Type argument inference

Calls supply all generic arguments, as in identity[list[i64]](values), or infer all from inputs, as in identity(values). Partial explicit lists and inference from an expected result type are unsupported. Output-only or unused parameters need an explicit list.

Inference structurally matches concrete arguments: &T against &Message learns T = Message; &dict[K, V] against &dict[str, u8] learns both parameters. Collections, ranges, generators, tuples, sums, callable signatures, and nominal generic class/enum arguments participate. Repeated parameters must agree after alias resolution. Nominal matching requires the same declaration as well as matching arguments. Value parameters are inferred from nominal arguments by the same structural match: Bounded[T, lo, hi] against Bounded[u8, 0, 100] learns all three parameters.

A shared-reference parameter supplies ordinary implicit borrowing, so a parameter value: &T can accept an owner directly. Mutable borrowing still needs &mut or an existing exclusive reference. Arguments evaluate once in source order.

A generic parameter position supplies no expected type to its argument. Unsuffixed integers default to i64 and floats to f64, independently of other arguments or the result context. add(1u8, 2u8) works; add(1u8, 2) conflicts. add[u8](1, 2) guides both literals. Nongeneric parameter positions retain their ordinary contextual typing. Empty literals and incomplete sum constructors may need an annotated binding or explicit arguments.

Callable constraints contribute evidence from a known callback signature: F: Callable[[], T] can determine T from the callback result. Parameterized protocol bounds likewise contribute evidence from accessible methods on the known class. Evidence from all inputs and constraints must agree. Inference does not widen numbers or search for an implementation class.

A generic function becomes a concrete function value using identity[u8] or an expected concrete Callable signature. A fully concrete callable constraint can also select a generic named function passed directly by value. This contextual selection does not change ordinary generic-call inference. OnceCallable constraints accept consuming callbacks with the same inference rules. Constraint signature shapes are checked at declaration; concrete ownership capabilities are checked when the body is specialized. Polymorphic function values are unsupported.