//
	// 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
			}

		Rbrace     token.Pos // position of "}"
		Incomplete bool      // true if (source) expressions are missing in the Elts list
	}

	// A ParenExpr node represents a parenthesized expression.
	ParenExpr struct {
		Lparen token.Pos // position of "("
		X      Expr      // parenthesized expression
		Rparen token.Pos // position of ")"
	}

		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)

	// children.
	for {
		check.recordTypeAndValue(f, builtin, sig, nil)
		switch p := f.(type) {
		case *syntax.Name, *syntax.SelectorExpr:
			return // we're done
		case *syntax.ParenExpr:
			f = p.X
		default:
			panic("unreachable")
		}
	}
}

// recordCommaOkTypes updates recorded types to reflect that x is used in a commaOk context
// (and therefore has tuple type).

				return
			}
			if bin.Name() != name {
				t.Errorf("%s: got built-in %s; want %s", src0, bin.Name(), name)
				return
			}
			return // we're done

		case *syntax.ParenExpr:
			fun = p.X // unpack

		case *syntax.SelectorExpr:
			// built-in from package unsafe - ignore details
			return // we're done

		default:
			t.Errorf("%s: invalid function call", src0)
			return

	// children.
	for {
		check.recordTypeAndValue(f, builtin, sig, nil)
		switch p := f.(type) {
		case *ast.Ident, *ast.SelectorExpr:
			return // we're done
		case *ast.ParenExpr:
			f = p.X
		default:
			panic("unreachable")
		}
	}
}

// recordCommaOkTypes updates recorded types to reflect that x is used in a commaOk context
// (and therefore has tuple type).

	{name: "binary", format: "package main; var x = «1+»1"},
	{name: "binaryparen", format: "package main; var x = «1+(«1»)»", parseMultiplier: 2}, // Parser nodes: BinaryExpr, ParenExpr
	{name: "unary", format: "package main; var x = «^»1"},
	{name: "addr", format: "package main; var x = «& »x"},
	{name: "star", format: "package main; var x = «*»x"},
	{name: "recv", format: "package main; var x = «<-»x"},

				return
			}
			if bin.Name() != name {
				t.Errorf("%s: got built-in %s; want %s", src0, bin.Name(), name)
				return
			}
			return // we're done

		case *ast.ParenExpr:
			fun = p.X // unpack

		case *ast.SelectorExpr:
			// built-in from package unsafe - ignore details
			return // we're done

		default:
			t.Errorf("%s: invalid function call", src0)
			return