Feat while statement

[alexgarzao]

This PR supports the while statement in the Pascal parser and code generator. The changes include additions to the JASM struct and methods to handle while statements, modifications to the TreeShapeListener to invoke these methods, and adjustments to the Pascal grammar file to correctly parse while statements. Test files have also been added to ensure the correct functionality.

Key changes include:

Support for while statement in the JASM code generator:

• codegen/jasm.go: Added whileTestLabel and nextStatementLabel to the JASM struct to handle while statements. Introduced StartWhileStatement, FinishWhileStatement, and StartWhileBlock methods to generate the appropriate JASM code for while statements. [1] [2]

Integration of while statement handling in the TreeShapeListener:

• codegen/tree_shape_listener.go: Added EnterWhileStatement, ExitWhileStatement, and EnterWhileBlock methods to the TreeShapeListener to invoke the corresponding methods in the JASM struct.

Changes to the Pascal grammar:

• parser/Pascal.g4: Modified the whileStatement rule to include a whileBlock, and added a new whileBlock rule to correctly parse while statements.

Addition of test files:

• tests/expected_jasm_files/while.jasm: Added an expected output file for a test case involving while statements.
• tests/pascal_programs/while.pas: Added a Pascal program to test the parsing and code generation of while statements.