Expression Semantics

This page will go over how semantic analysis handles expressions. It will cover the technical details behind return type prediction in inline calls and type promotion.

Currently, KSL will travel the expression in the AST and determine the smallest possible type for all literals and the types defined for each variable. It will then cross reference these anywhere there is an operation between them. It will pick the larger type of the two and "promote" the entire expression to that type. This way we can calculate expressions for differing types without losing data from downcasts.

In the future, we're likely to change this system so that the entire expression recieves a type hint ahead of time. It will attempt to convert all literals (and potentially variables) to this type. If the expression ends up with a larger type than the hint it will simply throw an error.

Additionally, if there is a type that doesn't match the rest that cannot be implicitly changed it will throw a warning or error to the programmer explaining that in order to "do this operation" they must cast to an acceptable type.