ScanFloats     = 1 << -Float // includes Ints and hexadecimal floats
	ScanChars      = 1 << -Char
	ScanStrings    = 1 << -String
	ScanRawStrings = 1 << -RawString
	ScanComments   = 1 << -Comment
	SkipComments   = 1 << -skipComment // if set with ScanComments, comments become white space
	GoTokens       = ScanIdents | ScanFloats | ScanChars | ScanStrings | ScanRawStrings | ScanComments | SkipComments
)

	// the floats in the source look like (invalid) octal ints
	// and ScanNumbers may return either Int or Float.
	testScanSelectedMode(t, ScanChars, Char)
	testScanSelectedMode(t, ScanStrings, String)
	testScanSelectedMode(t, SkipComments, 0)
	testScanSelectedMode(t, ScanComments, Comment)
}

func TestScanCustomIdent(t *testing.T) {
	const src = "faab12345 a12b123 a12 3b"

	p.scanner.Init(src)
	p.scanner.Error = func(_ *scanner.Scanner, msg string) { p.error(msg) }
	p.scanner.Mode = scanner.ScanIdents | scanner.ScanInts | scanner.ScanFloats | scanner.ScanStrings
	p.scanner.Whitespace = 1<<'\t' | 1<<' '
	p.scanner.Filename = filename // for good error messages
	p.next()
}

type importError struct {
	pos scanner.Position
	err error
}