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author | Eugene Burmako <xeno.by@gmail.com> | 2014-02-09 20:49:48 +0100 |
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committer | Eugene Burmako <xeno.by@gmail.com> | 2014-02-09 20:49:48 +0100 |
commit | 2606becba91fa3d31cdeb3069a5a35b0163a4cde (patch) | |
tree | 767e8a3a966a5d93e1e84875a7bbda2e8575ceb7 /test/files/pos/t8209b/Macros_1.scala | |
parent | 9dc60af28e2c17579c17e27168d1e29ef34efaef (diff) | |
download | scala-2606becba91fa3d31cdeb3069a5a35b0163a4cde.tar.gz scala-2606becba91fa3d31cdeb3069a5a35b0163a4cde.tar.bz2 scala-2606becba91fa3d31cdeb3069a5a35b0163a4cde.zip |
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".
Diffstat (limited to 'test/files/pos/t8209b/Macros_1.scala')
-rw-r--r-- | test/files/pos/t8209b/Macros_1.scala | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/test/files/pos/t8209b/Macros_1.scala b/test/files/pos/t8209b/Macros_1.scala new file mode 100644 index 0000000000..705f7d630c --- /dev/null +++ b/test/files/pos/t8209b/Macros_1.scala @@ -0,0 +1,17 @@ +import scala.language.experimental.macros +import scala.language.implicitConversions +import scala.reflect.macros.whitebox.Context + +class A +object A { implicit def a2b(a: A): B = ??? } +class B +class C extends A + +object Macros { + def impl(c: Context) = { + import c.universe._ + q"new C" + } + + def foo: A = macro impl +}
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