[ty] Co-locate retained definition usage state#26019
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charliermarsh merged 3 commits intoJun 25, 2026
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Typing conformance resultsNo changes detected ✅Current numbersThe percentage of diagnostics emitted that were expected errors held steady at 94.47%. The percentage of expected errors that received a diagnostic held steady at 89.19%. The number of fully passing files held steady at 95/134. |
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## Summary Stacked on #26019. We reserve `ScopedDefinitionId` zero for the implicit unbound or undeclared definition. The mutable use-def builder needs that sentinel while constructing its indexed flow state, but retaining an explicit `Undefined` entry in every frozen `UseDefMap` is unnecessary. This introduces a small retained-definition wrapper that omits the sentinel when freezing the map and synthesizes it for lookup and enumeration. Definition IDs and the builder representation remain unchanged. Coverage for an empty scope verifies that the implicit definition remains observable through both APIs.
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Summary
We now encode whether each retained definition is used directly in
RetainedDefinitionState, instead of retaining a separate parallel boolean vector inUseDefMap.The mutable builder continues to keep
all_definitionsandused_bindingsseparate, then combines them only when freezing the immutable map. This keeps mutation straightforward while removing one allocation and one byte per definition from the retained representation. A compile-time size assertion guarantees that the combined enum remains the same size asDefinitionState.