Generics (monomorphization)

As of x07AST schema_version x07.x07ast@0.4.0 (and later), X07 supports bounded generics via compile-time monomorphization.

• Generics are compile-time only: each tapp instantiation produces a specialized copy.
• The program given to the existing optimizer + C backend is fully monomorphic (no tapp / ty.* remains).

Schema + compatibility

• Use x07.x07ast@0.5.0 for new files (including any use of: type_params, structured type_ref, tapp, ty.*).
• The toolchain also accepts legacy x07.x07ast@0.4.0 for generics-only programs (no contracts).
• The toolchain still accepts legacy x07.x07ast@0.3.0 for concrete-only programs.

type_ref (structured type expressions)

In params[].ty and result, a type_ref can be either:

• a legacy concrete type token (string), like "i32", "bytes", or
• a structured type expression (array):
  • type variable: ["t","A"]
  • type application: ["option", ["t","A"]], ["result", "bytes_view"]

type_params (generic declarations)

defn / defasync may include type_params:

{
  "kind": "defn",
  "name": "main.id",
  "type_params": [{"bound":"num_like","name":"A"}],
  "params": [{"name":"x","ty":["t","A"]}],
  "result": ["t","A"],
  "body": "x"
}

Bounds are canonical and small:

• any (no constraint)
• bytes_like
• num_like
• value
• hashable
• orderable

Bounds (currently supported concrete types)

{
  "any": ["*"],
  "bytes_like": ["bytes", "bytes_view"],
  "num_like": ["i32", "u32"],
  "value": ["i32", "u32", "bytes", "bytes_view"],
  "hashable": ["i32", "u32", "bytes", "bytes_view"],
  "orderable": ["i32", "u32", "bytes", "bytes_view"]
}

tapp (generic instantiation at call sites)

Form:

["tapp", "<callee_symbol>", ["tys", <type_arg_0>, <type_arg_1>, ...], <value_arg_0>, ...]

Examples:

["tapp","std.heap.with_capacity",["tys","u32"],16]
["tapp","std.heap.push",["tys","u32"],"h",7]
["tapp","std.vec.with_capacity",["tys",["t","A"]],"cap"]

Local type inference + tapp elaboration (inside bodies)

When a call targets a generic function but omits tapp, x07 lint can infer the missing type arguments from local usage and emit a JSON Patch quickfix that rewrites the call into the canonical tapp form.

Use x07 fix --write to apply these rewrites.

Examples

• docs/examples/16_generics_identity.x07.json
• docs/examples/17_generics_containers.x07.json

Migration pattern (generic base + wrappers)

To migrate existing concrete-only APIs without breaking callers:

• Introduce a new generic base function (for example pkg.foo with type_params: [{ "name": "A" }]).
• Keep existing concrete entrypoints as thin wrappers that call the base via tapp (for example pkg.foo_u32 → ["tapp","pkg.foo",["tys","u32"], ...]).

Tooling support:

• x07 fix --suggest-generics emits a suggested x07.patchset@0.1.0 for converting near-identical type-suffixed functions into a generic base plus wrappers.

ty.* intrinsics (type-dependent ops inside generic bodies)

ty.* intrinsics are compile-time intrinsics that are lowered during monomorphization.

Supported (v0.4 toolchain):

• ty.size_bytes(T) / ty.size(T) → i32 constant (currently: i32/u32 only)
• ty.read_le_at(T, bytes_view, off) → std.u32.read_le_at(...) (currently: i32/u32 only)
• ty.write_le_at(T, bytes, off, x) → std.u32.write_le_at(...) (currently: i32/u32 only)
• ty.push_le(T, vec_u8, x) → std.u32.push_le(...) (currently: i32/u32 only)
• ty.clone(T, x) → T (does not consume x; for bytes does a deep clone)
• ty.drop(T, x) → i32 (consumes x; for bytes runs an explicit drop)
• ty.lt(T, a, b) → < or <u (bytes/bytes_view are lexicographic by contents)
• ty.eq(T, a, b) → i32 (bytes/bytes_view compare contents)
• ty.cmp(T, a, b) → i32 (bytes/bytes_view are lexicographic by contents)
• ty.hash32(T, x) → i32 (bytes/bytes_view hash contents via std.hash.fnv1a32_view + std.hash.mix32)

Budgets / caps

Monomorphization is bounded:

• max specializations: 4096
• max type expression depth: 64

When a cap is hit, compilation fails deterministically.

Monomorphization map (x07c --emit-mono-map)

The compiler can emit a machine-readable monomorphization map, describing which generic functions were specialized and where the tapp sites occurred.

• x07c compile --emit-mono-map <PATH> ...
• x07c build --emit-mono-map <PATH> ...

Schema: x07.mono.map@0.1.0 (spec/x07-mono.map.schema.json).