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| author | Jason Zaugg <jzaugg@gmail.com> | 2013-11-22 18:35:43 +0100 |
|---|---|---|
| committer | Jason Zaugg <jzaugg@gmail.com> | 2013-11-27 09:09:46 +0100 |
| commit | 28d3390e07715b0dcb5ce2f68d72d5a44e6ca74d (patch) | |
| tree | 8ac9461aa99fd6a2d6b7a937d0459ed8b9c84653 /test/files/neg/t2066.check | |
| parent | 073ebbd20ce9775260b83a78ecf9ed6a3e6d3d9e (diff) | |
| download | scala-28d3390e07715b0dcb5ce2f68d72d5a44e6ca74d.tar.gz scala-28d3390e07715b0dcb5ce2f68d72d5a44e6ca74d.tar.bz2 scala-28d3390e07715b0dcb5ce2f68d72d5a44e6ca74d.zip | |
SI-2066 Plug a soundness hole higher order type params, overriding
PolyType-s parameterized by higher order type parameters (HOTPs)
should only be relatable with <:< or =:= if the variances of their
type parameters line up. This is only enforced for HOTPs defined in
method type arguments.
Invariant type parameters subsume variant ones. Concretely, as
described by @S11001001:
> A method taking [F[_]] can implement a method taking [F[+_]].
> Likewise, a method taking [F[_[+_]]] can implement a method
> taking [F[_[_]]], as with [F[_[_[_]]]] implementing [F[_[_[+_]]]],
> and so on, the variance subsumption flipping at each step.
>
> This is just the opposite of the variance for passing type
> parameters to either instantiate types or call methods; a F[+_]
> is a suitable F[_]-argument, a F[_[_]] a suitable F[_[+_]]-argument,
> and so on.
>
> All of the above rules can be duplicated for contravariant positions
> by substituting - for +. Also, something similar happens for
> weakening/strengthening bounds, I believe.
These cases are tested in the `// okay` lines in `neg/t2066.scala`.
Diffstat (limited to 'test/files/neg/t2066.check')
| -rw-r--r-- | test/files/neg/t2066.check | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/test/files/neg/t2066.check b/test/files/neg/t2066.check new file mode 100644 index 0000000000..efade87e26 --- /dev/null +++ b/test/files/neg/t2066.check @@ -0,0 +1,21 @@ +t2066.scala:6: error: overriding method f in trait A1 of type [T[_]]=> Unit; + method f has incompatible type + override def f[T[+_]] = () + ^ +t2066.scala:10: error: overriding method f in trait A1 of type [T[_]]=> Unit; + method f has incompatible type + override def f[T[-_]] = () + ^ +t2066.scala:23: error: overriding method f in trait A2 of type [T[+_]]=> Unit; + method f has incompatible type + override def f[T[-_]] = () + ^ +t2066.scala:45: error: overriding method f in trait A4 of type [T[X[+_]]]=> Unit; + method f has incompatible type + override def f[T[X[_]]] = () + ^ +t2066.scala:53: error: overriding method f in trait A5 of type [T[X[-_]]]=> Unit; + method f has incompatible type + override def f[T[X[_]]] = () + ^ +5 errors found |