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author | Jason Zaugg <jzaugg@gmail.com> | 2013-11-22 18:35:43 +0100 |
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committer | Jason Zaugg <jzaugg@gmail.com> | 2013-11-27 09:09:46 +0100 |
commit | 28d3390e07715b0dcb5ce2f68d72d5a44e6ca74d (patch) | |
tree | 8ac9461aa99fd6a2d6b7a937d0459ed8b9c84653 /src | |
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 'src')
-rw-r--r-- | src/reflect/scala/reflect/internal/tpe/TypeComparers.scala | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/src/reflect/scala/reflect/internal/tpe/TypeComparers.scala b/src/reflect/scala/reflect/internal/tpe/TypeComparers.scala index b60fecd66e..2623a47be6 100644 --- a/src/reflect/scala/reflect/internal/tpe/TypeComparers.scala +++ b/src/reflect/scala/reflect/internal/tpe/TypeComparers.scala @@ -170,11 +170,20 @@ trait TypeComparers { // corresponds does not check length of two sequences before checking the predicate, // but SubstMap assumes it has been checked (SI-2956) ( sameLength(tparams1, tparams2) - && (tparams1 corresponds tparams2)((p1, p2) => p1.info =:= subst(p2.info)) + && (tparams1 corresponds tparams2)((p1, p2) => methodHigherOrderTypeParamsSameVariance(p1, p2) && p1.info =:= subst(p2.info)) && (res1 =:= subst(res2)) ) } + // SI-2066 This prevents overrides with incompatible variance in higher order type parameters. + private def methodHigherOrderTypeParamsSameVariance(sym1: Symbol, sym2: Symbol) = { + def ignoreVariance(sym: Symbol) = !(sym.isHigherOrderTypeParameter && sym.logicallyEnclosingMember.isMethod) + ignoreVariance(sym1) || ignoreVariance(sym2) || sym1.variance == sym2.variance + } + + private def methodHigherOrderTypeParamsSubVariance(low: Symbol, high: Symbol) = + methodHigherOrderTypeParamsSameVariance(low, high) || low.variance.isInvariant + def isSameType2(tp1: Type, tp2: Type): Boolean = { def retry(lhs: Type, rhs: Type) = ((lhs ne tp1) || (rhs ne tp2)) && isSameType(lhs, rhs) @@ -327,7 +336,10 @@ trait TypeComparers { val substitutes = if (isMethod) tparams1 else cloneSymbols(tparams1) def sub1(tp: Type) = if (isMethod) tp else tp.substSym(tparams1, substitutes) def sub2(tp: Type) = tp.substSym(tparams2, substitutes) - def cmp(p1: Symbol, p2: Symbol) = sub2(p2.info) <:< sub1(p1.info) + def cmp(p1: Symbol, p2: Symbol) = ( + methodHigherOrderTypeParamsSubVariance(p2, p1) + && sub2(p2.info) <:< sub1(p1.info) + ) (tparams1 corresponds tparams2)(cmp) && (sub1(res1) <:< sub2(res2)) } |