Fix raw SetProperty on builtin-shaped hosts landing in an invisible dictionary#2591
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…ictionary SetProperty(Key, ...) deopted hidden-class ShapeMode objects before storing a raw descriptor, but not BuiltinShapeMode hosts: the write created a side _properties dictionary that the shape-mode read paths never consult, so the property silently did not exist. Reachable through the public FastSetProperty API on any shaped built-in (Math, JSON, prototypes, ...) since the shapes migration. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Note for reviewers: while writing the regression test I found a related but distinct pre-existing edge — a raw \SetProperty/\FastSetProperty\ issued before a generated host's lazy \Initialize\ has run gets wiped when initialization later replaces the property bag (\SetProperties), and that affects dictionary-path hosts too, not just shaped ones. This PR intentionally fixes only the post-initialization shaped-host case (the write landing in a dictionary the shape reads never consult); the pre-init store is left as a separate issue since it predates the shapes work. |
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…2601) A raw SetProperty/FastSetProperty on a lazily-initialized host landed in _properties (or _symbols) without triggering initialization; the first read then ran Initialize(), whose generated CreateProperties_Generated/ CreateSymbols_Generated replaced the bag wholesale via SetProperties/ SetSymbols and silently dropped the earlier write. Documented as a known edge in #2591's review; affects dictionary hosts and shaped hosts alike. SetProperty(Key) and the symbol arm of SetPropertyUnlikely now run EnsureInitialized() first, so raw stores always apply on top of the initialized state - dictionary hosts append to the installed bag and builtin-shaped hosts route through the hybrid side-dictionary arm. EngineConstruction A/B: allocation byte-identical (6.63 KB BuildEngine, 7.24 KB EvaluateSimple), time within noise - nothing in engine or realm construction hits the new initialization path. Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
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`SetProperty(Key, ...)` deopted hidden-class \ShapeMode\ objects before storing a raw descriptor, but not \BuiltinShapeMode\ hosts: the write created a side _properties\ dictionary that the shape-mode read paths never consult, so the property silently did not exist. Reachable through the public \FastSetProperty\ API on any shaped built-in (\Math, \JSON, prototypes, ...) since the shapes migration.
Regression test included (raw store on shaped \Math: value visible, enumerable via \getOwnPropertyNames, existing shape members still functional after the deopt).
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