"NoSuchElementException: head of empty list" caused by asInstanceOf with higher kinds #10700
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Just for fun, eliminating the import scala.language.higherKinds
class Foo[X]
class Bar[X]
class CrashIt[A[_] >: Null] {
def cast(a: Any): A[Int] = null
}
val c = if (true) new CrashIt[Foo] else new CrashIt[Bar]
val x = c.cast("") |
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Even shorter: without (That's not purely code-golfing, this has fewer syntactic elements, and it has the advantage of a somewhat shorter stack trace of the error.) |
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Ugh, just this line kills the REPL: class CrashIt[A[_]]
if (true) new CrashIt[Option] else new CrashIt[List] |
Yes, but it "works" outside of the REPL though... |
hrhino
changed the title
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This goes way farther back (before 2.11, even). |
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Uh-oh, note the ill-kinded type inference: scala> List(new CrashIt[Option], new CrashIt[List])
<console>:39: error: type mismatch;
found : CrashIt[Option]
required: CrashIt[_ >: List with Option <: Product with Serializable]
List(new CrashIt[Option], new CrashIt[List])
^
<console>:39: error: type mismatch;
found : CrashIt[List]
required: CrashIt[_ >: List with Option <: Product with Serializable]
List(new CrashIt[Option], new CrashIt[List])
^Also, I don't understand why:
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joroKr21
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Mar 14, 2018
When computing the `lub/glb` of HKTs take care to produce well-kinded types. Improves type inference. A few tests with `-Xstrict-inference` were changed. Other tests reveal a limitation of higher-kinded existentials. Fixes scala/bug#8882 and promotes scala/bug#10700 to an error.
joroKr21
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Apr 24, 2018
When computing the `lub/glb` of HKTs take care to produce well-kinded types. Improves type inference. A few tests with `-Xstrict-inference` were changed. Other tests reveal a limitation of higher-kinded existentials. Fixes scala/bug#8882 and promotes scala/bug#10700 to an error.
joroKr21
added a commit
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Apr 25, 2018
When computing the `lub/glb` of HKTs take care to produce well-kinded types. Improves type inference. A few tests with `-Xstrict-inference` were changed. Other tests reveal a limitation of higher-kinded existentials. Fixes scala/bug#8882 and promotes scala/bug#10700 to an error.
joroKr21
added a commit
to joroKr21/scala
that referenced
this issue
Apr 25, 2018
When computing the `lub/glb` of HKTs take care to produce well-kinded types. Improves type inference. A few tests with `-Xstrict-inference` were changed. Other tests reveal a limitation of higher-kinded existentials. Fixes scala/bug#8882 and promotes scala/bug#10700 to an error.
joroKr21
added a commit
to joroKr21/scala
that referenced
this issue
Apr 25, 2018
When computing the `lub/glb` of HKTs take care to produce well-kinded types. Improves type inference. A few tests with `-Xstrict-inference` were changed. Other tests reveal a limitation of higher-kinded existentials. Fixes scala/bug#8882 and promotes scala/bug#10700 to an error.
joroKr21
added a commit
to joroKr21/scala
that referenced
this issue
May 26, 2018
When computing the `lub/glb` of HKTs take care to produce well-kinded types. Improves type inference. A few tests with `-Xstrict-inference` were changed. Other tests reveal a limitation of higher-kinded existentials. Fixes scala/bug#8882 and promotes scala/bug#10700 to an error.
adriaanm
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that referenced
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Aug 3, 2018
When computing the `lub/glb` of HKTs take care to produce well-kinded types when merging type constructor arguments that are supplied for a type constructor parameter. This improves type inference. A few tests with `-Xstrict-inference` were changed. Other tests reveal a limitation of higher-kinded existentials. Fixes scala/bug#8882 and promotes scala/bug#10700 to an error.
adriaanm
pushed a commit
to scala/scala
that referenced
this issue
Aug 3, 2018
When computing the `lub/glb` of HKTs take care to produce well-kinded types when merging type constructor arguments that are supplied for a type constructor parameter. This improves type inference. A few tests with `-Xstrict-inference` were changed. Other tests reveal a limitation of higher-kinded existentials. Fixes scala/bug#8882 and promotes scala/bug#10700 to an error.
adriaanm
pushed a commit
to joroKr21/scala
that referenced
this issue
Aug 6, 2018
When computing the `lub/glb` of HKTs take care to produce well-kinded types when merging type constructor arguments that are supplied for a type constructor parameter. This improves type inference. A few tests with `-Xstrict-inference` were changed. Other tests reveal a limitation of higher-kinded existentials. Fixes scala/bug#8882 and promotes scala/bug#10700 to an error.
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scala/scala#6352 promotes this to an error for 2.13 |
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My PR is just not to crash when constructing a string. |
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scala 2.12.4 typechecker crashes when trying to run the following script with "scala script.scala":
Stack trace:
Information about the used compiler and environment:
Some observations:
c.cast("")is removedThe text was updated successfully, but these errors were encountered: