tightened rules for specifying modifiers

* Instead of separate stand-alone commands, they are now allowed only immediately
  in front of the commands that accept them.
* The order is still insignificant if both `@` and `:` are accepted.
* The number of colon modifiers is now also checked.
  We basically get this for free.
* `@` has syntactic significance, so it could not be set conditionally anyway.
  Still, it was possible to provoke bugs were `@` was interpreted conditionally
  as in `@ 2<I/foo/$>`.
* Even when not causing bugs, a mistyped `@` would often influence the
  __next__ command, causing unexpected behavior, for instance when
  typing `@(233C)W`.
* While it was theoretically possible to set `:` conditionally, it could also
  be "passed through" accidentally to some command where it wasn't expected as in
  `:Ifoo$ C`.
  I do not know of any real useful application or idiom of a conditionally set `:`.
  If there would happen to be some kind of useful application, `:'` and `:|` could
  be re-allowed easily, though.
* I was condidering introducing a common parser state for modified commands,
  but that would have been tricky and introduce a lot of redundant command lists.
  So instead, we now simply everywhere check for excess modifiers.
  To simplify this task, teco_machine_main_transition_t now contains flags
  signaling whether the transition is allowed with `@` or `:` modifiers set.
  It currently only has to be checked in the start state, after `E` and `F`.

1 files changed, 19 insertions, 0 deletions

diff --git a/src/parser.h b/src/parser.h
index fe8e764..050467c 100644
--- a/src/parser.h
+++ b/src/parser.h
@@ -544,8 +544,27 @@ gboolean teco_execute_macro(const gchar *macro, gsize macro_len,
 gboolean teco_execute_file(const gchar *filename, teco_qreg_table_t *qreg_table_locals, GError **error);
 
 typedef const struct {
+	/** next state after receiving the input character */
 	teco_state_t *next;
+	/**
+	 * Optional function to call during the state transition.
+	 *
+	 * It is called only in normal execution mode.
+	 */
 	void (*transition_cb)(teco_machine_main_t *ctx, GError **error);
+	/**
+	 * Maximum number of `:` modifiers, that \b can be set on the input character.
+	 *
+	 * Colon modifiers are completely ignored in parse-only modes.
+	 */
+	guint modifier_colon : 2;
+	/**
+	 * TRUE if `@`-modifier \b can be set on the input character.
+	 *
+	 * Since `@` has syntactic significance,
+	 * it is checked even in parse-only mode.
+	 */
+	bool modifier_at : 1;
 } teco_machine_main_transition_t;
 
 /*