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Modifies "maybeRewrap" to focus more on the maybe.

Existential types are rewrapped under a bunch of conditions
unless the operation performed on the underlying type returns
the same type by reference equality. That depends on a
foundation of predictability which doesn't exist. The upshot is
that existential types were rewrapped with abandon, even when
the type were identical.

This had both performance and correctness implications.
Note where the test case output changes like so:

  -scala.collection.immutable.List[Any]
  +scala.collection.immutable.List[<?>]

That's correctness.
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commit 76b92ef78d3cb68d7e517bb4611efff45955f1e9 1 parent 2d4ed8e
Paul Phillips paulp authored
9 src/reflect/scala/reflect/internal/Types.scala
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@@ -234,7 +234,14 @@ trait Types extends api.Types { self: SymbolTable =>
* forwarded here. Some operations are rewrapped again.
*/
trait RewrappingTypeProxy extends SimpleTypeProxy {
- protected def maybeRewrap(newtp: Type) = if (newtp eq underlying) this else rewrap(newtp)
+ protected def maybeRewrap(newtp: Type) = (
+ if (newtp eq underlying) this
+ // BoundedWildcardTypes reach here during erroneous compilation: neg/t6258
+ // Higher-kinded exclusion is because [x]CC[x] compares =:= to CC: pos/t3800
+ // Otherwise, if newtp =:= underlying, don't rewrap it.
+ else if (!newtp.isWildcard && !newtp.isHigherKinded && (newtp =:= underlying)) this
+ else rewrap(newtp)
+ )
protected def rewrap(newtp: Type): Type
// the following are all operations in class Type that are overridden in some subclass
32 test/files/run/t6329_repl.check
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@@ -3,11 +3,37 @@ Type :help for more information.
scala>
-scala> classManifest[List[_]]
+scala> import scala.reflect.classTag
+import scala.reflect.classTag
+
+scala> classManifest[scala.List[_]]
warning: there were 1 deprecation warnings; re-run with -deprecation for details
-res0: scala.reflect.ClassTag[List[_]] = scala.collection.immutable.List[Any]
+res0: scala.reflect.ClassTag[List[_]] = scala.collection.immutable.List[<?>]
-scala> scala.reflect.classTag[List[_]]
+scala> classTag[scala.List[_]]
res1: scala.reflect.ClassTag[List[_]] = scala.collection.immutable.List
+scala> classManifest[scala.collection.immutable.List[_]]
+warning: there were 1 deprecation warnings; re-run with -deprecation for details
+res2: scala.reflect.ClassTag[List[_]] = scala.collection.immutable.List[<?>]
+
+scala> classTag[scala.collection.immutable.List[_]]
+res3: scala.reflect.ClassTag[List[_]] = scala.collection.immutable.List
+
+scala> classManifest[Predef.Set[_]]
+warning: there were 1 deprecation warnings; re-run with -deprecation for details
+res4: scala.reflect.ClassTag[scala.collection.immutable.Set[_]] = scala.collection.immutable.Set[<?>]
+
+scala> classTag[Predef.Set[_]]
+res5: scala.reflect.ClassTag[scala.collection.immutable.Set[_]] = scala.collection.immutable.Set
+
+scala> classManifest[scala.collection.immutable.Set[_]]
+warning: there were 1 deprecation warnings; re-run with -deprecation for details
+res6: scala.reflect.ClassTag[scala.collection.immutable.Set[_]] = scala.collection.immutable.Set[<?>]
+
+scala> classTag[scala.collection.immutable.Set[_]]
+res7: scala.reflect.ClassTag[scala.collection.immutable.Set[_]] = scala.collection.immutable.Set
+
+scala>
+
scala>
13 test/files/run/t6329_repl.scala
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@@ -2,7 +2,14 @@ import scala.tools.partest.ReplTest
object Test extends ReplTest {
def code = """
- |classManifest[List[_]]
- |scala.reflect.classTag[List[_]]
- |""".stripMargin
+ |import scala.reflect.classTag
+ |classManifest[scala.List[_]]
+ |classTag[scala.List[_]]
+ |classManifest[scala.collection.immutable.List[_]]
+ |classTag[scala.collection.immutable.List[_]]
+ |classManifest[Predef.Set[_]]
+ |classTag[Predef.Set[_]]
+ |classManifest[scala.collection.immutable.Set[_]]
+ |classTag[scala.collection.immutable.Set[_]]
+ """.stripMargin
}
8 test/files/run/t6329_vanilla.check
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@@ -1,2 +1,8 @@
-scala.collection.immutable.List[Any]
+scala.collection.immutable.List[<?>]
scala.collection.immutable.List
+scala.collection.immutable.List[<?>]
+scala.collection.immutable.List
+scala.collection.immutable.Set[<?>]
+scala.collection.immutable.Set
+scala.collection.immutable.Set[<?>]
+scala.collection.immutable.Set
14 test/files/run/t6329_vanilla.scala
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@@ -1,4 +1,12 @@
+import scala.reflect.classTag
+
object Test extends App {
- println(classManifest[List[_]])
- println(scala.reflect.classTag[List[_]])
-}
+ println(classManifest[scala.List[_]])
+ println(classTag[scala.List[_]])
+ println(classManifest[scala.collection.immutable.List[_]])
+ println(classTag[scala.collection.immutable.List[_]])
+ println(classManifest[Predef.Set[_]])
+ println(classTag[Predef.Set[_]])
+ println(classManifest[scala.collection.immutable.Set[_]])
+ println(classTag[scala.collection.immutable.Set[_]])
+}
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