Another AssertionError with TypedDict and --cache-fine-grained in v1.11.0

[andersk]

dmypy crashes on import stripe, and I reduced the failure to the minimal test case below with no external dependencies. This is similar to

• AssertionError with TypedDict and --cache-fine-grained in v1.11.0 #17515,

but it remains a problem on current master (e67decb) even after #17515 was marked fixed. This is a regression in v1.11.0, and git bisect shows it was introduced by 1072c78 (#17148, cc @JelleZijlstra).

test.py

from typing import TypedDict

class A(TypedDict):
    b: "B"

class B(TypedDict):
    c: "C"

class C(TypedDict):
    d: "D"

class D:
    pass

$ mypy --show-traceback --cache-fine-grained test.py
test.py: error: INTERNAL ERROR -- Please try using mypy master on GitHub:
https://mypy.readthedocs.io/en/stable/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 1.12.0+dev.e67decb91ea5aacbb1e126463b02d78ded680a90
Traceback (most recent call last):
  File "/tmp/venv/bin/mypy", line 8, in <module>
    sys.exit(console_entry())
  File "/home/anders/python/mypy/mypy/__main__.py", line 15, in console_entry
    main()
  File "/home/anders/python/mypy/mypy/main.py", line 103, in main
    res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
  File "/home/anders/python/mypy/mypy/main.py", line 187, in run_build
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "/home/anders/python/mypy/mypy/build.py", line 193, in build
    result = _build(
  File "/home/anders/python/mypy/mypy/build.py", line 268, in _build
    graph = dispatch(sources, manager, stdout)
  File "/home/anders/python/mypy/mypy/build.py", line 2950, in dispatch
    process_graph(graph, manager)
  File "/home/anders/python/mypy/mypy/build.py", line 3348, in process_graph
    process_stale_scc(graph, scc, manager)
  File "/home/anders/python/mypy/mypy/build.py", line 3453, in process_stale_scc
    graph[id].finish_passes()
  File "/home/anders/python/mypy/mypy/build.py", line 2372, in finish_passes
    with self.wrap_context():
  File "/nix/store/z7xxy35k7620hs6fn6la5fg2lgklv72l-python3-3.12.4/lib/python3.12/contextlib.py", line 158, in __exit__
    self.gen.throw(value)
  File "/home/anders/python/mypy/mypy/build.py", line 2069, in wrap_context
    yield
  File "/home/anders/python/mypy/mypy/build.py", line 2409, in finish_passes
    self.update_fine_grained_deps(self.manager.fg_deps)
  File "/home/anders/python/mypy/mypy/build.py", line 2467, in update_fine_grained_deps
    merge_dependencies(self.compute_fine_grained_deps(), deps)
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/anders/python/mypy/mypy/build.py", line 2455, in compute_fine_grained_deps
    return get_dependencies(
           ^^^^^^^^^^^^^^^^^
  File "/home/anders/python/mypy/mypy/server/deps.py", line 187, in get_dependencies
    target.accept(visitor)
  File "/home/anders/python/mypy/mypy/nodes.py", line 372, in accept
    return visitor.visit_mypy_file(self)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/anders/python/mypy/mypy/server/deps.py", line 250, in visit_mypy_file
    super().visit_mypy_file(o)
  File "/home/anders/python/mypy/mypy/traverser.py", line 116, in visit_mypy_file
    d.accept(self)
  File "/home/anders/python/mypy/mypy/nodes.py", line 1183, in accept
    return visitor.visit_class_def(self)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/anders/python/mypy/mypy/server/deps.py", line 310, in visit_class_def
    super().visit_class_def(o)
  File "/home/anders/python/mypy/mypy/traverser.py", line 152, in visit_class_def
    o.defs.accept(self)
  File "/home/anders/python/mypy/mypy/nodes.py", line 1264, in accept
    return visitor.visit_block(self)
           ^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/anders/python/mypy/mypy/server/deps.py", line 429, in visit_block
    super().visit_block(o)
  File "/home/anders/python/mypy/mypy/traverser.py", line 120, in visit_block
    s.accept(self)
  File "/home/anders/python/mypy/mypy/nodes.py", line 1351, in accept
    return visitor.visit_assignment_stmt(self)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/anders/python/mypy/mypy/server/deps.py", line 490, in visit_assignment_stmt
    self.add_type_dependencies(o.type)
  File "/home/anders/python/mypy/mypy/server/deps.py", line 887, in add_type_dependencies
    for trigger in self.get_type_triggers(typ):
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/anders/python/mypy/mypy/server/deps.py", line 940, in get_type_triggers
    return get_type_triggers(typ, self.use_logical_deps())
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/anders/python/mypy/mypy/server/deps.py", line 947, in get_type_triggers
    return typ.accept(TypeTriggersVisitor(use_logical_deps, seen_aliases))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/anders/python/mypy/mypy/types.py", line 2708, in accept
    assert isinstance(visitor, SyntheticTypeVisitor)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: 
test.py: : note: use --pdb to drop into pdb

[andersk]

Is this the right fix or is something deeper going on?

--- a/mypy/types.py
+++ b/mypy/types.py
@@ -2705,6 +2705,8 @@ class RawExpressionType(ProperType):
         return self.base_type_name.replace("builtins.", "")
 
     def accept(self, visitor: TypeVisitor[T]) -> T:
+        if self.node is not None:
+            return self.node.accept(visitor)
         assert isinstance(visitor, SyntheticTypeVisitor)
         ret: T = visitor.visit_raw_expression_type(self)
         return ret

• Fix RawExpressionType.accept crash with --cache-fine-grained #17588