docs: Update docs

Co-authored-by: Copilot <copilot@github.com>

Author: AndyElessar

docs/Ioc/12_Container.md

@@ -128,7 +128,7 @@ Configure generation with `IocContainerAttribute` properties:
 > The container generated by `SourceGen.Ioc` does not resolve `IServiceCollection` by itself. If you want to integrate with `IServiceCollection`, you must ensure that the generated container should be constructed with an external `IServiceProvider`.
 
 > [!TIP]
-> For most .NET applications, the simplest way to integrate the generated container is to use it with `MS.E.DI`. Since the container implements `IServiceProviderFactory<IServiceCollection>`, you can call `new AppContainer(null).CreateServiceProvider(services)` to build a container that uses `MS.E.DI` as the fallback `IServiceProvider`.
+> For most .NET applications, the simplest way to integrate the generated container is to use it with `MS.E.DI`. Since the container implements `IServiceProviderFactory<IServiceCollection>`, you can call `new AppContainer().CreateServiceProvider(services)` to build a container that uses `MS.E.DI` as the fallback `IServiceProvider`.
 
 ## Filtering by Tags
 
@@ -496,14 +496,196 @@ This ensures that cached `ObjectFactory` instances and property activator delega
 > The hot reload handler is only generated when at least one of `IComponentActivator` or `IComponentPropertyActivator` is implemented.
 > `ClearCache` only clears the caches that actually exist based on which interfaces are implemented.
 
+## Partial Accessors (Fast-Path Service Resolution)
+
+Declare **partial methods** or **partial properties** in the `[IocContainer]` class to get strongly-typed, fast-path accessors for registered services. The generator implements them automatically — no dictionary lookup, no boxing.
+
+### Supported Patterns
+
+|Pattern|Declaration|Generated Implementation|
+|:---|:---|:---|
+|Partial method|`public partial IMyService GetMyService();`|Calls the internal resolver directly|
+|Partial property|`public partial IMyService MyService { get; }`|Calls the internal resolver directly|
+|Nullable (optional)|`public partial IMyService? TryGetMyService();`|Returns `null` if unresolvable|
+|Keyed service|`[IocInject("key")] public partial IMyService GetMyService();`|Resolves with the specified key|
+
+### Basic Partial Method
+
+```csharp
+public interface IMyService { }
+
+[IocRegister<IMyService>(ServiceLifetime.Singleton)]
+public class MyService : IMyService { }
+
+[IocContainer]
+public partial class AppContainer
+{
+    public partial IMyService GetMyService();
+}
+```
+
+<details>
+<summary>Generated Code</summary>
+
+```csharp
+// <auto-generated/>
+partial class AppContainer
+{
+    // Internal resolver
+    private global::TestNamespace.MyService _testNamespace_MyService = null!;
+    private global::TestNamespace.MyService GetTestNamespace_MyService()
+    {
+        if(_testNamespace_MyService is not null) return _testNamespace_MyService;
+
+        var instance = new global::TestNamespace.MyService();
+
+        _testNamespace_MyService = instance;
+        return instance;
+    }
+
+    // Partial accessor — direct call, no dictionary lookup
+    public partial global::TestNamespace.IMyService GetMyService() => GetTestNamespace_MyService();
+}
+```
+
+</details>
+
+### Partial Property
+
+```csharp
+[IocContainer]
+public partial class AppContainer
+{
+    public partial IMyService MyService { get; }
+}
+```
+
+<details>
+<summary>Generated Code</summary>
+
+```csharp
+// <auto-generated/>
+partial class AppContainer
+{
+    public partial global::TestNamespace.IMyService MyService { get => GetTestNamespace_MyService(); }
+}
+```
+
+</details>
+
+### Nullable (Optional) Accessor
+
+When the return type is nullable, the accessor falls back to the container's `GetService` and returns `null` if the service is not registered — it never throws.
+
+```csharp
+[IocContainer]
+public partial class AppContainer
+{
+    public partial IMyService? TryGetMyService();
+}
+```
+
+<details>
+<summary>Generated Code</summary>
+
+```csharp
+// <auto-generated/>
+partial class AppContainer
+{
+    public partial global::TestNamespace.IMyService? TryGetMyService()
+        => GetService(typeof(global::TestNamespace.IMyService)) as global::TestNamespace.IMyService;
+}
+```
+
+</details>
+
+### Keyed Service Accessor
+
+Add `[IocInject("key")]` to resolve a keyed registration:
+
+```csharp
+public interface ICache { }
+
+[IocRegister<ICache>(ServiceLifetime.Singleton, Key = "redis")]
+public class RedisCache : ICache { }
+
+[IocContainer]
+public partial class AppContainer
+{
+    [IocInject("redis")]
+    public partial ICache GetRedisCache();
+}
+```
+
+<details>
+<summary>Generated Code</summary>
+
+```csharp
+// <auto-generated/>
+partial class AppContainer
+{
+    public partial global::TestNamespace.ICache GetRedisCache() => GetTestNamespace_RedisCache__redis_();
+}
+```
+
+</details>
+
+### Resolution Rules
+
+1. The return type is matched against registered service types (fully qualified name).
+2. If `[IocInject]` is present, its `Key` is used for keyed service resolution.
+3. If a matching internal resolver exists, it is called directly (fast-path).
+4. If no internal resolver exists but `IntegrateServiceProvider = true`, fallback to `GetService` / `GetRequiredService`.
+5. If no resolver exists and `IntegrateServiceProvider = false`:
+   - **Nullable** return type → returns `default`
+   - **Non-nullable** return type → `throw new InvalidOperationException(…)` (and reports `SGIOC021`)
+
+### Naming Conflict Handling
+
+If a user-declared partial method name collides with an internally generated resolver name (e.g., both named `GetMyService`), the generator automatically renames the internal resolver with a `_Resolve` suffix:
+
+```csharp
+// User declares:
+public partial IMyService GetMyService();
+
+// Generator renames internal resolver to avoid conflict:
+// GetMyService → GetMyService_Resolve
+```
+
+<details>
+<summary>Generated Code</summary>
+
+```csharp
+// <auto-generated/>
+partial class TestContainer
+{
+    // Internal resolver — renamed to avoid conflict
+    private global::MyService _myService = null!;
+    private global::MyService GetMyService_Resolve()
+    {
+        if(_myService is not null) return _myService;
+
+        var instance = new global::MyService();
+
+        _myService = instance;
+        return instance;
+    }
+
+    // Partial accessor calls the renamed resolver
+    public partial global::IMyService GetMyService() => GetMyService_Resolve();
+}
+```
+
+</details>
+
 ## Diagnostics
 
 |ID|Severity|Description|
 |:---|:---|:---|
 |SGIOC018|Error|Container cannot resolve a dependency when `IntegrateServiceProvider = false`.|
 |SGIOC019|Error|Container class must be `partial` and cannot be `static`.|
 |SGIOC020|Warning|`UseSwitchStatement = true` is ignored when importing modules.|
-|SGIOC021|Error|Partial accessor return type cannot be resolved when `IntegrateServiceProvider = false`.|
+|SGIOC021|Error|Non-nullable partial accessor return type is not a registered service when `IntegrateServiceProvider = false`.|
 
 ---