		// Find pattern like (*a.b)(x)
		c, ok := n.(*ast.CallExpr)
		if !ok {
			return
		}
		if len(c.Args) != 1 {
			return
		}
		p, ok := c.Fun.(*ast.ParenExpr)
		if !ok {
			return
		}
		s, ok := p.X.(*ast.StarExpr)
		if !ok {
			return
		}
		t, ok := s.X.(*ast.SelectorExpr)
		if !ok {
			return
		}
		pkg, ok := t.X.(*ast.Ident)

	case *ast.KeyValueExpr:
		return 1 << nKeyValueExpr
	case *ast.LabeledStmt:
		return 1 << nLabeledStmt
	case *ast.MapType:
		return 1 << nMapType
	case *ast.Package:
		return 1 << nPackage
	case *ast.ParenExpr:
		return 1 << nParenExpr
	case *ast.RangeStmt:
		return 1 << nRangeStmt
	case *ast.ReturnStmt:
		return 1 << nReturnStmt
	case *ast.SelectStmt:
		return 1 << nSelectStmt
	case *ast.SelectorExpr:

		buf.WriteString(" literal)") // shortened

	case *ast.CompositeLit:
		WriteExpr(buf, x.Type)
		buf.WriteByte('{')
		if len(x.Elts) > 0 {
			buf.WriteString("…")
		}
		buf.WriteByte('}')

	case *ast.ParenExpr:
		buf.WriteByte('(')
		WriteExpr(buf, x.X)
		buf.WriteByte(')')

	case *ast.SelectorExpr:
		WriteExpr(buf, x.X)
		buf.WriteByte('.')
		buf.WriteString(x.Sel.Name)

			Walk(v, n.Elt)
		}

	case *FuncLit:
		Walk(v, n.Type)
		Walk(v, n.Body)

	case *CompositeLit:
		if n.Type != nil {
			Walk(v, n.Type)
		}
		walkList(v, n.Elts)

	case *ParenExpr:
		Walk(v, n.X)

	case *SelectorExpr:
		Walk(v, n.X)
		Walk(v, n.Sel)

	case *IndexExpr:
		Walk(v, n.X)
		Walk(v, n.Index)

	case *IndexListExpr:
		Walk(v, n.X)
		walkList(v, n.Indices)

	// Key: Value
	KeyValueExpr struct {
		Key, Value Expr
		expr
	}

	// func Type { Body }
	FuncLit struct {
		Type *FuncType
		Body *BlockStmt
		expr
	}

	// (X)
	ParenExpr struct {
		X Expr
		expr
	}

	// X.Sel
	SelectorExpr struct {
		X   Expr
		Sel *Name
		expr
	}

	// X[Index]
	// X[T1, T2, ...] (with Ti = Index.(*ListExpr).ElemList[i])

	{"CompositeLit", `@{}`},
	{"CompositeLit", `T@{}`},
	{"CompositeLit", `struct{x, y int}@{}`},

	{"KeyValueExpr", `"foo"@: true`},
	{"KeyValueExpr", `"a"@: b`},

	{"FuncLit", `@func (){}`},
	{"ParenExpr", `@(x)`},
	{"SelectorExpr", `a@.b`},
	{"IndexExpr", `a@[i]`},

	{"SliceExpr", `a@[:]`},
	{"SliceExpr", `a@[i:]`},
	{"SliceExpr", `a@[:j]`},
	{"SliceExpr", `a@[i:j]`},
	{"SliceExpr", `a@[i:j:k]`},