Avoid crash by relaxing TyperState assertion #13150
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Flushing a reporter might force error messages (in particular when a StoreReporter is flushed into a non-StoreReporter), and the TyperState of the context captured in an error message might already be committed at this point. In ea6449f I tried to deal with this by flushing before committing but that's not sufficient since the reporter we're flushing might contain error messages from a more deeply nested TyperState. So this commit just relaxes the assertion (ideally we would also check that only TyperStates created in a committed TyperState can be committed in one, but keeping track of that would require an extra field in TyperState).
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An already-committed TyperState might be committed again when errors are flushed (cf scala#12827, scala#13150) and `commit()` calls `gc()`. This operation could crash before this commit because we attempted to instantiate type variables no longer owned by the TyperState. We fix this by clearing `ownedVars` when committing a TyperState (because after committing it no longer owns any type variable). Fixes scala#13407.
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An already-committed TyperState might be committed again when errors are flushed (cf scala#12827, scala#13150) and `commit()` calls `gc()`. This operation could crash before this commit because we attempted to instantiate type variables no longer owned by the TyperState. We fix this by clearing `ownedVars` when committing a TyperState (because after committing it no longer owns any type variable). Fixes scala#13407.
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Flushing a reporter might force error messages (in particular when a
StoreReporter is flushed into a non-StoreReporter), and the TyperState
of the context captured in an error message might already be committed
at this point. In ea6449f I tried to
deal with this by flushing before committing but that's not sufficient
since the reporter we're flushing might contain error messages from a
more deeply nested TyperState. So this commit just relaxes the assertion
(ideally we would also check that only TyperStates created in a
committed TyperState can be committed in one, but keeping track of that
would require an extra field in TyperState).
Fixes #13101.
I nominate this PR for backporting since it fixes a regression with respect to 3.0.0