ballercatWalt Plugin Closures
This is a reference implementation of Closures plugin for the Walt WebAssembly Compiler.
Syntax
type Func = () => i32;
// New GenericType "Lambda<Type>"
type Closure = Lambda<Func>;
// Closures require a table, because closure calls are indirect_call
const table: Table = { initial: 1, element: 'anyfunc' };
function getClosure(): Closure {
const x: i32 = 0;
// Closures can be defined with arrow function syntax
return (): i32 => {
x += 1;
return x;
};
}
export function run(): i32 {
const closure: Closure = getClosure();
closure();
closure();
return closure(); // 3
}Install
npm install walt-plugin-syntax-closure
API
import { compile } from 'walt-compiler';
import { plugin, imports } from 'walt-plugin-syntax-closure';
// .walt source with closures
const source = `...`;
// compiler options
const options = {
extensions: [plugin],
};
// Closures require an additional import for support. It's provided by the plugin
Promise.resolve(imports(options, compile))
.then(closureImports =>
WebAssembly.instantiate(compile(source, options).buffer(), closureImports)
)
.then(mod => mod.instance.exports.run());CLI
N/A
Reference
This plugin is meant to act as a reference example of plugins for the Walt compiler. To demonstrate this it extends the grammar(syntax), the semantic parser as well as provides a "side-module" import for it's run-time features.
Grammar
The plugin adds an additional Node type Closure and makes it a valid
Expression type. For the full grammar see the
Grammar File.
Semantic Parser
This plugin extends the semantic parser by parsing the new syntax down to the supported AST format of the core compiler. See the main plugin source for how the semantic parser is extended.
Imports
Ths plugin provides a run-time import for closure support. The following header is added to every module using closures.
// Start Closure Imports Header
import {
__closure_malloc: ClosureGeti32,
__closure_free: ClosureFree,
__closure_get_i32: ClosureGeti32,
__closure_get_f32: ClosureGetf32,
__closure_get_i64: ClosureGeti64,
__closure_get_f64: ClosureGetf64,
__closure_set_i32: ClosureSeti32,
__closure_set_f32: ClosureSetf32,
__closure_set_i64: ClosureSeti64,
__closure_set_f64: ClosureSetf64
} from 'walt-plugin-closure';
type ClosureFree = (i32) => void;
type ClosureGeti32 = (i32) => i32;
type ClosureGetf32 = (i32) => f32;
type ClosureGeti64 = (i32) => i64;
type ClosureGetf64 = (i32) => f64; type ClosureSeti32 = (i32, i32) => void;
type ClosureSetf32 = (i32, f32) => void;
type ClosureSeti64 = (i32, i64) => void;
type ClosureSetf64 = (i32, f64) => void;
// End Closure Imports HeaderNote: There is no memory cleanup in the reference implementation of the imports.
Note: You may provide your own import object under walt-plugin-closure as
long as it matches the API above. The buit-in import provided by plugin isn't
required.