Added #9

README.md

@@ -47,6 +47,24 @@ def fail_write() -> None:
             self.a = a
             self.b = b
     ```
+* Instance variables not used would be warned by the compiler, except for those
+  preceded by the pseudocomment `# nac3:no_warn_unused`. (#9) The comment can
+  either be placed on top of the variable or next to the variable. Example:
+  ```python
+  class Foo:
+      # nac3:no_warn_unused
+      a: int
+      b: int # nac3:no_warn_unused
+      def __init__(self):
+          pass
+  ```
+* Use-before-define:
+  * Host-only constructor: Error if a certain field `f` is
+    used in other kernel methods but missing from the object constructed in the
+    host.
+  * `@portable`/`@kernel` constructor: Error if a certain
+    field `f` is used in other kernel methods but not defined in the
+    constructor, or used in the constructor before definition.
 * Three types of instance variables: (Issue #5)
   * Host only variables: Do not add type annotation for it in the class.
   * Kernel only variables: Denoted with type `Kernel[T]`.