an ecmascript compiler with jit in rust

To build an ECMAScript(JavaScript) compiler with JIT in Rust, we can make use of the "rJS" library. "rJS" is a Rust implementation of JavaScript, built with a focus on high performance and compatibility with the ECMAScript specifications.

To use it, we need to add the following dependencies to our project's Cargo.toml file:

main.rs
[dependencies]
rjs = "0.2.0"
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Next, we create a new Rust file in our project and start setting up our compiler. The steps involved are:

1. Parse the input ECMAScript code using the rjs::parser::Parser module.
2. Generate intermediate code using the rjs::intermediate::Intermediate module.
3. Use the rjs::Jit module to compile the intermediate code into machine code.
4. Execute the compiled code using the rjs::vm::Vm module.

Here is an example implementation:

main.rs
use rjs::parser::Parser;
use rjs::intermediate::Intermediate;
use rjs::Jit;
use rjs::vm::Vm;

fn main() {
   // input JavaScript code
   let input = r#"
        function fib(n) {
            if (n == 0) {
                return 0;
            }
            if (n == 1) {
                return 1;
            }
            return fib(n - 1) + fib(n - 2);
        }
        print(fib(40));
    "#;

    // Parse input code
    let mut parser = Parser::new(input);
    let ast = parser.parse().unwrap();

    // Convert AST to intermediate code
    let mut intermediate = Intermediate::new();
    intermediate.generate(&ast);

    // JIT through rJS
    let code = Jit::new(intermediate).compile().unwrap();

    // Create & execute VM and run code
    let mut vm = Vm::new();
    vm.execute(&code);

    // Print result
    println!("Output: {}", vm.get_result());
}

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This implementation compiles a sample code that calculates the 40th Fibonacci number using recursion. The JIT compiler in "rJS" allows this code to execute much faster.

Note: This is a simple example implementation and further improvements and optimizations can be added based on project needs.