Workaround for #765

Avoid using unexpanded name because it can give wrong results for super accessors
of symbolic names. See #765. Without this commit t2183.scala crashes the compiler.

2 files changed, 12 insertions, 3 deletions

diff --git a/src/dotty/tools/dotc/core/NameOps.scala b/src/dotty/tools/dotc/core/NameOps.scala
index 593d5f036..cab47025e 100644
--- a/src/dotty/tools/dotc/core/NameOps.scala
+++ b/src/dotty/tools/dotc/core/NameOps.scala
@@ -167,6 +167,11 @@ object NameOps {
 
     def expandedName(prefix: Name): N = expandedName(prefix, nme.EXPAND_SEPARATOR)
 
+    /** Revert the expanded name. Note: This currently gives incorrect results
+     *  if the normal name contains `nme.EXPAND_SEPARATOR`, i.e. two consecutive '$'
+     *  signs. This can happen for instance if a super accessor is paired with
+     *  an encoded name, e.g. super$$plus$eq. See #765.
+     */
     def unexpandedName: N = {
       val idx = name.lastIndexOfSlice(nme.EXPAND_SEPARATOR)
       if (idx < 0) name else (name drop (idx + nme.EXPAND_SEPARATOR.length)).asInstanceOf[N]
diff --git a/src/dotty/tools/dotc/transform/ResolveSuper.scala b/src/dotty/tools/dotc/transform/ResolveSuper.scala
index c699476bb..26128cf33 100644
--- a/src/dotty/tools/dotc/transform/ResolveSuper.scala
+++ b/src/dotty/tools/dotc/transform/ResolveSuper.scala
@@ -59,9 +59,13 @@ class ResolveSuper extends MiniPhaseTransform with IdentityDenotTransformer { th
   private def rebindSuper(base: Symbol, acc: Symbol)(implicit ctx: Context): Symbol = {
     var bcs = base.info.baseClasses.dropWhile(acc.owner != _).tail
     var sym: Symbol = NoSymbol
-    val originalAccName =
-      if (acc.is(ExpandedName)) acc.name.unexpandedName else acc.name
-    val SuperAccessorName(memberName) = originalAccName: Name // dotty deviation: ": Name" needed otherwise pattern type is neither a subtype nor a supertype of selector type
+    val unexpandedAccName =
+      if (acc.is(ExpandedName))  // Cannot use unexpandedName because of #765. t2183.scala would fail if we did.
+        acc.name
+          .drop(acc.name.indexOfSlice(nme.EXPAND_SEPARATOR ++ nme.SUPER_PREFIX))
+          .drop(nme.EXPAND_SEPARATOR.length)
+      else acc.name
+    val SuperAccessorName(memberName) = unexpandedAccName: Name // dotty deviation: ": Name" needed otherwise pattern type is neither a subtype nor a supertype of selector type
     ctx.debuglog(i"starting rebindsuper from $base of ${acc.showLocated}: ${acc.info} in $bcs, name = $memberName")
     while (bcs.nonEmpty && sym == NoSymbol) {
       val other = bcs.head.info.nonPrivateDecl(memberName)