compress: Fix unsound optimization of new RegExp(…)
#7091
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
In swc-project#4932, an optimization was added that transforms `new RegExp(…)` to `RegExp(…)`. It seems to have been motivated by this sentence in the ECMAScript specification: “Thus the function call RegExp(…) is equivalent to the object creation expression new RegExp(…) with the same arguments.” But that sentence turns out to be wrong. It contradicts the detailed steps in the following section of the specification, as well as the empirical behavior of JavaScriptCore, SpiderMonkey, and V8: > r = /a/; /a/ > RegExp(r) === r true > new RegExp(r) === r false Restrict this optimization to the case where we can prove one of the first two arguments is a string. Fixes swc-project#6941. Signed-off-by: Anders Kaseorg <andersk@mit.edu>
kdy1
approved these changes
Mar 17, 2023
swc-bot
reviewed
Mar 17, 2023
Sign up for free
to subscribe to this conversation on GitHub.
Already have an account?
Sign in.
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Outdated suggestions cannot be applied.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 #4932, an optimization was added that transforms
new RegExp(…)toRegExp(…). It seems to have been motivated by this sentence in the ECMAScript specification:But that sentence turns out to be wrong. It contradicts the detailed steps in the following section of the specification, as well as the empirical behavior of JavaScriptCore, SpiderMonkey, and V8:
RegExp(…)andnew RegExp(…)doesn’t hold tc39/ecma262#3028Restrict this optimization to the case where we can prove one of the first two arguments is a string.
Fixes #6941.