src/vs/editor/common/services/languagesRegistry.ts/LanguagesRegistry/_registerLanguages
class LanguagesRegistry:	_registerLanguages(desc: ILanguageExtensionPoint[]): void {

		for (const d of desc) {
			this._registerLanguage(d);
		}

		// Rebuild fast path maps
		this._mimeTypesMap = {};
		this._nameMap = {};
		this._lowercaseNameMap = {};
		Object.keys(this._languages).forEach((langId) => {
			const language = this._languages[langId];
			if (language.name) {
				this._nameMap[language.name] = language.identifier;
			}
			language.aliases.forEach((alias) => {
				this._lowercaseNameMap[alias.toLowerCase()] = language.identifier;
			});
			language.mimetypes.forEach((mimetype) => {
				this._mimeTypesMap[mimetype] = language.identifier;
			});
		});

		Registry.as<IConfigurationRegistry>(Extensions.Configuration).registerOverrideIdentifiers(this.getRegisteredLanguageIds());

		this._onDidChange.fire();
	}