Support variance annotations in -Ykind-projector mode
#12341
Merged
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
smarter
requested changes
May 5, 2021
| private def makeKindProjectorTypeDef(name: TypeName): TypeDef = | ||
| TypeDef(name, WildcardTypeBoundsTree()).withFlags(Param) | ||
| private def makeKindProjectorTypeDef(name: TypeName): TypeDef = { | ||
| val isVarianceAnnotated = name.lastPart.startsWith("+") || name.lastPart.startsWith("-") |
There was a problem hiding this comment.
Couldn't name.startsWith be used given that these are user-written names and so should only have one part?
There was a problem hiding this comment.
@smarter Changed to name.startsWith
| TypeDef(name, WildcardTypeBoundsTree()).withFlags(Param) | ||
| private def makeKindProjectorTypeDef(name: TypeName): TypeDef = { | ||
| val isVarianceAnnotated = name.lastPart.startsWith("+") || name.lastPart.startsWith("-") | ||
| val unannotatedName = if (isVarianceAnnotated) name.mapLast(_.drop(1)) else name |
There was a problem hiding this comment.
Would be nice to add a comment mentioning that we can strip the variance because it's inferred.
There was a problem hiding this comment.
@smarter Added a comment explaining the decision to just strip the variance
neko-kai
force-pushed
the
feature/kind-projector-parse-variance-annotations
branch
from
fe8ebd7 to
536661d
Compare
This change expands the supported subset of `kind-projector` syntax, specifically: * `+*` and `-*` variance annotated variants of `*` placeholder * Variance annotated named parameters in `λ` - `λ[(`-R`, `+E`, `+A`) => F[R, E, A]]`
neko-kai
force-pushed
the
feature/kind-projector-parse-variance-annotations
branch
from
536661d to
653c5fd
Compare
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 change expands the supported subset of
kind-projectorsyntax, specifically:+*and-*variance annotated versions of the*placeholderλsyntax -λ[(`-R`, `+E`, `+A`) => F[R, E, A]]This change ignores the variance flag specified using
kind-projector's syntax – since variance annotations in type lambdas are deprecated in Scala 3, the real variance of a variable will be inferred separately. I believe that may be acceptable since-Ykind-projector's raison d'être is to allow cross-compilation with existing Scala 2 code, not for writing new code, that is the variance annotations may be assumed to have been checked by the Scala 2 compiler.Related PRs and issues: #7139 #7775
Prompted by discussion in scala/scala#9605