Type conversions

[augustt198]

Type conversion needs to be further developed. It's currently limited to conversions between primitives in additive/multiplicative expressions.

Implicit conversions needed:

• Boxing
• Unboxing
• Primitive widening
• Reference widening

_{(Identity conversion has been omitted because it is obvious)}

Method selection also has to be improved. It currently only matches methods with the exact same name, arity, and type.

New algorithm for matching methods:

• Match methods with the same name
• Match methods with the same arity
• Match methods applicable by subtyping
• Match methods applicable by method invocation conversion
• If multiple methods are still applicable, choose the most specific method (closest subtype)