Rename and rewrite the "question mark operator" #1931
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This renames the "question mark operator" section to the "try propagation expression", and also drops the grammar name "error propagation expression". The "error propagation expression" isn't really accurate, since `?` isn't just for errors. The intent is to describe the expression by what it does (as most other expressions do) instead of how it looks. It also felt a little awkward to call it the "question mark expression".
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This moves the examples to the intro. It also adds a ControlFlow example. The intent here is to prepare for changing the rest of the text, and the examples won't quite fit like the used to. I also prefer the idea of having an example near every intro section. Edited-by: TC
This rewrites the section to say that it uses the `Try` trait. I felt it was a bit too awkward to avoid it (since it is unstable). This keeps an explicit list of the types that the `Try` trait is implemented for, and adds the missing types (like `ControlFlow`). The intent is that when `Try` is stabilized that the desuggaring note moves to a normative rule, the `expr.try.restricted-types` rule is removed (and instead direct the user to the standard library documentation). I'm still holding out hope that they change the terminology, since I think the current choice is going to be confusing. This has a hack to allow `feature(try_trait_v2)` by abusing the style checker by adding some spaces. I really wanted to keep this example tested to ensure that it is kept up-to-date. However, I may regret this in the future. Fixes rust-lang#1927 Edited-by: TC
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Update books ## rust-lang/book 5 commits in b2d1a0821e12a676b496d61891b8e3d374a8e832..3e9dc46aa563ca0c53ec826c41b05f10c5915925 2025-08-02 01:33:29 UTC to 2025-07-14 21:23:38 UTC - Appendix B and Appendix D from tech review (rust-lang/book#4466) - Chapter 21 from tech review (rust-lang/book#4464) - Chapter 20 from tech review (rust-lang/book#4460) - Chapter 19 from tech review (rust-lang/book#4446) - Chapter 18 from tech review (rust-lang/book#4445) ## rust-lang/reference 12 commits in 1f45bd41fa6c17b7c048ed6bfe5f168c4311206a..1be151c051a082b542548c62cafbcb055fa8944f 2025-08-05 19:51:40 UTC to 2025-07-14 19:49:01 UTC - Fix build output directory in README (rust-lang/reference#1950) - Update `link_name` to use the attribute template (rust-lang/reference#1896) - Update `no_link` to use the attribute template (rust-lang/reference#1898) - Update `proc_macro_derive` to use the attribute template (rust-lang/reference#1888) - Update `automatically_derived` to use the attribute template (rust-lang/reference#1884) - Update `derive` to use the attribute template (rust-lang/reference#1883) - Fix and clarify CR LF normalization and CR in string literals (rust-lang/reference#1944) - glossary.md: tweak description of "dispatch" (rust-lang/reference#1938) - add missing id, r[asm.operand-type.supported-operands.const] (rust-lang/reference#1939) - &str and &[u8] have the same layout (rust-lang/reference#1848) - Rename and rewrite the "question mark operator" (rust-lang/reference#1931) - Change "allocated object" to "allocation". (rust-lang/reference#1930) ## rust-lang/rust-by-example 3 commits in e386be5f44af711854207c11fdd61bb576270b04..bd1279cdc9865bfff605e741fb76a0b2f07314a7 2025-08-04 13:41:04 UTC to 2025-08-02 15:41:59 UTC - Improve the activity instructions in `print_display` (rust-lang/rust-by-example#1948) - Minor fixes (whitespace, typo, i32->u32) (rust-lang/rust-by-example#1947) - Document drawbacks of alternatives to match binding (rust-lang/rust-by-example#1946)
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Update books ## rust-lang/book 5 commits in b2d1a0821e12a676b496d61891b8e3d374a8e832..3e9dc46aa563ca0c53ec826c41b05f10c5915925 2025-08-02 01:33:29 UTC to 2025-07-14 21:23:38 UTC - Appendix B and Appendix D from tech review (rust-lang/book#4466) - Chapter 21 from tech review (rust-lang/book#4464) - Chapter 20 from tech review (rust-lang/book#4460) - Chapter 19 from tech review (rust-lang/book#4446) - Chapter 18 from tech review (rust-lang/book#4445) ## rust-lang/reference 12 commits in 1f45bd41fa6c17b7c048ed6bfe5f168c4311206a..1be151c051a082b542548c62cafbcb055fa8944f 2025-08-05 19:51:40 UTC to 2025-07-14 19:49:01 UTC - Fix build output directory in README (rust-lang/reference#1950) - Update `link_name` to use the attribute template (rust-lang/reference#1896) - Update `no_link` to use the attribute template (rust-lang/reference#1898) - Update `proc_macro_derive` to use the attribute template (rust-lang/reference#1888) - Update `automatically_derived` to use the attribute template (rust-lang/reference#1884) - Update `derive` to use the attribute template (rust-lang/reference#1883) - Fix and clarify CR LF normalization and CR in string literals (rust-lang/reference#1944) - glossary.md: tweak description of "dispatch" (rust-lang/reference#1938) - add missing id, r[asm.operand-type.supported-operands.const] (rust-lang/reference#1939) - &str and &[u8] have the same layout (rust-lang/reference#1848) - Rename and rewrite the "question mark operator" (rust-lang/reference#1931) - Change "allocated object" to "allocation". (rust-lang/reference#1930) ## rust-lang/rust-by-example 3 commits in e386be5f44af711854207c11fdd61bb576270b04..bd1279cdc9865bfff605e741fb76a0b2f07314a7 2025-08-04 13:41:04 UTC to 2025-08-02 15:41:59 UTC - Improve the activity instructions in `print_display` (rust-lang/rust-by-example#1948) - Minor fixes (whitespace, typo, i32->u32) (rust-lang/rust-by-example#1947) - Document drawbacks of alternatives to match binding (rust-lang/rust-by-example#1946)
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Rollup merge of #145026 - rustbot:docs-update, r=ehuss Update books ## rust-lang/book 5 commits in b2d1a0821e12a676b496d61891b8e3d374a8e832..3e9dc46aa563ca0c53ec826c41b05f10c5915925 2025-08-02 01:33:29 UTC to 2025-07-14 21:23:38 UTC - Appendix B and Appendix D from tech review (rust-lang/book#4466) - Chapter 21 from tech review (rust-lang/book#4464) - Chapter 20 from tech review (rust-lang/book#4460) - Chapter 19 from tech review (rust-lang/book#4446) - Chapter 18 from tech review (rust-lang/book#4445) ## rust-lang/reference 12 commits in 1f45bd41fa6c17b7c048ed6bfe5f168c4311206a..1be151c051a082b542548c62cafbcb055fa8944f 2025-08-05 19:51:40 UTC to 2025-07-14 19:49:01 UTC - Fix build output directory in README (rust-lang/reference#1950) - Update `link_name` to use the attribute template (rust-lang/reference#1896) - Update `no_link` to use the attribute template (rust-lang/reference#1898) - Update `proc_macro_derive` to use the attribute template (rust-lang/reference#1888) - Update `automatically_derived` to use the attribute template (rust-lang/reference#1884) - Update `derive` to use the attribute template (rust-lang/reference#1883) - Fix and clarify CR LF normalization and CR in string literals (rust-lang/reference#1944) - glossary.md: tweak description of "dispatch" (rust-lang/reference#1938) - add missing id, r[asm.operand-type.supported-operands.const] (rust-lang/reference#1939) - &str and &[u8] have the same layout (rust-lang/reference#1848) - Rename and rewrite the "question mark operator" (rust-lang/reference#1931) - Change "allocated object" to "allocation". (rust-lang/reference#1930) ## rust-lang/rust-by-example 3 commits in e386be5f44af711854207c11fdd61bb576270b04..bd1279cdc9865bfff605e741fb76a0b2f07314a7 2025-08-04 13:41:04 UTC to 2025-08-02 15:41:59 UTC - Improve the activity instructions in `print_display` (rust-lang/rust-by-example#1948) - Minor fixes (whitespace, typo, i32->u32) (rust-lang/rust-by-example#1947) - Document drawbacks of alternatives to match binding (rust-lang/rust-by-example#1946)
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Update books ## rust-lang/book 5 commits in b2d1a0821e12a676b496d61891b8e3d374a8e832..3e9dc46aa563ca0c53ec826c41b05f10c5915925 2025-08-02 01:33:29 UTC to 2025-07-14 21:23:38 UTC - Appendix B and Appendix D from tech review (rust-lang/book#4466) - Chapter 21 from tech review (rust-lang/book#4464) - Chapter 20 from tech review (rust-lang/book#4460) - Chapter 19 from tech review (rust-lang/book#4446) - Chapter 18 from tech review (rust-lang/book#4445) ## rust-lang/reference 12 commits in 1f45bd41fa6c17b7c048ed6bfe5f168c4311206a..1be151c051a082b542548c62cafbcb055fa8944f 2025-08-05 19:51:40 UTC to 2025-07-14 19:49:01 UTC - Fix build output directory in README (rust-lang/reference#1950) - Update `link_name` to use the attribute template (rust-lang/reference#1896) - Update `no_link` to use the attribute template (rust-lang/reference#1898) - Update `proc_macro_derive` to use the attribute template (rust-lang/reference#1888) - Update `automatically_derived` to use the attribute template (rust-lang/reference#1884) - Update `derive` to use the attribute template (rust-lang/reference#1883) - Fix and clarify CR LF normalization and CR in string literals (rust-lang/reference#1944) - glossary.md: tweak description of "dispatch" (rust-lang/reference#1938) - add missing id, r[asm.operand-type.supported-operands.const] (rust-lang/reference#1939) - &str and &[u8] have the same layout (rust-lang/reference#1848) - Rename and rewrite the "question mark operator" (rust-lang/reference#1931) - Change "allocated object" to "allocation". (rust-lang/reference#1930) ## rust-lang/rust-by-example 3 commits in e386be5f44af711854207c11fdd61bb576270b04..bd1279cdc9865bfff605e741fb76a0b2f07314a7 2025-08-04 13:41:04 UTC to 2025-08-02 15:41:59 UTC - Improve the activity instructions in `print_display` (rust-lang/rust-by-example#1948) - Minor fixes (whitespace, typo, i32->u32) (rust-lang/rust-by-example#1947) - Document drawbacks of alternatives to match binding (rust-lang/rust-by-example#1946)
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This renames the "question mark operator" section, and rewrites it to reference the
Trytrait. See individual commits for a more detailed description.Fixes #1927