Merge pull request #3580 from gkossakowski/issue/SI-8330

SI-8330: Mismatch in stack heights

3 files changed, 30 insertions, 3 deletions

diff --git a/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala b/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala
index 81fbbfcabf..1cea4bedda 100644
--- a/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala
+++ b/src/compiler/scala/tools/nsc/backend/icode/GenICode.scala
@@ -1011,9 +1011,10 @@ abstract class GenICode extends SubComponent  {
       // emit conversion
       if (generatedType != expectedType) {
         tree match {
-          case Literal(Constant(null)) if generatedType == NullReference =>
+          case Literal(Constant(null)) if generatedType == NullReference && expectedType != UNIT =>
             // literal null on the stack (as opposed to a boxed null, see SI-8233),
             // we can bypass `adapt` which would otherwise emitt a redundant [DROP, CONSTANT(null)]
+            // except one case: when expected type is UNIT (unboxed) where we need to emit just a DROP
           case _ =>
             adapt(generatedType, expectedType, resCtx, tree.pos)
         }
diff --git a/test/files/run/t8233-bcode.scala b/test/files/run/t8233-bcode.scala
index fae1c2b702..72d013e553 100644
--- a/test/files/run/t8233-bcode.scala
+++ b/test/files/run/t8233-bcode.scala
@@ -11,8 +11,21 @@ object Test {
     bar(a)
   }
 
-  def main(args: Array[String]) = {
+  /** Check SI-8330 for details */
+  def expectedUnitInABranch(b: Boolean): Boolean = {
+    if (b) {
+      val x = 12
+      ()
+    } else {
+      // here expected type is (unboxed) Unit
+      null
+    }
+    true
+  }
+
+  def main(args: Array[String]): Unit = {
     try { nullReference } catch { case _: NoSuchElementException => }
     literal
+    expectedUnitInABranch(true)
   }
 }
diff --git a/test/files/run/t8233.scala b/test/files/run/t8233.scala
index fae1c2b702..97a98a2e21 100644
--- a/test/files/run/t8233.scala
+++ b/test/files/run/t8233.scala
@@ -11,8 +11,21 @@ object Test {
     bar(a)
   }
 
-  def main(args: Array[String]) = {
+  /** Check SI-8330 for details */
+  def expectedUnitInABranch(b: Boolean): Boolean = {
+    if (b) {
+      val x = 12
+      ()
+    } else {
+      // here expected type is (unboxed) Unit
+      null
+    }
+    true
+  }
+
+  def main(args: Array[String]): Unit = {
     try { nullReference } catch { case _: NoSuchElementException => }
     literal
+    expectedUnitInABranch(true) // Was: VerifyError under GenICode
   }
 }