Feature	Java	Scala	Kotlin	Rust	Go	Zig	Python	JavaScript	TypeScript
Implementation Strategy	Type erasure	Type erasure (JVM) but with TypeTag/ClassTag	Type erasure (JVM) but with reified for inline	Monomorphization	GCShape stenciling (hybrid)	Monomorphization via comptime	Runtime duck typing, optional static analysis	No type system	Structural type system, compiles to JS
Syntax	<T> angle brackets	[T] square brackets	<T> angle brackets	<T> angle brackets	[T] square brackets	comptime T: type parameter	[T] square brackets (3.9+)	N/A	<T> angle brackets
Type Checking	Compile-time, mandatory	Compile-time, mandatory	Compile-time, mandatory	Compile-time, mandatory	Compile-time, mandatory	Compile-time, mandatory	Optional via external tools (mypy)	❌ None	Compile-time, optional enforcement
Runtime Type Enforcement	⚠️ Erased but checked at boundaries	⚠️ Erased unless TypeTag	⚠️ Erased unless reified	❌ None (monomorphized)	❌ None	❌ None	❌ None (hints ignored)	❌ None	❌ None (erased to JS)
Primitive Type Support	❌ Must box (Integer, Double)	⚠️ Yes with @specialized	✅ Automatic optimization	✅ Full support	✅ Full support	✅ Full support	✅ No distinction (all objects)	✅ No distinction	✅ No distinction (JS runtime)
Runtime Type Info	❌ Erased (except raw types)	⚠️ Available with TypeTag	⚠️ Available with reified	❌ Not available	❌ Not available	❌ Not available by default	✅ Full via annotations	❌ None	❌ Erased to JS
Performance Cost	⚠️ Boxing overhead, vtable calls	⚠️ Similar to Java unless specialized	⚠️ Better than Java, some optimization	✅ Zero-cost abstraction	✅ Near zero-cost	✅ Zero-cost abstraction	N/A (dynamic, hints are free)	N/A (dynamic)	N/A (JS performance)
Variance	Use-site only (? extends, ? super)	Declaration-site (+T, -T) and use-site	Declaration-site (out, in) and use-site	Automatic inference	❌ Invariant only	❌ Invariant only	Declaration-site (TypeVar covariant/contravariant)	N/A	Bivariant by default, can specify
Type Bounds	extends for upper bounds	Upper (<:), lower (>:), context, view	Upper (:) with multiple where	Trait bounds with where	Interface constraints	❌ Duck typing at comptime	bound= and constraints in TypeVar	N/A	extends for upper bounds
Higher-Kinded Types	❌ Not supported	✅ Full support F[_]	❌ Not supported	⚠️ Via GATs (Generic Associated Types)	❌ Not supported	⚠️ Via comptime metaprogramming	❌ Not supported	N/A	❌ Not supported
Const/Value Generics	❌ Not supported	❌ Not supported	❌ Not supported	✅ const N: usize	❌ Not supported	✅ Any comptime value	⚠️ Limited via TypeVarTuple	N/A	❌ Not supported
Type Inference	⚠️ Limited, improved with var	✅ Excellent	✅ Excellent	✅ Excellent	✅ Excellent	✅ Excellent	✅ Excellent (mypy)	N/A	✅ Excellent
Null Safety Integration	❌ No integration	⚠️ Via Option[T]	✅ Built-in T vs T?	✅ Via Option	⚠️ Via pointers vs values	⚠️ Via ?T optionals	⚠️ Via Optional[T] or T | None	❌ None	⚠️ Via T | null | undefined
Duck Typing	❌ Nominal typing only	❌ Nominal typing only	❌ Nominal typing only	❌ Nominal typing only	⚠️ Interface satisfaction	⚠️ Structural at comptime	✅ Native, fundamental	✅ Native, fundamental	⚠️ Structural typing
Structural Typing	❌ Not supported	❌ Not supported	❌ Not supported	❌ Not supported	✅ Yes (interfaces)	⚠️ Via comptime	✅ Protocols (PEP 544)	✅ Native	✅ Core feature
Array Handling	⚠️ Covariant arrays, invariant generics	✅ Invariant, consistent	✅ Invariant, consistent	✅ Invariant, consistent	✅ Invariant slices	✅ Consistent	✅ Lists are objects	✅ Arrays are objects	✅ Arrays typed as T[]
Generic Arrays/Collections	❌ Cannot create new T[]	⚠️ Workarounds with ClassTag	⚠️ Some limitations	✅ Full support	✅ Full support	✅ Full support	✅ Full support (runtime)	✅ Full support	✅ Type checking only
Specialization	❌ Not available	✅ @specialized annotation	⚠️ Automatic for primitives	✅ Automatic monomorphization	⚠️ GCShape groups	✅ Full monomorphization	N/A	N/A	N/A
Associated Types	❌ Not supported	⚠️ Via type members	❌ Not supported	✅ Native support	❌ Not supported	⚠️ Via comptime structs	❌ Not supported	N/A	⚠️ Via mapped types
Union Types	❌ Not supported	⚠️ Via sealed traits	❌ Not supported	⚠️ Via enums	❌ Not supported	⚠️ Via tagged unions	✅ Full support (int | str)	✅ Dynamic (anything)	✅ Full support (T | U)
Intersection Types	⚠️ Via bounds T extends A & B	✅ Via with keyword	⚠️ Via where clause	⚠️ Via multiple trait bounds	❌ Not supported	❌ Not supported	❌ Not supported	N/A	✅ Full support (T & U)
Literal Types	❌ Not supported	❌ Not supported	❌ Not supported	❌ Not supported	❌ Not supported	⚠️ Via comptime	✅ Literal[value]	N/A	✅ Native support
Type Aliases	❌ Not supported	✅ type keyword	✅ typealias	✅ type keyword	✅ type keyword	✅ Implicit via const	✅ type keyword (3.12+)	N/A	✅ type keyword
Conditional Types	❌ Not supported	⚠️ Limited via implicits	❌ Not supported	❌ Not supported	❌ Not supported	✅ Via comptime if	❌ Not supported	N/A	✅ T extends U ? X : Y
Mapped Types	❌ Not supported	❌ Not supported	❌ Not supported	❌ Not supported	❌ Not supported	⚠️ Via comptime	❌ Not supported	N/A	✅ { [K in T]: U }
Template Literal Types	❌ Not supported	❌ Not supported	❌ Not supported	❌ Not supported	❌ Not supported	❌ Not supported	❌ Not supported	N/A	✅ `prefix${T}`
Operator Constraints	❌ Only via interfaces	❌ Only via type classes	❌ Only via interfaces	⚠️ Via traits (Add, Mul, etc.)	✅ comparable, Ordered	❌ Duck typing	❌ Duck typing	N/A	❌ Not supported
Reflection/Introspection	⚠️ Limited, especially with generics	✅ TypeTag/Manifest	⚠️ reified for inline	⚠️ Limited (type_name, TypeId)	⚠️ Limited (reflect package)	✅ Full @typeInfo at comptime	✅ Full annotations	✅ Full (typeof, instanceof)	❌ Erased at runtime
Method-Level Type Params	✅ Yes	✅ Yes	✅ Yes	✅ Yes	⚠️ Not on generic type methods	✅ Yes (via comptime)	✅ Yes	N/A	✅ Yes
Wildcard/Existential Types	⚠️ Wildcards ?	✅ Existential types	⚠️ Star projection *	⚠️ impl Trait	❌ Not supported	⚠️ anytype	⚠️ Any type	N/A	⚠️ unknown type
Self-Referential Types	⚠️ Recursive bounds hack	✅ this.type	✅ Via generics	⚠️ Via traits	❌ Not supported	⚠️ Via comptime	✅ Self (3.11+)	N/A	✅ this type
Error Messages	⚠️ Confusing wildcard captures	⚠️ Can be very complex	✅ Generally good	⚠️ Can be verbose	✅ Simple and clear	⚠️ Comptime errors can be cryptic	✅ Tool-dependent (mypy is good)	N/A	✅ Generally excellent
Binary Size Impact	✅ Single version (small)	✅ Single version (small)	✅ Single version (small)	❌ Large (each instantiation)	⚠️ Moderate (grouped)	❌ Large (each instantiation)	N/A	N/A	N/A
Compilation Speed	✅ Fast	⚠️ Slower	✅ Moderate	❌ Slow (monomorphization)	✅ Fast	⚠️ Moderate-slow (comptime)	✅ Instant (no compilation)	✅ Instant	⚠️ Moderate (type checking)
Learning Curve	⚠️ Moderate (wildcards confusing)	❌ Steep (many features)	✅ Gentle	❌ Steep (lifetimes, ownership)	✅ Very gentle	⚠️ Moderate (comptime concept)	✅ Optional, gradual	✅ None needed	⚠️ Moderate (advanced types)
Maturity	✅ 20+ years (since 2004)	✅ 15+ years	✅ Mature (since 2016)	✅ Mature (since 2015)	⚠️ New (since 2022)	⚠️ Language still evolving	⚠️ Types since 2015, evolving	N/A	✅ Mature (since 2012)
Standard Library Usage	✅ Pervasive (Collections, etc.)	✅ Pervasive	✅ Pervasive	✅ Pervasive	⚠️ Minimal (slices, maps packages)	✅ Pervasive	⚠️ Growing adoption	N/A	✅ In @types definitions
Gradual Typing	❌ All-or-nothing	❌ All-or-nothing	❌ All-or-nothing	❌ All-or-nothing	❌ All-or-nothing	❌ All-or-nothing	✅ Core philosophy	N/A	⚠️ Via any type
Types as First-Class Values	❌ Not supported	⚠️ Via reflection	❌ Not supported	❌ Not supported	❌ Not supported	✅ Full support	⚠️ Via annotations	✅ Yes (constructors)	❌ Only at type level
Inline/Unrolling Control	⚠️ JIT decides	⚠️ @inline hints	⚠️ inline keyword hint	✅ #[inline] attribute	⚠️ Compiler decides	✅ inline keyword guaranteed	N/A	N/A	N/A
Generic Exceptions	❌ Cannot extend Throwable	⚠️ Via type bounds	❌ Limited	✅ Result<T, E> pattern	❌ No exceptions	✅ Error unions !T	✅ Any type can be exception	✅ Any type can be thrown	⚠️ Typed but not enforced
Type Narrowing	⚠️ Via instanceof	⚠️ Pattern matching	⚠️ Smart casts	⚠️ Pattern matching	⚠️ Type switches	⚠️ Via comptime	✅ isinstance guards	✅ typeof guards	✅ Control flow analysis
Tuple Types	❌ Not supported	✅ Native tuples	❌ Use data classes	✅ Native tuples	❌ Not supported	✅ Native tuples	✅ Tuple[T, U]	⚠️ Arrays only	✅ [T, U] tuples
Readonly/Immutability	⚠️ Via final keyword	⚠️ Via val keyword	⚠️ Via val keyword	✅ Core feature (ownership)	❌ Not enforced	⚠️ Via const	❌ Not enforced	❌ Not enforced	✅ readonly modifier
Excess Property Checking	✅ Yes	✅ Yes	✅ Yes	✅ Yes	✅ Yes	✅ Yes	⚠️ Limited (mypy strict mode)	❌ None	✅ For object literals

Legend

• ✅ Full support / Excellent
• ⚠️ Partial support / With limitations
• ❌ Not supported / Poor
• N/A - Not applicable to language paradigm