Fix crashes on variadic unpacking in synthetic types (#21555)

Fixes #21237 (and similar crashes).

The problem is that we cannot do some of the type argument normalization
early in `typeanal.py` (since that will cause crashes on some
pathological recursive aliases), so we do it in `semanal_typeargs.py`
later. However, the mixed traverser visitor is somewhat incomplete (most
notably w.r.t. generated methods). I add (most of) the missing parts.

Author: ilevkivskyi

mypy/mixedtraverser.py

@@ -16,6 +16,7 @@
     TypeApplication,
     TypedDictExpr,
     TypeFormExpr,
+    TypeInfo,
     TypeVarExpr,
     Var,
     WithStmt,
@@ -41,15 +42,29 @@ def visit_func(self, o: FuncItem, /) -> None:
         self.visit_optional_type(o.type)
 
     def visit_class_def(self, o: ClassDef, /) -> None:
-        # TODO: Should we visit generated methods/variables as well, either here or in
-        #       TraverserVisitor?
         super().visit_class_def(o)
-        info = o.info
-        if info:
-            for base in info.bases:
-                base.accept(self)
-            if info.special_alias:
-                info.special_alias.accept(self)
+        if o.info:
+            self.process_type_info(o.info)
+
+    def process_type_info(self, info: TypeInfo) -> None:
+        # TODO: Should we visit generated methods/variables as well?
+        # We should for methods generated by us (see below). But it is less clear for
+        # 3rd party plugin generated methods (since we don't want to emit errors there).
+        for base in info.bases:
+            base.accept(self)
+        if info.special_alias:
+            # We need to accept all types that are conceptually identical like special
+            # alias target and corresponding tuple_type or typeddict_type, since those
+            # may be copies, and not the same object.
+            info.special_alias.accept(self)
+        if info.tuple_type:
+            info.tuple_type.accept(self)
+        if info.typeddict_type:
+            info.typeddict_type.accept(self)
+        if info.is_named_tuple or info.is_newtype:
+            for sym in info.names.values():
+                if sym.plugin_generated and sym.node:
+                    sym.node.accept(self)
 
     def visit_type_alias_expr(self, o: TypeAliasExpr, /) -> None:
         super().visit_type_alias_expr(o)
@@ -64,19 +79,20 @@ def visit_type_var_expr(self, o: TypeVarExpr, /) -> None:
 
     def visit_typeddict_expr(self, o: TypedDictExpr, /) -> None:
         super().visit_typeddict_expr(o)
-        self.visit_optional_type(o.info.typeddict_type)
+        self.process_type_info(o.info)
 
     def visit_namedtuple_expr(self, o: NamedTupleExpr, /) -> None:
         super().visit_namedtuple_expr(o)
-        assert o.info.tuple_type
-        o.info.tuple_type.accept(self)
+        self.process_type_info(o.info)
 
     def visit__promote_expr(self, o: PromoteExpr, /) -> None:
         super().visit__promote_expr(o)
         o.type.accept(self)
 
     def visit_newtype_expr(self, o: NewTypeExpr, /) -> None:
         super().visit_newtype_expr(o)
+        if o.info:
+            self.process_type_info(o.info)
         self.visit_optional_type(o.old_type)
 
     # Statements

mypy/typetraverser.py

@@ -82,7 +82,11 @@ def visit_instance(self, t: Instance, /) -> None:
         self.traverse_type_tuple(t.args)
 
     def visit_callable_type(self, t: CallableType, /) -> None:
-        # FIX generics
+        for tv in t.variables:
+            tv.upper_bound.accept(self)
+            if isinstance(tv, TypeVarType):
+                for v in tv.values:
+                    v.accept(self)
         self.traverse_type_list(t.arg_types)
         t.ret_type.accept(self)
         t.fallback.accept(self)

test-data/unit/check-python312.test

@@ -2293,3 +2293,27 @@ reveal_type(x)  # N: Revealed type is "__main__.C[()]"
 y: T[bool]
 reveal_type(y)  # N: Revealed type is "__main__.C[()]"
 [builtins fixtures/tuple.pyi]
+
+[case testTupleBaseTupleTypeUnpack]
+class X(tuple[*tuple[int], *tuple[int]]):
+    pass
+x = X((1, 2))
+reveal_type(x)  # N: Revealed type is "tuple[builtins.int, builtins.int, fallback=__main__.X]"
+[builtins fixtures/tuple.pyi]
+
+[case testNewTypeTupleTypeUnpack]
+from typing import NewType
+
+T = NewType("T", tuple[*tuple[int], *tuple[int]])
+t = T((1, 2))
+reveal_type(t)  # N: Revealed type is "tuple[builtins.int, builtins.int, fallback=__main__.T]"
+[builtins fixtures/tuple.pyi]
+
+[case testNamedTupleTupleTypeUnpack]
+from typing import NamedTuple
+
+class N(NamedTuple):
+    x: tuple[*tuple[int], *tuple[int]]
+n = N((1, 2))
+reveal_type(n)  # N: Revealed type is "tuple[tuple[builtins.int, builtins.int], fallback=__main__.N]"
+[builtins fixtures/tuple.pyi]