Trigger "Expression is always true" warning on a helper function

I have a function called isDefined, which is implemented like so:

export function isDefined<T>(value: T): value is NonNullable<T> {
    return value !== undefined && value !== null;
}

Functionality, it works. But, there's one small thing that I try to accomplis. Let's take this code for example:

const a: number | null | undefined = 1;

if (a !== undefined && a !== null) {
  // a is inferred here as `number`
  ...

  if (a !== undefined) {
    //^^^^^^^^^^^^^^^ tslint/eslint will throw the following warning: 
    // "Expression is always true. (strict-type-predicates)"

  }
}

Since I've already checked if a is defined, the lint will throw a warning that stating that again would be redundant.

If I try to replace it with isDefined, No warning will be thrown:

if (isDefined(a)) {
  // a is inferred here as `number`
  ...

  if (isDefined(a)) {
    // linter throws nothing
  }
}

I wasn't able to reproduce it in codesandbox since I cannot configure the eslint, but this is the code:

export function isDefined<T>(value: T): value is NonNullable<T> {
  return value !== undefined && value !== null;
}

function linterWillThrowWarning<T>(value: T | null | undefined) {
  if (value !== null && value !== undefined) {
    if (value !== null) {
      console.log(value);
    }
  }
}

function linterWontThrowWarning<T>(value: T | null | undefined) {
  if (isDefined(value)) {
    if (isDefined(value)) { // (I want it to throw)
      console.log(value);
    }
  }
}