This commit introduces NODE_BEGIN as a distinct AST node type for
explicit begin...end blocks, separate from NODE_STMTS which represents
general statement sequences. This distinction will be essential for
implementing CRuby-compatible begin...end while/until constructs.
Key changes:
- Added NODE_BEGIN enum in node.h
- Added new_begin() function in parse.y using optimized cons() structure
- Modified begin...end grammar rule to generate NODE_BEGIN nodes
- Added NODE_BEGIN codegen support in codegen.c
- Added NODE_BEGIN to parser dump functionality
NODE_BEGIN uses a simpler cons() structure instead of list2() for
better memory efficiency, as it only contains a single body node.
Co-Authored-By: Claude <noreply@anthropic.com>
Yukihiro "Matz" Matsumoto
ebc10f3c57