Binary operator checking

[kaleidawave]

Current the functions to doing binary operations don't check the types of either side. First a bit of background:

There are two functions for binary operators, they are split between

• Mathematical and bitwise operations. Both sides have to be checked as there is no short circuiting behavior
• Logical operators. These can have logical operators (and in the future the RHS can be narrowed for && operations)

in and instanceof operators are handled specially on Environment

There is a also a current option strict_casts (it should probably be renamed to no_implicit_casts) in TypeCheckOptions. When this is true should not allow operations like "hi" + 2.

These two functions are currently set up to return a Result. However both the logic for checking the sides and the diagnostic has not been implemented. For example

https://github.com/kaleidawave/ezno/blob/502126217170121cadb12cad3debe1ff388a37f1/checker/src/behavior/operations.rs#L76-L84

There are several things to carefully consider here

• Still want to enable Symbol.toPrimative behaviour with hints and such (that will require these functions to have all the context to be able to do a call_type
  • This should disallow Object.toPrimative fall through as this result are not useful