op := *x
				op.X = lhs
				return name, &op
			}
		}
	case *CallExpr:
		if name, _ := x.Fun.(*Name); name != nil {
			if len(x.ArgList) == 1 && !x.HasDots && (force || isTypeElem(x.ArgList[0])) {
				// x = name "(" x.ArgList[0] ")"
				return name, x.ArgList[0]
			}
		}
	}
	return nil, x
}

// isTypeElem reports whether x is a (possibly parenthesized) type element expression.