document CodegenTrait

fredemmott · fredemmott · commit 9fa1c0ad647d · 2017-02-22T21:17:15.000-08:00
diff --git a/docs/_data/nav_docs.yml b/docs/_data/nav_docs.yml
@@ -21,6 +21,7 @@
   - id: classes-codegen-class-base
   - id: classes-codegen-interface
   - id: classes-codegen-class
+  - id: classes-codegen-trait
   - id: classes-codegen-enum
 
 # n title:, 1 items: per title:, n id: per items:
diff --git a/docs/_docs/classes/codegen-trait.md b/docs/_docs/classes/codegen-trait.md
@@ -0,0 +1,16 @@
+---
+docid: classes-codegen-trait
+title: CodegenTrait
+layout: docs
+permalink: /docs/classes/CodegenTrait/
+---
+
+A `CodegenTrait` is created with `$factory->codegenInterface(name)`; it can
+be marked as implementing interfaces with
+`->addInterface($codegen_implements_interface)`, and also adds two Hack-specific
+features on top of `CodegenBaseClass`:
+
+ - `->addRequireClass(string $class)`: only allow the trait to be used by `$class`
+   or subclasses of `$class`.
+ - `->addRequireInterface(string $class)`: only allow the trait to be used classes
+   that implement the specified interface.
