What feature enhances coding efficiency in an active context by providing suggestions?

The feature that enhances coding efficiency in an active context by providing suggestions is the content assist functionality. This tool is designed to streamline the coding process by offering relevant suggestions as a developer types. For instance, it may propose variable names, method signatures, or other contextual snippets that can be quickly inserted into the code. This not only helps in reducing the amount of typing required but also minimizes the chances of errors that could arise from manual input.

In contrast, while the contextual help system provides guidance and information about features or functions, it does not actively suggest code snippets or completions in the way content assist does. Syntax error notifications alert developers to mistakes in the code but do not foster efficiency by providing suggestions. Similarly, a code refactoring tool helps in improving and restructuring existing code but does not actively assist in the writing process. Thus, content assist functionality stands out as the feature specifically designed to enhance coding efficiency through proactive suggestions.