Minimal support for dependent case classes #21698
Open
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
I am doing some experiment with dependent pattern match in CC, and this PR is useful for me as well! I modified the desuger so |
smarter
force-pushed
the
i8073
branch
2 times, most recently
from
83c5e98
to
8d1c7fb
Compare
|
@noti0na1 Awesome! Let me know how it goes. |
smarter
force-pushed
the
i8073
branch
3 times, most recently
from
b3b5331
to
3f3ce18
Compare
This used to fail with:
trait <refinement> in value x extends enum EC, but extending enums is prohibited.
This lets us write:
trait A:
type B
case class CC(a: A, b: a.B)
Pattern matching works but isn't dependent yet:
x match
case CC(a, b) =>
val a1: A = a
// Dependent pattern matching is not currently supported
// val b1: a1.B = b
val b1 = b // Type is CC#a.B
(for my usecase this isn't a problem, I'm working on a type constraint API
which lets me write things like `case class CC(a: Int, b: Int
GreaterThan[a.type])`)
Because case class pattern matching relies on the product selectors `_N`, making
it dependent is a bit tricky, currently we generate:
case class CC(a: A, b: a.B):
def _1: A = a
def _2: a.B = b
So the type of `_2` is not obviously related to the type of `_1`, we probably
need to change what we generate into:
case class CC(a: A, b: a.B):
@uncheckedStable def _1: a.type = a
def _2: _1.B = b
But this can be done in a separate PR.
Fixes scala#8073.
|
I think it's probably better to wait after the cutoff with this? |
|
So 3.6.1 rather than 3.6.0? |
|
Yes, 3.6.1 should work OK. |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
This lets us write:
Pattern matching works but isn't dependent yet:
(for my usecase this isn't a problem, I'm working on a type constraint API which lets me write things like
case class CC(a: Int, b: Int GreaterThan[a.type]))Because case class pattern matching relies on the product selectors
_N, making it dependent is a bit tricky, currently we generate:So the type of
_2is not obviously related to the type of_1, we probably need to change what we generate into:But this can be done in a separate PR.
Fixes #8073.