diff --git a/standard/attributes.md b/standard/attributes.md index 664c6ba19..9b5c89d5b 100644 --- a/standard/attributes.md +++ b/standard/attributes.md @@ -541,7 +541,7 @@ A class that is decorated with the `AttributeUsage` attribute shall derive from #### 22.5.3.1 General -The attribute `Conditional` enables the definition of ***conditional methods*** and ***conditional attribute classes***. +The attribute `Conditional` enables the definition of ***conditional methods***, ***conditional local functions***, and ***conditional attribute classes***. #### 22.5.3.2 Conditional methods @@ -692,6 +692,12 @@ The use of conditional methods in an inheritance chain can be confusing. Calls m > > *end example* +#### §conditional-local-function Conditional local functions + +A local function may be made conditional in the same sense as a conditional method ([§22.5.3.2](attributes.md#22532-conditional-methods)). + +A conditional local function shall have the modifier `static`. + #### 22.5.3.3 Conditional attribute classes An attribute class ([§22.2](attributes.md#222-attribute-classes)) decorated with one or more `Conditional` attributes is a conditional attribute class. A conditional attribute class is thus associated with the conditional compilation symbols declared in its `Conditional` attributes. @@ -861,6 +867,39 @@ For invocations that occur within field or event initializers, the member name u For invocations that occur within declarations of instance constructors, static constructors, finalizers and operators the member name used is implementation-dependent. +> *Example*: Consider the following: +> +> +> ```csharp +> class Program +> { +> static void Main() +> { +> F1(); +> +> void F1([CallerMemberName] string? name = null) +> { +> Console.WriteLine($"F1 MemberName: |{name}|"); +> F2(); +> } +> +> static void F2([CallerMemberName] string? name = null) +> { +> Console.WriteLine($"F2 MemberName: |{name}|"); +> } +> } +> } +> ``` +> +> which produces the output +> +> ```console +> F1 MemberName: |Main| +> F2 MemberName: |Main| +> ``` +> +> This attribute supplies the name of the calling function member, which for local function `F1` is the method `Main`. And even though `F2` is called by `F1`, a local function is *not* a function member, so the reported caller of `F2` is also `Main`. *end example* + ### 22.5.7 Code analysis attributes #### 22.5.7.1 General diff --git a/standard/statements.md b/standard/statements.md index 4348a0894..c77b8941b 100644 --- a/standard/statements.md +++ b/standard/statements.md @@ -487,15 +487,15 @@ A *local_function_declaration* declares a local function. ```ANTLR local_function_declaration - : local_function_modifier* return_type local_function_header + : attributes? local_function_modifier* return_type local_function_header local_function_body - | ref_local_function_modifier* ref_kind ref_return_type + | attributes? ref_local_function_modifier* ref_kind ref_return_type local_function_header ref_local_function_body ; local_function_header - : identifier '(' parameter_list? ')' - | identifier type_parameter_list '(' parameter_list? ')' + : identifier parameter_list? + | identifier type_parameter_list parameter_list? type_parameter_constraints_clause* ; @@ -505,7 +505,7 @@ local_function_modifier ; ref_local_function_modifier - : 'static' + : 'extern' | unsafe_modifier // unsafe code support ; @@ -513,11 +513,13 @@ local_function_body : block | '=>' null_conditional_invocation_expression ';' | '=>' expression ';' + | ';' ; ref_local_function_body : block | '=>' 'ref' variable_reference ';' + | ';' ; ``` @@ -562,7 +564,11 @@ Unless specified otherwise below, the semantics of all grammar elements is the s The *identifier* of a *local_function_declaration* shall be unique in its declared block scope, including any enclosing local variable declaration spaces. One consequence of this is that overloaded *local_function_declaration*s are not allowed. -A *local_function_declaration* may include one `async` ([§15.15](classes.md#1515-async-functions)) modifier and one `unsafe` ([§23.1](unsafe-code.md#231-general)) modifier. If the declaration includes the `async` modifier then the return type shall be `void` or a `«TaskType»` type ([§15.15.1](classes.md#15151-general)). If the declaration includes the `static` modifier, the function is a ***static local function***; otherwise, it is a ***non-static local function***. It is a compile-time error for *type_parameter_list* or *parameter_list* to contain *attributes*. If the local function is declared in an unsafe context ([§23.2](unsafe-code.md#232-unsafe-contexts)), the local function may include unsafe code, even if the local function declaration doesn’t include the `unsafe` modifier. +A *local_function_declaration* may include a set of *attributes* ([§22](attributes.md#22-attributes)), one `async` ([§15.15](classes.md#1515-async-functions)) modifier, one `extern` ([§15.6.8](classes.md#1568-external-methods)) modifier, and one `unsafe` ([§23.1](unsafe-code.md#231-general)) modifier. If the declaration includes the `async` modifier then the return type shall be `void` or a `«TaskType»` type ([§15.15.1](classes.md#15151-general)). The `unsafe` modifier uses the containing lexical scope. The `async` modifier does not use the containing lexical scope. + +An external local function shall have the modifier `static`, and its *local_function_body* or *ref_local_function_body* shall be a semicolon. + +A *local_function_body* or *ref_local_function_body* shall be a semicolon only for an external local function. A local function is declared at block scope. A non-static local function may capture variables from the enclosing scope while a static local function shall not (so it has no access to enclosing locals, parameters, non-static local functions, or `this`). It is a compile-time error if a captured variable is read by the body of a non-static local function but is not definitely assigned before each call to the function. A compiler shall determine which variables are definitely assigned on return ([§9.4.4.33](variables.md#94433-rules-for-variables-in-local-functions)).