extensions/typescript-language-features/src/languageFeatures/quickFix.ts/SupportedCodeActionProvider/fixableDiagnosticCodes
class SupportedCodeActionProvider:	private get fixableDiagnosticCodes(): Thenable<Set<string>> {
		return this.client.execute('getSupportedCodeFixes', null, nulToken)
			.then(response => response.type === 'response' ? response.body || [] : [])
			.then(codes => new Set(codes));
	}