Merge pull request #3428 from retronym/ticket/6260

SI-6260 Avoid double-def error with lambdas over value classes

2 files changed, 36 insertions, 21 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/Delambdafy.scala b/src/compiler/scala/tools/nsc/transform/Delambdafy.scala
index 933a2f70a1..d81a5d5755 100644
--- a/src/compiler/scala/tools/nsc/transform/Delambdafy.scala
+++ b/src/compiler/scala/tools/nsc/transform/Delambdafy.scala
@@ -232,6 +232,10 @@ abstract class Delambdafy extends Transform with TypingTransformers with ast.Tre
         val parents = addSerializable(abstractFunctionErasedType)
         val funOwner = originalFunction.symbol.owner
 
+        // TODO harmonize the naming of delamdafy anon-fun classes with those spun up by Uncurry
+        //      - make `anonClass.isAnonymousClass` true.
+        //      - use `newAnonymousClassSymbol` or push the required variations into a similar factory method
+        //      - reinstate the assertion in `Erasure.resolveAnonymousBridgeClash`
         val suffix = "$lambda$" + (
           if (funOwner.isPrimaryConstructor) ""
           else "$" + funOwner.name
@@ -282,18 +286,11 @@ abstract class Delambdafy extends Transform with TypingTransformers with ast.Tre
         if (sym == NoSymbol) sym.toString
         else s"$sym: ${sym.tpe} in ${sym.owner}"
 
-      def clashError(bm: Symbol) = {
-        unit.error(
-          applyMethodDef.symbol.pos,
-            sm"""bridge generated for member ${fulldef(applyMethodDef.symbol)}
-                |which overrides ${fulldef(getMember(abstractFunctionErasedType.typeSymbol, nme.apply))}
-                |clashes with definition of the member itself;
-                |both have erased type ${exitingPostErasure(bm.tpe)}""")
-        }
-
         bridgeMethod foreach (bm =>
+          // TODO SI-6260 maybe just create the apply method with the signature (Object => Object) in all cases
+          //      rather than the method+bridge pair.
           if (bm.symbol.tpe =:= applyMethodDef.symbol.tpe)
-            clashError(bm.symbol)
+            erasure.resolveAnonymousBridgeClash(applyMethodDef.symbol, bm.symbol)
         )
 
         val body = members ++ List(constr, applyMethodDef) ++ bridgeMethod
diff --git a/src/compiler/scala/tools/nsc/transform/Erasure.scala b/src/compiler/scala/tools/nsc/transform/Erasure.scala
index ccfddab94a..60c1553ef3 100644
--- a/src/compiler/scala/tools/nsc/transform/Erasure.scala
+++ b/src/compiler/scala/tools/nsc/transform/Erasure.scala
@@ -403,19 +403,19 @@ abstract class Erasure extends AddInterfaces
      *  @param  other    The overidden symbol for which the bridge was generated
      *  @param  bridge   The bridge
      */
-    def checkBridgeOverrides(member: Symbol, other: Symbol, bridge: Symbol): Boolean = {
+    def checkBridgeOverrides(member: Symbol, other: Symbol, bridge: Symbol): Seq[(Position, String)] = {
       def fulldef(sym: Symbol) =
         if (sym == NoSymbol) sym.toString
         else s"$sym: ${sym.tpe} in ${sym.owner}"
       var noclash = true
+      val clashErrors = mutable.Buffer[(Position, String)]()
       def clashError(what: String) = {
-        noclash = false
-        unit.error(
-          if (member.owner == root) member.pos else root.pos,
-          sm"""bridge generated for member ${fulldef(member)}
-              |which overrides ${fulldef(other)}
-              |clashes with definition of $what;
-              |both have erased type ${exitingPostErasure(bridge.tpe)}""")
+        val pos = if (member.owner == root) member.pos else root.pos
+        val msg = sm"""bridge generated for member ${fulldef(member)}
+                      |which overrides ${fulldef(other)}
+                      |clashes with definition of $what;
+                      |both have erased type ${exitingPostErasure(bridge.tpe)}"""
+        clashErrors += Tuple2(pos, msg)
       }
       for (bc <- root.baseClasses) {
         if (settings.debug)
@@ -440,7 +440,7 @@ abstract class Erasure extends AddInterfaces
           }
         }
       }
-      noclash
+      clashErrors
     }
 
     /** TODO - work through this logic with a fine-toothed comb, incorporating
@@ -478,8 +478,18 @@ abstract class Erasure extends AddInterfaces
       bridge setInfo (otpe cloneInfo bridge)
       bridgeTarget(bridge) = member
 
-      if (!(member.tpe exists (_.typeSymbol.isDerivedValueClass)) ||
-          checkBridgeOverrides(member, other, bridge)) {
+      def sigContainsValueClass = (member.tpe exists (_.typeSymbol.isDerivedValueClass))
+
+      val shouldAdd = (
+            !sigContainsValueClass
+        ||  (checkBridgeOverrides(member, other, bridge) match {
+              case Nil => true
+              case es if member.owner.isAnonymousClass => resolveAnonymousBridgeClash(member, bridge); true
+              case es => for ((pos, msg) <- es) unit.error(pos, msg); false
+            })
+      )
+
+      if (shouldAdd) {
         exitingErasure(root.info.decls enter bridge)
         if (other.owner == root) {
           exitingErasure(root.info.decls.unlink(other))
@@ -1127,5 +1137,13 @@ abstract class Erasure extends AddInterfaces
     }
   }
 
+  final def resolveAnonymousBridgeClash(sym: Symbol, bridge: Symbol) {
+    // TODO reinstate this after Delambdafy generates anonymous classes that meet this requirement.
+    // require(sym.owner.isAnonymousClass, sym.owner)
+    log(s"Expanding name of ${sym.debugLocationString} as it clashes with bridge. Renaming deemed safe because the owner is anonymous.")
+    sym.expandName(sym.owner)
+    bridge.resetFlag(BRIDGE)
+  }
+
   private class TypeRefAttachment(val tpe: TypeRef)
 }