perf(compile): use toArrayOf instead of toArray.map(_.asInstanceOf) - #76
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optionalFlags / transientDefaultFlags / outOfOrderFlags already had containsOnly evidence available (like the two summonAll calls just above them) — building each flag Array[Boolean] via toArray.map(cast) allocates an intermediate Array[Any] and boxes/unboxes through it. toArrayOf[Boolean] builds the Array[Boolean] directly in one pass, same as the rest of deriveProduct's array construction already does. Same-session N=50 compile: 7.49s -> ~7.38s (-1.5%); one-time codec construction cost, not the read/write hot path, so no runtime bench needed. All 186 tests green (JVM + JS + Native compile clean). Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
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Summary
deriveProductalready builds most of its arrays withcommons'toArrayOf[T](single-pass, no intermediateArray[Any]) — the three annotation-flag arrays (optionalFlags,transientDefaultFlags,outOfOrderFlags) were the exception, still going through.toArray.map(_.asInstanceOf[Boolean]). Switched them to the sametoArrayOf[Boolean]pattern, with an explicit(using containsOnly.refl)— same as the twosummonAll[...].toArrayOf[MCodec[Any]]calls just above already do, since the tuple's type after destructuring a 3-wayhasAnnotationsByTyperesult doesn't syntactically match the automaticcontainsOnlygiven.Measured (same-session, N=50 generated project,
-Yprofile-trace, 3-run mean)Small, since this only touches codec construction (one array alloc removed per flag column, once per derived type) rather than the read/write hot path — no JMH rerun needed.
Test plan
./mill jvm.test— 186/186 green./mill js.compile native.compile— clean🤖 Generated with Claude Code