diff --git a/mypy/build.py b/mypy/build.py
index bfcc897cf2fa..3e8da93b4eae 100644
--- a/mypy/build.py
+++ b/mypy/build.py
@@ -83,15 +83,32 @@
     WORKER_START_TIMEOUT,
 )
 from mypy.error_formatter import OUTPUT_CHOICES, ErrorFormatter
-from mypy.errors import CompileError, ErrorInfo, Errors, ErrorTuple, report_internal_error
+from mypy.errors import (
+    CompileError,
+    ErrorInfo,
+    Errors,
+    ErrorTuple,
+    ErrorTupleRaw,
+    report_internal_error,
+)
 from mypy.graph_utils import prepare_sccs, strongly_connected_components, topsort
 from mypy.indirection import TypeIndirectionVisitor
 from mypy.ipc import BadStatus, IPCClient, IPCMessage, read_status, ready_to_read, receive, send
 from mypy.messages import MessageBuilder
-from mypy.nodes import Import, ImportAll, ImportBase, ImportFrom, MypyFile, SymbolTable
+from mypy.nodes import (
+    ClassDef,
+    Context,
+    Import,
+    ImportAll,
+    ImportBase,
+    ImportFrom,
+    MypyFile,
+    SymbolTable,
+)
 from mypy.partially_defined import PossiblyUndefinedVariableVisitor
 from mypy.semanal import SemanticAnalyzer
 from mypy.semanal_pass1 import SemanticAnalyzerPreAnalysis
+from mypy.traverser import find_definitions
 from mypy.util import (
     DecodeError,
     decode_python_encoding,
@@ -866,6 +883,10 @@ def __init__(
         self.queue_order: int = 0
         # Is this an instance used by a parallel worker?
         self.parallel_worker = parallel_worker
+        # Cache for ASTs created during error message generation. Note these are
+        # raw parsed trees not analyzed with mypy. We use these to find absolute
+        # location of a symbol used as a location for an error message.
+        self.extra_trees: dict[str, MypyFile] = {}
 
     def dump_stats(self) -> None:
         if self.options.dump_build_stats:
@@ -1028,6 +1049,58 @@ def report_file(
         if self.reports is not None and self.source_set.is_source(file):
             self.reports.file(file, self.modules, type_map, options)
 
+    def resolve_location(self, graph: dict[str, State], fullname: str) -> Context | None:
+        """Resolve an absolute location of a symbol with given fullname."""
+        rest = []
+        head = fullname
+        while True:
+            # TODO: this mimics the logic in lookup.py but it is actually wrong.
+            # This is because we don't distinguish between submodule and a local symbol
+            # with the same name.
+            head, tail = head.rsplit(".", maxsplit=1)
+            rest.append(tail)
+            if head in graph:
+                state = graph[head]
+                break
+            if "." not in head:
+                return None
+        *prefix, name = reversed(rest)
+        # If this happens something is wrong, but it is better to give slightly
+        # less helpful error message than crash.
+        if state.path is None:
+            return None
+        if state.tree is not None and state.tree.defs:
+            # We usually free ASTs after processing, but reuse an existing AST if
+            # it is still available.
+            tree = state.tree
+        elif state.id in self.extra_trees:
+            tree = self.extra_trees[state.id]
+        else:
+            if state.source is not None:
+                # Sources are usually discarded after processing as well, check
+                # if we still have one just in case.
+                source = state.source
+            else:
+                path = state.manager.maybe_swap_for_shadow_path(state.path)
+                source = decode_python_encoding(state.manager.fscache.read(path))
+            tree = parse(source, state.path, state.id, state.manager.errors, state.options)
+            self.extra_trees[state.id] = tree
+        statements = tree.defs
+        while prefix:
+            part = prefix.pop(0)
+            for statement in statements:
+                defs = find_definitions(statement, part)
+                if not defs or not isinstance((defn := defs[0]), ClassDef):
+                    continue
+                statements = defn.defs.body
+                break
+            else:
+                return None
+        for statement in statements:
+            if defs := find_definitions(statement, name):
+                return defs[0]
+        return None
+
     def verbosity(self) -> int:
         return self.options.verbosity
 
@@ -2359,7 +2432,7 @@ def load_tree(self, temporary: bool = False) -> None:
 
     def fix_cross_refs(self) -> None:
         assert self.tree is not None, "Internal error: method must be called on parsed file only"
-        # We need to set allow_missing when doing a fine grained cache
+        # We need to set allow_missing when doing a fine-grained cache
         # load because we need to gracefully handle missing modules.
         fixup_module(self.tree, self.manager.modules, self.options.use_fine_grained_cache)
 
@@ -3558,7 +3631,9 @@ def find_stale_sccs(
                     path = manager.errors.simplify_path(graph[id].xpath)
                     formatted = manager.errors.format_messages(
                         path,
-                        deserialize_codes(graph[id].error_lines),
+                        transform_error_tuples(
+                            manager, graph, deserialize_codes(graph[id].error_lines)
+                        ),
                         formatter=manager.error_formatter,
                     )
                     manager.flush_errors(path, formatted, False)
@@ -3813,7 +3888,9 @@ def process_stale_scc(
         if graph[id].xpath not in manager.errors.ignored_files:
             errors = manager.errors.file_messages(graph[id].xpath)
             formatted = manager.errors.format_messages(
-                graph[id].xpath, errors, formatter=manager.error_formatter
+                graph[id].xpath,
+                transform_error_tuples(manager, graph, errors),
+                formatter=manager.error_formatter,
             )
             manager.flush_errors(manager.errors.simplify_path(graph[id].xpath), formatted, False)
             errors_by_id[id] = errors
@@ -3972,14 +4049,37 @@ def write_undocumented_ref_info(
     metastore.write(ref_info_file, json_dumps(deps_json))
 
 
-def serialize_codes(errs: list[ErrorTuple]) -> list[SerializedError]:
+def transform_error_tuples(
+    manager: BuildManager, graph: dict[str, State], error_tuples_rel: list[ErrorTupleRaw]
+) -> list[ErrorTuple]:
+    """Transform raw error tuples by resolving relative error locations."""
+    error_tuples = []
+    for e in error_tuples_rel:
+        file, line_rel, column, end_line, end_column, severity, message, code = e
+        if isinstance(line_rel, int):
+            line = line_rel
+        else:
+            assert file is not None
+            loc = manager.resolve_location(graph, line_rel)
+            if loc is not None:
+                line = loc.line
+                column = loc.column
+                end_line = loc.end_line or -1
+                end_column = loc.end_column or -1
+            else:
+                line = -1
+        error_tuples.append((file, line, column, end_line, end_column, severity, message, code))
+    return error_tuples
+
+
+def serialize_codes(errs: list[ErrorTupleRaw]) -> list[SerializedError]:
     return [
         (path, line, column, end_line, end_column, severity, message, code.code if code else None)
         for path, line, column, end_line, end_column, severity, message, code in errs
     ]
 
 
-def deserialize_codes(errs: list[SerializedError]) -> list[ErrorTuple]:
+def deserialize_codes(errs: list[SerializedError]) -> list[ErrorTupleRaw]:
     return [
         (
             path,
diff --git a/mypy/cache.py b/mypy/cache.py
index f67bd627d3b8..81915821e19e 100644
--- a/mypy/cache.py
+++ b/mypy/cache.py
@@ -71,7 +71,7 @@
 # High-level cache layout format
 CACHE_VERSION: Final = 1
 
-SerializedError: _TypeAlias = tuple[str | None, int, int, int, int, str, str, str | None]
+SerializedError: _TypeAlias = tuple[str | None, int | str, int, int, int, str, str, str | None]
 
 
 class CacheMeta:
@@ -479,7 +479,10 @@ def write_errors(data: WriteBuffer, errs: list[SerializedError]) -> None:
     for path, line, column, end_line, end_column, severity, message, code in errs:
         write_tag(data, TUPLE_GEN)
         write_str_opt(data, path)
-        write_int(data, line)
+        if isinstance(line, str):
+            write_str(data, line)
+        else:
+            write_int(data, line)
         write_int(data, column)
         write_int(data, end_line)
         write_int(data, end_column)
@@ -493,10 +496,17 @@ def read_errors(data: ReadBuffer) -> list[SerializedError]:
     result = []
     for _ in range(read_int_bare(data)):
         assert read_tag(data) == TUPLE_GEN
+        path = read_str_opt(data)
+        tag = read_tag(data)
+        if tag == LITERAL_STR:
+            line: str | int = read_str_bare(data)
+        else:
+            assert tag == LITERAL_INT
+            line = read_int_bare(data)
         result.append(
             (
-                read_str_opt(data),
-                read_int(data),
+                path,
+                line,
                 read_int(data),
                 read_int(data),
                 read_int(data),
diff --git a/mypy/errors.py b/mypy/errors.py
index edfb3bd1607a..559fcbda6d85 100644
--- a/mypy/errors.py
+++ b/mypy/errors.py
@@ -130,6 +130,7 @@ def __init__(
         target: str | None = None,
         priority: int = 0,
         parent_error: ErrorInfo | None = None,
+        location_ref: str | None = None,
     ) -> None:
         self.import_ctx = import_ctx
         self.file = file
@@ -151,12 +152,18 @@ def __init__(
         if parent_error is not None:
             assert severity == "note", "Only notes can specify parent errors"
         self.parent_error = parent_error
+        self.location_ref = location_ref
 
 
 # Type used internally to represent errors:
 #   (path, line, column, end_line, end_column, severity, message, code)
 ErrorTuple: _TypeAlias = tuple[str | None, int, int, int, int, str, str, ErrorCode | None]
 
+# A raw version of the above that can refer to either absolute or relative location.
+# If the location is relative, the first item (line) is a string with a symbol fullname,
+# and three other values (column, end_line, end_column) are set to -1.
+ErrorTupleRaw: _TypeAlias = tuple[str | None, int | str, int, int, int, str, str, ErrorCode | None]
+
 
 class ErrorWatcher:
     """Context manager that can be used to keep track of new errors recorded
@@ -569,6 +576,7 @@ def report(
         end_line: int | None = None,
         end_column: int | None = None,
         parent_error: ErrorInfo | None = None,
+        location_ref: str | None = None,
     ) -> ErrorInfo:
         """Report message at the given line using the current error context.
 
@@ -635,6 +643,7 @@ def report(
             origin=(self.file, origin_span),
             target=self.current_target(),
             parent_error=parent_error,
+            location_ref=location_ref,
         )
         self.add_error_info(info)
         return info
@@ -1014,6 +1023,8 @@ def raise_error(self, use_stdout: bool = True) -> NoReturn:
         """
         # self.new_messages() will format all messages that haven't already
         # been returned from a file_messages() call.
+        # TODO: pass resolve_location callback here.
+        # This will be needed if we are going to use relative locations in blocker errors.
         raise CompileError(
             self.new_messages(), use_stdout=use_stdout, module_with_blocker=self.blocker_module()
         )
@@ -1076,7 +1087,7 @@ def format_messages_default(
                     a.append(" " * (DEFAULT_SOURCE_OFFSET + column) + marker)
         return a
 
-    def file_messages(self, path: str) -> list[ErrorTuple]:
+    def file_messages(self, path: str) -> list[ErrorTupleRaw]:
         """Return an error tuple list of new error messages from a given file."""
         if path not in self.error_info_map:
             return []
@@ -1119,7 +1130,9 @@ def find_shadow_file_mapping(self, path: str) -> str | None:
                 return i[1]
         return None
 
-    def new_messages(self) -> list[str]:
+    def new_messages(
+        self, resolve_location: Callable[[str], Context | None] | None = None
+    ) -> list[str]:
         """Return a string list of new error messages.
 
         Use a form suitable for displaying to the user.
@@ -1129,7 +1142,29 @@ def new_messages(self) -> list[str]:
         msgs = []
         for path in self.error_info_map.keys():
             if path not in self.flushed_files:
-                error_tuples = self.file_messages(path)
+                error_tuples_rel = self.file_messages(path)
+                error_tuples = []
+                for e in error_tuples_rel:
+                    # This has a bit of code duplication with build.py, but it is hard
+                    # to avoid without either an import cycle or a performance penalty.
+                    file, line_rel, column, end_line, end_column, severity, message, code = e
+                    if isinstance(line_rel, int):
+                        line = line_rel
+                    elif resolve_location is not None:
+                        assert file is not None
+                        loc = resolve_location(line_rel)
+                        if loc is not None:
+                            line = loc.line
+                            column = loc.column
+                            end_line = loc.end_line or -1
+                            end_column = loc.end_column or -1
+                        else:
+                            line = -1
+                    else:
+                        line = -1
+                    error_tuples.append(
+                        (file, line, column, end_line, end_column, severity, message, code)
+                    )
                 msgs.extend(self.format_messages(path, error_tuples))
         return msgs
 
@@ -1141,7 +1176,7 @@ def targets(self) -> set[str]:
             info.target for errs in self.error_info_map.values() for info in errs if info.target
         }
 
-    def render_messages(self, errors: list[ErrorInfo]) -> list[ErrorTuple]:
+    def render_messages(self, errors: list[ErrorInfo]) -> list[ErrorTupleRaw]:
         """Translate the messages into a sequence of tuples.
 
         Each tuple is of form (path, line, col, severity, message, code).
@@ -1149,7 +1184,7 @@ def render_messages(self, errors: list[ErrorInfo]) -> list[ErrorTuple]:
         The path item may be None. If the line item is negative, the
         line number is not defined for the tuple.
         """
-        result: list[ErrorTuple] = []
+        result: list[ErrorTupleRaw] = []
         prev_import_context: list[tuple[str, int]] = []
         prev_function_or_member: str | None = None
         prev_type: str | None = None
@@ -1224,9 +1259,21 @@ def render_messages(self, errors: list[ErrorInfo]) -> list[ErrorTuple]:
                 else:
                     result.append((file, -1, -1, -1, -1, "note", f'In class "{e.type}":', None))
 
-            result.append(
-                (file, e.line, e.column, e.end_line, e.end_column, e.severity, e.message, e.code)
-            )
+            if e.location_ref is not None:
+                result.append((file, e.location_ref, -1, -1, -1, e.severity, e.message, e.code))
+            else:
+                result.append(
+                    (
+                        file,
+                        e.line,
+                        e.column,
+                        e.end_line,
+                        e.end_column,
+                        e.severity,
+                        e.message,
+                        e.code,
+                    )
+                )
 
             prev_import_context = e.import_ctx
             prev_function_or_member = e.function_or_member
diff --git a/mypy/lookup.py b/mypy/lookup.py
index 640481ff703c..e3b195567fa0 100644
--- a/mypy/lookup.py
+++ b/mypy/lookup.py
@@ -32,6 +32,9 @@ def lookup_fully_qualified(
             if raise_on_missing:
                 assert "." in head, f"Cannot find module for {name}"
             return None
+        # TODO: this logic is not correct as it confuses a submodule and a local symbol.
+        # A potential solution may be to use format like pkg.mod:Cls.method for fullname,
+        # but this is a relatively big change.
         head, tail = head.rsplit(".", maxsplit=1)
         rest.append(tail)
         mod = modules.get(head)
diff --git a/mypy/messages.py b/mypy/messages.py
index 0a255582d139..c5756a463894 100644
--- a/mypy/messages.py
+++ b/mypy/messages.py
@@ -266,6 +266,11 @@ def span_from_context(ctx: Context) -> Iterable[int]:
             assert origin_span is not None
             origin_span = itertools.chain(origin_span, span_from_context(secondary_context))
 
+        location_ref = None
+        if file is not None and file != self.errors.file:
+            assert isinstance(context, SymbolNode), "Only symbols can be locations in other files"
+            location_ref = context.fullname
+
         return self.errors.report(
             context.line if context else -1,
             context.column if context else -1,
@@ -278,6 +283,7 @@ def span_from_context(ctx: Context) -> Iterable[int]:
             end_column=context.end_column if context else -1,
             code=code,
             parent_error=parent_error,
+            location_ref=location_ref,
         )
 
     def fail(
diff --git a/mypy/plugins/functools.py b/mypy/plugins/functools.py
index c8b370f15e6d..1de0d9efae56 100644
--- a/mypy/plugins/functools.py
+++ b/mypy/plugins/functools.py
@@ -305,6 +305,9 @@ def handle_partial_with_callee(ctx: mypy.plugin.FunctionContext, callee: Type) -
     if not mypy.checker.is_valid_inferred_type(ret_type, ctx.api.options):
         ret_type = fn_type.ret_type  # same kind of hack as above
 
+    # Technically, we should set definition to None here, since it will not be recovered
+    # on warm cache runs in fixup.py. This however may hide some helpful info in error
+    # messages, so we are keeping it for now. See also issue #20640.
     partially_applied = fn_type.copy_modified(
         arg_types=partial_types,
         arg_kinds=partial_kinds,
diff --git a/mypy/server/update.py b/mypy/server/update.py
index f2e3554abda8..8ecfc95c373d 100644
--- a/mypy/server/update.py
+++ b/mypy/server/update.py
@@ -136,6 +136,7 @@
 from mypy.fscache import FileSystemCache
 from mypy.modulefinder import BuildSource
 from mypy.nodes import (
+    Context,
     Decorator,
     FuncDef,
     ImportFrom,
@@ -295,7 +296,7 @@ def update(
                 if not changed_modules:
                     # Preserve state needed for the next update.
                     self.previous_targets_with_errors = self.manager.errors.targets()
-                    messages = self.manager.errors.new_messages()
+                    messages = self.manager.errors.new_messages(self.resolve_location_cb)
                     break
 
         messages = sort_messages_preserving_file_order(messages, self.previous_messages)
@@ -319,9 +320,12 @@ def trigger(self, target: str) -> list[str]:
         )
         # Preserve state needed for the next update.
         self.previous_targets_with_errors = self.manager.errors.targets()
-        self.previous_messages = self.manager.errors.new_messages().copy()
+        self.previous_messages = self.manager.errors.new_messages(self.resolve_location_cb).copy()
         return self.update(changed_modules, [])
 
+    def resolve_location_cb(self, fullname: str) -> Context | None:
+        return self.manager.resolve_location(self.graph, fullname)
+
     def flush_cache(self) -> None:
         """Flush AST cache.
 
diff --git a/mypy/test/testcheck.py b/mypy/test/testcheck.py
index 5e533e3c245d..00268ea998df 100644
--- a/mypy/test/testcheck.py
+++ b/mypy/test/testcheck.py
@@ -141,6 +141,7 @@ def run_case_once(
             options.fixed_format_cache = True
             if testcase.output_files:
                 raise pytest.skip("Reports are not supported in parallel mode")
+            # Note: do not use this unless really needed!
             if testcase.name.endswith("_no_parallel"):
                 raise pytest.skip("Test not supported in parallel mode yet")
 
@@ -163,7 +164,7 @@ def run_case_once(
 
         sources = []
         for module_name, program_path, program_text in module_data:
-            # Always set to none so we're forced to reread the module in incremental mode
+            # Always set to None, so we're forced to reread the module in incremental mode
             sources.append(
                 BuildSource(program_path, module_name, None if incremental_step else program_text)
             )
diff --git a/mypy/traverser.py b/mypy/traverser.py
index baf234cc1b25..83b64ea21e1b 100644
--- a/mypy/traverser.py
+++ b/mypy/traverser.py
@@ -66,6 +66,7 @@
     SetExpr,
     SliceExpr,
     StarExpr,
+    Statement,
     StrExpr,
     SuperExpr,
     TempNode,
@@ -96,7 +97,7 @@
     StarredPattern,
     ValuePattern,
 )
-from mypy.visitor import NodeVisitor
+from mypy.visitor import NodeVisitor, StatementVisitor
 
 
 @trait
@@ -108,6 +109,10 @@ class TraverserVisitor(NodeVisitor[None]):
     should override visit methods to perform actions during
     traversal. Calling the superclass method allows reusing the
     traversal implementation.
+
+    TODO: split this into more limited visitor (e.g. statements-only etc).
+    This will improve performance since in many cases we don't need to recurse
+    all the way down in various visitors that subclass this.
     """
 
     def __init__(self) -> None:
@@ -1084,3 +1089,115 @@ def visit_assignment_stmt(self, stmt: AssignmentStmt) -> None:
 
     def visit_yield_from_expr(self, expr: YieldFromExpr) -> None:
         self.yield_from_expressions.append((expr, self.in_assignment))
+
+
+def find_definitions(o: Statement, name: str) -> list[Statement]:
+    visitor = DefinitionSeeker(name)
+    o.accept(visitor)
+    return visitor.found
+
+
+class DefinitionSeeker(StatementVisitor[None]):
+    def __init__(self, name: str) -> None:
+        self.name = name
+        self.found: list[Statement] = []
+
+    def visit_assignment_stmt(self, o: AssignmentStmt, /) -> None:
+        # TODO: support more kinds of locations (like assignment statements).
+        # the latter will be helpful for type old-style aliases.
+        pass
+
+    def visit_for_stmt(self, o: ForStmt, /) -> None:
+        o.body.accept(self)
+        if o.else_body:
+            o.else_body.accept(self)
+
+    def visit_with_stmt(self, o: WithStmt, /) -> None:
+        o.body.accept(self)
+
+    def visit_del_stmt(self, o: DelStmt, /) -> None:
+        pass
+
+    def visit_func_def(self, o: FuncDef, /) -> None:
+        if o.name == self.name:
+            self.found.append(o)
+
+    def visit_overloaded_func_def(self, o: OverloadedFuncDef, /) -> None:
+        if o.name == self.name:
+            self.found.append(o)
+
+    def visit_class_def(self, o: ClassDef, /) -> None:
+        if o.name == self.name:
+            self.found.append(o)
+
+    def visit_global_decl(self, o: GlobalDecl, /) -> None:
+        pass
+
+    def visit_nonlocal_decl(self, o: NonlocalDecl, /) -> None:
+        pass
+
+    def visit_decorator(self, o: Decorator, /) -> None:
+        if o.name == self.name:
+            self.found.append(o)
+
+    def visit_import(self, o: Import, /) -> None:
+        pass
+
+    def visit_import_from(self, o: ImportFrom, /) -> None:
+        pass
+
+    def visit_import_all(self, o: ImportAll, /) -> None:
+        pass
+
+    def visit_block(self, o: Block, /) -> None:
+        for s in o.body:
+            s.accept(self)
+
+    def visit_expression_stmt(self, o: ExpressionStmt, /) -> None:
+        pass
+
+    def visit_operator_assignment_stmt(self, o: OperatorAssignmentStmt, /) -> None:
+        pass
+
+    def visit_while_stmt(self, o: WhileStmt, /) -> None:
+        o.body.accept(self)
+        if o.else_body:
+            o.else_body.accept(self)
+
+    def visit_return_stmt(self, o: ReturnStmt, /) -> None:
+        pass
+
+    def visit_assert_stmt(self, o: AssertStmt, /) -> None:
+        pass
+
+    def visit_if_stmt(self, o: IfStmt, /) -> None:
+        for b in o.body:
+            b.accept(self)
+        if o.else_body:
+            o.else_body.accept(self)
+
+    def visit_break_stmt(self, o: BreakStmt, /) -> None:
+        pass
+
+    def visit_continue_stmt(self, o: ContinueStmt, /) -> None:
+        pass
+
+    def visit_pass_stmt(self, o: PassStmt, /) -> None:
+        pass
+
+    def visit_raise_stmt(self, o: RaiseStmt, /) -> None:
+        pass
+
+    def visit_try_stmt(self, o: TryStmt, /) -> None:
+        o.body.accept(self)
+        if o.else_body is not None:
+            o.else_body.accept(self)
+        if o.finally_body is not None:
+            o.finally_body.accept(self)
+
+    def visit_match_stmt(self, o: MatchStmt, /) -> None:
+        for b in o.bodies:
+            b.accept(self)
+
+    def visit_type_alias_stmt(self, o: TypeAliasStmt, /) -> None:
+        pass
diff --git a/mypy/types.py b/mypy/types.py
index 025812e25f0a..c75397224f2b 100644
--- a/mypy/types.py
+++ b/mypy/types.py
@@ -2241,7 +2241,7 @@ def copy_modified(
         ret_type: Bogus[Type] = _dummy,
         fallback: Bogus[Instance] = _dummy,
         name: Bogus[str | None] = _dummy,
-        definition: Bogus[SymbolNode] = _dummy,
+        definition: Bogus[SymbolNode | None] = _dummy,
         variables: Bogus[Sequence[TypeVarLikeType]] = _dummy,
         line: int = _dummy_int,
         column: int = _dummy_int,
diff --git a/test-data/unit/check-classes.test b/test-data/unit/check-classes.test
index 61e332f8566f..7fd96f9abf94 100644
--- a/test-data/unit/check-classes.test
+++ b/test-data/unit/check-classes.test
@@ -7683,7 +7683,7 @@ class Child(metaclass=M, thing=0):
     pass
 [builtins fixtures/object_with_init_subclass.pyi]
 
-[case testTooManyArgsForObject_no_parallel]
+[case testTooManyArgsForObject]
 class A(thing=5):
     pass
 [out]
diff --git a/test-data/unit/check-ignore.test b/test-data/unit/check-ignore.test
index 0c373c0e2788..d0f6bb6aeb60 100644
--- a/test-data/unit/check-ignore.test
+++ b/test-data/unit/check-ignore.test
@@ -198,7 +198,7 @@ bar(Child())
 [out]
 main:19: error: Argument 1 to "bar" has incompatible type "Child"; expected "Base[str, str]"
 
-[case testTypeIgnoreLineNumberWithinFile_no_parallel]
+[case testTypeIgnoreLineNumberWithinFile]
 import m
 pass # type: ignore
 m.f(kw=1)
diff --git a/test-data/unit/check-incremental.test b/test-data/unit/check-incremental.test
index d6020be9937d..1f640e6bc61b 100644
--- a/test-data/unit/check-incremental.test
+++ b/test-data/unit/check-incremental.test
@@ -1090,7 +1090,7 @@ import foo # type: ignore
 [builtins fixtures/module.pyi]
 [stale]
 
-[case testIncrementalWithSilentImportsAndIgnore_no_parallel]
+[case testIncrementalWithSilentImportsAndIgnore]
 # cmd: mypy -m main b
 # cmd2: mypy -m main c c.submodule
 # flags: --follow-imports=skip
@@ -6919,7 +6919,7 @@ class TheClass:
 [out2]
 tmp/a.py:3: note: Revealed type is "def (value: builtins.object) -> lib.TheClass.pyenum@6"
 
-
+-- Note: do not use _no_parallel unless really needed!
 [case testIncrementalFunctoolsPartial_no_parallel]
 import a
 
@@ -7700,3 +7700,52 @@ tmp/b.py:1: error: Cannot resolve name "no_such_export" (possible cyclic definit
 [out2]
 tmp/b.py:1: error: Cannot resolve name "no_such_export" (possible cyclic definition)
 tmp/m.py:2: note: Revealed type is "Any"
+
+[case testCachedUnexpectedKeywordArgument]
+import m
+[file m.py]
+import a
+[file a.py]
+import b
+b.lol(uhhhh=12) # tweak
+[file a.py.2]
+import b
+b.lol(uhhhh=12)
+[file b.py]
+def lol() -> None: pass
+[file b.py.3]
+# space
+def lol() -> None: pass
+[file m.py.4]
+import a  # touch
+[out]
+tmp/a.py:2: error: Unexpected keyword argument "uhhhh" for "lol"
+tmp/b.py:1: note: "lol" defined here
+[out2]
+tmp/a.py:2: error: Unexpected keyword argument "uhhhh" for "lol"
+tmp/b.py:1: note: "lol" defined here
+[out3]
+tmp/a.py:2: error: Unexpected keyword argument "uhhhh" for "lol"
+tmp/b.py:2: note: "lol" defined here
+[out4]
+tmp/a.py:2: error: Unexpected keyword argument "uhhhh" for "lol"
+tmp/b.py:2: note: "lol" defined here
+
+[case testCachedUnexpectedKeywordArgumentNested]
+import a
+[file a.py]
+import b
+b.lol(uhhhh=12) # tweak
+[file a.py.2]
+import b
+b.lol(uhhhh=12)
+[file b.py]
+while True:
+    if True:
+        def lol() -> None: pass
+[out]
+tmp/a.py:2: error: Unexpected keyword argument "uhhhh" for "lol"
+tmp/b.py:3: note: "lol" defined here
+[out2]
+tmp/a.py:2: error: Unexpected keyword argument "uhhhh" for "lol"
+tmp/b.py:3: note: "lol" defined here
diff --git a/test-data/unit/check-kwargs.test b/test-data/unit/check-kwargs.test
index 4099716bcf6b..5ef3a2e45aec 100644
--- a/test-data/unit/check-kwargs.test
+++ b/test-data/unit/check-kwargs.test
@@ -467,7 +467,7 @@ class A:
             pass
 A.B(x=1)  # E: Unexpected keyword argument "x" for "B"
 
-[case testUnexpectedMethodKwargFromOtherModule_no_parallel]
+[case testUnexpectedMethodKwargFromOtherModule]
 import m
 m.A(x=1)
 [file m.py]
diff --git a/test-data/unit/check-namedtuple.test b/test-data/unit/check-namedtuple.test
index a24a3964692f..c67c7b62b69b 100644
--- a/test-data/unit/check-namedtuple.test
+++ b/test-data/unit/check-namedtuple.test
@@ -115,7 +115,7 @@ a, b = x
 a, b, c = x  # E: Need more than 2 values to unpack (3 expected)
 [builtins fixtures/tuple.pyi]
 
-[case testNamedTupleAdditionalArgs_no_parallel]
+[case testNamedTupleAdditionalArgs]
 from collections import namedtuple
 
 A = namedtuple('A', 'a b')
diff --git a/test-data/unit/check-serialize.test b/test-data/unit/check-serialize.test
index 9932d5e134e7..592f77268b60 100644
--- a/test-data/unit/check-serialize.test
+++ b/test-data/unit/check-serialize.test
@@ -158,7 +158,7 @@ def f(__x: int) -> None: pass
 [out2]
 tmp/a.py:3: error: Argument 1 to "f" has incompatible type "str"; expected "int"
 tmp/a.py:4: error: Unexpected keyword argument "__x" for "f"
-tmp/b.py: note: "f" defined here
+tmp/b.py:1: note: "f" defined here
 
 [case testSerializeArgumentKindsErrors]
 import a
@@ -224,7 +224,7 @@ def f(x: int) -> int: pass
 [out2]
 tmp/a.py:2: note: Revealed type is "builtins.str"
 tmp/a.py:3: error: Unexpected keyword argument "x" for "f"
-tmp/b.py: note: "f" defined here
+tmp/b.py:3: note: "f" defined here
 
 [case testSerializeTypeGuardFunction]
 import a
diff --git a/test-data/unit/fine-grained.test b/test-data/unit/fine-grained.test
index faa46374023a..41fb0ed18ba8 100644
--- a/test-data/unit/fine-grained.test
+++ b/test-data/unit/fine-grained.test
@@ -11518,3 +11518,17 @@ class Sub(Base[Concatenate[str, P]]): ...
 [out]
 ==
 impl.py:7: error: Argument 1 to "meth" of "Base" has incompatible type "int"; expected "str"
+
+[case testFineGrainedUnexpectedKeywordArgument]
+import a
+[file a.py]
+import b
+[file a.py.2]
+import b
+b.lol(uhhhh=12)
+[file b.py]
+def lol() -> None: pass
+[out]
+==
+a.py:2: error: Unexpected keyword argument "uhhhh" for "lol"
+b.py:1: note: "lol" defined here