Adds pass support (#299)

* Adds `pass` support, closes #284

* Fixes CI

* Fixes CI

Author: sobolevn

classes/contrib/mypy/validation/validate_typeclass_def.py

@@ -1,6 +1,13 @@
 from typing import Union
 
-from mypy.nodes import ARG_POS, EllipsisExpr, ExpressionStmt, FuncDef, StrExpr
+from mypy.nodes import (
+    ARG_POS,
+    EllipsisExpr,
+    ExpressionStmt,
+    FuncDef,
+    PassStmt,
+    StrExpr,
+)
 from mypy.plugin import FunctionContext, MethodContext
 from mypy.types import CallableType, Instance
 from typing_extensions import Final
@@ -58,8 +65,10 @@ def _check_body(
     if body:
         is_useless_body = (
             len(body) == 1 and
-            isinstance(body[0], ExpressionStmt) and
-            isinstance(body[0].expr, (EllipsisExpr, StrExpr))
+            (isinstance(body[0], PassStmt) or (
+                isinstance(body[0], ExpressionStmt) and
+                isinstance(body[0].expr, (EllipsisExpr, StrExpr))
+            ))
         )
         if is_useless_body:
             # We allow a single ellipsis in function a body.

typesafety/test_associated_type/test_validation/test_bodies.yml

@@ -27,3 +27,16 @@
         ...
   out: |
     main:6: error: Associated types must not have bodies
+
+
+- case: associated_type_with_pass
+  disable_cache: false
+  main: |
+    from classes import AssociatedType, typeclass
+
+    class MyType(AssociatedType):
+        pass
+
+    @typeclass
+    def sum_all(instance) -> int:
+        pass

typesafety/test_typeclass/test_validation/test_body.yml

@@ -30,6 +30,16 @@
      main:3: error: Typeclass definitions must not have bodies
 
 
+- case: typeclass_with_pass_body
+  disable_cache: false
+  main: |
+    from classes import typeclass
+
+    @typeclass
+    def sum_all(instance) -> int:
+        pass
+
+
 - case: typeclass_with_body_and_associated_type
   disable_cache: false
   main: |