[CP] Fix infinite loop in DDC compiler

[nshahan]

Commit(s) to merge

be6a560

Target

stable and beta

Prepared changelist for stable/beta

Stable: https://dart-review.googlesource.com/c/sdk/+/312709,
Beta: https://dart-review.googlesource.com/c/sdk/+/312710

Issue Description

Some web development compiles of libraries containing is or as with specific record types will hang and never complete.

A minimal reproduction:

main() {
  Object value = 'x';
  (a: 'a', b: value) as ({String a, String b});
}

What is the fix

Some record type comparison operations were not properly incrementing a loop variable when iterating the named elements. With this fix the execution can properly exit the loop and the compile succeeds.

Why cherry-pick

Some type operations using record types will cause the DDC to hang while compiling preventing use of either the record types or web development compiler.

A user reported hitting this in a flutter application and could not compile their app for web development.

Risk

low

Issue link(s)

#52817, flutter/flutter#129482

Extra Info

cc @sigmundch

[sigmundch]

Given the low risk and how its surfaced to users (the compiler hangs), I'm very much in favor of cherry-picking to both channels to ensure it makes it to both 3.0 and 3.1.

[itsjustkevin]

@athomas based on the timing of the next beta release, do you have opinions on when this should be merged to beta?

[vsmenon]

lgtm

[itsjustkevin]

Stable cherry-pick has landed, keeping this open until the beta cherry-pick has landed in a release.

[nshahan]

@athomas Any update on landing this in the beta branch?

[sigmundch]

I see a beta released after @nshahan's change landed, so it may potentially have this change. That said, the commit of the cherry-pick CL doesn't have a tag with the corresponding beta.

@athomas - do we set the tags only on commits from the main branch, or do we also do it for these ad-hoc commits that are not always a clean cherry-pick? If not, would it be possible to tag them too?

[itsjustkevin]

@nshahan this was landed on the beta branch https://dart.googlesource.com/sdk/+log/1b6421ac0ba6e5196b58bce150495d872433151d.

@sigmundch I am going to close this to clear up the queue, please feel free to open a new issue to track the commit tag discussion 🙂.