This commit applies `strictNullChecks` to the entire codebase to improve
maintainability and type safety. Key changes include:
- Remove some explicit null-checks where unnecessary.
- Add necessary null-checks.
- Refactor static factory functions for a more functional approach.
- Improve some test names and contexts for better debugging.
- Add unit tests for any additional logic introduced.
- Refactor `createPositionFromRegexFullMatch` to its own function as the
logic is reused.
- Prefer `find` prefix on functions that may return `undefined` and
`get` prefix for those that always return a value.
Rework code validation to be bound to a context and not
context-independent. It means that the generated code is validated based
on different phases during the compilation. This is done by moving
validation from `ScriptCode` constructor to a different callable
function.
It removes duplicate detection for function calls once a call is fully
compiled, but still checks for duplicates inside each function body that
has inline code. This allows for having duplicates in final scripts
(thus relaxing the duplicate detection), e.g., when multiple calls to
the same function is made.
It fixes non-duplicates (when using common syntax) being misrepresented
as duplicate lines.
It improves the output of errors, such as printing valid lines, to give
more context. This improvement also fixes empty line validation not
showing the right empty lines in the error output. Empty line validation
shows tabs and whitespaces more clearly.
Finally, it adds more tests including tests for existing logic, such as
singleton factories.
