Fix crash with malformed TypedDicts and disllow-any-expr (#13963)

Fixes #13066

During the semanal phase, mypy opts to ignore and skip processing any
malformed or illegal statements inside of a TypedDict class definition,
such as method definitions.

Skipping semanal analysis on these statements can cause any number of
odd downstream problems: the type-checking phase assumes that all
semanal-only semantic constructs (e.g. FakeInfo) have been purged by
this point, and so can crash at any point once this precondition has
been violated.

This diff opts to solve this problem by filtering down the list of
statements so we keep only the ones we know are legal within a TypedDict
definition.

The other possible solution to this problem is to modify mypy so we skip
checking TypedDict class bodies entirely during type checking and
fine-grained deps analysis. Doing this would also let address #10007 and
supersede my other diff #13732.

I decided against doing this for now because:

1. I wasn't sure if this was actually safe, especially in the
fine-grained deps phase and for mypyc.
2. I think no matter what, the semanal phase should not leak
semanal-only types: relaxing this postcondition would make it harder to
reason about mypy. So, we'd probably want to make this change regardless
of what we do in the later phases.

Author: Michael0x2a

mypy/semanal_typeddict.py

@@ -23,6 +23,7 @@
     NameExpr,
     PassStmt,
     RefExpr,
+    Statement,
     StrExpr,
     TempNode,
     TupleExpr,
@@ -93,7 +94,7 @@ def analyze_typeddict_classdef(self, defn: ClassDef) -> tuple[bool, TypeInfo | N
             and defn.base_type_exprs[0].fullname in TPDICT_NAMES
         ):
             # Building a new TypedDict
-            fields, types, required_keys = self.analyze_typeddict_classdef_fields(defn)
+            fields, types, statements, required_keys = self.analyze_typeddict_classdef_fields(defn)
             if fields is None:
                 return True, None  # Defer
             info = self.build_typeddict_typeinfo(
@@ -102,6 +103,7 @@ def analyze_typeddict_classdef(self, defn: ClassDef) -> tuple[bool, TypeInfo | N
             defn.analyzed = TypedDictExpr(info)
             defn.analyzed.line = defn.line
             defn.analyzed.column = defn.column
+            defn.defs.body = statements
             return True, info
 
         # Extending/merging existing TypedDicts
@@ -139,7 +141,12 @@ def analyze_typeddict_classdef(self, defn: ClassDef) -> tuple[bool, TypeInfo | N
         # Iterate over bases in reverse order so that leftmost base class' keys take precedence
         for base in reversed(typeddict_bases):
             self.add_keys_and_types_from_base(base, keys, types, required_keys, defn)
-        new_keys, new_types, new_required_keys = self.analyze_typeddict_classdef_fields(defn, keys)
+        (
+            new_keys,
+            new_types,
+            new_statements,
+            new_required_keys,
+        ) = self.analyze_typeddict_classdef_fields(defn, keys)
         if new_keys is None:
             return True, None  # Defer
         keys.extend(new_keys)
@@ -151,6 +158,7 @@ def analyze_typeddict_classdef(self, defn: ClassDef) -> tuple[bool, TypeInfo | N
         defn.analyzed = TypedDictExpr(info)
         defn.analyzed.line = defn.line
         defn.analyzed.column = defn.column
+        defn.defs.body = new_statements
         return True, info
 
     def add_keys_and_types_from_base(
@@ -250,7 +258,7 @@ def map_items_to_base(
 
     def analyze_typeddict_classdef_fields(
         self, defn: ClassDef, oldfields: list[str] | None = None
-    ) -> tuple[list[str] | None, list[Type], set[str]]:
+    ) -> tuple[list[str] | None, list[Type], list[Statement], set[str]]:
         """Analyze fields defined in a TypedDict class definition.
 
         This doesn't consider inherited fields (if any). Also consider totality,
@@ -259,17 +267,22 @@ def analyze_typeddict_classdef_fields(
         Return tuple with these items:
          * List of keys (or None if found an incomplete reference --> deferral)
          * List of types for each key
+         * List of statements from defn.defs.body that are legally allowed to be a
+           part of a TypedDict definition
          * Set of required keys
         """
         fields: list[str] = []
         types: list[Type] = []
+        statements: list[Statement] = []
         for stmt in defn.defs.body:
             if not isinstance(stmt, AssignmentStmt):
-                # Still allow pass or ... (for empty TypedDict's).
-                if not isinstance(stmt, PassStmt) and not (
+                # Still allow pass or ... (for empty TypedDict's) and docstrings
+                if isinstance(stmt, PassStmt) or (
                     isinstance(stmt, ExpressionStmt)
                     and isinstance(stmt.expr, (EllipsisExpr, StrExpr))
                 ):
+                    statements.append(stmt)
+                else:
                     self.fail(TPDICT_CLASS_ERROR, stmt)
             elif len(stmt.lvalues) > 1 or not isinstance(stmt.lvalues[0], NameExpr):
                 # An assignment, but an invalid one.
@@ -281,8 +294,9 @@ def analyze_typeddict_classdef_fields(
                 if name in fields:
                     self.fail(f'Duplicate TypedDict key "{name}"', stmt)
                     continue
-                # Append name and type in this case...
+                # Append stmt, name, and type in this case...
                 fields.append(name)
+                statements.append(stmt)
                 if stmt.type is None:
                     types.append(AnyType(TypeOfAny.unannotated))
                 else:
@@ -293,9 +307,9 @@ def analyze_typeddict_classdef_fields(
                         and not self.api.is_func_scope(),
                     )
                     if analyzed is None:
-                        return None, [], set()  # Need to defer
+                        return None, [], [], set()  # Need to defer
                     types.append(analyzed)
-                # ...despite possible minor failures that allow further analyzis.
+                # ...despite possible minor failures that allow further analysis.
                 if stmt.type is None or hasattr(stmt, "new_syntax") and not stmt.new_syntax:
                     self.fail(TPDICT_CLASS_ERROR, stmt)
                 elif not isinstance(stmt.rvalue, TempNode):
@@ -317,7 +331,7 @@ def analyze_typeddict_classdef_fields(
             t.item if isinstance(t, RequiredType) else t for t in types
         ]
 
-        return fields, types, required_keys
+        return fields, types, statements, required_keys
 
     def check_typeddict(
         self, node: Expression, var_name: str | None, is_func_scope: bool

test-data/unit/check-typeddict.test

@@ -221,6 +221,19 @@ reveal_type(d)  # N: Revealed type is "TypedDict('__main__.D', {'y': builtins.in
 [builtins fixtures/dict.pyi]
 [typing fixtures/typing-typeddict.pyi]
 
+[case testCannotCreateTypedDictWithDecoratedFunction]
+# flags: --disallow-any-expr
+# https://github.com/python/mypy/issues/13066
+from typing import TypedDict
+class D(TypedDict):
+    @classmethod  # E: Invalid statement in TypedDict definition; expected "field_name: field_type"
+    def m(self) -> D:
+        pass
+d = D()
+reveal_type(d)  # N: Revealed type is "TypedDict('__main__.D', {})"
+[builtins fixtures/dict.pyi]
+[typing fixtures/typing-typeddict.pyi]
+
 [case testTypedDictWithClassmethodAlternativeConstructorDoesNotCrash]
 # https://github.com/python/mypy/issues/5653
 from typing import TypedDict