)

func PackIndexExpr(x ast.Expr, lbrack token.Pos, exprs []ast.Expr, rbrack token.Pos) ast.Expr {
	switch len(exprs) {
	case 0:
		panic("internal error: PackIndexExpr with empty expr slice")
	case 1:
		return &ast.IndexExpr{
			X:      x,
			Lbrack: lbrack,
			Index:  exprs[0],
			Rbrack: rbrack,
		}
	default:
		return &ast.IndexListExpr{
			X:       x,
			Lbrack:  lbrack,
			Indices: exprs,
			Rbrack:  rbrack,

// will panic.
func PackIndexExpr(x ast.Expr, lbrack token.Pos, indices []ast.Expr, rbrack token.Pos) ast.Expr {
	switch len(indices) {
	case 0:
		panic("empty indices")
	case 1:
		return &ast.IndexExpr{
			X:      x,
			Lbrack: lbrack,
			Index:  indices[0],
			Rbrack: rbrack,
		}
	default:
		return &ast.IndexListExpr{
			X:       x,
			Lbrack:  lbrack,
			Indices: indices,
			Rbrack:  rbrack,
		}
	}

				index[2] = &ast.BadExpr{From: colons[1] + 1, To: rbrack}
			}
		}
		return &ast.SliceExpr{X: x, Lbrack: lbrack, Low: index[0], High: index[1], Max: index[2], Slice3: slice3, Rbrack: rbrack}
	}

	if len(args) == 0 {
		// index expression
		return &ast.IndexExpr{X: x, Lbrack: lbrack, Index: index[0], Rbrack: rbrack}
	}

	// instance expression

	GTR    // >
	ASSIGN // =
	NOT    // !

	NEQ      // !=
	LEQ      // <=
	GEQ      // >=
	DEFINE   // :=
	ELLIPSIS // ...

	LPAREN // (
	LBRACK // [
	LBRACE // {
	COMMA  // ,
	PERIOD // .

	RPAREN    // )
	RBRACK    // ]
	RBRACE    // }
	SEMICOLON // ;
	COLON     // :
	operator_end

	keyword_beg
	// Keywords
	BREAK
	CASE
	CHAN
	CONST
	CONTINUE

	DEFAULT

		children = append(children,
			tok(n.TokPos, len(n.Tok.String())))

	case *ast.IndexExpr:
		children = append(children,
			tok(n.Lbrack, len("[")),
			tok(n.Rbrack, len("]")))

	case *ast.IndexListExpr:
		children = append(children,
			tok(n.Lbrack, len("[")),
			tok(n.Rbrack, len("]")))

	case *ast.InterfaceType:
		children = append(children,
			tok(n.Interface, len("interface")))

	p.closeScope()
	rbrace := p.expect(token.RBRACE)

	return &ast.BlockStmt{lbrace, list, rbrace}
}

func (p *parser) parseBlockStmt() *ast.BlockStmt {
	if p.trace {
		defer un(trace(p, "BlockStmt"))
	}

	lbrace := p.expect(token.LBRACE)
	p.openScope()
	list := p.parseStmtList()
	p.closeScope()
	rbrace := p.expect(token.RBRACE)

	return &ast.BlockStmt{lbrace, list, rbrace}
}

func (x *CompositeLit) End() token.Pos   { return x.Rbrace + 1 }
func (x *ParenExpr) End() token.Pos      { return x.Rparen + 1 }
func (x *SelectorExpr) End() token.Pos   { return x.Sel.End() }
func (x *IndexExpr) End() token.Pos      { return x.Rbrack + 1 }
func (x *IndexListExpr) End() token.Pos  { return x.Rbrack + 1 }
func (x *SliceExpr) End() token.Pos      { return x.Rbrack + 1 }

		p.setPos(x.Lbrack)
		p.print(token.LBRACK)
		p.expr0(x.Index, depth+1)
		p.setPos(x.Rbrack)
		p.print(token.RBRACK)

	case *ast.IndexListExpr:
		// TODO(gri): as for IndexExpr, should treat [] like parentheses and undo
		// one level of depth
		p.expr1(x.X, token.HighestPrec, 1)
		p.setPos(x.Lbrack)
		p.print(token.LBRACK)
		p.exprList(x.Lbrack, x.Indices, depth+1, commaTerm, x.Rbrack, false)

pkg go/ast, type FuncType struct, TypeParams *FieldList
pkg go/ast, type IndexListExpr struct
pkg go/ast, type IndexListExpr struct, Indices []Expr
pkg go/ast, type IndexListExpr struct, Lbrack token.Pos
pkg go/ast, type IndexListExpr struct, Rbrack token.Pos
pkg go/ast, type IndexListExpr struct, X Expr
pkg go/ast, type TypeSpec struct, TypeParams *FieldList
pkg go/constant, method (Kind) String() string
pkg go/token, const TILDE = 88

		x.mode = invalid
		return
	}

	x.mode = value

	// spec: "Only the first index may be omitted; it defaults to 0."
	if e.Slice3 && (e.High == nil || e.Max == nil) {
		check.error(inNode(e, e.Rbrack), InvalidSyntaxTree, "2nd and 3rd index required in 3-index slice")
		x.mode = invalid
		return
	}

	// check indices
	var ind [3]int64
	for i, expr := range []ast.Expr{e.Low, e.High, e.Max} {