go.scanner.scanComments.go

func (s *Scanner) scanComment() string {
	// initial '/' already consumed; s.ch == '/' || s.ch == '*'
	offs := s.offset - 1 // position of initial '/'
	next := -1           // position immediately following the comment; < 0 means invalid comment
	numCR := 0

	if s.ch == '/' {
		//-style comment
		// (the final '\n' is not considered part of the comment)
		s.next()
		for s.ch != '\n' && s.ch >= 0 {
			if s.ch == '\r' {
				numCR++
			}
			s.next()
		}
		// if we are at '\n', the position following the comment is afterwards
		next = s.offset
		if s.ch == '\n' {
			next++
		}
		goto exit
	}

	/*-style comment */
	s.next()
	for s.ch >= 0 {
		ch := s.ch
		if ch == '\r' {
			numCR++
		}
		s.next()
		if ch == '*' && s.ch == '/' {
			s.next()
			next = s.offset
			goto exit
		}
	}

	s.error(offs, "comment not terminated")

exit:
	lit := s.src[offs:s.offset]

	// On Windows, a (//-comment) line may end in "\r\n".
	// Remove the final '\r' before analyzing the text for
	// line directives (matching the compiler). Remove any
	// other '\r' afterwards (matching the pre-existing be-
	// havior of the scanner).
	if numCR > 0 && len(lit) >= 2 && lit[1] == '/' && lit[len(lit)-1] == '\r' {
		lit = lit[:len(lit)-1]
		numCR--
	}

	// interpret line directives
	// (//line directives must start at the beginning of the current line)
	if next >= 0 /* implies valid comment */ && (lit[1] == '*' || offs == s.lineOffset) && bytes.HasPrefix(lit[2:], prefix) {
		s.updateLineInfo(next, offs, lit)
	}

	if numCR > 0 {
		lit = stripCR(lit, lit[1] == '*')
	}

	return string(lit)
}