Type inference to make JavaScript as fast as statically typed languages?

“Type Inference brings JS improvements to Firefox Beta” by Brian Hackett:

TI [Type Inference] is a feature in the SpiderMonkey Javascript engine which generates type information about Javascript programs through a combination of analyzing the program’s code and monitoring the types of values as the program executes.
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With these projects, ... we hope to close the performance gap with Java completely.

Related talk: “JavaScript JITs” by David Mandelin and David Anderson at JSConf.eu 2011.