Update logging source generator docs for generic method support, SYSLIB1028, and SYSLIB1029

docs/core/extensions/logging/source-generation.md

@@ -119,7 +119,8 @@ Logging methods that are decorated with `LoggerMessageAttribute` must meet the f
 - Logging methods must be `partial` and return `void`.
 - Logging method names must *not* start with an underscore.
 - Parameter names of logging methods must *not* start with an underscore.
-- Logging methods *can't* be generic.
+- Logging methods support generic type parameters, but the C# 13 `allows ref struct` anti-constraint isn't supported.
+- Logging method parameters can't use the `params`, `scoped`, or `out` modifiers, and can't be ref struct types.
 - If a logging method is `static`, the `ILogger` instance is required as a parameter.
 
 The code-generation model depends on code being compiled with a modern C# compiler, that is, version 9 or later. For information about changing the language version, see [C# language versioning](../../../csharp/language-reference/configure-language-version.md).

docs/fundamentals/syslib-diagnostics/source-generator-overview.md

@@ -30,7 +30,7 @@ The following table provides an index to the `SYSLIB1XXX` diagnostics in .NET 6
 | [SYSLIB1008][1008] | One of the arguments to a logging method must implement the `Microsoft.Extensions.Logging.ILogger` interface |
 | [SYSLIB1009][1009] | Logging methods must be `static`                                                                             |
 | [SYSLIB1010][1010] | Logging methods must be `partial`                                                                            |
-| [SYSLIB1011][1011] | Logging methods cannot be generic                                                                            |
+| [SYSLIB1011][1011] | Logging methods cannot use the `allows ref struct` constraint                                                |
 | [SYSLIB1012][1012] | Redundant qualifier in logging message                                                                       |
 | [SYSLIB1013][1013] | Don't include exception parameters as templates in the logging message                                       |
 | [SYSLIB1014][1014] | Logging template has no corresponding method argument                                                        |
@@ -47,8 +47,8 @@ The following table provides an index to the `SYSLIB1XXX` diagnostics in .NET 6
 | [SYSLIB1025][1025] | Multiple logging methods cannot use the same event name within a class |
 | [SYSLIB1026][1026] | C# language version not supported by the logging source generator. |
 | [SYSLIB1027][1027] | Primary constructor parameter of type `Microsoft.Extensions.Logging.ILogger` is hidden by a field |
-| SYSLIB1028 | (Reserved for logging.) |
-| SYSLIB1029 | (Reserved for logging.) |
+| [SYSLIB1028][1028] | Logging method argument uses unsupported `params` or `scoped` parameter modifier |
+| [SYSLIB1029][1029] | Logging method parameter is a ref struct |
 | [SYSLIB1030][1030] | The `System.Text.Json` source generator did not generate serialization metadata for type |
 | [SYSLIB1031][1031] | The `System.Text.Json` source generator encountered a duplicate `JsonTypeInfo` property name |
 | [SYSLIB1032][1032] | The `System.Text.Json` source generator encountered a context class that is not partial |
@@ -198,6 +198,8 @@ The following table provides an index to the `SYSLIB1XXX` diagnostics in .NET 6
 [1025]: syslib1025.md
 [1026]: syslib1026.md
 [1027]: syslib1027.md
+[1028]: syslib1028.md
+[1029]: syslib1029.md
 [1030]: syslib1030.md
 [1031]: syslib1031.md
 [1032]: syslib1032.md

docs/fundamentals/syslib-diagnostics/syslib1011.md

@@ -1,17 +1,17 @@
 ---
 title: SYSLIB1011 error
 description: Learn about the diagnostic that generates compile-time error SYSLIB1011.
-ms.date: 05/07/2021
+ms.date: 02/23/2026
 f1_keywords:
   - syslib1011
 ---
 
-# SYSLIB1011: Logging methods cannot be generic
+# SYSLIB1011: Logging methods cannot use the `allows ref struct` constraint
 
-A method annotated with the `LoggerMessageAttribute` contains parameters with generic types.
+A method annotated with `LoggerMessageAttribute` uses the C# 13 `allows ref struct` anti-constraint on a type parameter. The logging source generator stores parameters in struct fields, so it can't hold ref struct type arguments.
 
 ## Workarounds
 
-Logging methods cannot have any generically typed parameters. Use fully resolved types instead.
+Logging methods support generic type parameters and most constraint forms (`class`, `struct`, `unmanaged`, `notnull`, base types, interfaces, and `new()`). Remove the `allows ref struct` anti-constraint from the type parameter to resolve this error.
 
 [!INCLUDE [suppress-syslib-warning](includes/suppress-source-generator-diagnostics.md)]

docs/fundamentals/syslib-diagnostics/syslib1028.md

@@ -0,0 +1,17 @@
+---
+title: SYSLIB1028 error
+description: Learn about the diagnostic that generates compile-time error SYSLIB1028.
+ms.date: 02/25/2026
+f1_keywords:
+  - SYSLIB1028
+---
+
+# SYSLIB1028: Argument is using an unsupported parameter modifier
+
+The `params` and `scoped` parameter modifiers aren't supported for <xref:Microsoft.Extensions.Logging.LoggerMessageAttribute>-annotated logging methods.
+
+## Workarounds
+
+Remove the `params` or `scoped` modifier from the parameter.
+
+[!INCLUDE [suppress-syslib-warning](includes/suppress-source-generator-diagnostics.md)]

docs/fundamentals/syslib-diagnostics/syslib1029.md

@@ -0,0 +1,17 @@
+---
+title: SYSLIB1029 error
+description: Learn about the diagnostic that generates compile-time error SYSLIB1029.
+ms.date: 02/25/2026
+f1_keywords:
+  - SYSLIB1029
+---
+
+# SYSLIB1029: Logging method parameter is a ref struct
+
+Ref struct types aren't supported as parameters for <xref:Microsoft.Extensions.Logging.LoggerMessageAttribute>-annotated logging methods. The logging source generator stores parameters in struct fields, which can't hold ref struct values.
+
+## Workarounds
+
+Use a non-ref struct type for the parameter.
+
+[!INCLUDE [suppress-syslib-warning](includes/suppress-source-generator-diagnostics.md)]