Traits

[rachel-bousfield]

Types can now carry method data, which can provide type-checkable syntactic sugar.

type array<T> = struct {
    size: uint,
    topstep: uint,
    contents: block<T>,
    trait access: array_get::<T>,
};

The above declares an array type with the access trait equal to its specialized variant of the array_get function. Calling [] on an instance of this type as below performs a type-checked call.

let a = array_new::<string>(8, 0);
assert(a[0] == array_get::<string>(a, 0));

Additionally, this PR

• Makes type printing better by removing extraneous spacing and commas
• Refactors type_tree to better reflect its purpose