oden/fine/design.md

Design Notes for the Fine Language

This language is being designed as I go, because the main thing I'm interested in is building something that's fun and productive for me personally. That means, rather than being super careful, I'm just building the thing that pleases me at any given moment.

Here are some notes. The notes are for me in the future, in case I'm wondering why the language is one way instead of another way.

The new keyword

I really like rust's "just use a type name with curly braces to construct new values". It's really clean! Unfortunately it leads to an ambiguity in the syntax that I don't like:

if something { ...

In the code above, after I have parsed something and I see {, am I:

• Parsing an object construction expression for the type something?
• Parsing something as a boolean value reference and { as the start of the block?

Naively you would expect the latter, but if I scan ahead a little more:

if something { foo: true }.foo { }

Rust does not allow struct literals in the condition of the if, which is correct, but that's more work than I want to do here. There's just a lot of context flowing around about whether or not I can parse a structure literal in any particular situation.

The new keyword is a compromise: we know that the context immediately following the new keyword is always a type expression, so we know that e.g. < or whatever means "generic type parameter" and not "less than".