Grammar: Functions, methods, impl, traits, extern.

src/items/associated-items.md

@@ -79,17 +79,31 @@ let _: f64 = f64::from_i32(42);
 
 ### Methods
 
+> _Method_ :\
+> &nbsp;&nbsp; [_FunctionFront_] `fn` [IDENTIFIER]&nbsp;[_Generics_]<sup>?</sup>\
+> &nbsp;&nbsp; &nbsp;&nbsp; `(` _SelfParam_ (`,` [_FunctionParam_])<sup>\*</sup> `,`<sup>?</sup> `)`\
+> &nbsp;&nbsp; &nbsp;&nbsp; [_FunctionReturnType_]<sup>?</sup> [_WhereClause_]<sup>?</sup>\
+> &nbsp;&nbsp; &nbsp;&nbsp; [_BlockExpression_]
+>
+> _SelfParam_ :\
+> &nbsp;&nbsp; &nbsp;&nbsp; (`&` | `&` [_Lifetime_])<sup>?</sup> `mut`<sup>?</sup> `self`\
+> &nbsp;&nbsp; | `mut`<sup>?</sup> `self` (`:` [_Type_])<sup>?</sup>
+
 Associated functions whose first parameter is named `self` are called *methods*
 and may be invoked using the [method call operator], for example, `x.foo()`, as
 well as the usual function call notation.
 
-The `self` parameter must have one of the following types. As a result, the
-following shorthands may be used to declare `self`:
+If the type of the `self` parameter is specified, it is limited to the type
+being implemented (or `Self`), or a reference or mutable reference to the
+type, or a boxed value of the type being implemented (such as `Box<Self>`).
+Shorthand syntax can be used without specifying a type, which have the
+following equivalents:
 
-* `self` -> `self: Self`
-* `&'lifetime self` -> `self: &'lifetime Self`
-* `&'lifetime mut self` -> `self: &'lifetime mut Self`
-* `self : Box<Self>` (no shorthand)
+Shorthand             | Equivalent
+----------------------|-----------
+`self`                | `self: Self`
+`&'lifetime self`     | `self: &'lifetime Self`
+`&'lifetime mut self` | `self: &'lifetime mut Self`
 
 > Note: Lifetimes can be and usually are elided with this shorthand.
 
@@ -272,6 +286,14 @@ fn main() {
 }
 ```
 
+[_BlockExpression_]: expressions/block-expr.html
+[_FunctionFront_]: items/functions.html
+[_FunctionParam_]: items/functions.html
+[_FunctionReturnType_]: items/functions.html
+[_Generics_]: items/generics.html
+[_Lifetime_]: trait-bounds.html
+[_Type_]: types.html
+[_WhereClause_]: items/generics.html#where-clauses
 [trait]: items/traits.html
 [traits]: items/traits.html
 [type aliases]: items/type-aliases.html

src/items/external-blocks.md

@@ -1,12 +1,42 @@
 # External blocks
 
+> **<sup>Syntax</sup>**\
+> _ExternBlock_ :\
+> &nbsp;&nbsp; `extern` [_Abi_]<sup>?</sup> `{`\
+> &nbsp;&nbsp; &nbsp;&nbsp; [_InnerAttribute_]<sup>\*</sup>\
+> &nbsp;&nbsp; &nbsp;&nbsp; _ExternalItem_<sup>\*</sup>\
+> &nbsp;&nbsp; `}`
+>
+> _ExternalItem_ :\
+> &nbsp;&nbsp; [_OuterAttribute_]<sup>\*</sup>\
+> &nbsp;&nbsp; [_Visibility_]<sup>?</sup>\
+> &nbsp;&nbsp; ( _ExternalStaticItem_ | _ExternalFunctionItem_ )
+>
+> _ExternalStaticItem_ :\
+> &nbsp;&nbsp; `static` `mut`<sup>?</sup> [IDENTIFIER] `:` [_Type_] `;`
+>
+> _ExternalFunctionItem_ :\
+> &nbsp;&nbsp; `fn` [IDENTIFIER]&nbsp;[_Generics_]<sup>?</sup>\
+> &nbsp;&nbsp; `(` _NamedFunctionParameters_<sup>?</sup> | _NamedFunctionParametersWithVariadics_ ) `)`\
+> &nbsp;&nbsp; [_FunctionReturnType_]<sup>?</sup> [_WhereClause_]<sup>?</sup> `;`
+>
+> _NamedFunctionParameters_ :\
+> &nbsp;&nbsp; _NamedFunctionParam_ ( `,` _NamedFunctionParam_ )<sup>\*</sup> `,`<sup>?</sup>
+>
+> _NamedFunctionParam_ :\
+> &nbsp;&nbsp; ( [IDENTIFIER] | `_` ) `:` [_Type_]
+>
+> _NamedFunctionParametersWithVariadics_ :\
+> &nbsp;&nbsp; ( _NamedFunctionParam_ `,` )<sup>\*</sup> _NamedFunctionParam_ `,` `...`
+
 External blocks form the basis for Rust's foreign function interface.
 Declarations in an external block describe symbols in external, non-Rust
 libraries.
 
 Functions within external blocks are declared in the same way as other Rust
 functions, with the exception that they may not have a body and are instead
-terminated by a semicolon.
+terminated by a semicolon. Patterns are not allowed in parameters, only
+[IDENTIFIER] or `_` may be used.
 
 Functions within external blocks may be called by Rust code, just like
 functions defined in Rust. The Rust compiler automatically translates between
@@ -23,8 +53,6 @@ extern {
 
 A number of [attributes] control the behavior of external blocks.
 
-[attributes]: attributes.html#ffi-attributes
-
 By default external blocks assume that the library they are calling uses the
 standard C ABI on the specific platform. Other ABIs may be specified using an
 `abi` string, as shown here:
@@ -81,3 +109,16 @@ It is valid to add the `link` attribute on an empty extern block. You can use
 this to satisfy the linking requirements of extern blocks elsewhere in your
 code (including upstream crates) instead of adding the attribute to each extern
 block.
+
+[IDENTIFIER]: identifiers.html
+[_Abi_]: items/functions.html
+[_FunctionParam_]: items/functions.html
+[_FunctionParameters_]: items/functions.html
+[_FunctionReturnType_]: items/functions.html
+[_Generics_]: items/generics.html
+[_InnerAttribute_]: attributes.html
+[_OuterAttribute_]: attributes.html
+[_Type_]: types.html
+[_Visibility_]: visibility-and-privacy.html
+[_WhereClause_]: items/generics.html#where-clauses
+[attributes]: attributes.html#ffi-attributes

src/items/functions.md

@@ -1,5 +1,27 @@
 # Functions
 
+> **<sup>Syntax</sup>**\
+> _Function_ :\
+> &nbsp;&nbsp; _FunctionFront_ `fn` [IDENTIFIER]&nbsp;[_Generics_]<sup>?</sup>\
+> &nbsp;&nbsp; &nbsp;&nbsp; `(` _FunctionParameters_<sup>?</sup> `)`\
+> &nbsp;&nbsp; &nbsp;&nbsp; _FunctionReturnType_<sup>?</sup> [_WhereClause_]<sup>?</sup>\
+> &nbsp;&nbsp; &nbsp;&nbsp; [_BlockExpression_]
+>
+> _FunctionFront_ :\
+> &nbsp;&nbsp; `unsafe`<sup>?</sup> (`extern` _Abi_<sup>?</sup>)<sup>?</sup>
+>
+> _Abi_ :\
+> &nbsp;&nbsp; [STRING_LITERAL] | [RAW_STRING_LITERAL]
+>
+> _FunctionParameters_ :\
+> &nbsp;&nbsp; _FunctionParam_ (`,` _FunctionParam_)<sup>\*</sup> `,`<sup>?</sup>
+>
+> _FunctionParam_ :\
+> &nbsp;&nbsp; [_Pattern_] `:` [_Type_]
+>
+> _FunctionReturnType_ :\
+> &nbsp;&nbsp; `->` [_Type_]
+
 A _function_ consists of a [block], along with a name and a set of parameters.
 Other than a name, all these are optional. Functions are declared with the
 keyword `fn`. Functions may declare a set of *input* [*variables*][variables]
@@ -138,6 +160,16 @@ attributes], [`must_use`], [the procedural macro attributes], [the testing
 attributes], and [the optimization hint
 attributes].
 
+[IDENTIFIER]: identifiers.html
+[RAW_STRING_LITERAL]: tokens.html#raw-string-literals
+[STRING_LITERAL]: tokens.html#string-literals
+[_BlockExpression_]: expressions/block-expr.html
+[_Generics_]: items/generics.html
+[_InnerAttribute_]: attributes.html
+[_Pattern_]: patterns.html
+[_Statement_]: statements.html
+[_Type_]: types.html
+[_WhereClause_]: items/generics.html#where-clauses
 [external blocks]: items/external-blocks.html
 [path]: paths.html
 [block]: expressions/block-expr.html

src/items/implementations.md

@@ -1,5 +1,34 @@
 # Implementations
 
+> **<sup>Syntax</sup>**\
+> _Implementation_ :\
+> &nbsp;&nbsp; _InherentImpl_ | _TraitImpl_
+>
+> _InherentImpl_ :\
+> &nbsp;&nbsp; `impl` [_Generics_]&nbsp;[_Type_]&nbsp;[_WhereClause_]<sup>?</sup> `{`\
+> &nbsp;&nbsp; &nbsp;&nbsp; [_InnerAttribute_]<sup>\*</sup>\
+> &nbsp;&nbsp; &nbsp;&nbsp; _InherentImplItem_<sup>\*</sup>\
+> &nbsp;&nbsp; `}`
+>
+> _InherentImplItem_ :\
+> &nbsp;&nbsp; [_OuterAttribute_]<sup>\*</sup>\
+> &nbsp;&nbsp; [_Visibility_]<sup>?</sup>\
+> &nbsp;&nbsp; ( [_ConstantItem_] | [_Function_] | [_Method_] )
+>
+> _TraitImpl_ :\
+> &nbsp;&nbsp; `unsafe`<sup>?</sup> `impl` [_Generics_] `!`<sup>?</sup>
+>              [_TypePath_] `for` [_Type_]\
+> &nbsp;&nbsp; [_WhereClause_]<sup>?</sup>\
+> &nbsp;&nbsp; `{`\
+> &nbsp;&nbsp; &nbsp;&nbsp; [_InnerAttribute_]<sup>\*</sup>\
+> &nbsp;&nbsp; &nbsp;&nbsp; _TraitImplItem_<sup>\*</sup>\
+> &nbsp;&nbsp; `}`
+>
+> _TraitImplItem_ :\
+> &nbsp;&nbsp; [_OuterAttribute_]<sup>\*</sup>\
+> &nbsp;&nbsp; [_Visibility_]<sup>?</sup>\
+> &nbsp;&nbsp; ( [_TypeAlias_] | [_ConstantItem_] | [_Function_] | [_Method_] )
+
 An _implementation_ is an item that associates items with an _implementing type_.
 Implementations are defined with the keyword `impl` and contain functions
 that belong to an instance of the type that is being implemented or to the
@@ -59,6 +88,9 @@ The path to the associated items is `<` followed by a path to the implementing
 type followed by `as` followed by a path to the trait followed by `>` as a path
 component followed by the associated item's path component.
 
+[Unsafe traits] require the trait implementation to begin with the `unsafe`
+keyword.
+
 ```rust
 # #[derive(Copy, Clone)]
 # struct Point {x: f64, y: f64};
@@ -143,9 +175,22 @@ attributes must come before any associated items. That attributes that have
 meaning here are [`cfg`], [`deprecated`], [`doc`], and [the lint check
 attributes].
 
+[IDENTIFIER]: identifiers.html
+[_ConstantItem_]: items/constant-items.html
+[_Function_]: items/functions.html
+[_Generics_]: items/generics.html
+[_InnerAttribute_]: attributes.html
+[_Method_]: items/associated-items.html#methods
+[_OuterAttribute_]: attributes.html
+[_TypeAlias_]: items/type-aliases.html
+[_TypePath_]: paths.html#paths-in-types
+[_Type_]: types.html
+[_Visibility_]: visibility-and-privacy.html
+[_WhereClause_]: items/generics.html#where-clauses
 [trait]: items/traits.html
 [attributes]: attributes.html
 [`cfg`]: conditional-compilation.html
 [`deprecated`]: attributes.html#deprecation
 [`doc`]: attributes.html#documentation
 [the lint check attributes]: attributes.html#lint-check-attributes
+[Unsafe traits]: items/traits.html#unsafe-traits

src/items/traits.md

@@ -1,5 +1,44 @@
 # Traits
 
+> **<sup>Syntax</sup>**\
+> _Trait_ :\
+> &nbsp;&nbsp; `unsafe`<sup>?</sup> `trait` [IDENTIFIER]&nbsp;
+>              [_Generics_]<sup>?</sup>
+>              [_WhereClause_]<sup>?</sup> `{`\
+> &nbsp;&nbsp;&nbsp;&nbsp; _TraitItem_<sup>\*</sup>\
+> &nbsp;&nbsp; `}`
+>
+> _TraitItem_ :\
+> &nbsp;&nbsp; [_OuterAttribute_]<sup>\*</sup> (_TraitFunc_ | _TraitMethod_ | _TraitConst_ | _TraitType_)
+>
+> _TraitFunc_ :\
+> &nbsp;&nbsp; &nbsp;&nbsp; _TraitFunctionDecl_ ( `;` | [_BlockExpression_] )
+>
+> _TraitMethod_ :\
+> &nbsp;&nbsp; &nbsp;&nbsp; _TraitMethodDecl_ ( `;` | [_BlockExpression_] )
+>
+> _TraitFunctionDecl_ :\
+> &nbsp;&nbsp; [_FunctionFront_] `fn` [IDENTIFIER]&nbsp;[_Generics_]<sup>?</sup>\
+> &nbsp;&nbsp; &nbsp;&nbsp; `(` _TraitFunctionParameters_<sup>?</sup> `)`\
+> &nbsp;&nbsp; &nbsp;&nbsp; [_FunctionReturnType_]<sup>?</sup> [_WhereClause_]<sup>?</sup>
+>
+> _TraitMethodDecl_ :\
+> &nbsp;&nbsp; [_FunctionFront_] `fn` [IDENTIFIER]&nbsp;[_Generics_]<sup>?</sup>\
+> &nbsp;&nbsp; &nbsp;&nbsp; `(` [_SelfParam_] (`,` _TraitFunctionParam_)<sup>\*</sup> `,`<sup>?</sup> `)`\
+> &nbsp;&nbsp; &nbsp;&nbsp; [_FunctionReturnType_]<sup>?</sup> [_WhereClause_]<sup>?</sup>
+>
+> _TraitFunctionParameters_ :\
+> &nbsp;&nbsp; _TraitFunctionParam_ (`,` _TraitFunctionParam_)<sup>\*</sup> `,`<sup>?</sup>
+>
+> _TraitFunctionParam_<sup>[†](#parameter-patterns)</sup> :\
+> &nbsp;&nbsp; ( [_Pattern_] `:` )<sup>?</sup> [_Type_]
+>
+> _TraitConst_ :\
+> &nbsp;&nbsp; `const` [IDENTIFIER] ( ( `:` [_Type_] ) ( `=` [_Expression_] )<sup>?</sup> )<sup>?</sup> `;`
+>
+> _TraitType_ :\
+> &nbsp;&nbsp; `type` [IDENTIFIER] ( `:` [_TypeParamBounds_] )<sup>?</sup> `;`
+
 A _trait_ describes an abstract interface that types can implement. This
 interface consists of [associated items], which come in three varieties:
 
@@ -115,6 +154,63 @@ let circle = Box::new(circle) as Box<dyn Circle>;
 let nonsense = circle.radius() * circle.area();
 ```
 
+## Unsafe traits
+
+Traits items that begin with the `unsafe` keyword indicate that *implementing* the
+trait may be [unsafe]. It is safe to use a correctly implemented unsafe trait.
+The [trait implementation] must also begin with the `unsafe` keyword.
+
+[`Sync`] and [`Send`] are examples of unsafe traits.
+
+## Parameter patterns
+
+Function or method declarations without a body only allow [IDENTIFIER] or
+`_` [wild card][WildcardPattern] patterns. `mut` [IDENTIFIER] is currently
+allowed, but it is deprecated and will become a hard error in the future.
+<!-- https://github.com/rust-lang/rust/issues/35203 -->
+
+In the 2015 edition, the pattern for a trait function or method parameter is
+optional:
+
+```rust
+trait T {
+    fn f(i32);  // Parameter identifiers are not required.
+}
+```
+
+The kinds of patterns for parameters is limited to one of the following:
+
+* [IDENTIFIER]
+* `mut` [IDENTIFIER]
+* [`_`][WildcardPattern]
+* `&` [IDENTIFIER]
+* `&&` [IDENTIFIER]
+
+Beginning in the 2018 edition, function or method parameter patterns are no
+longer optional. Also, all irrefutable patterns are allowed as long as there
+is a body. Without a body, the limitations listed above are still in effect.
+
+```rust,edition2018
+trait T {
+    fn f1((a, b): (i32, i32)) {}
+    fn f2(_: (i32, i32));  // Cannot use tuple pattern without a body.
+}
+```
+
+[IDENTIFIER]: identifiers.html
+[WildcardPattern]: patterns.html#wildcard-pattern
+[_BlockExpression_]: expressions/block-expr.html
+[_Expression_]: expressions.html
+[_FunctionFront_]: items/functions.html
+[_FunctionParam_]: items/functions.html
+[_FunctionReturnType_]: items/functions.html
+[_Generics_]: items/generics.html
+[_OuterAttribute_]: attributes.html
+[_Pattern_]: patterns.html
+[_SelfParam_]: items/associated-items.html#methods
+[_TypeParamBounds_]: trait-bounds.html
+[_Type_]: types.html
+[_WhereClause_]: items/generics.html#where-clauses
 [bounds]: trait-bounds.html
 [trait object]: types.html#trait-objects
 [explicit]: expressions/operator-expr.html#type-cast-expressions
@@ -125,3 +221,7 @@ let nonsense = circle.radius() * circle.area();
 [generics]: items/generics.html
 [where clauses]: items/generics.html#where-clauses
 [generic functions]: items/functions.html#generic-functions
+[unsafe]: unsafety.html
+[trait implementation]: items/implementations.html#trait-implementations
+[`Send`]: special-types-and-traits.html#send
+[`Sync`]: special-types-and-traits.html#sync

src/unsafety.md

@@ -6,9 +6,15 @@ guarantees of Rust's static semantics.
 The following language level features cannot be used in the safe subset of
 Rust:
 
-- Dereferencing a [raw pointer](types.html#pointer-types).
-- Reading or writing a [mutable static variable](items/static-items.html#mutable-statics).
-- Reading a field of a [`union`](items/unions.html), or writing to a field of a
-  union that isn't [`Copy`](special-types-and-traits.html#copy).
+- Dereferencing a [raw pointer].
+- Reading or writing a [mutable static variable].
+- Reading a field of a [`union`], or writing to a field of a
+  union that isn't [`Copy`].
 - Calling an unsafe function (including an intrinsic or foreign function).
-- Implementing an unsafe trait.
+- Implementing an [unsafe trait].
+
+[`Copy`]: special-types-and-traits.html#copy
+[`union`]: items/unions.html
+[mutable static variable]: items/static-items.html#mutable-statics
+[raw pointer]: types.html#pointer-types
+[unsafe trait]: items/traits.html#unsafe-traits