func (t *Tokenizer) Base() *src.PosBase {
	return t.base
}

func (t *Tokenizer) SetBase(base *src.PosBase) {
	t.base = base
}

func (t *Tokenizer) Line() int {
	return t.line
}

func (t *Tokenizer) Col() int {
	return t.s.Pos().Column
}

func (t *Tokenizer) Next() ScanToken {
	s := t.s
	for {
		t.tok = ScanToken(s.Scan())
		if t.tok != scanner.Comment {
			break
		}
		text := s.TokenText()

// The argument list is nil for no parens on the definition; otherwise a list of
// formal argument names.
func (in *Input) macroDefinition(name string) ([]string, []Token) {
	prevCol := in.Stack.Col()
	tok := in.Stack.Next()
	if tok == '\n' || tok == scanner.EOF {
		return nil, nil // No definition for macro
	}
	var args []string
	// The C preprocessor treats
	//	#define A(x)
	// and

}

func (s *Stack) SetBase(base *src.PosBase) {
	s.tr[len(s.tr)-1].SetBase(base)
}

func (s *Stack) Line() int {
	return s.tr[len(s.tr)-1].Line()
}

func (s *Stack) Col() int {
	return s.tr[len(s.tr)-1].Col()
}

func (s *Stack) Close() { // Unused.

	// Cannot happen because we only have slices of already-scanned text,
	// but be prepared.
	s.base = base
}

func (s *Slice) Line() int {
	return s.line
}

func (s *Slice) Col() int {
	// TODO: Col is only called when defining a macro and all it cares about is increasing
	// position to discover whether there is a blank before the parenthesis.
	// We only get here if defining a macro inside a macro.

	Base() *src.PosBase
	// SetBase sets the position base.
	SetBase(*src.PosBase)
	// Line reports the source line number of the token.
	Line() int
	// Col reports the source column number of the token.
	Col() int
	// Close does any teardown required.
	Close()
}

// A Token is a scan token plus its string value.
// A macro is stored as a sequence of Tokens with spaces stripped.

		),
		"THIS.\n",
	},
	{
		"nested #define with args",
		lines(
			"#define A #define B(x) x",
			"A",
			"B(THIS)",
		),
		"THIS.\n",
	},
	/* This one fails. See comment in Slice.Col.
	{
		"nested #define with args",
		lines(
			"#define A #define B (x) x",
			"A",
			"B(THIS)",
		),
		"x.\n",
	},
	*/
}

func TestLex(t *testing.T) {