Transform Python AST (M1) to MetaAST (M2).

Implements the abstraction function α_Python that lifts Python-specific AST structures to the meta-level representation.

Transformation Strategy

Python's AST is represented as nested maps with "_type" keys. We pattern match on these structures and transform them to MetaAST tuples.

M2.1 (Core Layer)

• Literals: Constant nodes → {:literal, type, value}
• Variables: Name nodes → {:variable, name}
• Binary operators: BinOp → {:binary_op, category, op, left, right}
• Unary operators: UnaryOp → {:unary_op, category, op, operand}
• Function calls: Call → {:function_call, name, args}
• Conditionals: If, IfExp → {:conditional, condition, then, else}
• Blocks: Module, multiple statements → {:block, statements}
• Early returns: Return, Break, Continue → {:early_return, kind, value}

M2.2 (Extended Layer)

• Loops: While → {:loop, :while, condition, body}
• Loops: For → {:loop, :for_each, iterator, collection, body}
• Lambdas: Lambda → {:lambda, params, captures, body}
• Collection ops: Simple ListComp → {:collection_op, :map, lambda, collection}
• Exception handling: Try → {:exception_handling, try_block, rescue_clauses, finally_block}

Metadata Preservation

The transformation preserves Python-specific information:

• :lineno - line number
• :col_offset - column offset
• :python_node_type - original Python AST node type

This enables high-fidelity round-trips (M1 → M2 → M1).