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Associated type projections don't count for local types in trait impls #87350
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A-associated-items
Area: Associated items (types, constants & functions)
A-coherence
Area: Coherence
C-bug
Category: This is a bug.
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
T-types
Relevant to the types team, which will review and decide on the PR/issue.
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This works ok if you rewrite it to |
jyn514
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Category: This is a bug.
A-coherence
Area: Coherence
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Apr 9, 2023
lcnr
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May 12, 2024
matthiaskrgr
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Aug 14, 2024
…=scottmcm Explicitly specify type parameter on FromResidual for Option and ControlFlow. ~~Remove type parameter default `R = <Self as Try>::Residual` from `FromResidual`~~ _Specify default type parameter on `FromResidual` impls in the stdlib_ to work around rust-lang#99940 / rust-lang#87350 ~~as mentioned in rust-lang#84277 (comment). This does not completely fix the issue, but works around it for `Option` and `ControlFlow` specifically (`Result` does not have the issue since it already did not use the default parameter of `FromResidual`). ~~(Does this need an ACP or similar?)~~ ~~This probably needs at least an FCP since it changes the API described in [the RFC](rust-lang/rfcs#3058). Not sure if T-lang, T-libs-api, T-libs, or some combination (The tracking issue is tagged T-lang, T-libs-api).~~ This probably doesn't need T-lang input, since it is not changing the API of `FromResidual` from the RFC? Maybe needs T-libs-api FCP?
jieyouxu
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…=scottmcm Explicitly specify type parameter on FromResidual for Option and ControlFlow. ~~Remove type parameter default `R = <Self as Try>::Residual` from `FromResidual`~~ _Specify default type parameter on `FromResidual` impls in the stdlib_ to work around rust-lang#99940 / rust-lang#87350 ~~as mentioned in rust-lang#84277 (comment). This does not completely fix the issue, but works around it for `Option` and `ControlFlow` specifically (`Result` does not have the issue since it already did not use the default parameter of `FromResidual`). ~~(Does this need an ACP or similar?)~~ ~~This probably needs at least an FCP since it changes the API described in [the RFC](rust-lang/rfcs#3058). Not sure if T-lang, T-libs-api, T-libs, or some combination (The tracking issue is tagged T-lang, T-libs-api).~~ This probably doesn't need T-lang input, since it is not changing the API of `FromResidual` from the RFC? Maybe needs T-libs-api FCP?
rust-timer
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Aug 14, 2024
Rollup merge of rust-lang#128954 - zachs18:fromresidual-no-default, r=scottmcm Explicitly specify type parameter on FromResidual for Option and ControlFlow. ~~Remove type parameter default `R = <Self as Try>::Residual` from `FromResidual`~~ _Specify default type parameter on `FromResidual` impls in the stdlib_ to work around rust-lang#99940 / rust-lang#87350 ~~as mentioned in rust-lang#84277 (comment). This does not completely fix the issue, but works around it for `Option` and `ControlFlow` specifically (`Result` does not have the issue since it already did not use the default parameter of `FromResidual`). ~~(Does this need an ACP or similar?)~~ ~~This probably needs at least an FCP since it changes the API described in [the RFC](rust-lang/rfcs#3058). Not sure if T-lang, T-libs-api, T-libs, or some combination (The tracking issue is tagged T-lang, T-libs-api).~~ This probably doesn't need T-lang input, since it is not changing the API of `FromResidual` from the RFC? Maybe needs T-libs-api FCP?
fmease
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Nov 3, 2024
Fixed by #117164. |
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Labels
A-associated-items
Area: Associated items (types, constants & functions)
A-coherence
Area: Coherence
C-bug
Category: This is a bug.
T-compiler
Relevant to the compiler team, which will review and decide on the PR/issue.
T-types
Relevant to the types team, which will review and decide on the PR/issue.
I ran into a case with generated code today where I believe the compiler is giving a false error trying to verify a trait implementation.
Given a crate
foo
defined as:and then a consumer crate
bar
:when compiled this yields:
I don't believe that the error here is accurate since
A
,B
,C
, andMyType
are all local to the crate and the compiler would ideally follow the projection to conclude that this trait implementation is valid.The text was updated successfully, but these errors were encountered: