Mist — Rust with ergonomics

Performance

On my machines, the mist-test usually gets transpiled at ~13ms, which is good, but i'm unsatisfied, so i made it "transpile" at ~500µs, sometimes even 275µs, this of course is very dependent of the schedule and overhead.

This was achieved by caching the file's timestamps, and this also saves the Rust compiler a lot of work since it has the same caching system.

Errors & Mapping

You will notice that the output of the mist code contains something like this:

/* 9:5 */
let args: Vec<String> = env::args().collect();
/* 11:5 */
if args.len() < 2
{
    /* 12:9 */
    print_usage();
    /* 13:9 */
    process::exit(1);
}

Those are mappings, the line of the rust file will translate to the line on the comment, example:

src/main.mist:12:9
 Error: cannot find function `print_usage` in this scope
        process::exit(1);

This is what the input is:

Vec<String> args = env::args().collect();

if (args.len() < 2) {
    print_usage();
    process::exit(1);
}

The error itself is taken via --message-format=json on cargo with the cargo_metadata crate.

Syntax changes

Match

Match patterns now allow |:

match (args[1].as_str()) {
    "run" | "build" | "check" | "r" | "b" | "c" => {
        var (config, root) = transpiler::build();
    }

    _ => {}
}

Strings & Macros

After using macros and strings, i noticed that there was bugs everywhere, i now ensure more stable macros, and strings now allow different escape sequences.

Variables and other statements

Fixed variables declarations like

Vec<String> args;

And also function calls:

my_func();

The reason why bugs occur with these statements is due to ambiguity, at first, they are right, for example:

// <type> <pattern>
my_func (); // () used to be a pattern.

This fix is not perfect, you may encounter the same issues when passing arguments that are also within the pattern range (meaning not full expressions).