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Fix the grammar of function pointer types #2240

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Fix the grammar of function pointer types #2240

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b6bc1cd
Fix grammar and notes pertaining to the `safe` and `unsafe` modifiers
fmease Apr 24, 2026
7fdaa3f
Fix grammar pertaining to C variadics in function pointer types
fmease Apr 24, 2026
957daaf
Fix grammar to accept self params in function pointer types
fmease Apr 24, 2026
01e9ac6
Fix the grammar of parameter patterns in function pointer types
fmease Apr 24, 2026
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10 changes: 5 additions & 5 deletions src/items/functions.md
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Expand Up @@ -9,9 +9,9 @@ Function ->
FunctionReturnType? WhereClause?
( BlockExpression | `;` )

FunctionQualifiers -> `const`? `async`?[^async-edition] ItemSafety?[^extern-qualifiers] (`extern` Abi?)?
FunctionQualifiers -> `const`? `async`?[^async-edition] Safety?[^extern-qualifiers] (`extern` Abi?)?

ItemSafety -> `safe`[^extern-safe] | `unsafe`
Safety -> `safe`[^safe-semantics] | `unsafe`

Abi -> STRING_LITERAL | RAW_STRING_LITERAL

Expand All @@ -34,12 +34,12 @@ FunctionReturnType -> `->` Type

[^async-edition]: The `async` qualifier is not allowed in the 2015 edition.

[^extern-safe]: The `safe` function qualifier is only allowed semantically within `extern` blocks.

[^extern-qualifiers]: *Relevant to editions earlier than Rust 2024*: Within `extern` blocks, the `safe` or `unsafe` function qualifier is only allowed when the `extern` is qualified as `unsafe`.
[^extern-qualifiers]: The `safe` or `unsafe` qualifiers are only allowed semantically within `extern` blocks. *Relevant to editions earlier than Rust 2024*: More specifically within `extern` blocks that are qualified as `unsafe`.

[^fn-param-2015]: Function parameters with only a type are only allowed in an associated function of a [trait item] in the 2015 edition.

[^safe-semantics]: The `safe` qualifier is only allowed semantically on functions within `extern` blocks.

r[items.fn.intro]
A _function_ consists of a [block] (that's the _body_ of the function), along with a name, a set of parameters, and an output type. Other than a name, all these are optional.

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4 changes: 2 additions & 2 deletions src/items/static-items.md
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Expand Up @@ -4,10 +4,10 @@ r[items.static]
r[items.static.syntax]
```grammar,items
StaticItem ->
ItemSafety?[^extern-safety] `static` `mut`? IDENTIFIER `:` Type ( `=` Expression )? `;`
Safety?[^extern-qualifiers] `static` `mut`? IDENTIFIER `:` Type ( `=` Expression )? `;`
```

[^extern-safety]: The `safe` and `unsafe` function qualifiers are only allowed semantically within `extern` blocks.
[^extern-qualifiers]: The `safe` and `unsafe` qualifiers are only allowed semantically within `extern` blocks. *Relevant to editions earlier than Rust 2024*: More specifically within `extern` blocks that are qualified as `unsafe`.

r[items.static.intro]
A *static item* is similar to a [constant], except that it represents an allocation in the program that is initialized with the initializer expression. All references and raw pointers to the static refer to the same allocation.
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16 changes: 7 additions & 9 deletions src/types/function-pointer.md
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Expand Up @@ -5,23 +5,21 @@ r[type.fn-pointer.syntax]
```grammar,types
BareFunctionType ->
ForLifetimes? FunctionTypeQualifiers `fn`
`(` FunctionParametersMaybeNamedVariadic? `)` BareFunctionReturnType?
`(` MaybeNamedFunctionParameters? `)` BareFunctionReturnType?

FunctionTypeQualifiers -> `unsafe`? (`extern` Abi?)?
FunctionTypeQualifiers -> Safety? (`extern` Abi?)?

BareFunctionReturnType -> `->` TypeNoBounds

FunctionParametersMaybeNamedVariadic ->
MaybeNamedFunctionParameters | MaybeNamedFunctionParametersVariadic

MaybeNamedFunctionParameters ->
MaybeNamedParam ( `,` MaybeNamedParam )* `,`?
SelfParam `,`?
| (SelfParam `,`)? MaybeNamedParam ( `,` MaybeNamedParam )* `,`?

MaybeNamedParam ->
OuterAttribute* ( ( IDENTIFIER | `_` ) `:` )? Type
OuterAttribute* ( MaybeNamedPattern `:` )? ( Type | `...` )

MaybeNamedFunctionParametersVariadic ->
( MaybeNamedParam `,` )* MaybeNamedParam `,` OuterAttribute* `...`
MaybeNamedPattern ->
`mut`? IDENTIFIER | ( `&` | `&&` )? ( `_` | `false` | `true` | IDENTIFIER )
```

r[type.fn-pointer.intro]
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