Unbox more closures in the libraries #20363
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r+. Giving high priority as this is an urgent language change. |
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The the last argument of the `ItemDecorator::expand` method has changed to `Box<FnMut>`. Syntax extensions will break. [breaking-change] --- This PR removes pretty much all the remaining uses of boxed closures from the libraries. There are still boxed closures under the `test` directory, but I think those should be removed or replaced with unboxed closures at the same time we remove boxed closures from the language. In a few places I had to do some contortions (see the first commit for an example) to work around issue #19596. I have marked those workarounds with FIXMEs. In the future when `&mut F where F: FnMut` implements the `FnMut` trait, we should be able to remove those workarounds. I've take care to avoid placing the workaround functions in the public API. Since `let f = || {}` always gets type checked as a boxed closure, I have explictly annotated those closures (with e.g. `|&:| {}`) to force the compiler to type check them as unboxed closures. Instead of removing the type aliases (like `GetCrateDataCb`), I could have replaced them with newtypes. But this seemed like overcomplicating things for little to no gain. I think we should be able to remove the boxed closures from the languge after this PR lands. (I'm being optimistic here) r? @alexcrichton or @aturon cc @nikomatsakis
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The the last argument of the
ItemDecorator::expandmethod has changed toBox<FnMut>. Syntax extensions will break.[breaking-change]
This PR removes pretty much all the remaining uses of boxed closures from the libraries. There are still boxed closures under the
testdirectory, but I think those should be removed or replaced with unboxed closures at the same time we remove boxed closures from the language.In a few places I had to do some contortions (see the first commit for an example) to work around issue #19596. I have marked those workarounds with FIXMEs. In the future when
&mut F where F: FnMutimplements theFnMuttrait, we should be able to remove those workarounds. I've take care to avoid placing the workaround functions in the public API.Since
let f = || {}always gets type checked as a boxed closure, I have explictly annotated those closures (with e.g.|&:| {}) to force the compiler to type check them as unboxed closures.Instead of removing the type aliases (like
GetCrateDataCb), I could have replaced them with newtypes. But this seemed like overcomplicating things for little to no gain.I think we should be able to remove the boxed closures from the languge after this PR lands. (I'm being optimistic here)
r? @alexcrichton or @aturon
cc @nikomatsakis