fix(eslint-plugin): [explicit-module-boundary-types] fixes #2864 related to functions in nested object properties

[grumd]

Fixes #2864

Gist of it:

explicit-module-boundary-types and explicit-function-return-type both have an option allowTypedFunctionExpressions.
It makes this code correct:

interface ObjectType {
  foo(): number;
}
export const obj: ObjectType = {
  foo: () => 1,
};

The issue is that the following code is not correct even with the option set to true:

interface ObjectType {
  foo: { bar: () => number }; 
}
export const obj: ObjectType = {
  foo: { bar: () => 1 },
};

My PR fixes the issue for both of these rules and adds relevant tests.

My fork can be used with npm/yarn using this, that's what I temporarily will do.

"@typescript-eslint/eslint-plugin": "https://gitpkg.now.sh/grumd/typescript-eslint/packages/eslint-plugin?build",

[typescript-eslint]

Thanks for the PR, @grumd!

typescript-eslint is a 100% community driven project, and we are incredibly grateful that you are contributing to that community.

The core maintainers work on this in their personal time, so please understand that it may not be possible for them to review your work immediately.

Thanks again!

---

🙏 Please, if you or your company is finding typescript-eslint valuable, help us sustain the project by sponsoring it transparently on https://opencollective.com/typescript-eslint. As a thank you, your profile/company logo will be added to our main README which receives thousands of unique visitors per day.

[armano2]

can you add unit tests for explicit-module-boundary-types

[grumd]

can you add unit tests for explicit-module-boundary-types

Added

[bradzacher]

thanks!