[Proposal] const keyword in function arguments

[Protryon]

💥 Proposal

We want to add a const keyword prefixed to function declaration arguments. This would enable function calls to trivially do const checking in a user-friendly way, and opens the path to generics.

Syntax

function_definition_head := "function" ident "(" (argument ",")* argument? ")"
argument := "const"? ident ":" type_ref

Semantics

Functions would treat the specific argument as a const value, and function call expressions would enforce constness of the argument.

[collinc97]

This looks great @Protryon!

To confirm the visualization, an example of the new Leo syntax would be:

function foo(const x: u32) {
    ...
}

[collinc97]

This feature will also encompass the features of generics.

It will close #479

[acoglio]

This looks good to me.

[collinc97]

Implemented by #617