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POType inference in Java (à la C#)
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copied!<p>Ever since I heard of type inference (in Haskell), I lived under the impression that Java is the exact opposite, i.e., it has no type inference. Recently though, I had an aha moment and realized that Java employs type inference in its generics implementation.</p> <p>Then, I read two papers by Gilad Bracha (one of the people behind the generics implementation in Java, as far as I understand). The first paper is a <a href="http://java.sun.com/j2se/1.5/pdf/generics-tutorial.pdf">tutorial about generics</a> (PDF), in which he explicitly says that the compiler will <em>infer</em> the actual type argument used to replace the format type parameter. So, there's type inference in Java, but why only for generics, why not something like C#'s <code>var</code> keyword? And this is my question to you.</p> <p>Why doesn't Java has more type inference built into the compiler?</p> <p>I will suggest an answer though, and this is related to the second paper that I read, <a href="http://bracha.org/pluggableTypesPosition.pdf">Pluggable Type Systems</a> (PDF). It seems, Gilad Bracha believes that the inference part shouldn't be part of the compiler, but an IDE feature or similar (section 4, paragraph 6 in the above mentioned paper):</p> <blockquote> <p>A better engineering approach is to implement type inference as a separate tool, available in the IDE. Programmers who find entering type annotations tiresome can invoke an inferencer on demand.</p> </blockquote> <p>What do you think?</p>

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