src/vs/workbench/common/editor/textEditorModel.ts/BaseTextEditorModel/setLanguageIdInternal
class BaseTextEditorModel:	private setLanguageIdInternal(languageId: string): void {
		if (!this.isResolved()) {
			return;
		}

		if (!languageId || languageId === this.textEditorModel.getLanguageId()) {
			return;
		}

		this.modelService.setMode(this.textEditorModel, this.languageService.createById(languageId));
	}