of an error message on a given line to deduce the information it
needs. The program is syntactically valid regardless of whether each
name is a type or an ordinary identifier, so there will be no syntax
errors that might stop parsing early.

An error on not-declared:1 indicates that foo is undeclared.
An error on not-type:1 indicates that foo is not a type (if declared at all, it is an identifier).

// returned by a Split function to indicate that the scanning should stop
// with no error. If the token being delivered with this error is not nil,
// the token is the last token.
//
// The value is useful to stop processing early or when it is necessary to
// deliver a final empty token (which is different from a nil token).
// One could achieve the same behavior with a custom error value but
// providing one here is tidier.

func genLine(buf *bytes.Buffer, lineNum, n int, addNewline bool) {
	buf.Reset()
	doCR := lineNum%5 == 0
	if doCR {
		n--
	}
	for i := 0; i < n-1; i++ { // Stop early for \n.
		c := 'a' + byte(lineNum+i)
		if c == '\n' || c == '\r' { // Don't confuse us.
			c = 'N'
		}
		buf.WriteByte(c)
	}
	if addNewline {
		if doCR {
			buf.WriteByte('\r')
		}

      Clients of <a href="/pkg/go/types"><code>go/types</code></a> are urged to adjust their code as soon as possible
      to work with <code>gotypesalias=1</code> to eliminate problems early.
    </p>

    <p><!-- https://go.dev/issue/62605, CL 540056 -->
      The <a href="/pkg/go/types#Info"><code>Info</code></a> struct now exports the