subscriber: make FmtSubscriber's auto traits not depend on C
#2024
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this moves the "runtime configuration with subscribers" section into a subsection of "composing subscribers". Signed-off-by: Eliza Weisman <eliza@buoyant.io>
Signed-off-by: Eliza Weisman <eliza@buoyant.io>
Signed-off-by: Eliza Weisman <eliza@buoyant.io>
Signed-off-by: Eliza Weisman <eliza@buoyant.io>
## Motivation Currently, `FmtSubscriber` holds a `PhantomData<C>` with the `Collect` type it wraps. This is unfortunate because it means that the subscriber's auto traits such as `Send`, `Sync`, and `'static` (as well as `UnwindSafe`, `Unpin`, etc) depend on the collector type's auto traits...but the subscriber will never actually _store_ a value of type `C`. While all collectors will be `Send + Sync + 'static` in practice, the `PhantomData` means that functions returning a boxed `FmtSubscriber` must unnecessarily bound the collector type parameter. ## Solution This commit changes the `PhantomData` to `PhantomData<fn(C)>`, solving the problem.
davidbarsky
approved these changes
Mar 25, 2022
hawkw
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Mar 29, 2022
Depends on #2023 ## Motivation Currently, `FmtLayer` holds a `PhantomData<S>` with the `Subscriber` type it wraps. This is unfortunate because it means that the layer's auto traits such as `Send`, `Sync`, and `'static` (as well as `UnwindSafe`, `Unpin`, etc) depend on the `Subscriber` type's auto traits...but the layer will never actually _store_ a value of type `S`. While all `Subscriber` will be `Send + Sync + 'static` in practice, the `PhantomData` means that functions returning a boxed `FmtLayer` must unnecessarily bound the subscriber type parameter. ## Solution This commit changes the `PhantomData` to `PhantomData<fn(S)>`, solving the problem. Signed-off-by: Eliza Weisman <eliza@buoyant.io>
hawkw
added a commit
that referenced
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Mar 29, 2022
Depends on #2023 ## Motivation Currently, `FmtLayer` holds a `PhantomData<S>` with the `Subscriber` type it wraps. This is unfortunate because it means that the layer's auto traits such as `Send`, `Sync`, and `'static` (as well as `UnwindSafe`, `Unpin`, etc) depend on the `Subscriber` type's auto traits...but the layer will never actually _store_ a value of type `S`. While all `Subscriber` will be `Send + Sync + 'static` in practice, the `PhantomData` means that functions returning a boxed `FmtLayer` must unnecessarily bound the subscriber type parameter. ## Solution This commit changes the `PhantomData` to `PhantomData<fn(S)>`, solving the problem. Signed-off-by: Eliza Weisman <eliza@buoyant.io>
kaffarell
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to kaffarell/tracing
that referenced
this pull request
May 22, 2024
) Depends on tokio-rs#2023 ## Motivation Currently, `FmtLayer` holds a `PhantomData<S>` with the `Subscriber` type it wraps. This is unfortunate because it means that the layer's auto traits such as `Send`, `Sync`, and `'static` (as well as `UnwindSafe`, `Unpin`, etc) depend on the `Subscriber` type's auto traits...but the layer will never actually _store_ a value of type `S`. While all `Subscriber` will be `Send + Sync + 'static` in practice, the `PhantomData` means that functions returning a boxed `FmtLayer` must unnecessarily bound the subscriber type parameter. ## Solution This commit changes the `PhantomData` to `PhantomData<fn(S)>`, solving the problem. Signed-off-by: Eliza Weisman <eliza@buoyant.io>
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Depends on #2023
Motivation
Currently,
FmtSubscriberholds aPhantomData<C>with theCollecttype it wraps. This is unfortunate because it means that the
subscriber's auto traits such as
Send,Sync, and'static(as wellas
UnwindSafe,Unpin, etc) depend on the collector type's autotraits...but the subscriber will never actually store a value of type
C. While all collectors will beSend + Sync + 'staticin practice,the
PhantomDatameans that functions returning a boxedFmtSubscribermust unnecessarily bound the collector type parameter.
Solution
This commit changes the
PhantomDatatoPhantomData<fn(C)>, solvingthe problem.