diff --git a/stdlib/re.pyi b/stdlib/re.pyi
index 4962ab8edad9..12771441b779 100644
--- a/stdlib/re.pyi
+++ b/stdlib/re.pyi
@@ -67,7 +67,9 @@ class Match(Generic[AnyStr]):
     @overload
     def expand(self: Match[str], template: str) -> str: ...
     @overload
-    def expand(self: Match[bytes], template: ReadableBuffer) -> bytes: ...
+    def expand(self: Match[bytes], template: ReadableBuffer) -> bytes: ...  # type: ignore[misc]
+    @overload
+    def expand(self, template: AnyStr) -> AnyStr: ...
     # group() returns "AnyStr" or "AnyStr | None", depending on the pattern.
     @overload
     def group(self, __group: Literal[0] = ...) -> AnyStr: ...
@@ -115,46 +117,62 @@ class Pattern(Generic[AnyStr]):
     @overload
     def search(self: Pattern[str], string: str, pos: int = ..., endpos: int = ...) -> Match[str] | None: ...
     @overload
-    def search(self: Pattern[bytes], string: ReadableBuffer, pos: int = ..., endpos: int = ...) -> Match[bytes] | None: ...
+    def search(self: Pattern[bytes], string: ReadableBuffer, pos: int = ..., endpos: int = ...) -> Match[bytes] | None: ...  # type: ignore[misc]
+    @overload
+    def search(self, string: AnyStr, pos: int = ..., endpos: int = ...) -> Match[AnyStr] | None: ...
     @overload
     def match(self: Pattern[str], string: str, pos: int = ..., endpos: int = ...) -> Match[str] | None: ...
     @overload
-    def match(self: Pattern[bytes], string: ReadableBuffer, pos: int = ..., endpos: int = ...) -> Match[bytes] | None: ...
+    def match(self: Pattern[bytes], string: ReadableBuffer, pos: int = ..., endpos: int = ...) -> Match[bytes] | None: ...  # type: ignore[misc]
+    @overload
+    def match(self, string: AnyStr, pos: int = ..., endpos: int = ...) -> Match[AnyStr] | None: ...
     @overload
     def fullmatch(self: Pattern[str], string: str, pos: int = ..., endpos: int = ...) -> Match[str] | None: ...
     @overload
-    def fullmatch(self: Pattern[bytes], string: ReadableBuffer, pos: int = ..., endpos: int = ...) -> Match[bytes] | None: ...
+    def fullmatch(self: Pattern[bytes], string: ReadableBuffer, pos: int = ..., endpos: int = ...) -> Match[bytes] | None: ...  # type: ignore[misc]
+    @overload
+    def fullmatch(self, string: AnyStr, pos: int = ..., endpos: int = ...) -> Match[AnyStr] | None: ...
     @overload
     def split(self: Pattern[str], string: str, maxsplit: int = ...) -> list[str | Any]: ...
     @overload
     def split(self: Pattern[bytes], string: ReadableBuffer, maxsplit: int = ...) -> list[bytes | Any]: ...
+    @overload
+    def split(self, string: AnyStr, maxsplit: int = ...) -> list[AnyStr | Any]: ...
     # return type depends on the number of groups in the pattern
     @overload
     def findall(self: Pattern[str], string: str, pos: int = ..., endpos: int = ...) -> list[Any]: ...
     @overload
     def findall(self: Pattern[bytes], string: ReadableBuffer, pos: int = ..., endpos: int = ...) -> list[Any]: ...
     @overload
+    def findall(self, string: AnyStr, pos: int = ..., endpos: int = ...) -> list[AnyStr]: ...
+    @overload
     def finditer(self: Pattern[str], string: str, pos: int = ..., endpos: int = ...) -> Iterator[Match[str]]: ...
     @overload
-    def finditer(self: Pattern[bytes], string: ReadableBuffer, pos: int = ..., endpos: int = ...) -> Iterator[Match[bytes]]: ...
+    def finditer(self: Pattern[bytes], string: ReadableBuffer, pos: int = ..., endpos: int = ...) -> Iterator[Match[bytes]]: ...  # type: ignore[misc]
+    @overload
+    def finditer(self, string: AnyStr, pos: int = ..., endpos: int = ...) -> Iterator[Match[AnyStr]]: ...
     @overload
     def sub(self: Pattern[str], repl: str | Callable[[Match[str]], str], string: str, count: int = ...) -> str: ...
     @overload
-    def sub(
+    def sub(  # type: ignore[misc]
         self: Pattern[bytes],
         repl: ReadableBuffer | Callable[[Match[bytes]], ReadableBuffer],
         string: ReadableBuffer,
         count: int = ...,
     ) -> bytes: ...
     @overload
+    def sub(self, repl: AnyStr | Callable[[Match[AnyStr]], AnyStr], string: AnyStr, count: int = ...) -> AnyStr: ...
+    @overload
     def subn(self: Pattern[str], repl: str | Callable[[Match[str]], str], string: str, count: int = ...) -> tuple[str, int]: ...
     @overload
-    def subn(
+    def subn(  # type: ignore[misc]
         self: Pattern[bytes],
         repl: ReadableBuffer | Callable[[Match[bytes]], ReadableBuffer],
         string: ReadableBuffer,
         count: int = ...,
     ) -> tuple[bytes, int]: ...
+    @overload
+    def subn(self, repl: AnyStr | Callable[[Match[AnyStr]], AnyStr], string: AnyStr, count: int = ...) -> tuple[AnyStr, int]: ...
     def __copy__(self) -> Pattern[AnyStr]: ...
     def __deepcopy__(self, __memo: Any) -> Pattern[AnyStr]: ...
     if sys.version_info >= (3, 9):
diff --git a/test_cases/stdlib/check_re.py b/test_cases/stdlib/check_re.py
new file mode 100644
index 000000000000..b6ab2b0d59d2
--- /dev/null
+++ b/test_cases/stdlib/check_re.py
@@ -0,0 +1,26 @@
+from __future__ import annotations
+
+import mmap
+import re
+import typing as t
+from typing_extensions import assert_type
+
+
+def check_search(str_pat: re.Pattern[str], bytes_pat: re.Pattern[bytes]) -> None:
+    assert_type(str_pat.search("x"), t.Optional[t.Match[str]])
+    assert_type(bytes_pat.search(b"x"), t.Optional[t.Match[bytes]])
+    assert_type(bytes_pat.search(bytearray(b"x")), t.Optional[t.Match[bytes]])
+    assert_type(bytes_pat.search(mmap.mmap(0, 10)), t.Optional[t.Match[bytes]])
+
+
+def check_search_with_AnyStr(pattern: re.Pattern[t.AnyStr], string: t.AnyStr) -> re.Match[t.AnyStr]:
+    """See issue #9591"""
+    match = pattern.search(string)
+    if match is None:
+        raise ValueError(f"'{string!r}' does not match {pattern!r}")
+    return match
+
+
+def check_no_ReadableBuffer_false_negatives() -> None:
+    re.compile("foo").search(bytearray(b"foo"))  # type: ignore
+    re.compile("foo").search(mmap.mmap(0, 10))  # type: ignore
diff --git a/test_cases/stdlib/typing/check_pattern.py b/test_cases/stdlib/typing/check_pattern.py
deleted file mode 100644
index ec5c1c4f6141..000000000000
--- a/test_cases/stdlib/typing/check_pattern.py
+++ /dev/null
@@ -1,10 +0,0 @@
-from __future__ import annotations
-
-from typing import Match, Optional, Pattern
-from typing_extensions import assert_type
-
-
-def test_search(str_pat: Pattern[str], bytes_pat: Pattern[bytes]) -> None:
-    assert_type(str_pat.search("x"), Optional[Match[str]])
-    assert_type(bytes_pat.search(b"x"), Optional[Match[bytes]])
-    assert_type(bytes_pat.search(bytearray(b"x")), Optional[Match[bytes]])