refactor: Convert renderer typecheck methods to typeguards. #4612

	name: Assign requested reviewers

	# This workflow adds requested reviewers as assignees. If you remove a
	# requested reviewer, it will not remove them as an assignee.
	#
	# See https://github.com/google/blockly/issues/5643 for more
	# information on why this was added.
	#
	# N.B.: Runs with a read-write repo token. Do not check out the
	# submitted branch!
	on:
	pull_request_target:
	types: [review_requested]

	jobs:
	requested-reviewer:
	runs-on: ubuntu-latest
	steps:
	- name: Assign requested reviewer
	uses: actions/github-script@v7
	with:
	script: \|
	try {
	if (context.payload.pull_request === undefined) {
	throw new Error("Can't get pull_request payload. " +
	'Check a request reviewer event was triggered.');
	}
	const reviewers = context.payload.pull_request.requested_reviewers;
	// Assignees takes in a list of logins rather than the
	// reviewer object.
	const reviewerNames = reviewers.map(reviewer => reviewer.login);
	const {number:issue_number} = context.payload.pull_request;
	github.rest.issues.addAssignees({
	owner: context.repo.owner,
	repo: context.repo.repo,
	issue_number: issue_number,
	assignees: reviewerNames
	});
	} catch (error) {
	core.setFailed(error.message);
	}

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