Early error vs. error on first call to function vs. runtime error

Brendan Eich brendan at mozilla.org
Wed Oct 3 22:06:24 PDT 2012

Oliver Hunt wrote:
> I still don't understand this desire to delay semantic analysis, where are the examples of sema being a performance bottleneck?  Just basic parsing already requires us to do a reasonable amount of analysis anyway, and while parsing shows up as being a problem, the bulk of that time seems to be lexing, and lexing is unavoidable even if all you want to do is syntactic analysis (unless we're proposing a delayed syntactic check mode?????)

You make good points. The counter-arguments were from Microsoft at the 
last TC39 meeting (two weeks ago). The followup from them (and from all 
implementors) was to provide more detail from profiling on where the 
costs lie. If they're mostly irreducible lexing, then you're right.


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