reorg record-related text

Author: RexJaeschke

standard/classes.md

@@ -5663,6 +5663,67 @@ An enumerable object provides an implementation of the `GetEnumerator` methods o
 
 An asynchronous enumerable object provides an implementation of the `GetAsyncEnumerator` method of the `IAsyncEnumerable<T>` interface. This method returns an available asynchronous enumerator object. The enumerator object is initialized with the argument values and instance value saved when the enumerable object was initialized, including the optional cancellation token, but otherwise the enumerator object functions as described in [§15.15.5](classes.md#15155-enumerator-objects). An asynchronous iterator method can mark one parameter as the cancellation token using `System.Runtime.CompilerServices.EnumeratorCancellationAttribute` ([§23.5.8](attributes.md#2358-the-enumeratorcancellation-attribute)). An implementation shall provide a mechanism to combine cancellation tokens such that an asynchronous iterator is canceled when either cancellation token (the argument to `GetAsyncEnumerator` or the argument attributed with the attribute `System.Runtime.CompilerServices.EnumeratorCancellationAttribute`) requests cancellation.
 
+## §rec-class Record classes
+
+### §rec-class-general General
+
+A record class is a specialized reference type that is optimized for storing data rather than behavior. It provides built-in functionality that would normally require significant “boilerplate” code in a non-record class, such as value-based equality and easy immutability.
+
+```ANTLR
+record_class_declaration
+    : attributes? class_modifier* 'partial'? 'record' identifier 
+      type_parameter_list? delimited_parameter_list? class_base? 
+      type_parameter_constraints_clause* record_class_body
+    ;
+```
+
+A *record_class_declaration* consists of an optional set of *attributes* ([§21](attributes.md#21-attributes)), followed by an optional set of *class_modifier*s ([§14.2.2](classes.md#1422-class-modifiers)), followed by an optional `partial` modifier ([§14.2.7](classes.md#1427-partial-declarations)), followed by the keyword `record` and an *identifier* that names the class, followed by an optional *type_parameter_list* ([§14.2.3](classes.md#1423-type-parameters)), followed by an optional *delimited_parameter_list* ([§15.6.2.1]( classes.md#15621-general)), followed by an optional *class_base* specification ([§14.2.4](classes.md#1424-class-base-specification)), followed by an optional set of *type_parameter_constraints_clause*s ([§14.2.5](classes.md#1425-type-parameter-constraints)), followed by a *record_class_body* (§rec-class-record-class-body).
+
+*class_modifier* shall not be `static`.
+
+A *record_class_declaration* having a *delimited_parameter_list* declares a ***positional record class***.
+
+At most only one partial type declaration of a partial record class may provide a *delimited_parameter_list*.
+
+Parameters in * delimited_parameter_list* shall not have `ref`, `out` or `this` modifiers; however, `in` and `params` modifiers are permitted.
+
+### §rec-class-class-base-specification Class base specification
+
+```ANTLR
+base_argument_list
+    : '(' argument_list? ')'
+    ;
+```
+
+### §rec-class-record-class-body Record class body
+
+The *record_class_body* of a record class defines the members of that class.
+
+```ANTLR
+record_class_body
+    : class_body ';'?
+    | ';'
+    ;
+```
+
+The *record_class_body*s `{}`, `{};`, and `;` are equivalent. They all indicate that the only members are those synthesized by the compiler (§synth-members).
+
+### §rec-class-class-members Class members
+
+For a record class, the member set also includes the synthesized members generated by the compiler (§synth-members).
+
+It is an error for a member of a record class to be named `Clone`.
+
+It is an error for an instance field of a record class to have an unsafe type.
+
+### §rec-class-instance-constructors Instance constructors
+
+A positional record class (§rec-class-general) has a synthesized primary constructor; see §rec-class-pos-mem-pricon for more information.
+
+
+
+
+
 ## §synth-members Synthesized record class members
 
 ### §synth-members-general General