Reset comparersInUse to zero in ContextState.reset
#18915
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nicolasstucki
approved these changes
Nov 14, 2023
| def impl()(using Quotes): Expr[Unit] = '{()} | ||
| inline def run(): Unit = ${impl()} | ||
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| @@ -1063,6 +1063,7 @@ object Contexts { | |||
| sources.clear() | |||
| files.clear() | |||
| comparers.clear() // forces re-evaluation of top and bottom classes in TypeComparer | |||
| comparersInUse = 0 | |||
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For additional context, this needs to be reset because the compilation unit was suspended due to the macro dependency. We need to set it back to 0 each time we restart compilation after the suspension.
| @@ -0,0 +1,3 @@ | |||
| import scala.language.experimental.captureChecking | |||
| val x = run() | |||
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| def impl()(using Quotes): Expr[Unit] = '{()} | ||
| inline def run(): Unit = ${impl()} | ||
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Fixes #18855
The code in #18855 used to crash the compiler with an out-of-bound access exception. It was because, previously,
ContextState.resetclears thecomparers, the cached pool ofTypeComparers, while keeping the variablecomparersInUseintact. However, thecomparermethod of a context assumescomparershas a size greater than or equal tocomparersInUse. So the invariant is clearly violated here and thus triggers the crash.This PR proposes a straightforward fix. Yet, the reason why only under both macros and cc this code path will be triggered remains to be investigated.