Rollup merge of #112942 - joshtriplett:style-guide-tweaks, r=compiler-errors

style-guide: Organizational and editing tweaks (no semantic changes)

I'd recommend reviewing this PR commit-by-commit; each commit is self-contained
and should be easy to review at a glance.

- style-guide: Move text about block vs visual indent to indentation section
- style-guide: Move and expand text about trailing commas
- style-guide: s/right-ward/rightward/
- style-guide: Consistently refer to rustfmt as `rustfmt`
- style-guide: Remove inaccurate statement about rustfmt
- style-guide: Define (and capitalize) "ASCIIbetically"
- style-guide: Update cargo.md for authors being optional and not recommended
- style-guide: Avoid normative recommendations for formatting tool configurability
- style-guide: Clarify advice on names matching keywords
- style-guide: Reword an awkwardly phrased recommendation (and fix a typo)
- style-guide: Rephrase a confusingly ordered, ambiguous sentence (and fix a typo)
- style-guide: Avoid hyphenating "semicolon"
- style-guide: Make link text in SUMMARY.md match the headings in the linked pages
- style-guide: Define what an item is
- style-guide: Avoid referring to the style team in the past tense

Author: matthiaskrgr

Diff for: src/doc/style-guide/src/README.md

@@ -16,8 +16,8 @@ Rust code has similar formatting, less mental effort is required to comprehend a
 new project, lowering the barrier to entry for new developers.
 
 Thus, there are productivity benefits to using a formatting tool (such as
-rustfmt), and even larger benefits by using a community-consistent formatting,
-typically by using a formatting tool's default settings.
+`rustfmt`), and even larger benefits by using a community-consistent
+formatting, typically by using a formatting tool's default settings.
 
 
 ## Formatting conventions
@@ -28,8 +28,47 @@ typically by using a formatting tool's default settings.
 * Each level of indentation must be four spaces (that is, all indentation
   outside of string literals and comments must be a multiple of four).
 * The maximum width for a line is 100 characters.
-* A tool should be configurable for all three of these variables.
+* A tool may choose to make some of these configurable.
 
+#### Block indent
+
+Prefer block indent over visual indent:
+
+```rust
+// Block indent
+a_function_call(
+    foo,
+    bar,
+);
+
+// Visual indent
+a_function_call(foo,
+                bar);
+```
+
+This makes for smaller diffs (e.g., if `a_function_call` is renamed in the above
+example) and less rightward drift.
+
+### Trailing commas
+
+Lists should have a trailing comma when followed by a newline:
+
+```rust
+function_call(
+    argument,
+    another_argument,
+);
+
+let array = [
+    element,
+    another_element,
+    yet_another_element,
+];
+```
+
+This makes moving code (e.g., by copy and paste) easier, and makes diffs
+smaller, as appending or removing items does not require modifying another line
+to add or remove a comma.
 
 ### Blank lines
 
@@ -48,11 +87,7 @@ fn bar() {}
 fn baz() {}
 ```
 
-Formatting tools should make the bounds on blank lines configurable: there
-should be separate minimum and maximum numbers of newlines between both
-statements and (top-level) items (i.e., four options). As described above, the
-defaults for both statements and items should be minimum: 1, maximum: 2.
-
+Formatting tools may wish to make the bounds on blank lines configurable.
 
 ### [Module-level items](items.md)
 ### [Statements](statements.md)

Diff for: src/doc/style-guide/src/SUMMARY.md

@@ -2,10 +2,10 @@
 
 [Introduction](README.md)
 
-- [Module-level items](items.md)
+- [Items](items.md)
 - [Statements](statements.md)
 - [Expressions](expressions.md)
-- [Types](types.md)
-- [Non-formatting conventions](advice.md)
+- [Types and Bounds](types.md)
+- [Other style advice](advice.md)
 - [`Cargo.toml` conventions](cargo.md)
-- [Principles used for deciding these guidelines](principles.md)
+- [Guiding principles and rationale](principles.md)

Diff for: src/doc/style-guide/src/advice.md

@@ -25,9 +25,9 @@ if y {
  * Local variables shall be `snake_case`,
  * Macro names shall be `snake_case`,
  * Constants (`const`s and immutable `static`s) shall be `SCREAMING_SNAKE_CASE`.
- * When a name is forbidden because it is a reserved word (e.g., `crate`), use a
-   trailing underscore to make the name legal (e.g., `crate_`), or use raw
-   identifiers if possible.
+ * When a name is forbidden because it is a reserved word (such as `crate`),
+   either use a raw identifier (`r#crate`) or use a trailing underscore
+   (`crate_`). Don't misspell the word (`krate`).
 
 ### Modules
 

Diff for: src/doc/style-guide/src/cargo.md

@@ -1,4 +1,4 @@
-# Cargo.toml conventions
+# `Cargo.toml` conventions
 
 ## Formatting conventions
 
@@ -25,16 +25,17 @@ not indent any key names; start all key names at the start of a line.
 Use multi-line strings (rather than newline escape sequences) for any string
 values that include multiple lines, such as the crate description.
 
-For array values, such as a list of authors, put the entire list on the same
+For array values, such as a list of features, put the entire list on the same
 line as the key, if it fits. Otherwise, use block indentation: put a newline
 after the opening square bracket, indent each item by one indentation level,
 put a comma after each item (including the last), and put the closing square
 bracket at the start of a line by itself after the last item.
 
 ```rust
-authors = [
-    "A Uthor <[email protected]>",
-    "Another Author <[email protected]>",
+some_feature = [
+    "another_feature",
+    "yet_another_feature",
+    "some_dependency?/some_feature",
 ]
 ```
 
@@ -54,11 +55,11 @@ version = "4.5.6"
 
 ## Metadata conventions
 
-The authors list should consist of strings that each contain an author name
-followed by an email address in angle brackets: `Full Name <email@address>`.
-It should not contain bare email addresses, or names without email addresses.
-(The authors list may also include a mailing list address without an associated
-name.)
+The authors list, if present, should consist of strings that each contain an
+author name followed by an email address in angle brackets: `Full Name
+<email@address>`. It should not contain bare email addresses, or names without
+email addresses. (The authors list may also include a mailing list address
+without an associated name.)
 
 The license field must contain a valid [SPDX
 expression](https://spdx.org/spdx-specification-21-web-version#h.jxpfx0ykyb60),

Diff for: src/doc/style-guide/src/items.md

@@ -1,5 +1,10 @@
 ## Items
 
+Items consist of the set of things permitted at the top level of a module.
+However, Rust also allows some items to appear within some other types of
+items, such as within a function. The same formatting conventions apply whether
+an item appears at module level or within another item.
+
 `extern crate` statements must be first in a file. They must be ordered
 alphabetically.
 
@@ -15,8 +20,8 @@ Tools should make the above ordering optional.
 
 ### Function definitions
 
-In Rust, one finds functions by searching for `fn [function-name]`; It's
-important that you style your code so that it's very searchable in this way.
+In Rust, people often find functions by searching for `fn [function-name]`, so
+the formatting of function definitions shold enable this.
 
 The proper ordering and spacing is:
 
@@ -63,8 +68,9 @@ let y = (11, 22, 33);
 
 In the declaration, put each variant on its own line, block indented.
 
-Format each variant accordingly as either a struct, tuple struct, or identifier,
-which doesn't require special formatting (but without the `struct` keyword.
+Format each variant accordingly as either a struct (but without the `struct`
+keyword), a tuple struct, or an identifier (which doesn't require special
+formatting):
 
 ```rust
 enum FooBar {
@@ -139,7 +145,7 @@ union Foo {
 
 Put the whole struct on one line if possible. Types in the parentheses should be
 separated by a comma and space with no trailing comma. No spaces around the
-parentheses or semi-colon:
+parentheses or semicolon:
 
 ```rust
 pub struct Foo(String, u8);
@@ -230,7 +236,7 @@ impl Bar
 
 `extern crate foo;`
 
-Use spaces around keywords, no spaces around the semi-colon.
+Use spaces around keywords, no spaces around the semicolon.
 
 
 ### Modules
@@ -245,7 +251,7 @@ mod foo;
 ```
 
 Use spaces around keywords and before the opening brace, no spaces around the
-semi-colon.
+semicolon.
 
 ### macro\_rules!
 
@@ -478,8 +484,8 @@ foo::{
 A *group* of imports is a set of imports on the same or sequential lines. One or
 more blank lines or other items (e.g., a function) separate groups of imports.
 
-Within a group of imports, imports must be sorted ascii-betically. Groups of
-imports must not be merged or re-ordered.
+Within a group of imports, imports must be sorted ASCIIbetically (uppercase
+before lowercase). Groups of imports must not be merged or re-ordered.
 
 
 E.g., input:
@@ -505,13 +511,9 @@ use b;
 Because of `macro_use`, attributes must also start a new group and prevent
 re-ordering.
 
-Note that tools which only have access to syntax (such as Rustfmt) cannot tell
-which imports are from an external crate or the std lib, etc.
-
-
 #### Ordering list import
 
-Names in a list import must be sorted ascii-betically, but with `self` and
+Names in a list import must be sorted ASCIIbetically, but with `self` and
 `super` first, and groups and glob imports last. This applies recursively. For
 example, `a::*` comes before `b::a` but `a::b` comes before `a::*`. E.g.,
 `use foo::bar::{a, b::c, b::d, b::d::{x, y, z}, b::{self, r, s}};`.

Diff for: src/doc/style-guide/src/principles.md

@@ -1,7 +1,7 @@
 # Guiding principles and rationale
 
-When deciding on style guidelines, the style team tried to be guided by the
-following principles (in rough priority order):
+When deciding on style guidelines, the style team follows these guiding
+principles (in rough priority order):
 
 * readability
     - scan-ability
@@ -19,35 +19,11 @@ following principles (in rough priority order):
 * specifics
     - compatibility with version control practices - preserving diffs,
       merge-friendliness, etc.
-    - preventing right-ward drift
+    - preventing rightward drift
     - minimising vertical space
 
 * application
     - ease of manual application
-    - ease of implementation (in Rustfmt, and in other tools/editors/code generators)
+    - ease of implementation (in `rustfmt`, and in other tools/editors/code generators)
     - internal consistency
     - simplicity of formatting rules
-
-
-## Overarching guidelines
-
-Prefer block indent over visual indent. E.g.,
-
-```rust
-// Block indent
-a_function_call(
-    foo,
-    bar,
-);
-
-// Visual indent
-a_function_call(foo,
-                bar);
-```
-
-This makes for smaller diffs (e.g., if `a_function_call` is renamed in the above
-example) and less rightward drift.
-
-Lists should have a trailing comma when followed by a newline, see the block
-indent example above. This choice makes moving code (e.g., by copy and paste)
-easier and makes smaller diffs.

Diff for: src/doc/style-guide/src/statements.md

@@ -1,7 +1,9 @@
+## Statements
+
 ### Let statements
 
 There should be spaces after the `:` and on both sides of the `=` (if they are
-present). No space before the semi-colon.
+present). No space before the semicolon.
 
 ```rust
 // A comment.
@@ -194,7 +196,7 @@ used to determine whether a let-else statement is *short*.
 ### Macros in statement position
 
 A macro use in statement position should use parentheses or square brackets as
-delimiters and should be terminated with a semi-colon. There should be no spaces
+delimiters and should be terminated with a semicolon. There should be no spaces
 between the name, `!`, the delimiters, or the `;`.
 
 ```rust
@@ -205,13 +207,13 @@ a_macro!(...);
 
 ### Expressions in statement position
 
-There should be no space between the expression and the semi-colon.
+There should be no space between the expression and the semicolon.
 
 ```
 <expr>;
 ```
 
-All expressions in statement position should be terminated with a semi-colon,
+All expressions in statement position should be terminated with a semicolon,
 unless they end with a block or are used as the value for a block.
 
 E.g.,
@@ -229,7 +231,7 @@ loop {
 }
 ```
 
-Use a semi-colon where an expression has void type, even if it could be
+Use a semicolon where an expression has void type, even if it could be
 propagated. E.g.,
 
 ```rust