From 2606becba91fa3d31cdeb3069a5a35b0163a4cde Mon Sep 17 00:00:00 2001 From: Eugene Burmako Date: Sun, 9 Feb 2014 20:49:48 +0100 Subject: changes the order of whitebox typechecks. yes, again. My first attempt at SI-6992 was about having whitebox expansions first typecheck against outerPt and only then verify that the result is compatible with innerPt. That was a nice try, but soon after it went live in 2.11.0-M8, we've got multiple reports with problems - both shapeless and then in a week specs2 started having issues with their whitebox macros. In shapeless, typecheck against outerPt screwed up type inference, which was more or less fixable by explicit type annotations, so I decided to wait a bit before jumping to conclusions. However, in specs2 the problem was more insidious. After being typechecked against outerPt, expansions were being implicitly converted to a type that became incompatible with innerPt. This revealed a fatal flaw of the implemented approach - if allowed to typecheck against outerPt first, whitebox macros could never be robust. Now realizing that "outerPt > innerPt" doesn't work, I nevertheless wasn't looking forward to rolling that back to "innerPt > outerPt", because that would revive SI-6992 and SI-8048 that are highly unintuitive, especially the latter one. Therefore, this commit combines the permissiveness of "... > innerPt" approaches with the robustness of "innerPt > outerPt", introducing "WildcardType > innerPt > outerPt". --- src/compiler/scala/tools/nsc/typechecker/Macros.scala | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'src') diff --git a/src/compiler/scala/tools/nsc/typechecker/Macros.scala b/src/compiler/scala/tools/nsc/typechecker/Macros.scala index cf82d6baac..677c94e063 100644 --- a/src/compiler/scala/tools/nsc/typechecker/Macros.scala +++ b/src/compiler/scala/tools/nsc/typechecker/Macros.scala @@ -620,9 +620,11 @@ trait Macros extends FastTrack with MacroRuntimes with Traces with Helpers { val expanded1 = atPos(enclosingMacroPosition.makeTransparent)(Typed(expanded0, TypeTree(innerPt))) typecheck("blackbox typecheck", expanded1, outerPt) } else { - val expanded1 = expanded0 - val expanded2 = typecheck("whitebox typecheck #1", expanded1, outerPt) - typecheck("whitebox typecheck #2", expanded2, innerPt) + // whitebox expansions need to be typechecked against WildcardType first in order to avoid SI-6992 and SI-8048 + // then we typecheck against innerPt, not against outerPt in order to prevent SI-8209 + val expanded1 = typecheck("whitebox typecheck #0", expanded0, WildcardType) + val expanded2 = typecheck("whitebox typecheck #1", expanded1, innerPt) + typecheck("whitebox typecheck #2", expanded2, outerPt) } } override def onDelayed(delayed: Tree) = { -- cgit v1.2.3