fix: implements check for indexed event arguments

prior to this commit, implementing an interface with wrong indexed
arguments for an event would pass the implements check. this commit
fixes the behavior.

chainsec june 2023 review 5.12

vyper/semantics/types/user.py

@@ -164,6 +164,7 @@ def __init__(self, name: str, arguments: dict, indexed: list) -> None:
         super().__init__(members=arguments)
         self.name = name
         self.indexed = indexed
+        assert len(self.indexed) == len(self.arguments)
         self.event_id = int(keccak256(self.signature.encode()).hex(), 16)
 
     # backward compatible
@@ -172,8 +173,13 @@ def arguments(self):
         return self.members
 
     def __repr__(self):
-        arg_types = ",".join(repr(a) for a in self.arguments.values())
-        return f"event {self.name}({arg_types})"
+        args = []
+        for is_indexed, (_, argtype) in zip(self.indexed, self.arguments.items()):
+            argtype_str = repr(argtype)
+            if is_indexed:
+                argtype_str = f"indexed({argtype_str})"
+            args.append(f"{argtype_str}")
+        return f"event {self.name}({','.join(args)})"
 
     # TODO rename to abi_signature
     @property
@@ -337,12 +343,12 @@ def _is_function_implemented(fn_name, fn_type):
 
         # check for missing events
         for name, event in self.events.items():
-            if (
-                name not in namespace
-                or not isinstance(namespace[name], EventT)
-                or namespace[name].event_id != event.event_id
-            ):
+            if ( name not in namespace):
                 unimplemented.append(name)
+            if not isinstance(namespace[name], EventT):
+                unimplemented.append(f"{name} is not an event!")
+            if namespace[name].event_id != event.event_id or namespace[name].indexed != event.indexed:
+                unimplemented.append(f"{name} is not implemented! (should be {event})")
 
         if len(unimplemented) > 0:
             # TODO: improve the error message for cases where the