Restricted strings to 7-bit ASCII, as in Michelson.

type:fixed

Didier found that UTF-8 encoded glyphs were valid data constructors. It was in fact strings that were not restricted to 7-bit ASCII characters. (Some control characters are allowed.)

Changelog details:

Description details: Restricted strings to 7-bit ASCII, as in Michelson. I completely rewrote the tests for the lexers (expect tests), as most were missing.