Fix SI-5853.

This solves two issues.

First, up to now the newly generated symbols for normalized
members were not being added to the declaration list of the
owner during `specialize`. Now they are.

Second, during `extmethods`, the extension methods generated
get an additional curried parameter list for `$this`.
Trouble was, after that, during `uncurry` and before `specialize`,
these curried parameter lists were merged into one list.
Specialization afterwards treats extension methods just
like normal methods and generates new symbols without the
curried parameter list.
The `extensionMethod` now takes this into account by checking
if the first parameter of a potential extension method has
the name `$this`.

Review by @dragos.
Review by @odersky.

2 files changed, 17 insertions, 1 deletions

diff --git a/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala b/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala
index 8556cc9ddc..7e0b87dbe1 100644
--- a/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala
+++ b/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala
@@ -77,11 +77,26 @@ abstract class ExtensionMethods extends Transform with TypingTransformers {
     matching.head
   }
 
+  /** This method removes the `$this` argument from the parameter list a method.
+   *  
+   *  A method may be a `PolyType`, in which case we tear out the `$this` and the class
+   *  type params from its nested `MethodType`.
+   *  It may be a `MethodType`, either with a curried parameter list in which the first argument
+   *  is a `$this` - we just return the rest of the list.
+   *  This means that the corresponding symbol was generated during `extmethods`.
+   *  
+   *  It may also be a `MethodType` in which the `$this` does not appear in a curried parameter list.
+   *  The curried lists disappear during `uncurry`, and the methods may be duplicated afterwards,
+   *  for instance, during `specialize`.
+   *  In this case, the first argument is `$this` and we just get rid of it.
+   */
   private def normalize(stpe: Type, clazz: Symbol): Type = stpe match {
     case PolyType(tparams, restpe) =>
       GenPolyType(tparams dropRight clazz.typeParams.length, normalize(restpe.substSym(tparams takeRight clazz.typeParams.length, clazz.typeParams), clazz))
-    case MethodType(tparams, restpe) =>
+    case MethodType(List(thiz), restpe) if thiz.name == nme.SELF =>
       restpe
+    case MethodType(tparams, restpe) =>
+      MethodType(tparams.drop(1), restpe)
     case _ =>
       stpe
   }
diff --git a/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala b/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
index f2e109a5ad..60461a524b 100644
--- a/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
+++ b/src/compiler/scala/tools/nsc/transform/SpecializeTypes.scala
@@ -821,6 +821,7 @@ abstract class SpecializeTypes extends InfoTransform with TypingTransformers {
           debuglog("%s expands to %s in %s".format(sym, specMember.name.decode, pp(env)))
           info(specMember) = NormalizedMember(sym)
           overloads(sym) ::= Overload(specMember, env)
+          owner.info.decls.enter(specMember)
           specMember
         }
       }