Generics in Java vs Go vs Rust

Comparison of generics feature in Java, Go, and Rust.

Java

• implements Type Erasure: deleting all types at runtime dan casted into object/bounded class/interface,
• compile-time type checking,
• run-time dynamic type(depends on boundaries),
• no monomorphization,
• overhead: run-time type casting

Go

• implements Stenciling: checks compatibility with GCShape(group of similar types), and adds metadata(dictionaries) for each shape(associated types).
• compile-time GCShape checking,
• run-time metadata(dictionaries) checking for function invocation
• partial monomorphization (monomorphized for same GCShape(group of types), not particular type)
• overhead: run-time metadata checking for generic pointer types dan their methods invocations, because all generic pointer types share same gcshape.

Rust

• implements Monomorphization(full): generates all form of instructions according to their types and optimize each of them.
• compile-time type checking
• compile-time type generation and optimization
• fully monomorphized
• overhead: zero-cost at runtime, only impact on slow compile-time for generation and optimization.

CMIIW