[backport] Cleanup code generation by avoiding redundant blocks

Don't bother adding `{ ...; () }` if we can use the original tree(s) instead,
e.g. if the last tree in `...` conforms to `Unit`.

This makes the debug output of the macro a little easier to read.

(cherry picked from commit de641dc265f34b06e17dfa7c64be00219f72b670)

1 files changed, 6 insertions, 6 deletions

diff --git a/src/main/scala/scala/async/internal/AsyncTransform.scala b/src/main/scala/scala/async/internal/AsyncTransform.scala
index 47a2704..b894e61 100644
--- a/src/main/scala/scala/async/internal/AsyncTransform.scala
+++ b/src/main/scala/scala/async/internal/AsyncTransform.scala
@@ -68,12 +68,12 @@ trait AsyncTransform {
     for ((state, flds) <- assignsOf) {
       val assigns = flds.map { fld =>
         val fieldSym = fld.symbol
-        Block(
-          List(
-            asyncBase.nullOut(global)(Expr[String](Literal(Constant(fieldSym.name.toString))), Expr[Any](Ident(fieldSym))).tree
-          ),
-          Assign(gen.mkAttributedStableRef(fieldSym.owner.thisType, fieldSym), mkZero(fieldSym.info))
-        )
+        val assign = Assign(gen.mkAttributedStableRef(fieldSym.owner.thisType, fieldSym), mkZero(fieldSym.info))
+        asyncBase.nullOut(global)(Expr[String](Literal(Constant(fieldSym.name.toString))), Expr[Any](Ident(fieldSym))).tree
+        match {
+          case Literal(Constant(value: Unit)) => assign
+          case x => Block(x :: Nil, assign)
+        }
       }
       val asyncState = asyncBlock.asyncStates.find(_.state == state).get
       asyncState.stats = assigns ++ asyncState.stats