我正在编写一个宏，需要创建一个重写特征的类，该类具有相同的特征方法/参数，但返回类型不同。
所以说我们有：
trait MyTrait[T]
{
def x(t1: T)(t2: T): T
}
@AnnProxy
class MyClass[T] extends MyTrait[T]
MyClass 将被重写为：
class MyClass[T] {
def x(t1: T)(t2: T): R[T]
}
（所以 x 现在将返回 R[T] 而不是 T）
我编写了宏并对其进行了调试，它生成了以下代码：
Expr[Any](class MyClass[T] extends scala.AnyRef {
def <init>() = {
super.<init>();
()
};
def x(t1: T)(t2: T): macrotests.R[T] = $qmark$qmark$qmark
})
@AnnProxy
正如你所看到的，签名似乎没问题。但是当尝试使用宏时，我收到编译错误：
val my = new MyClass[Int]
my.x(5)(6)
错误：(14, 7) 类型不匹配；
发现：整数(5)
必需：T
xx(5)(6)
^
所以看来该方法的泛型 T 与类 [T] 不同。有什么想法如何解决吗？
这是我到目前为止的宏。我对宏不太擅长（在 stackoverflow 的很多帮助下创造了这个），但这是当前状态：
@compileTimeOnly("enable macro paradise to expand macro annotations")
class AnnProxy extends StaticAnnotation
{
def macroTransform(annottees: Any*): Any = macro IdentityMacro.impl
}
trait R[T]
object IdentityMacro
{
private val SDKClasses = Set("java.lang.Object", "scala.Any")
def impl(c: whitebox.Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
import c.universe._
def showInfo(s: String) = c.info(c.enclosingPosition, s.split("\n").mkString("\n |---macro info---\n |", "\n |", ""), true)
val classDef = annottees.map(_.tree).head.asInstanceOf[ClassDef]
val clazz = c.typecheck(classDef).symbol.asClass
val tparams = clazz.typeParams
val baseClasses = clazz.baseClasses.tail.filter(clz => !SDKClasses(clz.fullName))
val methods = baseClasses.flatMap {
base =>
base.info.decls.filter(d => d.isMethod && d.isPublic).map { decl =>
val termName = decl.name.toTermName
val method = decl.asMethod
val params = method.paramLists.map(_.map {
s =>
val vd = internal.valDef(s)
val f = tparams.find(_.name == vd.tpt.symbol.name)
val sym = if (f.nonEmpty) f.get else vd.tpt.symbol
q"val ${vd.name} : $sym "
})
val paramVars = method.paramLists.flatMap(_.map(_.name))
q""" def $termName (...$params)(timeout:scala.concurrent.duration.FiniteDuration) : macrotests.R[${method.returnType}] = {
???
}"""
}
}
val cde = c.Expr[Any] {
q"""
class ${classDef.name} [..${classDef.tparams}] {
..$methods
}
"""
}
showInfo(show(cde))
cde
}
}
编辑：我设法通过将类构建为字符串然后使用 c.parse 来编译它来解决问题。感觉就像黑客，但它确实有效。一定有更好的方法来操纵树。
package macrotests
import scala.annotation.{StaticAnnotation, compileTimeOnly}
import scala.language.experimental.macros
import scala.reflect.macros.whitebox
@compileTimeOnly("enable macro paradise to expand macro annotations")
class AnnProxy extends StaticAnnotation
{
def macroTransform(annottees: Any*): Any = macro AnnProxyMacro.impl
}
trait R[T]
trait Remote[T]
object AnnProxyMacro
{
private val SDKClasses = Set("java.lang.Object", "scala.Any")
def impl(c: whitebox.Context)(annottees: c.Expr[Any]*): c.Expr[Any] = {
import c.universe._
val classDef = annottees.map(_.tree).head.asInstanceOf[ClassDef]
val clazz = c.typecheck(classDef).symbol.asClass
val baseClasses = clazz.baseClasses.tail.filter(clz => !SDKClasses(clz.fullName))
val methods = baseClasses.flatMap {
base =>
base.info.decls.filter(d => d.isMethod && d.isPublic).map { decl =>
val termName = decl.name.toTermName
val method = decl.asMethod
val params = method.paramLists.map(_.map {
s =>
val vd = internal.valDef(s)
val tq = vd.tpt
s"${vd.name} : $tq"
})
val paramVars = method.paramLists.flatMap(_.map(_.name))
val paramVarsArray = paramVars.mkString("Array(", ",", ")")
val paramsStr = params.map(_.mkString("(", ",", ")")).mkString(" ")
val retTpe = method.returnType.typeArgs.mkString("-unexpected-")
s""" def $termName $paramsStr (timeout:scala.concurrent.duration.FiniteDuration) : macrotests.Remote[$retTpe] = {
println($paramVarsArray.toList)
new macrotests.Remote[$retTpe] {}
}"""
}
}
val tparams = clazz.typeParams.map(_.name)
val tparamsStr = if (tparams.isEmpty) "" else tparams.mkString("[", ",", "]")
val code =
s"""
|class ${classDef.name}$tparamsStr (x:Int) {
|${methods.mkString("\n")}
|}
""".stripMargin
// print(code)
val cde = c.Expr[Any](c.parse(code))
cde
}
}
