1850723 - Add mozilla::Result<V1, E> constructor that receives mozilla::Result<V2, E> where V2 is subclass of V1

Status: RESOLVED FIXED

(Core :: MFBT, enhancement)

Description

[Tooru Fujisawa [:arai]]

mozilla::Result has the following constructor, which receives different mozilla::Result with convertible error.
Having the same for value type helps using it in bug 1849732 where value type is pointer and it can be subclass.

https://searchfox.org/mozilla-central/rev/e7b8d13b7513b6fbd97d69e882d7faeed05309d0/mfbt/Result.h#524-532

/**
 * Create a (success/error) result from another (success/error) result with a
 * different but convertible error type. */
template <typename E2,
          typename = std::enable_if_t<std::is_convertible_v<E2, E>>>
MOZ_IMPLICIT constexpr Result(Result<V, E2>&& aOther)
    : mImpl(aOther.isOk() ? Impl{aOther.unwrap()}
                          : Impl{aOther.unwrapErr()}) {}

Comment 1

[Tooru Fujisawa [:arai]]

this can be restricted to bug 1850710's case if necessary.

Comment 2

[Tooru Fujisawa [:arai]]

Attachment: Bug 1850723 - Make mozilla::Result constructor take another result with convertible value. r?emilio!

Also add std::in_place_t constructor to make the in-place constructor works.

Depends on D191537

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/7398cacb1ad3
Make mozilla::Result constructor take another result with convertible value. r=emilio,glandium

Comment 4

[Sandor Molnar[:smolnar]]

Backed out for causing failures on mfbt/tests/TestResult.cpp

Backout link: https://hg.mozilla.org/integration/autoland/rev/e8cea1e9bd584b4a98fb919ab50f3e997b4d5d14

Push with failures

Failure log -> SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /builds/worker/checkouts/gecko/mfbt/tests/TestResult.cpp:742:5 in

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/b8d7ddef8a12
Make mozilla::Result constructor take another result with convertible value. r=emilio,glandium

Comment 6

[Atila Butkovits]

https://hg.mozilla.org/mozilla-central/rev/b8d7ddef8a12