Better handling of type parameters in constructor pattern #15356
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
In a constructor pattern `C[T](x)` with some type parameter(s), we have two choices. 1. Interpret it as `C[T].unapply(selector)` 2. Interpret it as `C.unapply[T](selector)`. So far we always picked the first choice, which means that usually it will fail with a message such as "`C` does not take type parameters". In this PR, we pick the second choice if it can be typechecked without errors and fall back to the first choice otherwise.
|
test performance please |
|
performance test scheduled: 1 job(s) in queue, 0 running. |
|
Performance test finished successfully: Visit https://dotty-bench.epfl.ch/15356/ to see the changes. Benchmarks is based on merging with main (13ce496) |
|
Since this is a source breaking change, it would be good to ship it in 3.2.0. |
odersky
added a commit
to dotty-staging/dotty
that referenced
this pull request
Jul 13, 2022
scala#6551 introduced an exception where type tests of parameterized case classes were not flagged as "type test cannot be checked at runtime". The idea was that the parameters would be inferred by GADT reasoning and would therefore be correct. But with scala#15356 we now also allow explicit type arguments in extractors. If these are given we cannot guarantee that a type test for a case class in an unapply will always succeed. So we need an unchecked warning.
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Outdated suggestions cannot be applied.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.
In a constructor pattern
C[T](x)with some type parameter(s), we have two choices.C[T].unapply(selector)C.unapply[T](selector).So far we always picked the first choice, which means that usually it will fail with a
message such as "
Cdoes not take type parameters".In this PR, we pick the second choice if it can be typechecked without errors and
fall back to the first choice otherwise.