commit a9f684e62499e669294a07c3ce7d2aa7c545760a
author Jens Johansen <jensj@google.com> Mon Apr 22 14:08:20 2024 +0000
committer Commit Queue <dart-scoped@luci-project-accounts.iam.gserviceaccount.com> Mon Apr 22 14:08:20 2024 +0000
tree 63b82443760a14ca9836e4970cbc5e7f3a256b9b
parent 387a094cdd7a6cbc8da73449d9f0955f21b4de4d

[CFE/kernel/VM] Fix for crash when compiling after a reject in face of unnamed extension

In https://dartbug.com/55357 a crash is reported happening after a hot
restart (not reload!) with a compilation error. This causes a "reject"
call, which means we create a new incremental compiler, initializing it
from the component of the previous good world.

World 1: Initial state.
World 2: The library is new, but (most) references are reused because
         of advanced invaidation. References of unnamed extensions are
         not reused. Instead the canonical names are unbound (so they
         can successfully be bound to the new reference).
         We now have:
           * ref1 (from world1) pointing to no canonical name.
           * ref2 (from world2) pointing to the canonical name.
           * The canonical name pointing to ref2.
         This world is rejected.
World 3: We start from the world 1 state, but because world 2 *did*
         happen and that only most references (i.e. not references for
         unnamed extensions) were reused, when about to unbind the
         unnamed extenesion we are looking at ref1 and have nothing
         to unbind.
         Compiling creates ref3 (from world 3).
         Upon attempt to serialize we try to bind the canonical name to
         "ref3", but it is already bound to "ref2" and we crash.

The main problem here is that not only `Reference`s are reused,
but because `Reference`s point to `CanonicalName`s these are reused too.

This CL clears the canonical name in the references in the libraries that are reused, meaning that a whole new canonical name tree for those
libraries will be created. This is more in line with what the
non-advanced-invalidation does (by it not reusing references and
naturally getting a whole new canonical name tree).
In my opinion it even makes more sense --- and the fact that the
canonical names were reused was probably more me not thinking about it,
than it was a deliberate design decision.

Fixes https://github.com/dart-lang/sdk/issues/55357

Change-Id: I90bd579984f4aefad78243e8366ac0ab91a905bf
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/363563
Commit-Queue: Jens Johansen <jensj@google.com>
Reviewed-by: Johnni Winther <johnniwinther@google.com>