🐛 Bug: strictNonNullAssertions changes "return undefined" to "return undefined!"

[rubiesonthesky]

Bug Report Checklist

• I have tried restarting my IDE and the issue persists.
• I have pulled the latest main branch of the repository.
• I have searched for related issues and found none that matched my issue.

Expected

It should allow returning undefined here

const collectFileNamesFromGlobs = async (
	argv: TypeStatArgv,
	cwd: string,
	include: readonly string[] | undefined,
): Promise<[readonly string[], readonly string[]] | undefined> => {
	if (argv.args.length) {
		return [argv.args, await glob(argv.args)];
	}

	if (include === undefined) {
		return undefined;
	}

	return [
		include,
		await glob(include.map((subInclude) => path.join(cwd, subInclude))),
	];
};

Actual

The undefined return is changed to this

	if (include === undefined) {
		return undefined!;
	}

Additional Info

This is probably related to #1494 - it does not understand that the function accepts return type Promise<undefined>.

typestat.json

[
    {
        "fixes": {
            "strictNonNullAssertions": true
        },
        "include": [
            "src/**/*.{ts,tsx}"
        ],
        "projectPath": "./tsconfig.json",
        "types": {
            "strictNullChecks": true
        }
    }
]

tsconfig

{
	"compilerOptions": {
		"declaration": true,
		"declarationMap": true,
		"esModuleInterop": true,
		"module": "NodeNext",
		"moduleResolution": "NodeNext",
		"noEmit": true,
		"outDir": "lib",
		"resolveJsonModule": true,
		"skipLibCheck": true,
		"sourceMap": true,
		"strict": true,
		"target": "ES2022"
	},
	"include": ["src", "test/*.ts"]
}

[rubiesonthesky]

These work correctly in test setup, so I suspect that the issue is with returning Promise

const lambdaGivenUndefinedReturnsUndefined = (): string | undefined => {
  return undefined;
};

const lambdaGivenNullReturnsNull = (): string | null => {
  return null;
};