diff options
Diffstat (limited to 'src/main/scala/scala/async/internal/AnfTransform.scala')
| -rw-r--r-- | src/main/scala/scala/async/internal/AnfTransform.scala | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/src/main/scala/scala/async/internal/AnfTransform.scala b/src/main/scala/scala/async/internal/AnfTransform.scala index c722269..585f388 100644 --- a/src/main/scala/scala/async/internal/AnfTransform.scala +++ b/src/main/scala/scala/async/internal/AnfTransform.scala @@ -51,7 +51,17 @@ private[async] trait AnfTransform { expr match { case Apply(fun, args) if isAwait(fun) => val valDef = defineVal(name.await, expr, tree.pos) - stats :+ valDef :+ atPos(tree.pos)(gen.mkAttributedStableRef(valDef.symbol)).setType(tree.tpe) + val ref = gen.mkAttributedStableRef(valDef.symbol).setType(tree.tpe) + val ref1 = if (ref.tpe =:= definitions.UnitTpe) + // https://github.com/scala/async/issues/74 + // Use a cast to hide from "pure expression does nothing" error + // + // TODO avoid creating a ValDef for the result of this await to avoid this tree shape altogether. + // This will require some deeper changes to the later parts of the macro which currently assume regular + // tree structure around `await` calls. + gen.mkCast(ref, definitions.UnitTpe) + else ref + stats :+ valDef :+ atPos(tree.pos)(ref1) case If(cond, thenp, elsep) => // if type of if-else is Unit don't introduce assignment, |