Use correct type equality in divergence check #6163
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
odersky
approved these changes
Mar 25, 2019
Closed
milessabin
added a commit
to milessabin/dotty
that referenced
this pull request
Apr 17, 2019
The fix for scala#6058 in scala#6163 caused a significant performance regression in the inductive implicits benchmark because the use of =:= rather than == in the divergence check was significantly slower. It is the right test however, so we need a quicker check to rule out negative cases. We're already computing the covering sets and sizes of the two types being compared. tp1 =:= tp2 should entail (sz1 == sz2 && cs1 == cs2), so the contrapositive (sz1 != sz2 || cs1 != cs2) should entail that !(tp1 =:= tp2). However the covering set and size computations were incorrect (they missed types mentioned in bounds which should have been included, and included symbols for unsolved type variables which should not). This commit fixes the latter issue, which allows covering set and size tests to be used to avoid expensive full type equality tests.
milessabin
added a commit
to milessabin/dotty
that referenced
this pull request
Apr 24, 2019
The fix for scala#6058 in scala#6163 caused a significant performance regression in the inductive implicits benchmark because the use of =:= rather than == in the divergence check was significantly slower. It is the right test however, so we need a quicker check to rule out negative cases. We're already computing the covering sets and sizes of the two types being compared. tp1 =:= tp2 should entail (sz1 == sz2 && cs1 == cs2), so the contrapositive (sz1 != sz2 || cs1 != cs2) should entail that !(tp1 =:= tp2). However the covering set and size computations were incorrect (they missed types mentioned in bounds which should have been included, and included symbols for unsolved type variables which should not). This commit fixes the latter issue, which allows covering set and size tests to be used to avoid expensive full type equality tests.
anatoliykmetyuk
pushed a commit
to dotty-staging/dotty
that referenced
this pull request
May 2, 2019
The fix for scala#6058 in scala#6163 caused a significant performance regression in the inductive implicits benchmark because the use of =:= rather than == in the divergence check was significantly slower. It is the right test however, so we need a quicker check to rule out negative cases. We're already computing the covering sets and sizes of the two types being compared. tp1 =:= tp2 should entail (sz1 == sz2 && cs1 == cs2), so the contrapositive (sz1 != sz2 || cs1 != cs2) should entail that !(tp1 =:= tp2). However the covering set and size computations were incorrect (they missed types mentioned in bounds which should have been included, and included symbols for unsolved type variables which should not). This commit fixes the latter issue, which allows covering set and size tests to be used to avoid expensive full type equality tests.
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.
Fixes #6058.