SI-8143 Fix bug with super-accessors / dependent types

Super-accessors are generated as `DefDef`'s with `EmptyTree` as a
placeholder for the RHS. This is filled in later in `Mixin` in
`completeSuperAccessor`.

A change in `Uncurry` (SI-6443 / 493197f), however, converted this
to a `{ EmptyTree }`, which evaded the pattern match in mixin.

This commit adds a special case to the dependent method treatment
in Uncurry to avoid generating redundant blocks.

1 files changed, 7 insertions, 5 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/UnCurry.scala b/src/compiler/scala/tools/nsc/transform/UnCurry.scala
index 430129aaff..e61b35a621 100644
--- a/src/compiler/scala/tools/nsc/transform/UnCurry.scala
+++ b/src/compiler/scala/tools/nsc/transform/UnCurry.scala
@@ -878,11 +878,13 @@ abstract class UnCurry extends InfoTransform
           case Packed(param, tempVal) => (param, tempVal)
         }.unzip
 
-        val rhs1 = localTyper.typedPos(rhs.pos) {
-          // Patch the method body to refer to the temp vals
-          val rhsSubstituted = rhs.substituteSymbols(packedParams map (_.symbol), tempVals map (_.symbol))
-          // The new method body: { val p$1 = p.asInstanceOf[<dependent type>]; ...; <rhsSubstituted> }
-          Block(tempVals, rhsSubstituted)
+        val rhs1 = if (tempVals.isEmpty) rhs else {
+          localTyper.typedPos(rhs.pos) {
+            // Patch the method body to refer to the temp vals
+            val rhsSubstituted = rhs.substituteSymbols(packedParams map (_.symbol), tempVals map (_.symbol))
+            // The new method body: { val p$1 = p.asInstanceOf[<dependent type>]; ...; <rhsSubstituted> }
+            Block(tempVals, rhsSubstituted)
+          }
         }
 
         (allParams :: Nil, rhs1)