Scalameta Decl.Def does not work in attribute definition method
I am using Scalameta annotation (v1.8.0) for def declaration:
trait MyTrait {
@MyDeclDef
def f2(): Int
}
The annotation class has only defined the return input, since this is:
import scala.meta._
class MyDeclDef extends scala.annotation.StaticAnnotation {
inline def apply(defn: Any): Any = meta {
defn match {
case defn: Decl.Def =>
defn
case _ =>
println(defn.structure)
abort("@MyDeclDef most annotate a Decl.Def")
}
}
}
a compiler error occurs:
Error:'=' expected but eof found.
def f2(): Unit
Error:illegal start of simple expression
def f2(): Unit
Also, if I use Decl.Var
to var v2: Int
it works great.
How to properly comment on a trait def
? Thanks to
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I have not worked with scala-meta
before and have tried your example. It looks like we need to implement this method in macros. For example, if we provide a default implementation:
class MyDeclDef extends scala.annotation.StaticAnnotation {
inline def apply(defn: Any): Any = meta {
defn match {
case defn: Decl.Def =>
val q"def $name(): $tpe" = defn
q"def $name(): $tpe = 1"
we can instantiate MyTrait
and print the value of the method f2
:)
val x = new MyTrait
println(x.f2) // Prints 1
var v2: Int
works great because it fits case _
where we abort
are compiling.
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