Before You File a Proposal Please Confirm You Have Done The Following...

• I have searched for related issues and found none that match my proposal.
• I have searched the current rule list and found no rules that match my proposal.
• I have read the FAQ and my problem is not listed.

My proposal is suitable for this project

• I believe my proposal would be useful to the broader TypeScript community (meaning it is not a niche proposal).

Link to the rule's documentation

https://typescript-eslint.io/rules/no-unnecessary-type-assertion

Description

I propose that the no-unnecessary-type-assertion rule should also check for the return type of a function.

Fail

declare function foo(): number;
const a = foo()!; // no error report
const b = foo() as number; // report error but bad fixed: `const b = foo() ; `
const c = <number>foo(); // good now

Pass

declare function foo(): number;
const a = foo();
const b = foo();
const c = foo();

Additional Info

Im ready to send a PR after the issue is marked with the accepting prs label as indicated on the PR Checklist. Welcome to provide more test cases.