Several characters legal in bare identifiers cause confusing or ambiguous behavior

[hkolbeck-streem]

Currently, the characters /,*, +, and - are legal in bare identifiers and at their start. This leads to a few ambiguous situations while parsing. Some examples:

• -10/+10 are valid bare identifiers, at least in the node identifier position. How to parse things like -10=10 is a bit more difficult.
• a/**/ is a valid bare identifier
• a// is a valid bare identifier

It seems in keeping with the current rules about bare identifier start chars to add -/+ to the forbidden list. How to handle the latter case seems a bit tougher.

[hkolbeck-streem]

After some more thinking it feels reasonable to disallow just / in bare identifiers, as it already seems a little odd to allow a character that would require escaping in an escaped string. Raw strings could still surprise people, since you could have documents like:

node r"Hello,
//Here comes the cool part
World" 

which would be written "node Hello,\n\/\/Here comes the cool part\nWorld" if written with escaped strings. This still feels not entirely surprising because of the semantics of raw strings, and I don't see a way around it that would be less confusing.