The issue here is that the current expression is still there and
protected if there is a parse problem. So you need one more unprotect.
This does not give a problem in source() (the only internal use) as it
throws an error in those cases. (It also uses a different branch of the
code with n <
[this is from R-help, at the end of June]
Jim Lemon asked about parsing syntactically incorrect versus
incomplete lines, generating a couple of responses.
Philippe's suggestion isn't robust (e.g., "\nls)". Prof. Ripley's
comment lead me to R_ParseVector (the only exposed parse
routine). Unfortuna
