[英]macros, splice, and pattern matching
Is there a way to use an argument to a macro in a pattern match? 有没有办法在模式匹配中对宏使用参数? I would like to do this:
我想这样做:
def extr(X:AnyRef) = macro extrImpl
def extrImpl(c:Context)(X:c.Expr[AnyRef]):c.Expr[AnyRef] = {
import c.universe._
val tree = reify {
new {
def unapply(x:String):Option[String] = x match {
case X.splice => Some(x) //error
case _ => None
}
}
}.tree
c.Expr(c.typeCheck(tree))
}
But unfortunately the compiler says "stable identifier required, but X.splice found". 但是不幸的是,编译器说“需要稳定的标识符,但是找到了X.splice”。 Normally, one would solve this by assigning to a val first, such as:
通常,可以通过先分配一个val来解决此问题,例如:
val XX = X.splice
But of course that doesn't work with splice either. 但是,当然这对拼接也不起作用。
不幸的是,目前尚不可能(并且在2.10.0-final中将无法实现),但是我们正在进行一些工作,可能会在以后的版本发布中有所帮助:)
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