Implement type casting

[kjw142857]

This PR implements type casting for the Java implementation in Source Academy. Two forms of type casting will be supported:

1. Type casting between primitive types (including narrowing type conversions). To maintain ease of readability, type casting will be limited to within the int, long, float and double types.
2. Type casting between non-primitive types when one is a subtype of the other.

Explicit type casting will take the form of (TYPE) expression, where expression is of the target type and TYPE denotes the type to be cast to.

[gemini-code-assist]

Summary of Changes

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This pull request introduces comprehensive type casting capabilities to the Java implementation in Source Academy. It enables explicit conversions between primitive types, including narrowing conversions, and supports casting between non-primitive types where a subtype relationship exists. This enhancement significantly expands the language's expressiveness and aligns it more closely with standard Java behavior.

Highlights

• Type Casting Implementation: Implemented explicit type casting for both primitive types (int, long, float, double) and non-primitive types, supporting narrowing conversions and subtyping relationships.
• AST and Grammar Updates: Introduced a new CastExpression interface into the Abstract Syntax Tree (AST) and updated the grammar to correctly parse and represent cast expressions, distinguishing between primitive and reference type casts.
• Code Generation for Primitive Casts: Added code generation logic to emit appropriate JVM bytecode instructions (e.g., F2D, L2I) for handling primitive type conversions during compilation.
• Type Checking Integration: Integrated type checking for cast expressions, ensuring type compatibility and raising IncompatibleTypesError when necessary.
• Documentation and Testing: Updated the project documentation to reflect the newly supported type casting feature and added a dedicated test file with initial test cases for type conversions.

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[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🟡	Statements	73.57% (-0.38% 🔻)	7194/9779
🔴	Branches	59.87% (-0.52% 🔻)	2359/3940
🟡	Functions	69.52% (+0.07% 🔼)	1291/1857
🟡	Lines	74.49% (-0.4% 🔻)	6770/9089

Show new covered files 🐣

St.❔	File	Statements	Branches	Functions	Lines
🟢	... / typeConversion.test.ts	100%	100%	100%	100%

Show files with reduced coverage 🔻

St.❔	File	Statements	Branches	Functions	Lines
🟢	... / index.ts	71.68% (-2.7% 🔻)	49.62% (-3.39% 🔻)	95.65%	81.05% (-3.19% 🔻)
🟡	types/ast/utils.ts	76.92% (-2.02% 🔻)	42.86% (-3.3% 🔻)	62.5%	71.43% (-2.65% 🔻)
🟢	... / code-generator.ts	88.24% (-6.17% 🔻)	77.62% (-7.04% 🔻)	93.33% (+0.15% 🔼)	88.46% (-6.29% 🔻)

Test suite run success

1121 tests passing in 63 suites.

Report generated by 🧪jest coverage report action from e14a512

[gemini-code-assist]

Code Review

This pull request introduces comprehensive support for type casting in the Java-slang compiler, encompassing both primitive and reference type conversions. Key changes include defining a CastExpression AST node, updating the grammar to parse cast expressions, implementing code generation for various primitive type conversions, and adding type-checking logic to ensure compatibility. New test cases for type conversion have also been added. Feedback highlights several areas for improvement: a critical bug in the code generator where missing break statements lead to incorrect bytecode for primitive casts, an incomplete implementation for non-primitive casts lacking checkcast instructions, an inaccuracy in the README.md regarding explicit type conversion being a future feature, a suggestion to use the boolean primitive type instead of Boolean for isPrimitiveCast, a readability improvement for a destructuring assignment in tests, and a refactoring opportunity to reduce duplicated type-checking logic for CastExpression.

[martin-henz]

approved