A stop takes the window, because the next key is aimed at it

TODO.org

@@ -1,5 +1,5 @@
 #+TITLE: Flan
-#+TODO: TODO NEXT WAIT | DONE CANCELLED
+#+TODO: TODO WAIT | DONE CANCELLED
 #+ARCHIVE: ::* Archive
 
 Every decision, open question and known gap, one =**= heading each under the
@@ -470,7 +470,7 @@ an ordinary =defn= declares no environment and is byte-for-byte what it was. The
 static side does not pay for the dynamic side. Rejected names: Closure, Proc, Fun,
 Func, Fnptr.
 
-** NEXT Escaping closures, allocated on the GC side
+** TODO Escaping closures, allocated on the GC side
 The second half of "do both". What changes is where the environment points — a
 frame slot today, a collector allocation then — and the escape check goes away
 with it, along with the refusals on returning, storing, pointing at and pushing a
@@ -1731,6 +1731,51 @@ specification's own branch — the flag is the command and the printed shape is
 error pattern, so anyone who wants one has the four lines, and the manual carries
 them.
 
+** TODO The break buffer prints a condition's fields, not its message
+=ArithError — op 4, lhs -2147483648, rhs 2147483647= where the runtime's own
+sentence for that op is "this value does not fit the integer type it is cast
+to" (=runtime/flan_rt.c:986=). The good sentences exist and go to stderr on an
+unhandled stop; the buffer renders the struct generically instead. Either put
+the rendered sentence on the wire, or let a condition type carry a printer.
+=op= being a bare number is the same gap — it is an enum spelled as =i32=.
+
+** TODO A backtrace frame names the function, not the call
+=fninfo= (=lib/emit.ml:185=) holds one static =loc=, the =defn='s own, and
+=flan_frame= (=runtime/flan_dev.c:1011=) adds no per-call location — so two
+calls to the same function from one caller are indistinguishable in the stack.
+Wants the caller storing its call site into the frame before the call, which is
+a field and a store on every dev-build call.
+
+** TODO The condition buffer cannot jump to the source
+It prints the source line and carets for the stop (=flan-cnr.el:197=) and lists
+frames, but no key opens the file at that line. Wants RET-on-a-frame, or =M-.=,
+and =next-error= over the frame list.
+
+** TODO loop's bindings should be sequential, like let's
+=check_loop= (=lib/check.ml:4741=) checks every initialiser before binding any,
+so =(loop [curr-r r  next-r (inc curr-r)] ...)= cannot see =curr-r= and the
+refusal reads as an unknown name. Every binding form is sequential — there is
+no =let*= here and there is not going to be one. Check the other binding forms
+for the same gap while fixing it.
+
+** TODO C-c C-c reports one error, not every error in the form
+Whole-file paths use =Check.program_all= and report every bad declaration. The
+daemon asks for the sink off (=lib/loc.ml:185=) and gets one exception, so a
+function with three bad expressions takes three round trips. The sink is
+per-phase; making it per-form would need a resync point inside a body.
+
+** TODO A session should start before a program compiles
+=flan dev= builds the program first, so a =main= that does not compile gives no
+session. Want SBCL/nREPL order: empty image, then load a file into it. Needs a
+host built with no user program, and a load-file op — the reload machinery
+already builds a file as a module. Open: what =flan-rerun= does with no =main=,
+and a half-loaded file. =C-c C-k= is taken by the inspector.
+
+** TODO The daemon buffer is navigable but not coloured
+=*flan*= is all plain text. =compilation-minor-mode= is on (=emacs/flan.el:822=)
+so =next-error= works, but a minor mode installs no font-lock. Open: whether the
+program's output should look different from the compiler's.
+
 ** TODO compilation-mode steps over the notes
 Nothing sets the skip threshold, so =next-error= walks the errors and steps over
 the notes, which are still parsed, coloured and clickable. Labelling them as

emacs/flan.el

@@ -381,14 +381,13 @@ open, above its prompt, which is where whoever is typing there is looking."
 ;;
 ;; Three things had to be settled to build it, and they are settled here.
 ;;
-;; **It displays, it does not select.**  A program stops on its own clock, not
-;; the editor's: the likeliest moment is in a frame of its own game loop while
-;; someone is typing in another buffer.  Taking the window would send the next
-;; keystrokes somewhere they were not aimed, and `q' in a break buffer is not
-;; what a half-typed word wanted to be.  So `display-buffer': the buffer
-;; appears, point does not move, and the window that had focus keeps it.
-;; `flan-break-on-stop' can be set to `focus' by anyone who disagrees, and
-;; to nil to go back to the mode line alone.
+;; **It selects the window.**  A stop is a question, the answer is a restart
+;; taken in that buffer, and the next keystroke is aimed there — so going there
+;; is what it wanted.  This was `display' at first, on the argument that a
+;; program stops on its own clock and taking the window would send keystrokes
+;; somewhere they were not aimed; in use that argument lost, because every stop
+;; ended in the same two keys to get to the buffer anyway.  `display' is still
+;; there for anyone who prefers it, and nil goes back to the mode line alone.
 ;;
 ;; **`(pause)' is not a special case.**  It was worth asking — a breakpoint is
 ;; deliberate where an error is not, so it could be argued it has earned the
@@ -409,10 +408,13 @@ open, above its prompt, which is where whoever is typing there is looking."
 ;; stopped and `C-c C-b' still works, so nothing is lost but the automatic
 ;; part.
 
-(defcustom flan-break-on-stop 'display
+(defcustom flan-break-on-stop 'focus
   "What to do when the program stops.
-`display' shows the break buffer without taking focus, `focus' shows it and
-selects its window, and nil leaves it to the mode line and `C-c C-b'."
+`focus' shows the break buffer and selects its window, `display' shows it
+without taking focus, and nil leaves it to the mode line and `C-c C-b'.
+
+A stop is the program asking a question, and the answer is a restart taken in
+that buffer, so going there is what the next keystroke wants anyway."
   :type '(choice (const :tag "Show it" display)
                  (const :tag "Show it and go there" focus)
                  (const :tag "Only the mode line" nil)))