Check element types for Deque, MutableSequence and MutableSet

[sneha4175]

Changes

Typeguard checks the element types of List, Sequence, Set and FrozenSet annotations, but Deque[T], MutableSequence[T] and MutableSet[T] did not have their element types checked. Their origins (collections.deque, collections.abc.MutableSequence, collections.abc.MutableSet) were not registered in origin_type_checkers, so they fell through to the generic instance check, which validates the container type but ignores T.

As a result, a value with the wrong element type silently passed, even with the ALL_ITEMS collection check strategy:

from collections import deque
from typeguard import check_type, CollectionCheckStrategy

# All of these wrongly passed before this change:
check_type(deque([1, "a"]), Deque[int],
           collection_check_strategy=CollectionCheckStrategy.ALL_ITEMS)
check_type([1, "a"], MutableSequence[int],
           collection_check_strategy=CollectionCheckStrategy.ALL_ITEMS)
check_type({1, "a"}, MutableSet[int],
           collection_check_strategy=CollectionCheckStrategy.ALL_ITEMS)

check_set and check_mapping already branch on the origin type to handle their concrete/mutable variants (e.g. frozenset vs set, MutableMapping vs Mapping). This applies the same approach:

• check_sequence now handles collections.deque and MutableSequence.
• check_set now handles MutableSet.
• The three origins are registered in origin_type_checkers.

The stricter container-type check is preserved: a list is still rejected as a Deque, a tuple as a MutableSequence, and a frozenset as a MutableSet. The default FIRST_ITEM strategy behaviour is unchanged.

Checklist

• You've added tests (in tests/) which would fail without your patch
• You've updated the documentation (changelog entry in docs/versionhistory.rst)
• You've added a new changelog entry (in docs/versionhistory.rst)

Tests: TestDeque, TestMutableSequence and TestMutableSet were added in tests/test_checkers.py, mirroring the existing TestList/TestSequence/TestSet classes. The full suite passes (546 passed), and ruff, ruff-format and mypy are clean.

[coveralls]

coverage: 94.856% (+0.03%) from 94.83% — sneha4175:fix/check-deque-mutable-sequence-set-elements into agronholm:master