Add analysis of typeshed PRs causing ecosystem hits in ruff#23963

Identifies two typeshed PRs responsible for 139 new ecosystem diagnostics:
- python/typeshed#14284 (dict.__or__ overload removal): ~150 diagnostics
- python/typeshed#15470 (set/frozenset canonicalization): ~3 diagnostics

https://claude.ai/code/session_016z9Bez4viqJyDJAeZMQbWo

Author: claude

typeshed-ecosystem-analysis.md

@@ -0,0 +1,90 @@
+# Typeshed PR Ecosystem Analysis for ruff#23963
+
+## Summary
+
+The typeshed sync in [ruff#23963](https://github.com/astral-sh/ruff/pull/23963) covers commits
+`843c1fd..f8f0794` from [python/typeshed](https://github.com/python/typeshed). Of the 26 commits
+in this range, **two typeshed PRs** are responsible for all new ecosystem hits:
+
+### 1. [python/typeshed#15470](https://github.com/python/typeshed/pull/15470) — Canonicalized set/frozenset signatures
+
+**Commit:** `e8638cd0e`
+
+**What changed:**
+- `set.discard(element: _T)` → `set.discard(element: object)`
+- `set.difference/intersection/isdisjoint/issubset/issuperset(*s: Iterable[Any])` → `Iterable[object]`
+- `set.symmetric_difference(s: Iterable[_T])` → `set.symmetric_difference(s: Iterable[_S]) -> set[_T | _S]`
+- `frozenset.isdisjoint(s: Iterable[_T_co])` → `Iterable[object]`
+- `frozenset.__and__(value: AbstractSet[_T_co])` → `AbstractSet[object]`
+- `frozenset.symmetric_difference(s: Iterable[_T_co])` → `frozenset.symmetric_difference(s: Iterable[_S]) -> frozenset[_T_co | _S]`
+
+**Ecosystem impact:**
+- **Home Assistant (core):** New `invalid-method-override` error at `core_config.py:529` where
+  `_ComponentSet.discard(value: str)` overrides `set.discard(element: object)` — the parameter type
+  is narrower than the base class, which is now `object` instead of `_T` (i.e., `str`).
+- **Home Assistant (core):** New `unused-type-ignore-comment` — a `# type: ignore` comment that
+  suppressed the old `discard` signature mismatch is now unnecessary since the base method accepts
+  `object`.
+- **SymPy:** Error message text change — `set.intersection` parameter shown as `Iterable[object]`
+  instead of `Iterable[Any]` in diagnostic output.
+
+**Reproduction:**
+```python
+class MySet(set[str]):
+    def discard(self, value: str) -> None:  # error[invalid-method-override] with new stubs
+        pass
+```
+
+### 2. [python/typeshed#14284](https://github.com/python/typeshed/pull/14284) — Remove `dict.__or__` overloads
+
+**Commit:** `bfb7342f8`
+
+**What changed:**
+- Removed the identity overloads for `dict.__or__` and `dict.__ror__` that preserved the exact
+  type when merging dicts of the same type. Only the union-expanding overload
+  `def __or__(self, value: dict[_T1, _T2]) -> dict[_KT | _T1, _VT | _T2]` remains.
+
+**Ecosystem impact:**
+- **Pydantic:** `dict[str, Any] | dict[str, <specific>]` now infers `dict[str, Any | <specific>]`
+  instead of `dict[str, Any]`. This causes `CoreMetadata` TypedDict operations to produce
+  `dict[str, Divergent]` in some cyclic type resolution paths, triggering `invalid-parameter-default`
+  and `invalid-assignment` errors.
+- **Rotki:** `dict[str, Any] | dict[str, <typed-values>]` (used in `common_arguments` at
+  `schemas.py:690`) now infers `dict[str, Any | IncludeExcludeFilterData | list[Any] | None]`
+  instead of `dict[str, Any]`, causing `invalid-argument-type` errors when dict values are passed
+  to functions expecting specific types.
+- **OpenLibrary:** Similar dict merge patterns produce wider union types, causing
+  `invalid-argument-type` errors in `lists.py`.
+
+**Reproduction:**
+```python
+from typing import Any
+
+def get_base() -> dict[str, Any]:
+    return {}
+
+# Old: dict[str, Any] (identity overload matched same key type)
+# New: dict[str, Any | int] (only union overload remains)
+merged = get_base() | {"x": 1}
+```
+
+## Affected projects summary
+
+| Project | New diagnostics | Responsible typeshed PR |
+|---------|----------------|----------------------|
+| Rotki | ~137 `invalid-argument-type` | #14284 (dict.__or__) |
+| Pydantic | ~9 `invalid-parameter-default` / `invalid-assignment` | #14284 (dict.__or__) |
+| OpenLibrary | 4 `invalid-argument-type` | #14284 (dict.__or__) |
+| SymPy | 1 message text change | #15470 (set/frozenset) |
+| Home Assistant | 1 `invalid-method-override` + 1 `unused-type-ignore-comment` | #15470 (set/frozenset) |
+
+## Notes
+
+- The exact ecosystem hits could not be fully reproduced locally because the ecosystem analyzer
+  tests against unpinned project HEADs, which may have changed between the CI run (March 15, 2026)
+  and local testing.
+- Pydantic consistently causes stack overflows in non-release ty builds, making it difficult to
+  test locally.
+- The `dict.__or__` overload removal is the higher-impact change (affecting ~150 diagnostics across
+  3 projects), while the set/frozenset canonicalization has a smaller but still notable impact
+  (3 diagnostics across 2 projects).