Re: [heycam/webidl] Add a section on overloads vs. union/optional (#426)

annevk commented on this pull request.



> +Additionally, there are semantic differences as well. [=Union types=] are usually used in the sense
+that "any of the types would work in about the same way". In contrast, [=overloaded=] operations are
+designed to map well to language features such as C++ overloading, and are usually a better fit for
+operations with more substantial differences in what they do given arguments of different types.
+However, in most cases, operations with such substantial differences are best off with different
+names to avoid confusion for Web developers, since the ECMAScript language does not provide
+language-level overloading. As such, overloads are rarely appropriate for new APIs, instead often
+appearing in legacy APIs or in specialized circumstances.
+
+That being said, we offer the following recommendations and examples in case of difficulties to
+determine what Web IDL language feature to use:
+
+*   In the unusual case where the operation must return values of different types for different
+    argument types, [=overloaded|overloading=] should be used. <span class="note">This is almost
+    never appropriate API design, and separate operations with distinct names should be used for
+    such cases.</span>

"Could", "might", "can", "encouraged", "discouraged", "strongly encouraged", and "strongly discouraged" are the words I end up using at times. Some of this seems like it should be requirements, but I guess non-normative is fine for now.

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