This commit refactors the Binder implementation to better align with the
updated scope structure.
Key changes include:
- Introducing `ExprContext` to distinguish between statement and
expression contexts.
- Modifying `define_variable` to handle both global and local scope
definitions more robustly.
- Updating `resolve_variable` to correctly handle upvalue captures,
especially for global addresses.
- Adjusting `bind` and related functions to use the new `ExprContext`.
- Updating the refactoring log to reflect completed phases.
Implement strict block scoping and distinguish between statements and
expressions.
This change introduces hierarchical scopes for functions and blocks,
enforces that `def` is a statement with no return value, and prevents
statements from appearing in expression positions or as the last element
of a block. A new example `design-flaw.myc` is added to demonstrate
the uninitialized variable issue solved by these changes.
Michael Schimmel