iterator.repeat improvements and string.repeat
#356
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
irh
force-pushed
the
avoid-iterator-repeat-footgun
branch
from
8b469d3
to
27339fb
Compare
…tion - Temporary registers are reused more effectively while moving through the chain's nodes. - CallInstance has been added to ensure that the frame base is correctly initialized, in particular the frame base needs to be set to null when a standalone function is called. - If the instance register is at the top of the register stack then it gets used directly as the frame base, avoiding an unnecessary copy.
This avoids the footgun of calling something like `[1, 2, 3].repeat(5).to_list()`, expecting a repeated list. Instead what happens is that the instance (i.e. [1, 2, 3]) is ignored and the repeat count (5) is then interpreted as being the argument to repeat endlessly.
irh
force-pushed
the
avoid-iterator-repeat-footgun
branch
from
27339fb
to
56f9bde
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Outdated suggestions cannot be applied.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 PR prevents a case where
iterator.repeatcould be easily misused.For example:
It would be reasonable to expect a result here of
[[1, 2], [1, 2], [1, 2]], but instead it causes an infinite loop.iteratormodule when a matching item can't be found inlist.[1, 2]is passed toiterator.repeatas the instance for the call.iterator.repeatis intended to be used as a standalone function and ignores the instance.3is then treated as the value to repeat, without a count, producing an endless iterator.The solution here is to have
iterator.repeatcheck that it's being used as a standalone function.iterator.generateis less prone to misuse, but is now similarly restricted. The check is a bit hacky, it checks that the instance is eithernullor theiteratormodule, which means thatrepeatwon't work if it's added to another module and then called there. A more flexible solution would involve reworking the module system, which isn't a problem for today.The PR also adds a specialized version of
repeatfor strings, which seems useful enough to treat as a special case, e.g.Additionally, checking for standalone use of
repeatexposed a flaw where temporary values were left around and ending up in the instance register for standalone calls, so some work has gone into improving the use of temporary registers in lookup chains, and in ensuring that the instance register is cleared when necessary.