Macro with Unit type splicing non Unit fails with `splice outside quotes`

[nicolasstucki]

import scala.quoted._
object Macros {
  inline def foo(): Unit = ~impl()
  def impl(): Expr[Int] = '(1)
}

import scala.quoted._
import Macros._
class Test {
  val a: Unit = foo()
}

fails with

5 |    ~impl()
  |    ^^^^^^^
  |    splice outside quotes

because inline def foo(): Unit = ~impl() is transformed to
inline def foo(): Unit = { ~impl(); () }, which is correct.

We need a better error message for this.

[nicolasstucki]

This should probably be done in ReifyQuotes.

[odersky]

Why is this not expanded to a macro?

[nicolasstucki]

We could expand it to a macro. We would need to not insert the explicit () or to recognise that shape of tree as a macro body.

[biboudis]

Where is it best to transform the shape of the tree? In transform of ReifyQuotes right (link)?

[nicolasstucki]

Not sure, maybe it should be before. We should probably have it marked as a macro before that to make it take this branch Yes, the issue is probably there.

[nicolasstucki]

The following macro has a similar issue

import scala.quoted._
object Macros {
  inline def foo(): Int = { ~impl() }
  def impl(): Expr[Int] = '(1)
}

import scala.quoted._
import Macros._
class Test {
  val a: Unit = foo()
}

In both cases the code that is splices is found in a block as statement or expression position. We probably handle these as part of the Inlined branch conditions.