Max    Expr      // maximum capacity of slice; or nil
		Slice3 bool      // true if 3-index slice (2 colons present)
		Rbrack token.Pos // position of "]"
	}

	// A TypeAssertExpr node represents an expression followed by a
	// type assertion.
	//
	TypeAssertExpr struct {
		X      Expr      // expression
		Lparen token.Pos // position of "("
		Type   Expr      // asserted type; nil means type switch X.(type)

	case *ast.StructType:
		children = append(children, tok(n.Struct, len("struct")))

	case *ast.SwitchStmt:
		children = append(children, tok(n.Switch, len("switch")))

	case *ast.TypeAssertExpr:
		children = append(children,
			tok(n.Lparen-1, len(".")),
			tok(n.Lparen, len("(")),
			tok(n.Rparen, len(")")))

	case *ast.TypeSpec:
		// TODO(adonovan): TypeSpec.{Doc,Comment}?

		walkBeforeAfter(&n.X, before, after)
		if n.Low != nil {
			walkBeforeAfter(&n.Low, before, after)
		}
		if n.High != nil {
			walkBeforeAfter(&n.High, before, after)
		}
	case *ast.TypeAssertExpr:
		walkBeforeAfter(&n.X, before, after)
		walkBeforeAfter(&n.Type, before, after)
	case *ast.CallExpr:
		walkBeforeAfter(&n.Fun, before, after)
		walkBeforeAfter(&n.Args, before, after)
	case *ast.StarExpr:

		if n.Low != nil {
			f.walk(&n.Low, ctxExpr, visit)
		}
		if n.High != nil {
			f.walk(&n.High, ctxExpr, visit)
		}
		if n.Max != nil {
			f.walk(&n.Max, ctxExpr, visit)
		}
	case *ast.TypeAssertExpr:
		f.walk(&n.X, ctxExpr, visit)
		f.walk(&n.Type, ctxType, visit)
	case *ast.CallExpr:
		if context == ctxAssign2 {
			f.walk(&n.Fun, ctxCall2, visit)
		} else {
			f.walk(&n.Fun, ctxCall, visit)
		}

		a.applyList(n, "Indices")

	case *ast.SliceExpr:
		a.apply(n, "X", nil, n.X)
		a.apply(n, "Low", nil, n.Low)
		a.apply(n, "High", nil, n.High)
		a.apply(n, "Max", nil, n.Max)

	case *ast.TypeAssertExpr:
		a.apply(n, "X", nil, n.X)
		a.apply(n, "Type", nil, n.Type)

	case *ast.CallExpr:
		a.apply(n, "Fun", nil, n.Fun)
		a.applyList(n, "Args")

	case *ast.StarExpr:
		a.apply(n, "X", nil, n.X)

		n := n.(*ir.UnaryExpr)
		return walkUnsafeData(n, init)

	case ir.ODOT, ir.ODOTPTR:
		n := n.(*ir.SelectorExpr)
		return walkDot(n, init)

	case ir.ODOTTYPE, ir.ODOTTYPE2:
		n := n.(*ir.TypeAssertExpr)
		return walkDotType(n, init)

	case ir.ODYNAMICDOTTYPE, ir.ODYNAMICDOTTYPE2:
		n := n.(*ir.DynamicTypeAssertExpr)
		return walkDynamicDotType(n, init)

	case ir.OLEN, ir.OCAP:

		stmt := stmt.(*ir.AssignListStmt)
		r := rhs[0]

		switch r.Op() {
		case ir.OINDEXMAP:
			stmt.SetOp(ir.OAS2MAPR)
		case ir.ORECV:
			stmt.SetOp(ir.OAS2RECV)
		case ir.ODOTTYPE:
			r := r.(*ir.TypeAssertExpr)
			stmt.SetOp(ir.OAS2DOTTYPE)
			r.SetOp(ir.ODOTTYPE2)
		case ir.ODYNAMICDOTTYPE:
			r := r.(*ir.DynamicTypeAssertExpr)
			stmt.SetOp(ir.OAS2DOTTYPE)
			r.SetOp(ir.ODYNAMICDOTTYPE2)
		default:

			}
			typeof[n] = join(out)
			for i, arg := range n.Args {
				if i >= len(in) {
					break
				}
				if typeof[arg] == "" {
					typeof[arg] = in[i]
				}
			}

		case *ast.TypeAssertExpr:
			// x.(type) has type of x.
			if n.Type == nil {
				typeof[n] = typeof[n.X]
				return
			}
			// x.(T) has type T.
			if t := typeof[n.Type]; isType(t) {
				typeof[n] = getType(t)

	case ir.OAS2DOTTYPE, ir.OAS2RECV, ir.OAS2MAPR:
		n := n.(*ir.AssignListStmt)
		t := o.markTemp()
		o.exprList(n.Lhs)

		switch r := n.Rhs[0]; r.Op() {
		case ir.ODOTTYPE2:
			r := r.(*ir.TypeAssertExpr)
			r.X = o.expr(r.X, nil)
		case ir.ODYNAMICDOTTYPE2:
			r := r.(*ir.DynamicTypeAssertExpr)
			r.X = o.expr(r.X, nil)
			r.RType = o.expr(r.RType, nil)
			r.ITab = o.expr(r.ITab, nil)
		case ir.ORECV:

		n.SetOp(ir.OMETHVALUE)
		n.SetType(NewMethodType(n.Type(), nil))
	}
	return n
}

// tcDotType typechecks an ODOTTYPE node.
func tcDotType(n *ir.TypeAssertExpr) ir.Node {
	n.X = Expr(n.X)
	n.X = DefaultLit(n.X, nil)
	l := n.X
	t := l.Type()
	if t == nil {
		n.SetType(nil)
		return n
	}
	if !t.IsInterface() {