Consider the following macro declaration:

def someMacro[Alg[_[_]]](c: Context)(implicit alg: c.WeakTypeTag[Alg[_]])

Unfortunately it does not compile. The error:

 _$2 takes no type parameters, expected: 1

Is there a way to fix it up?

CodePudding user response：

Try WeakTypeTag for a higher-kinded existential type (in forSome notation)

def someMacro[Alg[_[_]]](c: Context)(implicit alg: c.WeakTypeTag[Alg[F]] forSome { type F[_] })

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