This implements parsing of /*line file:line*/ and /*line file:line:col*/
directives and also extends the optional column format to regular //line
directives, per #22662.
For a line directive to be recognized, its comment text must start with
the prefix "line " which is followed by one of the following:
:line
:line:col
filename:line
filename:line:col
with at least one : present. The line and col values must be unsigned
decimal integers; everything before is considered part of the filename.
Valid line directives are:
//line :123
//line :123:8
//line foo.go:123
//line C:foo.go:123 (filename is "C:foo.go")
//line C:foo.go:123:8 (filename is "C:foo.go")
/*line ::123*/ (filename is ":")
No matter the comment format, at the moment all directives act as if
they were in //line comments, and column information is ignored.
To be addressed in subsequent CLs.
For #22662.
Change-Id: I1a2dc54bacc94bc6cdedc5229ee13278971f314e
Reviewed-on: https://go-review.googlesource.com/86037 Reviewed-by: Matthew Dempsky <mdempsky@google.com>