The right-hand side of an arithmetic operation must be of type 'any', 'number', 'bigint' or an enum type.ts(2363)

[ubershmekel]

Suggestion

The following code errors:

      const x: Number = 5;
      const y = 5 - x;

With this:

The right-hand side of an arithmetic operation must be of type 'any', 'number', 'bigint' or an enum type.ts(2363)

Which is super confusing because it is a number. But I didn't realize the problem was the first letter capitalization. Number vs number.

🔍 Search Terms

right-hand side of an arithmetic

✅ Viability Checklist

My suggestion meets these guidelines:

• [v] This wouldn't be a breaking change in existing TypeScript/JavaScript code
• [v] This wouldn't change the runtime behavior of existing JavaScript code
• [v] This could be implemented without emitting different JS based on the types of the expressions
• [v] This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• [v] This feature would agree with the rest of TypeScript's Design Goals.

⭐ Suggestion

Would be nice if there was an error during the assignment, is Number also a number? Another option is error 2363 could mention this potential issue. E.g.

The right-hand side of an arithmetic operation must be of type 'any', 'number', 'bigint' or an enum type. Not 'Number' .ts(2363)

And replace 'Number' with whatever type was actually found.

📃 Motivating Example

      const x: Number = 5;
      const y = 5 - x;

Minor typos should have a clear error message.

[bxt]

I don't think the the first letter capitalization is the only problem. Consider Playground:

const x: Number = 1;
const y: Number = 2;
const z = x + y; // Operator '+' cannot be applied to types 'Number' and 'Number'.

const a: BigInt = 1n;
const b: BigInt = 2n;
const c = a + b; // Operator '+' cannot be applied to types 'BigInt' and 'BigInt'

So here the types are exactly the same, both starting with upper case, and still TS is complaining. This is very confusing.

I think this issue would be solved when #2361 is solved, it's not an exact duplicate though.