fix(angular): fix 5 compiler divergences from Angular reference

[Brooooooklyn]

1. Standalone connected blocks (@else, @empty, @Placeholder, @Loading,
   @error) now emit error diagnostics and produce UnknownBlock nodes
   instead of being silently dropped.

2. @defer connected block validation now rejects duplicate @placeholder/
   @loading/@error, @error with parameters, and unrecognized params in
   @placeholder/@Loading blocks.

3. @switch case groups now propagate i18n metadata via
   create_block_placeholder() instead of hardcoding None.

4. parse_track_expression now returns empty string for bare "track "
   so the downstream EmptyExpr check produces the correct diagnostic.

5. Comments between connected blocks are no longer marked as processed,
   matching Angular's findConnectedBlocks behavior.

Co-Authored-By: Claude Opus 4.6 noreply@anthropic.com

---

Note

Medium Risk
Changes parsing/validation behavior and emitted AST nodes for control-flow blocks, which may affect downstream consumers and error expectations despite being well-covered by new tests.

Overview
Fixes several Angular compiler divergences in the template-to-R3 transform.

Standalone connected blocks (@else, @empty, @placeholder, @loading, @error) now emit diagnostics and produce UnknownBlock nodes instead of being silently ignored, and comment nodes between connected blocks are skipped without being marked processed.

Tightens @defer connected-block handling to validate duplicates and parameters (rejects multiple connected blocks of the same type, forbids params on @error, and reports unrecognized params on @placeholder/@loading), propagates i18n metadata for @switch case groups, and adjusts @for track parsing to treat track as a match so the downstream empty-expression diagnostic is triggered (removing unused deferred-time param helpers accordingly).

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[Brooooooklyn]

• fix(angular): fix 5 compiler divergences from Angular reference #28 👈 (View in Graphite)
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