Add "Extract interface" code action to generate interfaces from classes

Author: AJenbo

docs/CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - **Convert to arrow function.** A new `refactor.rewrite` code action converts single-expression closures to arrow functions (`function($x) { return $x * 2; }` to `fn($x) => $x * 2`). The action is only offered when the conversion is safe: single return statement, no by-reference `use` captures, no `void`/`never` return type, and PHP >= 7.4.
+- **Extract interface.** A new `refactor.extract` code action generates an interface from a concrete class. All public method signatures (excluding the constructor) are extracted into a new `{ClassName}Interface.php` file in the same directory, and the class is updated with `implements {ClassName}Interface`. Class-level and method-level `@template` tags are preserved when referenced by extracted methods.
 - **`@template` on `@method` tags.** Virtual methods declared via `@method` PHPDoc tags can now define their own template parameters using the `<T of Bound>` syntax (e.g. `@method TVal get<TVal of mixed>(TVal $default)`). Template inference at call sites works the same as for real methods.
 - **Laravel custom Eloquent builder support.** Models using the `#[UseEloquentBuilder]` attribute now have their custom builder's methods forwarded as static methods on the model. `query()`, `newQuery()`, and `newModelQuery()` return the custom builder type with correct generic model substitution. Contributed by @MingJen in https://github.com/AJenbo/phpantom_lsp/pull/118.
 

docs/todo.md

@@ -27,7 +27,6 @@ within the same impact tier.
 | --- | --------------------------------------------------------------------------------------------------------------------- | ---------- | ------ |
 | C2  | [`#[ArrayShape]` return shapes on stub functions](todo/completion.md#c2-arrayshape-return-shapes-on-stub-functions)   | Medium     | Medium |
 | A3  | Switch → match conversion                                                                                             | Low-Medium | Medium |
-| A10 | [Generate interface from class](todo/actions.md#a10-generate-interface-from-class)                                    | Low-Medium | Medium |
 | D10 | [PHPMD diagnostic proxy](todo/diagnostics.md#d10-phpmd-diagnostic-proxy)                                              | Low        | Medium |
 
 ## Sprint 7 — 1.0 release & IDE extensions

docs/todo/actions.md

@@ -95,78 +95,6 @@ but bounded in scope.
 
 
 
----
-
-## A10. Generate Interface from Class
-
-**Impact: Low-Medium · Effort: Medium**
-
-Extract an interface from an existing class. The new interface contains
-method signatures for all public methods in the class, and the class is
-updated to implement it.
-
-### Behaviour
-
-- **Trigger:** Cursor is on a class declaration. The code action
-  "Extract interface" appears.
-- **Code action kind:** `refactor.extract`.
-- **Result:** A new file is created containing the interface, and the
-  original class is updated to add `implements InterfaceName`.
-
-### What gets extracted
-
-- All `public` methods (excluding the constructor) become interface
-  method signatures: visibility, name, parameters with types and
-  defaults, and return type.
-- PHPDoc blocks from the extracted methods are copied to the interface
-  (they often contain `@param`, `@return`, and `@template` tags that
-  are essential for type information).
-- Class-level `@template` tags are copied if any extracted method
-  references those template parameters.
-- Public constants are **not** extracted (interface constants have
-  different semantics and this is rarely what users want).
-
-### Naming
-
-Default interface name: `{ClassName}Interface`. Place it in the same
-namespace and directory as the class. If the file uses PSR-4, the
-interface file path is derived from the namespace.
-
-### Implementation
-
-- Parse the class to collect public method signatures and their
-  docblocks.
-- Collect class-level `@template` tags if referenced by extracted
-  methods.
-- Generate the interface source: namespace declaration, use imports
-  needed by the method signatures, interface declaration with method
-  stubs.
-- Build a `WorkspaceEdit` with two operations:
-  1. `CreateFile` + `TextEdit` for the new interface file.
-  2. `TextEdit` on the original class to add `implements InterfaceName`
-     (and a `use` import if the interface is in a different file, though
-     by default it's the same namespace).
-- Format the generated interface to match the project's indentation
-  style (detect from the source class).
-
-### Edge cases
-
-- **Class already implements interfaces:** Append to the existing
-  `implements` list rather than replacing it.
-- **Abstract methods:** Include them in the interface (they're already
-  stubs).
-- **Static methods:** Include them. Interfaces can declare static method
-  signatures.
-- **Generic classes:** If the class has `@template T` and a method
-  returns `T`, the interface needs the same `@template` tag.
-
-### Prerequisites
-
-| Feature                             | What it contributes                                                               |
-| ----------------------------------- | --------------------------------------------------------------------------------- |
-| Parser (`parser/classes.rs`)        | Extracts public method signatures with full type information                      |
-| Implement missing methods (shipped) | Shared infrastructure for generating method stubs and `implements` clause editing |
-
 ---
 
 ## A16. Snippet Placeholder for Extracted Method Name