Use From::from fn pointer to convert to boxed errors
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Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @marioidival (or someone else) some time within the next two weeks. |
jhpratt
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Update books ## rust-lang/book 2 commits in f78ab89d7545ac17780e6a367055cc089f4cd2ec..8c0eacd5c4acbb650497454f3a58c9e8083202a4 2025-11-18 15:36:41 UTC to 2025-11-18 15:33:41 UTC - Update ch07-02-defining-modules-to-control-scope-and-privacy.md (rust-lang/book#4570) - use AND for search terms (rust-lang/book#4573) ## rust-lang/reference 4 commits in f9f1d2a4149f02582aec2f8fcdfa5b596193b4e2..f2ac173df9906de5c03b0ee50653321ef1c4ebe8 2025-11-26 02:52:23 UTC to 2025-11-18 21:54:51 UTC - document `cfg` conditions on inline assembly templates and operands (rust-lang/reference#2063) - remove unused "link reference definitions" (rust-lang/reference#2092) - Add review process overview to review-policy.md (rust-lang/reference#2088) - Remove restriction on dereferencing pointers in const (rust-lang/reference#2090) ## rust-lang/rust-by-example 5 commits in f944161716230641605b5e3733e1c81f10047fd4..111cfae2f9c3a43f7b0ff8fa68c51cc8f930637c 2025-11-27 20:16:42 UTC to 2025-11-20 21:40:02 UTC - Use `From::from` fn pointer to convert to boxed errors (rust-lang/rust-by-example#1906) - link the _tuple_ page instead "TupleStruct" (rust-lang/rust-by-example#1909) - enum_use.md: avoid an uncommon term (rust-lang/rust-by-example#1976) - make search less surprising (rust-lang/rust-by-example#1975) - Update documentation for `any` function in iter_any.md (rust-lang/rust-by-example#1973)
rust-timer
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Rollup merge of #149424 - rustbot:docs-update, r=ehuss Update books ## rust-lang/book 2 commits in f78ab89d7545ac17780e6a367055cc089f4cd2ec..8c0eacd5c4acbb650497454f3a58c9e8083202a4 2025-11-18 15:36:41 UTC to 2025-11-18 15:33:41 UTC - Update ch07-02-defining-modules-to-control-scope-and-privacy.md (rust-lang/book#4570) - use AND for search terms (rust-lang/book#4573) ## rust-lang/reference 4 commits in f9f1d2a4149f02582aec2f8fcdfa5b596193b4e2..f2ac173df9906de5c03b0ee50653321ef1c4ebe8 2025-11-26 02:52:23 UTC to 2025-11-18 21:54:51 UTC - document `cfg` conditions on inline assembly templates and operands (rust-lang/reference#2063) - remove unused "link reference definitions" (rust-lang/reference#2092) - Add review process overview to review-policy.md (rust-lang/reference#2088) - Remove restriction on dereferencing pointers in const (rust-lang/reference#2090) ## rust-lang/rust-by-example 5 commits in f944161716230641605b5e3733e1c81f10047fd4..111cfae2f9c3a43f7b0ff8fa68c51cc8f930637c 2025-11-27 20:16:42 UTC to 2025-11-20 21:40:02 UTC - Use `From::from` fn pointer to convert to boxed errors (rust-lang/rust-by-example#1906) - link the _tuple_ page instead "TupleStruct" (rust-lang/rust-by-example#1909) - enum_use.md: avoid an uncommon term (rust-lang/rust-by-example#1976) - make search less surprising (rust-lang/rust-by-example#1975) - Update documentation for `any` function in iter_any.md (rust-lang/rust-by-example#1973)
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This PR changes the recommended way to convert to a boxed error
Box<dyn Error>for types that implError. It changes themap_err(|e| e.into())tomap_err(From::from)which I believe is much more concise and idiomatic (and satisfying!).Motivation
Like a lot of people I bashed my head on this problem of getting the compiler to accept the mapped error as a
Box<dyn Error>and not aBox<CustomError>. I eventually founde.into()and then I realized that means I can useFrom::from.I have done some searching on the StackOverflow and the Rust user forums to see how everyone else is solving this problem and I have yet to find an example of someone recommending
From::fromfn pointer. Everyone just suggests|e| e.into()even though the former does the same thing more concisely.I think it is just an oversight and it doesn't occur to the person helping that if
e.intoworks, that meansFrom::from(e)necessarily works as well. So I figured I would share this solution in the official example book if it is indeed an improvement over the current recommended method.Any way, let know what you guys think!