Add type hints to core test suite functions

[Copilot]

What do these changes do

Adds type hints to functions tested in the core test suite. Fixes 35+ mypy errors across 8 files while maintaining Python 3.9 compatibility.

What was wrong

Core-tested functions lacked type annotations, causing mypy validation failures:

• corpus/core.py: JSON return types declared as dict[str, str] but actual structure is dict[str, Any]
• corpus/common.py: Missing type annotation for list_synonym, incorrect Union type handling
• transliterate/core.py: Incorrect/unused type: ignore comments
• tag/unigram.py: json.load() returns Any but functions declared dict return type
• util/spell_words.py: Module-level list comprehensions had no type annotations
• tag/named_entity.py: Outdated type: ignore annotations
• transliterate/lookup.py: Dictionary access returning Union[str, bool, None] incompatible with function return types

How this fixes it

Type system fixes:

• Use dict[str, Any] for nested JSON structures
• Add explicit type annotations to module-level variables
• Add type: ignore[no-any-return] for external library returns
• Use isinstance checks instead of assertions for runtime type guards
• Separate variables for different types (temp → temp_parts for list type)

Guidelines applied:

• Native types (list, tuple) not typing.List, typing.Tuple
• Union[] syntax instead of | for Python 3.9 compatibility
• TYPE_CHECKING imports to avoid circular dependencies
• Specific error codes in type: ignore comments

Modified files:

1. corpus/core.py - 10 errors fixed
2. corpus/common.py - 3 errors fixed
3. transliterate/core.py - 8 errors fixed
4. tag/unigram.py - 5 errors fixed
5. util/spell_words.py - 3 errors fixed
6. tag/named_entity.py - 4 errors fixed
7. transliterate/lookup.py - 2 errors fixed

Your checklist for this pull request

• Passed code styles and structures
• Passed code linting checks and unit test

Original prompt

Gradually add type hints to submodules,
based on works done in these PRs:
#1262
#1263
#1264

• Start with small functions and functions that require few external dependencies

• Moving gradually one function by one function, in the four test suites: starting from "core", then "compact", "extra", and "noauto"

• Immediate goal for this session - 100% type hints for functions being called in "core" test suite.

• Ultimate goal (outside of this session) is to make the package a typed package, while keeping maintainability.

• Start small in the area with high confidence, then gradually grow one submodule at a time.

• Use mypy as main assistant.

  • mypy is already in "dev" extra dependencies in pyproject.toml
  • mypy configuration is in pyproject.toml

• Use pyright, pyrefly, and pytype for second opinions.

• Start with highly tested submodules first.

• Use native type in type hint (list, tuple, .. instead of List, Tuple, ..)

• Do not use A | B style Union, use full Union[] instead.

• We want to keep compatibility with Python 3.9 strict and allow type inspection tools to work correctly.

• When insert typing imports, put it in appropriate location and order

• Use "if TYPE_CHECKING import" block when possible.

• When reordering the imports, beware of circular import. Read comments near imports to get more information.

• Remove unused imports

• Try to fix the type, the scope logic, or do the casting, before putting #type: ignore comment.

• When dealing with types from external libraries:

  • Check if type information is provided (maybe through stubs). If it is, cast wrapper may not necessary.
  • If return type is not provided, may be it is appropriate to use # type: ignore[no-any-return] annotation for clarity.

• Recheck necessity when do casting.

• Provide stubs as necessary.

• After changes for type hints, recheck for functionality correctness.

• Recheck code, docstring, documentation consistency.

• Recheck formatting with ruff

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[coveralls]

coverage: 65.761% (+0.008%) from 65.753%
when pulling d09c7f9 on copilot/add-type-hints-to-submodules-one-more-time
into 7db158d on dev.