WIP 2

Author: cdce8p

mypy/expandtype.py

@@ -240,6 +240,14 @@ def visit_type_var(self, t: TypeVarType) -> Type:
     def visit_param_spec(self, t: ParamSpecType) -> Type:
         # Set prefix to something empty, so we don't duplicate it below.
         repl = self.variables.get(t.id, t.copy_modified(prefix=Parameters([], [], [])))
+        if isinstance(repl, ParamSpecType):
+            if (tvar_id := repl.id) in self.recursive_tvar_guard:
+                return self.recursive_tvar_guard[tvar_id] or repl
+            self.recursive_tvar_guard[tvar_id] = None
+            repl = repl.accept(self)
+            if isinstance(repl, ParamSpecType):
+                repl.default = repl.default.accept(self)
+            self.recursive_tvar_guard[tvar_id] = repl
         if isinstance(repl, ParamSpecType):
             return repl.copy_modified(
                 flavor=t.flavor,

test-data/unit/check-typevar-defaults.test

@@ -425,6 +425,32 @@ def func_d2(
     n = ClassD2[int, float, str]()
     reveal_type(n)  # N: Revealed type is "__main__.ClassD2[builtins.int, builtins.float, builtins.str]"
 
+[case testTypeVarDefaultsClassRecursive2]
+# flags: --disallow-any-generics
+from typing import Generic, ParamSpec
+
+P1 = ParamSpec("P1", default=[int, str])
+P2 = ParamSpec("P2", default=P1)
+P3 = ParamSpec("P3")
+
+class ClassE1(Generic[P1, P2]): ...
+
+def func_e1(
+    a: ClassE1,
+    b: ClassE1[[float]],
+    c: ClassE1[[float], [str]],
+) -> None:
+    reveal_type(a)  # N: Revealed type is "__main__.ClassE1[[builtins.int, builtins.str], [builtins.int, builtins.str]]"
+    reveal_type(b)  # N: Revealed type is "__main__.ClassE1[[builtins.float], [builtins.float]]"
+    reveal_type(c)  # N: Revealed type is "__main__.ClassE1[[builtins.float], [builtins.str]]"
+
+    k = ClassE1()
+    # reveal_type(k)  # Revealed type is "__main__.ClassE1[[builtins.int, builtins.str], [builtins.int, builtins.str]]"  # TODO
+    l = ClassE1[[float]]()
+    reveal_type(l)  # N: Revealed type is "__main__.ClassE1[[builtins.float], [builtins.float]]"
+    m = ClassE1[[float], [str]]()
+    reveal_type(m)  # N: Revealed type is "__main__.ClassE1[[builtins.float], [builtins.str]]"
+
 [case testTypeVarDefaultsClassRecursiveMultipleFiles]
 # flags: --disallow-any-generics
 from typing import Generic, TypeVar