[ty] fix incorrect lazy scope narrowing

[mtshiba]

Summary

This is a follow-up to #19321.

Narrowing constraints introduced in a class scope were not applied even when they can be applied in lazy nested scopes. This PR fixes so that they are now applied.
Conversely, there were cases where narrowing constraints were being applied in places where they should not, so it is also fixed.

Test Plan

Some TODOs in narrow/conditionals/nested.md are now work correctly.

[github-actions]

Diagnostic diff on typing conformance tests

Changes were detected when running ty on typing conformance tests

--- old-output.txt	2025-08-04 13:05:13.522782057 +0000
+++ new-output.txt	2025-08-04 13:05:13.590782200 +0000
@@ -532,31 +532,23 @@
 generics_type_erasure.py:40:16: error[invalid-argument-type] Argument to bound method `__init__` is incorrect: Expected `str | None`, found `Literal[0]`
 generics_type_erasure.py:47:1: error[type-assertion-failure] Argument does not have asserted type `int`
 generics_type_erasure.py:56:1: error[type-assertion-failure] Argument does not have asserted type `bytes`
-generics_typevartuple_args.py:16:34: error[invalid-return-type] Function always implicitly returns `None`, which is not assignable to return type `tuple[@Todo, ...]`
 generics_typevartuple_args.py:20:1: error[type-assertion-failure] Argument does not have asserted type `tuple[int, str]`
-generics_typevartuple_args.py:27:77: error[invalid-return-type] Function always implicitly returns `None`, which is not assignable to return type `tuple[@Todo, ...]`
 generics_typevartuple_args.py:31:1: error[type-assertion-failure] Argument does not have asserted type `tuple[()]`
 generics_typevartuple_args.py:32:1: error[type-assertion-failure] Argument does not have asserted type `tuple[int, str]`
 generics_typevartuple_basic.py:12:14: error[invalid-argument-type] `@Todo` is not a valid argument to `Generic`
-generics_typevartuple_basic.py:16:26: error[invalid-return-type] Function always implicitly returns `None`, which is not assignable to return type `tuple[@Todo, ...]`
 generics_typevartuple_basic.py:23:13: error[invalid-argument-type] `@Todo` is not a valid argument to `Generic`
-generics_typevartuple_basic.py:42:34: error[invalid-argument-type] Argument to bound method `__init__` is incorrect: Expected `tuple[@Todo, ...]`, found `Literal[1]`
 generics_typevartuple_basic.py:52:14: error[invalid-argument-type] `TypeVarTuple` is not a valid argument to `Generic`
 generics_typevartuple_basic.py:65:27: error[unknown-argument] Argument `covariant` does not match any known parameter of function `__new__`
 generics_typevartuple_basic.py:66:27: error[too-many-positional-arguments] Too many positional arguments to function `__new__`: expected 2, got 4
 generics_typevartuple_basic.py:67:27: error[unknown-argument] Argument `bound` does not match any known parameter of function `__new__`
-generics_typevartuple_basic.py:75:50: error[invalid-return-type] Function always implicitly returns `None`, which is not assignable to return type `tuple[@Todo, ...]`
 generics_typevartuple_basic.py:84:1: error[type-assertion-failure] Argument does not have asserted type `tuple[int]`
 generics_typevartuple_basic.py:106:14: error[invalid-argument-type] `@Todo` is not a valid argument to `Generic`
-generics_typevartuple_callable.py:29:57: error[invalid-return-type] Function always implicitly returns `None`, which is not assignable to return type `tuple[@Todo, ...]`
 generics_typevartuple_callable.py:33:54: error[invalid-return-type] Function always implicitly returns `None`, which is not assignable to return type `tuple[int | float | complex, str, int]`
 generics_typevartuple_callable.py:37:34: error[invalid-return-type] Function always implicitly returns `None`, which is not assignable to return type `tuple[str]`
 generics_typevartuple_callable.py:41:1: error[type-assertion-failure] Argument does not have asserted type `tuple[str, int, int | float | complex]`
 generics_typevartuple_callable.py:42:1: error[type-assertion-failure] Argument does not have asserted type `tuple[str]`
-generics_typevartuple_callable.py:45:43: error[invalid-return-type] Function always implicitly returns `None`, which is not assignable to return type `tuple[@Todo, ...]`
 generics_typevartuple_callable.py:49:1: error[type-assertion-failure] Argument does not have asserted type `tuple[int | float, str, int | float | complex]`
 generics_typevartuple_concat.py:22:13: error[invalid-argument-type] `@Todo` is not a valid argument to `Generic`
-generics_typevartuple_concat.py:47:42: error[invalid-return-type] Function always implicitly returns `None`, which is not assignable to return type `tuple[@Todo, ...]`
 generics_typevartuple_concat.py:52:1: error[type-assertion-failure] Argument does not have asserted type `tuple[int, bool, str]`
 generics_typevartuple_overloads.py:16:13: error[invalid-argument-type] `@Todo` is not a valid argument to `Generic`
 generics_typevartuple_specialization.py:16:13: error[invalid-argument-type] `@Todo` is not a valid argument to `Generic`
@@ -568,14 +560,15 @@
 generics_typevartuple_specialization.py:52:5: error[type-assertion-failure] Argument does not have asserted type `tuple[str, @Todo]`
 generics_typevartuple_specialization.py:52:37: error[invalid-type-form] Tuple literals are not allowed in this context in a type expression: Did you mean `tuple[()]`?
 generics_typevartuple_specialization.py:59:14: error[invalid-argument-type] `@Todo` is not a valid argument to `Generic`
+generics_typevartuple_specialization.py:92:67: error[invalid-type-form] Variable of type `type[@Todo]` is not allowed in a type expression
 generics_typevartuple_specialization.py:93:5: error[type-assertion-failure] Argument does not have asserted type `tuple[str, int]`
 generics_typevartuple_specialization.py:94:5: error[type-assertion-failure] Argument does not have asserted type `tuple[int | float]`
 generics_typevartuple_specialization.py:95:5: error[type-assertion-failure] Argument does not have asserted type `tuple[Any, *tuple[Any, ...]]`
-generics_typevartuple_specialization.py:130:35: error[invalid-return-type] Function always implicitly returns `None`, which is not assignable to return type `tuple[tuple[@Todo, ...], T1@func7, T2@func7]`
+generics_typevartuple_specialization.py:130:35: error[invalid-return-type] Function always implicitly returns `None`, which is not assignable to return type `tuple[@Todo, T1@func7, T2@func7]`
 generics_typevartuple_specialization.py:135:5: error[type-assertion-failure] Argument does not have asserted type `tuple[tuple[()], str, bool]`
 generics_typevartuple_specialization.py:136:5: error[type-assertion-failure] Argument does not have asserted type `tuple[tuple[str], bool, int | float]`
 generics_typevartuple_specialization.py:137:5: error[type-assertion-failure] Argument does not have asserted type `tuple[tuple[str, bool], int | float, int]`
-generics_typevartuple_specialization.py:143:39: error[invalid-return-type] Function always implicitly returns `None`, which is not assignable to return type `tuple[tuple[@Todo, ...], T1@func9, T2@func9, T3@func9]`
+generics_typevartuple_specialization.py:143:39: error[invalid-return-type] Function always implicitly returns `None`, which is not assignable to return type `tuple[@Todo, T1@func9, T2@func9, T3@func9]`
 generics_typevartuple_specialization.py:148:5: error[type-assertion-failure] Argument does not have asserted type `tuple[tuple[()], str, bool, int | float]`
 generics_typevartuple_specialization.py:149:5: error[type-assertion-failure] Argument does not have asserted type `tuple[tuple[bool], str, int | float, int]`
 generics_typevartuple_specialization.py:157:5: error[type-assertion-failure] Argument does not have asserted type `tuple[*tuple[int, ...], int]`
@@ -896,4 +889,4 @@
 tuples_type_form.py:36:1: error[invalid-assignment] Object of type `tuple[Literal[1], Literal[2], Literal[3], Literal[""]]` is not assignable to `tuple[int, ...]`
 typeddicts_operations.py:60:1: error[type-assertion-failure] Argument does not have asserted type `str | None`
 typeddicts_type_consistency.py:101:1: error[invalid-assignment] Object of type `Unknown | None` is not assignable to `str`
-Found 897 diagnostics
+Found 890 diagnostics

[github-actions]

mypy_primer results

Changes were detected when running on open source projects

openlibrary (https://github.com/internetarchive/openlibrary)
+ openlibrary/plugins/openlibrary/sentry.py:17:45: warning[possibly-unbound-attribute] Attribute `capture_exception_webpy` on type `Sentry | None` is possibly unbound
- Found 704 diagnostics
+ Found 705 diagnostics

No memory usage changes detected ✅