func()

in modfile/read.go [511:617]
78 lines of code
24 McCabe index (conditional complexity)

func (in *input) readToken() {
	// Skip past spaces, stopping at non-space or EOF.
	for !in.eof() {
		c := in.peekRune()
		if c == ' ' || c == '\t' || c == '\r' {
			in.readRune()
			continue
		}

		// Comment runs to end of line.
		if in.peekPrefix("//") {
			in.startToken()

			// Is this comment the only thing on its line?
			// Find the last \n before this // and see if it's all
			// spaces from there to here.
			i := bytes.LastIndex(in.complete[:in.pos.Byte], []byte("\n"))
			suffix := len(bytes.TrimSpace(in.complete[i+1:in.pos.Byte])) > 0
			in.readRune()
			in.readRune()

			// Consume comment.
			for len(in.remaining) > 0 && in.readRune() != '\n' {
			}

			// If we are at top level (not in a statement), hand the comment to
			// the parser as a _COMMENT token. The grammar is written
			// to handle top-level comments itself.
			if !suffix {
				in.endToken(_COMMENT)
				return
			}

			// Otherwise, save comment for later attachment to syntax tree.
			in.endToken(_EOLCOMMENT)
			in.comments = append(in.comments, Comment{in.token.pos, in.token.text, suffix})
			return
		}

		if in.peekPrefix("/*") {
			in.Error("mod files must use // comments (not /* */ comments)")
		}

		// Found non-space non-comment.
		break
	}

	// Found the beginning of the next token.
	in.startToken()

	// End of file.
	if in.eof() {
		in.endToken(_EOF)
		return
	}

	// Punctuation tokens.
	switch c := in.peekRune(); c {
	case '\n', '(', ')', '[', ']', '{', '}', ',':
		in.readRune()
		in.endToken(tokenKind(c))
		return

	case '"', '`': // quoted string
		quote := c
		in.readRune()
		for {
			if in.eof() {
				in.pos = in.token.pos
				in.Error("unexpected EOF in string")
			}
			if in.peekRune() == '\n' {
				in.Error("unexpected newline in string")
			}
			c := in.readRune()
			if c == quote {
				break
			}
			if c == '\\' && quote != '`' {
				if in.eof() {
					in.pos = in.token.pos
					in.Error("unexpected EOF in string")
				}
				in.readRune()
			}
		}
		in.endToken(_STRING)
		return
	}

	// Checked all punctuation. Must be identifier token.
	if c := in.peekRune(); !isIdent(c) {
		in.Error(fmt.Sprintf("unexpected input character %#q", c))
	}

	// Scan over identifier.
	for isIdent(in.peekRune()) {
		if in.peekPrefix("//") {
			break
		}
		if in.peekPrefix("/*") {
			in.Error("mod files must use // comments (not /* */ comments)")
		}
		in.readRune()
	}
	in.endToken(_IDENT)
}