import, export & modules syntax

[Vengarioth]

Syntax proposal

We need syntax to make things from other modules accessible. This proposal shows a possible solution.

• [ ] Parser parses import syntax
• [ ] Parser parses export syntax
• [ ] Identifiers in AST need to be replaced with Paths (module path + identifier)
• [ ] Compiler needs to process imported files (once)

implementation

import and export are top-level constructs and cannot exist inside of blocks, however they can be placed at any position within a file. There are no syntax for default exports or imports as this leads to issues when IDEs try to refactor code.

Allowed exports and imports are:

• Functions
• Structs

example

index.xs

import { Foo, Bar } from other_module;

struct Foobar {
    x: Foo;
    y: Bar;
}

other_module.xs

struct Foo {
    x: f32,
    y: f32,
}

struct Bar {
    x: f32,
    y: f32,
}

fn doFoo(in: Input) -> Output {
    // ...
}

export { Foo, Bar, doFoo };

export syntax

export a single item

export Foo;

export multiple items

export { Foo, Bar };

import syntax

import a single item

import Foo from bar;

import multiple items

import { Foo, Bar } from bar;

import all

import * from bar;

import from submodules

import * from foo/bar;

file resolution

File resolution is a tricky thing for module systems. How do we resolve the standard library? How do we resolve libraries from a potential package manager?

other module systems

• ES2015
• rust
• hlsl
• unity3d

[BoneCrasher]

things I'd like to suggest:

• import {x as y} from ...
• Module identification: -- packages have ids, e.g. 'xsstd' -- import like "import * from 'xsstd' or 'xsstd/submodule' -- resolution order: first packages, then local

[Vengarioth]

• 'as' syntax can later be added if needed.
• local first vs packages first has to be discussed