Rust is a hard way to make a web API

Re:Rust is a hard way to make a web API by 29athrowaway on Saturday January 16, 2021 @02:29AM (#25800757)

Run this, please.

    // 100% type-safe function :-)
    function f(a: Date): number {
        return a.getDate();
    }

    // Input to 100% type-safe function
    const p = new Proxy(new Date(), {
        get: function(target, prop, receiver) {
            if (prop !== 'getDate') {
                return Reflect.get(target, prop, receiver);
            }

            return function() {
                console.log('Not typesafe :(');
            };
        }
    });

    f(p);

Output: "Not typesafe :("

What happened? all type-safety was circumvented. The f function that should return a number did not return a number. In fact, it didn't return anything.

The TypeScript compiler didn't return any errors either. This is perfectly valid TypeScript.

Why? because TypeScript is based on JavaScript. It is not 100% typesafe and it will never be.

Is TypeScript an improvement? yes. Does it help a lot of people? yes. Is it 100% typesafe? no.

Did TypeScript "fix" JavaScript? Mostly, but no. I hope the mods unflag my original comment.

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Re:Rust is a hard way to make a web API by WClayFerguson on Saturday January 16, 2021 @03:11PM (#25805066)

I had already given two examples of how you can create non-type-safe code in TypeScript. I mentioned 1) the 'var/let' way and 2) The "Not including types on parameters" way.

You then gave an actual example of #2. lol.

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Re:Rust is a hard way to make a web API by 29athrowaway on Saturday January 16, 2021 @06:03PM (#25806359)

That is not what is happening here. TypeScript correctly infers that type of the variable is a Proxy for a Date object. If you do not supply a Date object as first argument, the code won't compile.

The part that breaks things is that when f invokes a.getDate(), the Proxy get trap changes will return another function instead of Date#getDate at runtime, and that wasn't validated at compile time.

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Re:Rust is a hard way to make a web API by WClayFerguson on Saturday January 16, 2021 @07:17PM (#25806818)

Proxy is part of JS. When did I ever say ANYTHING in JS is typesafe? Nothing in JS is typesafe.

However this is also simultaneously true: You can code in TypeScript and achieve 100% type safety by putting types on everything. If I claim all cubes can be painted red, you can't disprove that by proving green cubes exist.

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Re:Rust is a hard way to make a web API by 29athrowaway on Sunday January 17, 2021 @12:50AM (#25808510)

And what does TypeScript compile to? JavaScript.

Does TypeScript forbid using JavaScript features? no.

Can TypeScript realistically verify that your program is type-safe? no.

Is TypeScript 100% type-safe? no. They wanted fast adoption, therefore they allowed JavaScript and untyped variables.

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Re:Rust is a hard way to make a web API by WClayFerguson on Sunday January 17, 2021 @12:11PM (#25812441)

You can go into my 250,000 loc project and randomly pick any variable name, method name, parameter name, etc., and put a typo in it or wrong type, and the compiler will catch it.

I have 100% type safety, and it's all done by TypeScript and my programming language IS TypeScript (not JS)

The the final output format generated by a compiler has absolutely nothing to do with whether the Language being compiled is typesafe or not. That would be like saying since Bytecode is not typesafe therefore Java is not a type safe language.

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Re:Rust is a hard way to make a web API by 29athrowaway on Sunday January 17, 2021 @08:55PM (#25817332)

TypeScript is not the only way to achieve that.

Google closure compiler and JetBrains IDEs can use JSdoc to validate types. I have used those to a reasonable level of accuracy to document entire JavaScript projects where I cannot migrate to TypeScript.

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Re:Rust is a hard way to make a web API by WClayFerguson on Sunday January 17, 2021 @10:59PM (#25817955)

Excellent. Rock on man. I never thought I'd be a Microsoft fan again, but after they invented TypeScript/VSCode, I love them so much I might move to Redmond.

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