[ty] Narrow semantic node ID lookup tables#26363
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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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I'll wait for the conclusion on the base PR before reviewing this PR (the improvements look promising but we may need to move/change the PR depending on the outcome of the base PR)
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Store indexed semantic IDs as 16-bit values when every entry fits, with a full-width fallback for unusually large files. Apply the narrow representation to AST use IDs and scope lookups, partitioning primary and type-parameter scopes so distinct scope keys that share a node index remain separate.
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Summary
File-local semantic IDs are stored at their full width in several immutable lookup tables, even though almost every file uses fewer than 65,536 IDs.
This adds an independent
NarrowNodeIndexMap. When every value fits, it stores each mapping as a packed six-byte entry containing a 32-bit node index and a 16-bit semantic ID, avoiding the padding of a(NodeKey, u16)tuple. Unusually large files fall back to the existing full-widthFrozenMaprepresentation. This PR does not depend on #26350.We use the narrow representation for AST use IDs and scope lookups. Scope lookups keep module, primary-scope, and type-parameter-scope entries separate because a node can anchor both a primary scope and a type-parameter scope.