Add new diagnostics

docs/csharp/language-reference/compiler-messages/feature-version-errors.md

@@ -54,6 +54,7 @@ f1_keywords:
   - "CS9202"
   - "CS9211"
   - "CS9240"
+  - "CS9260"
 helpviewer_keywords:
   - "CS0171"
   - "CS0188"
@@ -107,7 +108,8 @@ helpviewer_keywords:
   - "CS9202"
   - "CS9211"
   - "CS9240"
-ms.date: 11/02/2023
+  - "CS9260"
+ms.date: 11/06/2024
 ---
 # Resolve warnings related to language features and versions
 
@@ -149,6 +151,7 @@ That's be design. The text closely matches the text of the compiler error / warn
 - **CS9202**: *Feature is not available in C# 12.0. Please use newer language version*
 - **CS9211**: *The diagnosticId argument to the 'Experimental' attribute must be a valid identifier.*
 - **CS9240**: *Target runtime doesn't support by-ref-like generics.*
+- **CS9260**: *Feature is not available in C# 13.0. Please use newer language version**
 
 In addition, the following errors and warnings relate to struct initialization changes in recent versions:
 

docs/csharp/language-reference/compiler-messages/inline-array-errors.md

@@ -16,6 +16,7 @@ f1_keywords:
   - "CS9183"
   - "CS9184"
   - "CS9189"
+  - "CS9259"
 helpviewer_keywords:
   - "CS9164"
   - "CS9165"
@@ -31,7 +32,8 @@ helpviewer_keywords:
   - "CS9183"
   - "CS9184"
   - "CS9189"
-ms.date: 11/02/2023
+  - "CS9259"
+ms.date: 11/06/2024
 ---
 # Resolve errors and warnings with inline array declarations
 
@@ -54,6 +56,7 @@ That's by design. The text closely matches the text of the compiler error / warn
 - [**CS9183**](#conversions-to-span): *Inline array conversion operator will not be used for conversion from expression of the declaring type.*
 - [**CS9184**](#inline-array-declaration): *'Inline arrays' language feature is not supported for inline array types with element field which is either a '`ref`' field, or has type that is not valid as a type argument.*
 - [**CS9189**](#element-access): *`foreach` statement on an inline array of type is not supported*
+- [**CS9259**](#inline-array-declaration): *Attribute <xref:System.Runtime.CompilerServices.InlineArrayAttribute?displayProperty=fullName> cannot be applied to a record struct.*
 
 ## Inline array declaration
 
@@ -64,6 +67,7 @@ You declare inline arrays as a `struct` type with a single field, and an attribu
 - **CS9169**: *Inline array struct must declare one and only one instance field which must not be a ref field.*
 - **CS9180**: *Inline array element field cannot be declared as required, readonly, volatile, or as a fixed size buffer.*
 - **CS9184**: *'Inline arrays' language feature is not supported for inline array types with element field which is either a '`ref`' field, or has type that is not valid as a type argument.*
+- **CS9259**: *Attribute <xref:System.Runtime.CompilerServices.InlineArrayAttribute?displayProperty=fullName> cannot be applied to a record struct.*
 
 To fix these arrays, ensure the following are true:
 
@@ -72,6 +76,7 @@ To fix these arrays, ensure the following are true:
 - The enclosing `struct` has a single instance field, and that instance field is not a `ref` field.
 - The single instance field is not a fixed size buffer.
 - The single instance field doesn't include the `required`, `volatile`, or `readonly` modifiers.
+- Remove the `record` modifier from your inline array declaration.
 
 ## Element access
 

docs/csharp/language-reference/compiler-messages/ref-modifiers-errors.md

@@ -66,6 +66,7 @@ f1_keywords:
   - "CS9199"
   - "CS9200"
   - "CS9201"
+  - "CS9265"
 helpviewer_keywords:
   - "CS0192"
   - "CS0199"
@@ -131,7 +132,8 @@ helpviewer_keywords:
   - "CS9199"
   - "CS9200"
   - "CS9201"
-ms.date: 11/02/2023
+  - "CS9265"
+ms.date: 11/06/2024
 ---
 # Errors and warnings associated with reference parameters, variables, and returns
 
@@ -207,6 +209,7 @@ The following warnings are generated when reference variables are used incorrect
 - [**CS9198**](#reference-variable-restrictions): *Reference kind modifier of parameter doesn't match the corresponding parameter in target.*
 - [**CS9200**](#reference-variable-restrictions): *A default value is specified for `ref readonly` parameter, but `ref readonly` should be used only for references. Consider declaring the parameter as `in`.*
 - [**CS9201**](#reference-variable-restrictions): *Ref field should be ref-assigned before use.*
+- [**CS9265**](#reference-variable-restrictions): *Field is never ref-assigned to, and will always have its default value (null reference)*
 
 These errors and warnings follow these themes:
 
@@ -261,6 +264,7 @@ The following warnings indicate that a reference variable shouldn't be used, and
 - **CS9198**:  *Reference kind modifier of parameter doesn't match the corresponding parameter in target.*
 - **CS9200**:  *A default value is specified for `ref readonly` parameter, but `ref readonly` should be used only for references. Consider declaring the parameter as `in`.*
 - **CS9201**:  *Ref field should be ref-assigned before use.*
+- **CS9265**: *Field is never ref-assigned to, and will always have its default value (null reference)*
 
 To fix the error, remove the reference variable where it isn't allowed:
 
@@ -277,6 +281,7 @@ To fix the error, remove the reference variable where it isn't allowed:
 - Methods attributed with <xref:System.Runtime.InteropServices.UnmanagedCallersOnlyAttribute?displayProperty=nameWithType> can't use reference parameters.
 - A Windows runtime event can't be passed as a reference variable.
 - A `ref readonly` parameter can't have the <xref:System.Runtime.InteropServices.OutAttribute?displayProperty=nameWithType> applied to it in remoting API.
+- Initialize a `ref` field in the constructor or as a field initializer.
 
 ## `unscoped ref` restrictions
 

docs/csharp/language-reference/compiler-messages/ref-struct-errors.md

@@ -15,6 +15,7 @@ f1_keywords:
   - "CS9245"
   - "CS9246"
   - "CS9247"
+  - "CS9267"
 helpviewer_keywords:
   - "CS8343"
   - "CS8344"
@@ -29,7 +30,8 @@ helpviewer_keywords:
   - "CS9245"
   - "CS9246"
   - "CS9247"
-ms.date: 07/30/2024
+  - "CS9267"
+ms.date: 11/06/2024
 ---
 # Errors and warnings associated with `ref struct` types
 
@@ -46,6 +48,7 @@ ms.date: 07/30/2024
 - [**CS9245**](#ref-struct-interface-implementations): *Type cannot implement interface member for `ref struct` type.*
 - [**CS9246**](#ref-struct-interface-implementations): *A non-virtual instance interface member cannot be accessed on a type parameter that allows ref struct.*
 - [**CS9247**](#ref-struct-interface-implementations): *foreach statement cannot operate on enumerators of type because it is a type parameter that allows ref struct and it is not known at compile time to implement `IDisposable`.*
+- [**CS9267**](#ref-struct-interface-implementations): *Element type of an iterator may not be a ref struct or a type parameter allowing ref structs*
 
 ## ref safety violations
 
@@ -74,6 +77,7 @@ Violating any of these rules produces one of the listed errors. If you intended
 - **CS9245**: *Type cannot implement interface member for `ref struct` type.*
 - **CS9246**: *A non-virtual instance interface member cannot be accessed on a type parameter that allows ref struct.*
 - **CS9247**: *foreach statement cannot operate on enumerators of type because it is a type parameter that allows ref struct and it is not known at compile time to implement `IDisposable`.*
+- **CS9267**: *Element type of an iterator may not be a ref struct or a type parameter allowing ref structs*
 
 Prior to C# 13, [`ref struct`](../builtin-types/ref-struct.md) types can't implement interfaces; the compiler generates *CS8343*. Beginning with C# 13, `ref struct` types can implement interfaces, subject to the following rules:
 
@@ -84,3 +88,4 @@ Beginning with C# 13, a `ref struct` can be used as a type argument for a generi
 
 - A `ref struct` is used as a type argument, the type parameter *must* have the `allows ref struct` anti-constraint.- The `allows ref struct` anti-constraint must be last in the `where` clause for that parameter
 - Uses of instances the type parameter must obey ref safety rules.
+- A `ref struct` or a type argument that can be a `ref struct` type can't be used as the element type for an [iterator method](../statements/yield.md).

docs/csharp/language-reference/toc.yml

@@ -437,7 +437,7 @@ items:
       CS0171, CS0188, CS0843, CS8904, CS1738, CS8022, CS8023, CS8024, CS8025, CS8026, CS8058, CS8059, CS8107, CS8192, CS8302,
       CS8303, CS8304, CS8305, CS8306, CS8314, CS8320, CS8370, CS8371, CS8400, CS8401, CS8511, CS8627, CS8630, CS8652, CS8703,
       CS8704, CS8706, CS8773, CS8912, CS8919, CS8929, CS8936, CS8957, CS8967, CS9014, CS9015, CS9016, CS9017, CS9058, CS9064,
-      CS9103, CS9171, CS9194, CS9202, CS9204, CS9240
+      CS9103, CS9171, CS9194, CS9202, CS9204, CS9240, CS9260
   - name: Assembly references
     href: ./compiler-messages/assembly-references.md
     displayName: >
@@ -463,12 +463,12 @@ items:
       CS7084, CS8166, CS8167, CS8168, CS8169. CS8325, CS8326, CS8327, CS8329, CS8330, CS8331, CS8332, CS8337, CS8338, CS8351,
       CS8373, CS8374, CS8388, CS8977, CS9072, CS9077, CS9078, CS9079, CS9085, CS9086, CS9087, CS9089, CS9091, CS9092, CS9093,
       CS9094, CS9095, CS9096, CS9097, CS9101, CS9102, CS9104, CS9190, CS9191, CS9192, CS9193, CS9195, CS9196, CS9197, CS9198,
-      CS9199, CS9200, CS9201
+      CS9199, CS9200, CS9201, CS9265
   - name: "`ref struct` types"
     href: ./compiler-messages/ref-struct-errors.md
     displayName: >
       ref struct,
-      CS8343, CS8344, CS8345, CS9048, CS9050, CS9059, CS9241, CS9242, CS9243, CS9244, CS9245, CS9246, CS9247
+      CS8343, CS8344, CS8345, CS9048, CS9050, CS9059, CS9241, CS9242, CS9243, CS9244, CS9245, CS9246, CS9247, CS9267
   - name: Iterator methods
     href: ./compiler-messages/iterator-yield.md
     displayName: >
@@ -503,7 +503,7 @@ items:
       CS9188, CS9203, CS9208, CS9209, CS9210
   - name: Inline arrays
     href: ./compiler-messages/inline-array-errors.md
-    displayName: CS9164, CS9165, CS9166, CS9167, CS9168, CS9169, CS9172, CS9173, CS9180, CS9181, CS9182, CS9183, CS9184
+    displayName: CS9164, CS9165, CS9166, CS9167, CS9168, CS9169, CS9172, CS9173, CS9180, CS9181, CS9182, CS9183, CS9184, CS9259
   - name: Lambda expressions
     href: ./compiler-messages/lambda-expression-errors.md
     displayName: >