[compiler] Remove transitive memo check in validatePreserveMemo #30630
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This was referenced Aug 7, 2024
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mofeiZ
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Aug 7, 2024
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| if ($[0] !== x) { | ||
| t0 = () => [x, []]; | ||
| $[0] = x; | ||
| $[1] = t0; | ||
| } else { | ||
| t0 = $[1]; | ||
| } |
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Note that this output correctly preserves manual memoization
mofeiZ
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Aug 7, 2024
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| if ($[1] !== a || $[2] !== t2) { | ||
| t3 = () => [a, x]; | ||
| $[1] = a; | ||
| $[2] = t2; | ||
| $[3] = t3; | ||
| } else { | ||
| t3 = $[3]; | ||
| } |
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This inferred memoization also preserves manual memo
mofeiZ
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Aug 7, 2024
| */ | ||
| scopes: Set<ScopeId> = new Set(); | ||
| prunedScopes: Set<ScopeId> = new Set(); | ||
| scopeMapping = new Map(); |
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(drive by dead code deletion)
josephsavona
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Aug 8, 2024
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This seems reasonable. We should probably still fix up ValidateMemoizedEffectDeps and do a transitive check there, but I agree it's fine for ValidatePreserveManualMemo to be only as precise as the original memoization. Especially given the very low percentage of files impacted.
| ``` | ||
| ### Eval output | ||
| (kind: exception) mutate is not defined No newline at end of file |
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Stack from ghstack (oldest at bottom):
The original version of validatePreserveMemo tried to check that all manual memo declarations are transitively memoized. This may have been intended to stabilize
useEffectby ensuring that optimized components trigger effects minimally.This transitive memoization check only rarely affects compilation output. (Syncing this PR resulted in 12 changes out of tens of thousands of files). This is likely because many
StartMemoizeandFinishMemoizedeps / decls are identifiers with no attached scopes (see #30603 for more complete explanation).Meta internal reviewers: see changes from this PR