Fix #3989: Fix several unsoundness problems related to variant refinement #4013

odersky · 2018-02-19T16:26:01Z

This solves a number of unsoundness problems related to variant refinement

implementation not covering the full member type (Unsoundness when inheriting conflicting type parameters #3989, 2nd part)
pattern matching unsoundness (Unsoundness when inheriting conflicting type parameters #3989, 1st part)
a variant of above, involving type patterns instead of unapply
the unsound protected[this] escape hatch for variance checking

Some tests had to be updated or re-classified because they were unsound before. The collection strawman needs to be updated to conform to the new rules.

Blaisorblade · 2018-02-19T16:32:19Z

compiler/src/dotty/tools/dotc/typer/RefChecks.scala

+        //  - members in other concrete classes, since these have been checked before
+        //    (this is done for efficiency)
+        //  - members in a prefix of inherited parents that all come from Java or Scala2
+        //    (this is done to avoid false negatives since Scala2's rules for checking are different)


"false negatives" = false errors from the typechecker? I'm used to "false positives" (which makes sense for error checking).

More importantly, this means that we should test that Scala 2 material indeed follows Scala 2 rules?

Blaisorblade · 2018-02-19T16:33:15Z

compiler/src/dotty/tools/dotc/typer/RefChecks.scala

+        val seenClasses = mutable.Set[Symbol]()
+        def addDecls(cls: Symbol): Unit =
+          if (!seenClasses.contains(cls)) {
+            seenClasses.+=(cls)


Why not seenClasses += cls? Has idiomatic style changed?

No, hat was an editing breakage.

odersky · 2018-02-19T16:40:15Z

test performance please

dottybot · 2018-02-19T16:41:01Z

performance test scheduled: 1 job(s) in queue, 0 running.

dottybot · 2018-02-19T18:38:52Z

Performance test finished successfully:

Visit http://dotty-bench.epfl.ch/4013/ to see the changes.

Benchmarks is based on merging with master (668c499)

odersky · 2018-02-20T10:41:53Z

That's what I feared - performance is dramatically worse for scala-library, slightly worse for everything else.

odersky · 2018-02-20T12:33:38Z

The collection strawman does not compile under this branch because it contains some patterns that are now recognized as unsound. Some have easy fixes. E.g. ArrayOps needs to extend IndexedSeqOps, not SeqOps. That was probably an oversight. The main cause of errors is WithFilter on maps and sets. Here we lose precision wrt collection.WithFilter which leads to type inconsistencies. /cc @julienrf.

I have disabled the tests involving strawman until this is fixed. We should re-enable them afterwards.

odersky · 2018-02-20T12:34:23Z

test performance please

dottybot · 2018-02-20T12:35:08Z

performance test scheduled: 1 job(s) in queue, 1 running.

julienrf · 2018-02-20T14:01:18Z

@odersky Do we have to change our implementation? I think the changes you’ve mentioned for ArrayOps are arleady done here. I have to have a look at withFilter…

odersky · 2018-02-20T14:18:12Z

@julienrf Yes, the ArrayOps changes seem to be already done. But WithFilter needs to be fixed. Can you take this branch and see what needs to be done? It already contains the changes to hk-equality which was the previous blocker for compiling the strawman with dotty.

dottybot · 2018-02-20T15:13:11Z

Performance test finished successfully:

Visit http://dotty-bench.epfl.ch/4013/ to see the changes.

Benchmarks is based on merging with master (9053964)

odersky · 2018-02-20T15:41:41Z

@julienrf Also, the later changes here could invalidate some pattern matches. This is because it propagates fewer types from scrutinees to pattern. To fix this, one needs to sometimes write an @unchecked type argument in the pattern. I have noted one such case in IterableOps which now fails.

odersky · 2018-02-20T15:47:03Z

test performance please

dottybot · 2018-02-20T15:48:01Z

performance test scheduled: 3 job(s) in queue, 1 running.

odersky · 2018-02-20T15:55:59Z

Now all variants of problems I could derive from #3989 seem to be fixed.

Blaisorblade · 2018-02-20T16:35:04Z

@odersky Just in case, is this example with protected[this] also fixed? scala/bug#7093 (comment)
(EDIT: maybe a good testcase, especially if somebody wants to try optimizations? what I sketched this morning would have broken).

dottybot · 2018-02-20T19:06:14Z

Performance test finished successfully:

Visit http://dotty-bench.epfl.ch/4013/ to see the changes.

Benchmarks is based on merging with master (2a019f3)

odersky · 2018-02-20T21:18:49Z

@Blaisorblade The protected[this] problem is fixed with latest commit. @julienrf: One more thing to update for the collection strawman. Hint: Compiling with -language:Scala2 -migration will give more specific error messages.

odersky · 2018-02-20T21:20:29Z

Regarding performance, I am inclined to not do anything right now. compileStdLib is an outlier, and I see no obviously safe way to reduce the number of checks.

odersky · 2018-02-20T21:27:38Z

@olafurpg Here's a problem scala-fix could help with: Insert @uncheckedVariance at the right places if a definition is no longer variance correct according to the new rules. dotc tried to do it, but it's more complex than it looks, so it's currently disabled. See f551646, in particular the two TODO comments there.

szeiger · 2018-02-21T10:34:19Z

Effect of this on collection strawman (with failures both in the original design and more in the changes I merged yesterday in scala/collection-strawman#468:

[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/BitSet.scala:40:23
[error] 40 |  protected[this] type BitSetC = C
[error]    |  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]    |covariant type C occurs in invariant position in type  = C of type BitSetC
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/Iterable.scala:29:43
[error] 29 |  protected[this] def fromSpecificIterable(coll: Iterable[A]): IterableCC[A] = iterableFactory.from(coll)
[error]    |                                           ^^^^^^^^^^^^^^^^^
[error]    |covariant type A occurs in contravariant position in type strawman.collection.Iterable[A] of value coll
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/Iterable.scala:30:22
[error] 30 |  protected[this] def newSpecificBuilder(): Builder[A, IterableCC[A]] = iterableFactory.newBuilder[A]()
[error]    |  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]    |covariant type A occurs in contravariant position in type (): strawman.collection.mutable.Builder[A, strawman.collection.Iterable[A]] of method newSpecificBuilder
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/Iterable.scala:750:24
[error] 750 |    protected[this] def filtered = View.Filter(toIterable, p, isFlipped = false)
[error]     |    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]     |covariant type A occurs in invariant position in type => strawman.collection.View.Filter[A] of method filtered
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/Iterable.scala:71:23
[error] 71 |  protected[this] type IterableCC[X] = CC[X]
[error]    |  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]    |covariant type CC occurs in invariant position in type  = CC of type IterableCC
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/Iterable.scala:90:43
[error] 90 |  protected[this] def fromSpecificIterable(coll: Iterable[A]): C
[error]    |                                           ^^^^^^^^^^^^^^^^^
[error]    |covariant type A occurs in contravariant position in type strawman.collection.Iterable[A] of value coll
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/Iterable.scala:110:22
[error] 110 |  protected[this] def newSpecificBuilder(): Builder[A, C]
[error]     |  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]     |covariant type A occurs in contravariant position in type (): strawman.collection.mutable.Builder[A, C] of method newSpecificBuilder
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/Map.scala:18:52
[error] 18 |  override protected[this] def fromSpecificIterable(coll: Iterable[(K, V)]): MapCC[K, V] = mapFactory.from(coll)
[error]    |                                                    ^^^^^^^^^^^^^^^^^^^^^^
[error]    |covariant type V occurs in contravariant position in type strawman.collection.Iterable[(K, V)] of value coll
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/Map.scala:19:31
[error] 19 |  override protected[this] def newSpecificBuilder(): mutable.Builder[(K, V), MapCC[K, V]] = mapFactory.newBuilder[K, V]()
[error]    |  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]    |covariant type V occurs in contravariant position in type (): strawman.collection.mutable.Builder[(K, V), strawman.collection.Map[K, V]] of method newSpecificBuilder
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/Map.scala:62:23
[error] 62 |  protected[this] type MapCC[K, V] = CC[K, V]
[error]    |  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]    |covariant type CC occurs in invariant position in type  = CC of type MapCC
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/SortedMap.scala:17:52
[error] 17 |  override protected[this] def fromSpecificIterable(coll: Iterable[(K, V)]): SortedMapCC[K, V] = sortedMapFactory.from(coll)
[error]    |                                                    ^^^^^^^^^^^^^^^^^^^^^^
[error]    |covariant type V occurs in contravariant position in type strawman.collection.Iterable[(K, V)] of value coll
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/SortedMap.scala:18:31
[error] 18 |  override protected[this] def newSpecificBuilder(): mutable.Builder[(K, V), SortedMapCC[K, V]] = sortedMapFactory.newBuilder[K, V]()
[error]    |  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]    |  covariant type V occurs in contravariant position in type ():
[error]    |    strawman.collection.mutable.Builder[(K, V),
[error]    |      strawman.collection.SortedMap[K, V]
[error]    |    ] of method newSpecificBuilder
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/SortedMap.scala:29:23
[error] 29 |  protected[this] type SortedMapCC[K, V] = CC[K, V]
[error]    |  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]    |covariant type CC occurs in invariant position in type  = CC of type SortedMapCC
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/SortedSet.scala:22:23
[error] 22 |  protected[this] type SortedIterableCC[X] = CC[X]
[error]    |  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]    |covariant type CC occurs in invariant position in type  = CC of type SortedIterableCC
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/immutable/ImmutableArray.scala:29:22
[error] 29 |  protected[this] def elemTag: ClassTag[A]
[error]    |  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]    |covariant type A occurs in invariant position in type => ClassTag[A] of method elemTag
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/immutable/ImmutableArray.scala:39:52
[error] 39 |  override protected[this] def fromSpecificIterable(coll: strawman.collection.Iterable[A]): ImmutableArray[A] = ImmutableArray.from[A](coll)(elemTag)
[error]    |                                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]    |covariant type A occurs in contravariant position in type strawman.collection.Iterable[A] of value coll
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/immutable/ImmutableArray.scala:41:31
[error] 41 |  override protected[this] def newSpecificBuilder(): Builder[A, ImmutableArray[A]] = ImmutableArray.newBuilder[A]()(elemTag)
[error]    |  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]    |  covariant type A occurs in contravariant position in type ():
[error]    |    strawman.collection.mutable.Builder[A,
[error]    |      strawman.collection.immutable.ImmutableArray[A]
[error]    |    ] of method newSpecificBuilder
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/immutable/IntMap.scala:172:52
[error] 172 |  override protected[this] def fromSpecificIterable(coll: strawman.collection.Iterable[(Int, T)]): IntMap[T] =
[error]     |                                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]     |covariant type T occurs in contravariant position in type strawman.collection.Iterable[(scala.Int, T)] of value coll
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/immutable/IntMap.scala:180:31
[error] 180 |  override protected[this] def newSpecificBuilder(): Builder[(Int, T), IntMap[T]] =
[error]     |  ^
[error]     |  covariant type T occurs in contravariant position in type ():
[error]     |    strawman.collection.mutable.Builder[(scala.Int, T),
[error]     |      strawman.collection.immutable.IntMap[T]
[error]     |    ] of method newSpecificBuilder
[error] 181 |    new ImmutableBuilder[(Int, T), IntMap[T]](empty) {
[error] 182 |      def addOne(elem: (Int, T)): this.type = { elems = elems + elem; this }
[error] 183 |    }
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/immutable/LazyList.scala:231:40
[error] 231 |  protected[this] def cons[T](hd: => T, tl: => CC[T]): CC[T]
[error]     |                                        ^^^^^^^^^^^^
[error]     |covariant type CC occurs in contravariant position in type => CC[T] of value tl
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/immutable/LazyList.scala:361:43
[error] 361 |  protected[this] def newCons[T](hd: => T, tl: => CC[T]): CC[T]
[error]     |                                           ^^^^^^^^^^^^
[error]     |covariant type CC occurs in contravariant position in type => CC[T] of value tl
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/immutable/LongMap.scala:164:52
[error] 164 |  override protected[this] def fromSpecificIterable(coll: strawman.collection.Iterable[(Long, T)]): LongMap[T] = {
[error]     |                                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]     |covariant type T occurs in contravariant position in type strawman.collection.Iterable[(scala.Long, T)] of value coll
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/immutable/LongMap.scala:171:31
[error] 171 |  override protected[this] def newSpecificBuilder(): Builder[(Long, T), LongMap[T]] =
[error]     |  ^
[error]     |  covariant type T occurs in contravariant position in type ():
[error]     |    strawman.collection.mutable.Builder[(scala.Long, T),
[error]     |      strawman.collection.immutable.LongMap[T]
[error]     |    ] of method newSpecificBuilder
[error] 172 |    new ImmutableBuilder[(Long, T), LongMap[T]](empty) {
[error] 173 |      def addOne(elem: (Long, T)): this.type = { elems = elems + elem; this }
[error] 174 |    }
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/immutable/Map.scala:155:54
[error] 155 |    override protected[this] def fromSpecificIterable(coll: collection.Iterable[(K, V)]): WithDefault[K, V] =
[error]     |                                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]     |covariant type V occurs in contravariant position in type strawman.collection.Iterable[(K, V)] of value coll
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/immutable/Map.scala:158:33
[error] 158 |    override protected[this] def newSpecificBuilder(): Builder[(K, V), WithDefault[K, V]] =
[error]     |    ^
[error]     |    covariant type V occurs in contravariant position in type ():
[error]     |      strawman.collection.mutable.Builder[(K, V),
[error]     |        strawman.collection.immutable.Map.WithDefault[K, V]
[error]     |      ] of method newSpecificBuilder
[error] 159 |      Map.newBuilder().mapResult((p: Map[K, V]) => new WithDefault[K, V](p, defaultValue))
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/immutable/SortedMap.scala:99:54
[error] 99 |    override protected[this] def fromSpecificIterable(coll: strawman.collection.Iterable[(K, V)]): WithDefault[K, V] =
[error]    |                                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]    |covariant type V occurs in contravariant position in type strawman.collection.Iterable[(K, V)] of value coll
[error] -- Error: /Users/szeiger/code/scala/collection-strawman/collections/src/main/scala/strawman/collection/immutable/SortedMap.scala:102:33
[error] 102 |    override protected[this] def newSpecificBuilder(): Builder[(K, V), WithDefault[K, V]] =
[error]     |    ^
[error]     |    covariant type V occurs in contravariant position in type ():
[error]     |      strawman.collection.mutable.Builder[(K, V),
[error]     |        strawman.collection.immutable.SortedMap.WithDefault[K, V]
[error]     |      ] of method newSpecificBuilder
[error] 103 |      SortedMap.newBuilder().mapResult((p: SortedMap[K, V]) => new WithDefault[K, V](p, defaultValue))
[error] 27 errors found

smarter · 2018-02-21T11:01:57Z

Once the collection-strawman is fixed, we should check the performance impact there too.

odersky · 2018-03-15T20:03:31Z

Seems I dropped the ball on this one... Let me take a look at the new issues.

This fixes the second half of scala#3989. Some tests had to be updated or re-classified because they were unsound before.

It's more efficient. Let's see whether that makes a difference.

Plugging the soundness hole in scala#3989 unveiled problems in the strawman. These need to be fixed before we can test it again in dotty.

i3989a.scala gives an example which is rejected under the new scheme. This would pass and fail at runtime under the previous scheme.

odersky · 2018-03-16T17:14:56Z

The problems reported by @liufengyun are now fixed as well. @liufengyun do you want to review the last two commits?

liufengyun

LGTM, cannot find another counter-example.

odersky · 2018-03-17T20:39:39Z

LGTM, cannot find another counter-example.

Good news!

This version of Dotty fixes several unsoundness issues and remove the unsound protected[this] escape hatch for variance checking. See scala/scala3#4013

adriaanm · 2018-04-13T12:40:29Z

Does this also close the unsoundness illustrated by @TomasMikula in scala/bug#10822 (comment), where GADT matching is unsoundly allowed because a covariant occurrence of a type param is hidden by a type ascription where it only occurs invariantly?

smarter · 2018-04-13T12:56:09Z

@adriaanm I think the unsoundness in scalac comes from allowing this to compile:

class Foo[A]
private[this] class Bar[+A] extends Foo[A]

Disabling the variance checks for private[this] is not sound here. In Dotty your example compiles because the variance checks for the extends clause are completely missing, but once we add them we won't special case them for private[this]: #2973

adriaanm · 2018-04-13T13:43:14Z

Gah, right! I should’ve caught that. Thanks for pointing it out.

…

On Fri, Apr 13, 2018 at 14:56 Guillaume Martres ***@***.***> wrote: @adriaanm <https://github.com/adriaanm> I think the unsoundness in scalac comes from allowing this to compile: class Foo[A]private[this] class Bar[+A] extends Foo[A] Disabling the variance checks for private[this] is not sound here. In Dotty your example compiles because the variance checks for the extends clause are completely missing, but once we add them we won't special case them for private[this]: #2973 <#2973> — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#4013 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAFjyzNnx6_lplbr1fjDn5aiKUGM7wsoks5toKBqgaJpZM4SKzvc> .

odersky mentioned this pull request Feb 19, 2018

Unsoundness when inheriting conflicting type parameters scala/bug#10735

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Blaisorblade reviewed Feb 19, 2018

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odersky force-pushed the fix-#3989 branch from b1ad9e0 to 7ae7560 Compare February 20, 2018 12:09

odersky assigned Blaisorblade Feb 20, 2018

odersky changed the title ~~Fix #3989: Check that members of concrete classes are type-correct~~ Fix #3989: Fix several unsoundness problem related to variant refinement Feb 20, 2018

odersky changed the title ~~Fix #3989: Fix several unsoundness problem related to variant refinement~~ Fix #3989: Fix several unsoundness problems related to variant refinement Feb 20, 2018

odersky mentioned this pull request Feb 20, 2018

Ensure conformance to new typing rules scala/collection-strawman#475

Closed

szeiger mentioned this pull request Feb 21, 2018

Fix the iterableFactory of mutable Sets scala/collection-strawman#470

Merged

odersky added 8 commits March 16, 2018 15:01

Fix scala#3989: Check that members of concrete classes are type-correct

e872aee

This fixes the second half of scala#3989. Some tests had to be updated or re-classified because they were unsound before.

Use util.HashSet for member checking

faae4da

It's more efficient. Let's see whether that makes a difference.

Disable strawman tests

08cef8c

Plugging the soundness hole in scala#3989 unveiled problems in the strawman. These need to be fixed before we can test it again in dotty.

Be more careful when constraining parameter types wrt scrutinees

07ced9d

i3989a.scala gives an example which is rejected under the new scheme. This would pass and fail at runtime under the previous scheme.

Ensure invariant refinement for classes extended case classes

7bac0a2

Use constrainPatternType also for unapply patterns

f00ac95

Close the protected[local] escape hatch

f89d207

Disallow extending a trait twice in the same class

1082eb5

odersky force-pushed the fix-#3989 branch from f551646 to 4258ca6 Compare March 16, 2018 17:10

Enforce non-variant refinement for parameterized base classes and traits

4feda4e

odersky force-pushed the fix-#3989 branch from 4258ca6 to 4feda4e Compare March 16, 2018 17:13

odersky assigned liufengyun and unassigned Blaisorblade Mar 16, 2018

liufengyun approved these changes Mar 17, 2018

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odersky merged commit b499a9a into scala:master Mar 17, 2018

Blaisorblade deleted the fix-#3989 branch March 18, 2018 14:04

allanrenucci added a commit to dotty-staging/collection-strawman that referenced this pull request Mar 19, 2018

Bump Dotty version

ae7d7e5

This version of Dotty fixes several unsoundness issues and remove the unsound protected[this] escape hatch for variance checking. See scala/scala3#4013

allanrenucci mentioned this pull request Mar 19, 2018

Dotty #4013 scala/collection-strawman#517

Closed

allanrenucci added a commit to dotty-staging/collection-strawman that referenced this pull request Mar 19, 2018

Bump Dotty version

0d638e7

This version of Dotty fixes several unsoundness issues and remove the unsound protected[this] escape hatch for variance checking. See scala/scala3#4013

allanrenucci mentioned this pull request Mar 22, 2018

Private types leaking in public signatures should be reported as errors even under -language:Scala2 #4154

Closed

julienrf mentioned this pull request Apr 10, 2018

Be more explicit about the unsoundness holes used by the collections. scala/scala#6508

Merged

TomasMikula mentioned this pull request Apr 13, 2018

unreachable code when using abstract case class pattern scala/bug#10822

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lrytz mentioned this pull request Mar 26, 2019

Integrate converters from java8-compat [ci: last-only] scala/scala#7458

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smarter mentioned this pull request Mar 14, 2022

No warning on uncheckable isInstanceOf call #11834

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Fix #3989: Fix several unsoundness problems related to variant refinement #4013

Fix #3989: Fix several unsoundness problems related to variant refinement #4013

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