Lift all non trivial prefixes for default parameters #19739
Merged
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
nicolasstucki
force-pushed
the
fix-15315
branch
from
08b1e9a to
c708ecf
Compare
odersky
requested changes
Feb 27, 2024
| * Note that default arguments will refer to the prefix, we do not want | ||
| * to re-evaluate a complex expression each time we access a getter. | ||
| */ | ||
| def liftPrefix(defs: mutable.ListBuffer[Tree], tree: Tree)(using Context): Tree = |
There was a problem hiding this comment.
Can we get the old behavior when there are no default arguments? We'd need a boolean passed to liftPrefix indicating whether the enclosing method has the HasDefaultParams flag.
There was a problem hiding this comment.
I split this definition into liftNonIdempotentPrefix and liftPrefix instead. Compining them made the documentation to convoluted. HasDefaultParams is used to choose which of those methods to call.
Checking if the prefix is pure is not enough to know if we need to list the prefix. In the case of default parameters, the prefix tree might be used several times to compute the default values. This expression should only be computed once and therefore it should be lifted if there is some computation/allocation involved. Furthermore, if the prefix contains a local definition, it must be lifted to avoid duplicating the definition. A similar situation could happen with dependent default parameters. This currently works as expected. Fixes scala#15315
nicolasstucki
force-pushed
the
fix-15315
branch
from
c708ecf to
71b983b
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Outdated suggestions cannot be applied.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.
Checking if the prefix is pure is not enough to know if we need to list the prefix. In the case of default parameters, the prefix tree might be used several times to compute the default values. This expression should only be computed once and therefore it should be lifted if there is some computation/allocation involved. Furthermore, if the prefix contains a local definition, it must be lifted to avoid duplicating the definition.
A similar situation could happen with dependent default parameters. This currently works as expected.
Fixes #15315