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Ensure that Fingerprint caching respects hashing configuration #92278

Merged
merged 3 commits into from
Jan 10, 2022
Merged

Ensure that Fingerprint caching respects hashing configuration #92278

merged 3 commits into from
Jan 10, 2022

Commits on Jan 5, 2022

  1. Ensure that Fingerprint caching respects hashing configuration 

    Fixes rust-lang#92266

In some `HashStable` impls, we use a cache to avoid re-computing
the same `Fingerprint` from the same structure (e.g. an `AdtDef`).
However, the `StableHashingContext` used can be configured to
perform hashing in different ways (e.g. skipping `Span`s). This
configuration information is not included in the cache key,
which will cause an incorrect `Fingerprint` to be used if
we hash the same structure with different `StableHashingContext`
settings.

To fix this, the configuration settings of `StableHashingContext`
are split out into a separate `HashingControls` struct. This
struct is used as part of the cache key, ensuring that our caches
always produce the correct result for the given settings.

With this in place, we now turn off `Span` hashing during the
entire process of computing the hash included in legacy symbols.
This current has no effect, but will matter when a future PR
starts hashing more `Span`s that we currently skip.
    @Aaron1011
    Aaron1011 committed Jan 5, 2022
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  2. Adjust assert_default_hashing_controls

    @Aaron1011
    Aaron1011 committed Jan 5, 2022
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  3. Address review comments

    @Aaron1011
    Aaron1011 committed Jan 5, 2022
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