Fix "BoxedUnit cannot be cast to String" error.

When convering If and Match nodes to ANF, set the type to Unit.
Otherwise, erasure might end up casting BoxedUnit to a real type.

2 files changed, 24 insertions, 3 deletions

diff --git a/src/main/scala/scala/async/internal/AnfTransform.scala b/src/main/scala/scala/async/internal/AnfTransform.scala
index 80f8161..c6e5bcb 100644
--- a/src/main/scala/scala/async/internal/AnfTransform.scala
+++ b/src/main/scala/scala/async/internal/AnfTransform.scala
@@ -87,7 +87,7 @@ private[async] trait AnfTransform {
                   case _                          => Assign(Ident(varDef.symbol), cast(orig))
                 }
               }.setType(orig.tpe)
-              val ifWithAssign = treeCopy.If(tree, cond, branchWithAssign(thenp), branchWithAssign(elsep))
+              val ifWithAssign = treeCopy.If(tree, cond, branchWithAssign(thenp), branchWithAssign(elsep)).setType(definitions.UnitTpe)
               stats :+ varDef :+ ifWithAssign :+ gen.mkAttributedStableRef(varDef.symbol)
             }
 
@@ -107,9 +107,9 @@ private[async] trait AnfTransform {
                     case b@Block(caseStats, caseExpr) => treeCopy.Block(b, caseStats, typedAssign(caseExpr))
                     case _                            => typedAssign(body)
                   }
-                  treeCopy.CaseDef(cd, pat, guard, newBody)
+                  treeCopy.CaseDef(cd, pat, guard, newBody).setType(definitions.UnitTpe)
               }
-              val matchWithAssign = treeCopy.Match(tree, scrut, casesWithAssign)
+              val matchWithAssign = treeCopy.Match(tree, scrut, casesWithAssign).setType(definitions.UnitTpe)
               require(matchWithAssign.tpe != null, matchWithAssign)
               stats :+ varDef :+ matchWithAssign :+ gen.mkAttributedStableRef(varDef.symbol)
             }
diff --git a/src/test/scala/scala/async/run/match0/Match0.scala b/src/test/scala/scala/async/run/match0/Match0.scala
index 49a3a69..7c392ab 100644
--- a/src/test/scala/scala/async/run/match0/Match0.scala
+++ b/src/test/scala/scala/async/run/match0/Match0.scala
@@ -125,4 +125,25 @@ class MatchSpec {
     }
     m4("") mustBe 0
   }
+
+  @Test def bugCastBoxedUnitToStringMatch() {
+    import scala.async.internal.AsyncId.{async, await}
+    def foo = async {
+      val p2 = await(5)
+      "foo" match {
+        case p3: String =>
+          p2.toString
+      }
+    }
+    foo mustBe "5"
+  }
+
+  @Test def bugCastBoxedUnitToStringIf() {
+    import scala.async.internal.AsyncId.{async, await}
+    def foo = async {
+      val p2 = await(5)
+      if (true) p2.toString else p2.toString
+    }
+    foo mustBe "5"
+  }
 }