From cb028ba477f37778bccfc23e597acc0284259681 Mon Sep 17 00:00:00 2001 From: Jason Zaugg Date: Fri, 6 Sep 2013 17:04:53 +0200 Subject: SI-7818 Cast our way out of extended existential angst `substituteSymbols` is not sophisticated enough to operate on `TypeSkolem`-s which are based on one of the "from" symbols. The pertinant usage of `substituteSymbols` for this bug in in `Extender`. Recapping on that transform: // orig class C[T](...) extends AnyVal { def foo[U] = } // transform class C[T] extends AnyVal { ... } object C { def foo$extension[T', U'] = } Where `` has been subtituted with, among other things, `[T, U] ~> [T', U']`. In this case our expected type contains a new type parameter (of the extension method), whereas the type of the RHS contains an existential skolem still pinned to the corresponding class type parameter. tree.tpe = Observable1#7037[_$1#12344] <_$1#12344>.info = <: T#7040 pt = Observable1#7037[T#15644] The limitation of substution is lamented in the comments of `adaptMismatchedSkolems`, which faces the harder version of the issue where the skolems are in the expected type. But, we're in the "easy" case with the skolems in the tree's type; we can cast our way out of the problem. See also f335e447 / ed915c54. --- src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'src') diff --git a/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala b/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala index bc54054028..e0c0cd0fdb 100644 --- a/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala +++ b/src/compiler/scala/tools/nsc/transform/ExtensionMethods.scala @@ -231,9 +231,14 @@ abstract class ExtensionMethods extends Transform with TypingTransformers { .substituteThis(origThis, extensionThis) .changeOwner(origMeth -> extensionMeth) ) + val castBody = + if (extensionBody.tpe <:< extensionMono.finalResultType) + extensionBody + else + gen.mkCastPreservingAnnotations(extensionBody, extensionMono.finalResultType) // SI-7818 e.g. mismatched existential skolems // Record the extension method ( FIXME: because... ? ) - extensionDefs(companion) += atPos(tree.pos)(DefDef(extensionMeth, extensionBody)) + extensionDefs(companion) += atPos(tree.pos)(DefDef(extensionMeth, castBody)) // These three lines are assembling Foo.bar$extension[T1, T2, ...]($this) // which leaves the actual argument application for extensionCall. -- cgit v1.2.3