Fix and simplify error de-duplication (#19247)

Fixes #19240
Fixes #13517
Fixes #17791

Existing de-duplication logic is both complicated and fragile. By
specifying a `parent_error` for a note explicitly, we can do everything
in a more robust and simple way. In addition, this new argument makes
error code matching simpler.

Author: ilevkivskyi

mypy/checker.py

@@ -25,7 +25,7 @@
 from mypy.constraints import SUPERTYPE_OF
 from mypy.erasetype import erase_type, erase_typevars, remove_instance_last_known_values
 from mypy.errorcodes import TYPE_VAR, UNUSED_AWAITABLE, UNUSED_COROUTINE, ErrorCode
-from mypy.errors import Errors, ErrorWatcher, LoopErrorWatcher, report_internal_error
+from mypy.errors import ErrorInfo, Errors, ErrorWatcher, LoopErrorWatcher, report_internal_error
 from mypy.expandtype import expand_type
 from mypy.literals import Key, extract_var_from_literal_hash, literal, literal_hash
 from mypy.maptype import map_instance_to_supertype
@@ -7181,7 +7181,7 @@ def check_subtype(
         if extra_info:
             msg = msg.with_additional_msg(" (" + ", ".join(extra_info) + ")")
 
-        self.fail(msg, context)
+        error = self.fail(msg, context)
         for note in notes:
             self.msg.note(note, context, code=msg.code)
         if note_msg:
@@ -7192,7 +7192,7 @@ def check_subtype(
             and supertype.type.is_protocol
             and isinstance(subtype, (CallableType, Instance, TupleType, TypedDictType))
         ):
-            self.msg.report_protocol_problems(subtype, supertype, context, code=msg.code)
+            self.msg.report_protocol_problems(subtype, supertype, context, parent_error=error)
         if isinstance(supertype, CallableType) and isinstance(subtype, Instance):
             call = find_member("__call__", subtype, subtype, is_operator=True)
             if call:
@@ -7521,12 +7521,11 @@ def temp_node(self, t: Type, context: Context | None = None) -> TempNode:
 
     def fail(
         self, msg: str | ErrorMessage, context: Context, *, code: ErrorCode | None = None
-    ) -> None:
+    ) -> ErrorInfo:
         """Produce an error message."""
         if isinstance(msg, ErrorMessage):
-            self.msg.fail(msg.value, context, code=msg.code)
-            return
-        self.msg.fail(msg, context, code=code)
+            return self.msg.fail(msg.value, context, code=msg.code)
+        return self.msg.fail(msg, context, code=code)
 
     def note(
         self,

mypy/checkexpr.py

@@ -2668,7 +2668,7 @@ def check_arg(
         elif self.has_abstract_type_part(caller_type, callee_type):
             self.msg.concrete_only_call(callee_type, context)
         elif not is_subtype(caller_type, callee_type, options=self.chk.options):
-            code = self.msg.incompatible_argument(
+            error = self.msg.incompatible_argument(
                 n,
                 m,
                 callee,
@@ -2679,10 +2679,12 @@ def check_arg(
                 outer_context=outer_context,
             )
             self.msg.incompatible_argument_note(
-                original_caller_type, callee_type, context, code=code
+                original_caller_type, callee_type, context, parent_error=error
             )
             if not self.msg.prefer_simple_messages():
-                self.chk.check_possible_missing_await(caller_type, callee_type, context, code)
+                self.chk.check_possible_missing_await(
+                    caller_type, callee_type, context, error.code
+                )
 
     def check_overload_call(
         self,