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Fix #2051: allow override T with => T or ()T #2096

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Merged
merged 3 commits into from
Mar 15, 2017
Merged

Fix #2051: allow override T with => T or ()T #2096

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f4ad535
fix #2051: allow override T with => T or ()T
liufengyun Mar 14, 2017
c08ea41
add neg test for #2051
liufengyun Mar 14, 2017
8644323
add more tests
liufengyun Mar 14, 2017
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7 changes: 4 additions & 3 deletions compiler/src/dotty/tools/dotc/core/Types.scala
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Expand Up @@ -727,8 +727,8 @@ object Types {

/** Is this type a legal type for a member that overrides another
* member of type `that`? This is the same as `<:<`, except that
* the types ()T and => T are identified, and T is seen as overriding
* either type.
* the types `()T`, `=> T` and `T` are seen as overriding
* each other.
*/
final def overrides(that: Type)(implicit ctx: Context) = {
def result(tp: Type): Type = tp match {
Expand All @@ -737,7 +737,8 @@ object Types {
}
(this frozen_<:< that) || {
val rthat = result(that)
(rthat ne that) && (result(this) frozen_<:< rthat)
val rthis = result(this)
(rthat.ne(that) || rthis.ne(this)) && (rthis frozen_<:< rthat)
}
}

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2 changes: 2 additions & 0 deletions tests/neg/i2051.scala
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@@ -0,0 +1,2 @@
abstract class C { val x: Int }
class D extends C { def x = 1 } // error: method x of type => Int needs to be a stable, immutable value
2 changes: 2 additions & 0 deletions tests/pos/i2051.scala
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@@ -0,0 +1,2 @@
class A[T](val x:T)
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it would be nice to add several fields to the body of the class that are overriden in a subclass.

It would also be nice to include tests with trait vals and trait constructors.

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Thanks @DarkDimius , I just added tests in the latest commit.

class B[T](override val x:T) extends A[T](x)