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Fix "Display type" to "Display trait" in ch19-03 #3835

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generalmimon
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Display is a trait, not a type. See https://doc.rust-lang.org/std/fmt/trait.Display.html:

Trait std::fmt::Display

pub trait Display {
    // Required method
    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>;
}

@chriskrycho
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Traits are types, so the text is accurate here! While it is sometimes important to distinguish between traits and other types, in this case the text seems perfectly fine as is, so I am going to close this. 😅 Thanks, though!

@generalmimon
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generalmimon commented Mar 27, 2024

@chriskrycho:

Traits are types, so the text is accurate here!

Really? Pretty much every answer by different people for example in this thread at Reddit says otherwise:

https://www.reddit.com/r/rust/comments/130cxak/comment/jhwadxr/

Firstly, traits are not types - you can't create instance of a trait. The purpose of traits is to define some functionality that types may share.

https://www.reddit.com/r/rust/comments/130cxak/comment/jhw8ewi/

Traits are not types in Rust. There are two ways you can use them in a type position: (...)

https://www.reddit.com/r/rust/comments/130cxak/comment/jhwotrm/

Traits aren't types. They can pretty much only be used to either organize your code better, or more importantly, tell Rust what kind of methods you can call on an "unknown" type.

https://www.reddit.com/r/rust/comments/130cxak/comment/ji8ha4t/

You can't use a trait as a type. It's way closer to a limited interface; a "contract" that dictates that everyone that implements it must implement one or more functions as well.


Are all these people wrong? And even if they are, it is still better to insist on keeping "Display type" in the text (when really the "Display trait" was intended) when it's clearly not aligned with what many people believe?

Also, for the sake of interest, this is the only occurrence of "Display type" in the entire book (see NOT path:nostarch "`Display` type"), whereas "Display trait" comes up 10 times (see NOT path:nostarch "`Display` trait"), out of which 4 times in the same chapter ch19-03 as this unique "Display type". Just saying...

@chriskrycho
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Interesting! I'll reevaluate and chat with @carols10cents – thanks.

@chriskrycho chriskrycho reopened this Mar 27, 2024
@carols10cents
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On further review, let's merge this. Thank you for your patience @generalmimon

@carols10cents carols10cents merged commit e58f1ca into rust-lang:main Apr 11, 2024
4 checks passed
@generalmimon generalmimon deleted the fix-display-type-in-ch19-03 branch April 11, 2024 20:51
GuillaumeGomez added a commit to GuillaumeGomez/rust that referenced this pull request Apr 22, 2024
Update books

## rust-lang/book

41 commits in 3131aa4642c627a24f523c82566b94a7d920f68c..d207d894cc5e1d496ab99beeacd1a420e5d4d238
2024-04-19 19:48:19 UTC to 2024-04-08 19:34:07 UTC

- Ch. 2: intentionally use `{}` at first (rust-lang/book#3898)
- Inline fmt lints for `redirects/` (rust-lang/book#3897)
- ch12-03: `expect` is not used multitude times by this chapter (rust-lang/book#3287)
- Inline format args to `tools/src` (rust-lang/book#3896)
- Improve awkward phrasing around the kinds of closures (rust-lang/book#3290)
- Ch. 14: clarify workspace dependency reuse (rust-lang/book#3890)
- Edit on line no. 153. Replaced fn add_to_waitlist with fn eat_at_restaurant.  (rust-lang/book#3281)
- Ch. 2: less ambiguity about numbers (rust-lang/book#3895)
- Clarified first slices paragraph (rust-lang/book#3363)
- Inline all format arguments (rust-lang/book#3385)
- Use v1.58 captured ident formatting in examples (rust-lang/book#3048)
- Revert "ch18-03: Guarded match arm exhaustivness clarification" (rust-lang/book#3894)
- Ch. 18: further clarify about irrefutable patterns (rust-lang/book#3893)
- ch18-02: Minor corrections (rust-lang/book#3381)
- Make style of listings 9-7 and 9-8 consistent with 9-6 (rust-lang/book#3217)
- ch18-03: Guarded match arm exhaustivness clarification (rust-lang/book#3397)
- ch11-03: Unnecessary import removal (rust-lang/book#3284)
- Update ch20-01-single-threaded.md (rust-lang/book#3394)
- In Appendix D, adds hyperlink to Appendix E (rust-lang/book#3418)
- Chapter 13-03 fixed Iterator 'type' to 'trait' (rust-lang/book#3433)
- Fix the expected substring in ch11-01 (rust-lang/book#3534)
- Ch. 17: clarify 'in order to compile' (rust-lang/book#3892)
- Revert "Chapter 15-05: Fix incorrect interpretation of compiler error" (rust-lang/book#3891)
- Chapter 15-05: Fix incorrect interpretation of compiler error (rust-lang/book#3501)
- Remove direction to authenticate with `cargo login {API token}` (rust-lang/book#3506)
- Update syn dependencies in Chapter 19 to 2.0 (rust-lang/book#3888)
- Chapter 3: Clarify `return` vs. `break`. (rust-lang/book#3889)
- Fix "`Display` type" to "`Display` trait" in ch19-03 (rust-lang/book#3835)
- Update listings in ch 11-01 to reflect current output from cargo new (rust-lang/book#3533)
- Fix "`test` module" to "`tests` module" in ch11-03 (rust-lang/book#3579)
- Ch. 2: fix wording about `cargo update` (rust-lang/book#3882)
- Remove hebrew niqqud in 8-14 String::from example (rust-lang/book#3648)
- Ch. 16: fix a grammar issue (rust-lang/book#3881)
- Update MSVC instructions (rust-lang/book#3616)
- Replace RLS with rust-analyzer in ch00 (rust-lang/book#3546)
- Fix em dashes (rust-lang/book#3570)
- Revert rust-lang#3711 (rust-lang/book#3880)
- Procedure Macro: Update dependencies  (rust-lang/book#3631)
- Parity with rustup's help (rust-lang/book#3642)
- Fix confusing sentence (rust-lang/book#3877)
- Ch. 7: add a note about the need for `pub` in one more place (rust-lang/book#3879)

## rust-lang/edition-guide

2 commits in eb3eb80e106d03250c1fb7c5666b1c8c59672862..0c68e90acaae5a611f8f5098a3c2980de9845ab2
2024-04-16 21:23:55 UTC to 2024-04-15 16:05:32 UTC

- Document RustcEncodable/RustcDecodable (rust-lang/edition-guide#298)
- Flesh out detail behind disallowing refs to static mut (rust-lang/edition-guide#299)

## rust-lang/reference

5 commits in 55694913b1301cc809f9bf4a1ad1b3d6920efbd9..5854fcc286557ad3ab34d325073d11d8118096b6
2024-04-21 13:47:07 UTC to 2024-04-15 16:12:40 UTC

- Stabilize Wasm target features that are in phase 4 and 5 (rust-lang/reference#1420)
- Expand and clarify primitive alignment (rust-lang/reference#1493)
- Update clone reference to include closures (rust-lang/reference#1492)
- Document how `non_exhaustive` interacts with tuple and unit-like structs. (rust-lang/reference#1491)
- Fix link to RISC-V Zkt spec; it was pointing to Zkr (rust-lang/reference#1490)

## rust-lang/rustc-dev-guide

4 commits in b77a34bd46399687b4ce6a17198e9f316c988794..07425fed36b00e60341c5e29e28d37d40cbd4451
2024-04-13 15:16:44 UTC to 2024-04-08 19:00:54 UTC

- Add a note about checks with multiple revisions (rust-lang/rustc-dev-guide#1963)
- compiletest: clarify that headers must be one header per line (rust-lang/rustc-dev-guide#1962)
- chore: fix some typos in conments (rust-lang/rustc-dev-guide#1961)
- compiletest: specify which special env var and which particular CI job (rust-lang/rustc-dev-guide#1960)
rust-timer added a commit to rust-lang-ci/rust that referenced this pull request Apr 23, 2024
Rollup merge of rust-lang#124268 - rustbot:docs-update, r=ehuss

Update books

## rust-lang/book

41 commits in 3131aa4642c627a24f523c82566b94a7d920f68c..d207d894cc5e1d496ab99beeacd1a420e5d4d238
2024-04-19 19:48:19 UTC to 2024-04-08 19:34:07 UTC

- Ch. 2: intentionally use `{}` at first (rust-lang/book#3898)
- Inline fmt lints for `redirects/` (rust-lang/book#3897)
- ch12-03: `expect` is not used multitude times by this chapter (rust-lang/book#3287)
- Inline format args to `tools/src` (rust-lang/book#3896)
- Improve awkward phrasing around the kinds of closures (rust-lang/book#3290)
- Ch. 14: clarify workspace dependency reuse (rust-lang/book#3890)
- Edit on line no. 153. Replaced fn add_to_waitlist with fn eat_at_restaurant.  (rust-lang/book#3281)
- Ch. 2: less ambiguity about numbers (rust-lang/book#3895)
- Clarified first slices paragraph (rust-lang/book#3363)
- Inline all format arguments (rust-lang/book#3385)
- Use v1.58 captured ident formatting in examples (rust-lang/book#3048)
- Revert "ch18-03: Guarded match arm exhaustivness clarification" (rust-lang/book#3894)
- Ch. 18: further clarify about irrefutable patterns (rust-lang/book#3893)
- ch18-02: Minor corrections (rust-lang/book#3381)
- Make style of listings 9-7 and 9-8 consistent with 9-6 (rust-lang/book#3217)
- ch18-03: Guarded match arm exhaustivness clarification (rust-lang/book#3397)
- ch11-03: Unnecessary import removal (rust-lang/book#3284)
- Update ch20-01-single-threaded.md (rust-lang/book#3394)
- In Appendix D, adds hyperlink to Appendix E (rust-lang/book#3418)
- Chapter 13-03 fixed Iterator 'type' to 'trait' (rust-lang/book#3433)
- Fix the expected substring in ch11-01 (rust-lang/book#3534)
- Ch. 17: clarify 'in order to compile' (rust-lang/book#3892)
- Revert "Chapter 15-05: Fix incorrect interpretation of compiler error" (rust-lang/book#3891)
- Chapter 15-05: Fix incorrect interpretation of compiler error (rust-lang/book#3501)
- Remove direction to authenticate with `cargo login {API token}` (rust-lang/book#3506)
- Update syn dependencies in Chapter 19 to 2.0 (rust-lang/book#3888)
- Chapter 3: Clarify `return` vs. `break`. (rust-lang/book#3889)
- Fix "`Display` type" to "`Display` trait" in ch19-03 (rust-lang/book#3835)
- Update listings in ch 11-01 to reflect current output from cargo new (rust-lang/book#3533)
- Fix "`test` module" to "`tests` module" in ch11-03 (rust-lang/book#3579)
- Ch. 2: fix wording about `cargo update` (rust-lang/book#3882)
- Remove hebrew niqqud in 8-14 String::from example (rust-lang/book#3648)
- Ch. 16: fix a grammar issue (rust-lang/book#3881)
- Update MSVC instructions (rust-lang/book#3616)
- Replace RLS with rust-analyzer in ch00 (rust-lang/book#3546)
- Fix em dashes (rust-lang/book#3570)
- Revert rust-lang#3711 (rust-lang/book#3880)
- Procedure Macro: Update dependencies  (rust-lang/book#3631)
- Parity with rustup's help (rust-lang/book#3642)
- Fix confusing sentence (rust-lang/book#3877)
- Ch. 7: add a note about the need for `pub` in one more place (rust-lang/book#3879)

## rust-lang/edition-guide

2 commits in eb3eb80e106d03250c1fb7c5666b1c8c59672862..0c68e90acaae5a611f8f5098a3c2980de9845ab2
2024-04-16 21:23:55 UTC to 2024-04-15 16:05:32 UTC

- Document RustcEncodable/RustcDecodable (rust-lang/edition-guide#298)
- Flesh out detail behind disallowing refs to static mut (rust-lang/edition-guide#299)

## rust-lang/reference

5 commits in 55694913b1301cc809f9bf4a1ad1b3d6920efbd9..5854fcc286557ad3ab34d325073d11d8118096b6
2024-04-21 13:47:07 UTC to 2024-04-15 16:12:40 UTC

- Stabilize Wasm target features that are in phase 4 and 5 (rust-lang/reference#1420)
- Expand and clarify primitive alignment (rust-lang/reference#1493)
- Update clone reference to include closures (rust-lang/reference#1492)
- Document how `non_exhaustive` interacts with tuple and unit-like structs. (rust-lang/reference#1491)
- Fix link to RISC-V Zkt spec; it was pointing to Zkr (rust-lang/reference#1490)

## rust-lang/rustc-dev-guide

4 commits in b77a34bd46399687b4ce6a17198e9f316c988794..07425fed36b00e60341c5e29e28d37d40cbd4451
2024-04-13 15:16:44 UTC to 2024-04-08 19:00:54 UTC

- Add a note about checks with multiple revisions (rust-lang/rustc-dev-guide#1963)
- compiletest: clarify that headers must be one header per line (rust-lang/rustc-dev-guide#1962)
- chore: fix some typos in conments (rust-lang/rustc-dev-guide#1961)
- compiletest: specify which special env var and which particular CI job (rust-lang/rustc-dev-guide#1960)
github-actions bot pushed a commit to rust-lang/miri that referenced this pull request Apr 23, 2024
Update books

## rust-lang/book

41 commits in 3131aa4642c627a24f523c82566b94a7d920f68c..d207d894cc5e1d496ab99beeacd1a420e5d4d238
2024-04-19 19:48:19 UTC to 2024-04-08 19:34:07 UTC

- Ch. 2: intentionally use `{}` at first (rust-lang/book#3898)
- Inline fmt lints for `redirects/` (rust-lang/book#3897)
- ch12-03: `expect` is not used multitude times by this chapter (rust-lang/book#3287)
- Inline format args to `tools/src` (rust-lang/book#3896)
- Improve awkward phrasing around the kinds of closures (rust-lang/book#3290)
- Ch. 14: clarify workspace dependency reuse (rust-lang/book#3890)
- Edit on line no. 153. Replaced fn add_to_waitlist with fn eat_at_restaurant.  (rust-lang/book#3281)
- Ch. 2: less ambiguity about numbers (rust-lang/book#3895)
- Clarified first slices paragraph (rust-lang/book#3363)
- Inline all format arguments (rust-lang/book#3385)
- Use v1.58 captured ident formatting in examples (rust-lang/book#3048)
- Revert "ch18-03: Guarded match arm exhaustivness clarification" (rust-lang/book#3894)
- Ch. 18: further clarify about irrefutable patterns (rust-lang/book#3893)
- ch18-02: Minor corrections (rust-lang/book#3381)
- Make style of listings 9-7 and 9-8 consistent with 9-6 (rust-lang/book#3217)
- ch18-03: Guarded match arm exhaustivness clarification (rust-lang/book#3397)
- ch11-03: Unnecessary import removal (rust-lang/book#3284)
- Update ch20-01-single-threaded.md (rust-lang/book#3394)
- In Appendix D, adds hyperlink to Appendix E (rust-lang/book#3418)
- Chapter 13-03 fixed Iterator 'type' to 'trait' (rust-lang/book#3433)
- Fix the expected substring in ch11-01 (rust-lang/book#3534)
- Ch. 17: clarify 'in order to compile' (rust-lang/book#3892)
- Revert "Chapter 15-05: Fix incorrect interpretation of compiler error" (rust-lang/book#3891)
- Chapter 15-05: Fix incorrect interpretation of compiler error (rust-lang/book#3501)
- Remove direction to authenticate with `cargo login {API token}` (rust-lang/book#3506)
- Update syn dependencies in Chapter 19 to 2.0 (rust-lang/book#3888)
- Chapter 3: Clarify `return` vs. `break`. (rust-lang/book#3889)
- Fix "`Display` type" to "`Display` trait" in ch19-03 (rust-lang/book#3835)
- Update listings in ch 11-01 to reflect current output from cargo new (rust-lang/book#3533)
- Fix "`test` module" to "`tests` module" in ch11-03 (rust-lang/book#3579)
- Ch. 2: fix wording about `cargo update` (rust-lang/book#3882)
- Remove hebrew niqqud in 8-14 String::from example (rust-lang/book#3648)
- Ch. 16: fix a grammar issue (rust-lang/book#3881)
- Update MSVC instructions (rust-lang/book#3616)
- Replace RLS with rust-analyzer in ch00 (rust-lang/book#3546)
- Fix em dashes (rust-lang/book#3570)
- Revert #3711 (rust-lang/book#3880)
- Procedure Macro: Update dependencies  (rust-lang/book#3631)
- Parity with rustup's help (rust-lang/book#3642)
- Fix confusing sentence (rust-lang/book#3877)
- Ch. 7: add a note about the need for `pub` in one more place (rust-lang/book#3879)

## rust-lang/edition-guide

2 commits in eb3eb80e106d03250c1fb7c5666b1c8c59672862..0c68e90acaae5a611f8f5098a3c2980de9845ab2
2024-04-16 21:23:55 UTC to 2024-04-15 16:05:32 UTC

- Document RustcEncodable/RustcDecodable (rust-lang/edition-guide#298)
- Flesh out detail behind disallowing refs to static mut (rust-lang/edition-guide#299)

## rust-lang/reference

5 commits in 55694913b1301cc809f9bf4a1ad1b3d6920efbd9..5854fcc286557ad3ab34d325073d11d8118096b6
2024-04-21 13:47:07 UTC to 2024-04-15 16:12:40 UTC

- Stabilize Wasm target features that are in phase 4 and 5 (rust-lang/reference#1420)
- Expand and clarify primitive alignment (rust-lang/reference#1493)
- Update clone reference to include closures (rust-lang/reference#1492)
- Document how `non_exhaustive` interacts with tuple and unit-like structs. (rust-lang/reference#1491)
- Fix link to RISC-V Zkt spec; it was pointing to Zkr (rust-lang/reference#1490)

## rust-lang/rustc-dev-guide

4 commits in b77a34bd46399687b4ce6a17198e9f316c988794..07425fed36b00e60341c5e29e28d37d40cbd4451
2024-04-13 15:16:44 UTC to 2024-04-08 19:00:54 UTC

- Add a note about checks with multiple revisions (rust-lang/rustc-dev-guide#1963)
- compiletest: clarify that headers must be one header per line (rust-lang/rustc-dev-guide#1962)
- chore: fix some typos in conments (rust-lang/rustc-dev-guide#1961)
- compiletest: specify which special env var and which particular CI job (rust-lang/rustc-dev-guide#1960)
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3 participants