Fix #2201: Less aggressive type application reduction for better inference #2204
Conversation
This file contains hidden or 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
… inference Previously we believed that reducing type applications did not affect type inference as long as the reduced type constructor had the same arity as the unreduced one, for example reducing `Foo[X, Y]` is fine when `Foo` is defined as: type Foo[A, B] = Bar[A, B] but not when it's defined as: type Foo[A] = Bar[A, A] But this is not a sufficient condition: the bounds of the type constructor arguments also matter for type inference, so we need to be more strict and disallow reductions in cases like: type Foo[A, B] = Bar[B, A] and: type Foo[A, B] = Bar[A, Int]
|
LGTM |
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Outdated suggestions cannot be applied.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.
Previously we believed that reducing type applications did not affect
type inference as long as the reduced type constructor had the same
arity as the unreduced one, for example reducing
Foo[X, Y]is finewhen
Foois defined as:but not when it's defined as:
But this is not a sufficient condition: the bounds of the type
constructor arguments also matter for type inference, so we need to be
more strict and disallow reductions in cases like:
and: