The bootstrap.

Here's the moment everything has been building toward. Four commands:

# Step 1: Compile the compiler with our Zig implementation
zig build-exe minizig.zig && ./minizig < compiler.lang > compiler.wat

# Step 2: Assemble to WASM
wat2wasm compiler.wat -o compiler.wasm

# Step 3: Run the WASM compiler on its own source
node run.js compiler.wasm < compiler.lang > compiler2.wat

# Step 4: Compare
diff compiler.wat compiler2.wat

run.js is a small Node.js script that loads the WASM module with I/O imports:

const fs = require('fs');
const wasm = fs.readFileSync(process.argv[2]);
const input = fs.readFileSync('/dev/stdin');

WebAssembly.instantiate(wasm, {
    env: {
        read_input: () => {
            for (let i = 0; i < input.length; i++)
                mem[i] = input[i];
            return input.length;
        },
        print_char: (c) => process.stdout.write(Buffer.from([Number(c)])),
    }
}).then(({ instance }) => {
    mem = new Uint8Array(instance.exports.memory.buffer);
    instance.exports.main();
});