commit bb0580f5a5461bbabc2b17ea0399aa450f75ad3b
author Konstantin Shcheglov <scheglov@google.com> Tue Aug 19 11:28:39 2025 -0700
committer Commit Queue <dart-scoped@luci-project-accounts.iam.gserviceaccount.com> Tue Aug 19 11:28:39 2025 -0700
tree 07cfbbfd0f17fabe39d78b13987be00083e6dd9e
parent 37ac8e4b4c3f93a2aabacf5341fd81a67f67846b

Elements. Unify interface-cycle handling for extension types

Unifies extension type cycle breaking with the existing
`breakInterfaceCycles()` flow used for other elements and removes the
bespoke walker in `summary2/extension_type.dart`. This consolidates the
logic and ensures consistent behavior across element kinds.

Key changes:
- Move `hasImplementsSelfReference` and
  `hasRepresentationSelfReference` from fragments to
  `ExtensionTypeElementImpl`. Flags are now owned and serialized by the
  element.
- Update summary I/O: writer emits and reader consumes the flags at the
  element level; fragment-level reads/writes are removed.
- Adjust `ErrorVerifier` to read flags via `fragment.element`.
- Handle extension types inside `interface_cycles.dart`: on an SCC,
  mark `hasImplementsSelfReference` and replace `interfaces` with
  `Object` or `Object?` depending on the representation’s nullability.
- Bump `DATA_VERSION` to 524 due to summary layout changes.

Why:
- Eliminates duplicate, divergent cycle-breaking logic for extension
  types.
- Clarifies ownership of self-reference state and simplifies
  serialization.
- Produces consistent diagnostics and interface normalization across
  element kinds.

Impact:
- Requires a format bump; older summaries are invalidated as intended.
- Fragment-level self-reference bits are removed in favor of
  element-level flags.

Change-Id: Ifabb0acb2ce60353bbfe10ee5877c0c66cee5202
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/445961
Commit-Queue: Konstantin Shcheglov <scheglov@google.com>
Reviewed-by: Paul Berry <paulberry@google.com>