Minification bug: erroneous fusion of operator symbols

Terminology: a lexer is responsible for tokenisation of the input—breaking it into words, if you will, like if, camelVar, 6.02e+23, {, 'string', + and +=—while the parser is responsible for syntactic analysis, the grouping of those tokens into statements and expressions (with, admittedly, a few grey areas such as backquotes and regular expressions). It's not a logical necessity that languages be designed with this distinction, but as a practical matter almost all programming languages since the 60s seem to in one way or another. In the C family (to which JS belongs notationally, though not semantically), it's pretty crucial to understanding what's going on, and the formal concept (though not a typical implementation—and certainly not this implementation) is that tokenisation is a separate process that runs ‘before’ parsing. In any case, in JS, -- is one token and - - is two, just as xx is different from x x and == is different from = =, so in this case, the space is significant. The language processor, taken as a whole. is wrong to treat - - as --, and would be just as wrong to treat -- as - -.
Espruino does not always make this mistake—var x does not get confused with varx and the far more obscure example do x(); while (!done()); does not get misinterpreted as the (equally legal) dox(); while (!done());, even during full file interactive upload to the emulator (the context that triggers the bug I was reporting).