Extensive notes; wrap body in save-excursion

Originally, all of these functions were inside one huge save-excursion form. To
my surprise, they typically need their _own_ save excursion wrapping to make
sure everything is consistent, particularly under test.

Also added, a great deal of notes about the function itself and how it works.

fsharp-mode-structure.el

@@ -570,40 +570,60 @@ This function is normally bound to `indent-line-function' so
       )))
 
 
+;; NOTE[gastove|2019-10-25] An interesting point: this function is *only* ever
+;; called if `open-bracket-pos' is non-nil; `open-bracket-pos' is generated by
+;; `fsharp-nesting-level', which *only* returns non nil for non-string
+;; characters. And yet: we don't just rely on `open-bracket-pos' as we compute
+;; indentation, and I'm honestly not sure why.
 (defun fsharp--compute-indentation-open-bracket (open-bracket-pos)
   "Computes indentation for a line within an open bracket expression."
-  (let ((startpos (point))
-        placeholder)
-    ;; align with first item in list; else a normal
-    ;; indent beyond the line with the open bracket
-    (goto-char (1+ open-bracket-pos)) ; just beyond bracket
-    ;; is the first list item on the same line?
-    (skip-chars-forward " \t")
-    (if (and (null (memq (following-char) '(?\n ?# ?\\)))
-             (not fsharp-conservative-indentation-after-bracket))
+  (save-excursion
+    (let ((startpos (point))
+          placeholder)
+      ;; align with first item in list; else a normal
+      ;; indent beyond the line with the open bracket
+      (goto-char (1+ open-bracket-pos)) ; just beyond bracket
+      ;; NOTE[gastove|2019-10-25] -- consider switching to a forward regexp search
+      ;;     with a whitepsace character class.
+      ;; is the first list item on the same line?
+      (skip-chars-forward " \t")
+      (if (and (null (memq (following-char) '(?\n ?# ?\\)))
+               (not fsharp-conservative-indentation-after-bracket))
                                         ; yes, so line up with it
-        (current-column)
-      ;; first list item on another line, or doesn't exist yet
-      (forward-line 1)
-      (while (and (< (point) startpos)
-                  (looking-at "[ \t]*\\(//\\|[\n\\\\]\\)")) ; skip noise
-        (forward-line 1))
-      (if (and (< (point) startpos)
-               (/= startpos
-                   (save-excursion
-                     (goto-char (1+ open-bracket-pos))
-                     (forward-comment (point-max))
-                     (point))))
-          ;; again mimic the first list item
-          (current-indentation)
-        ;; else they're about to enter the first item
-        (goto-char open-bracket-pos)
-        (setq placeholder (point))
-        (fsharp-goto-initial-line)
-        (fsharp-goto-beginning-of-tqs
-         (save-excursion (nth 3 (parse-partial-sexp
-                                 placeholder (point)))))
-        (+ (current-indentation) fsharp-indent-offset)))))
+          (current-column)
+        ;; here follows the else
+        ;; first list item on another line, or doesn't exist yet
+        ;; TODO[gastove|2019-10-25] this needs to skip past whitespace, newlines,
+        ;; *and* comments. I'm not convinced it does.
+        (forward-line 1)
+        (while (and (< (point) startpos)
+                    (looking-at "[ \t]*\\(//\\|[\n\\\\]\\)")) ; skip noise
+          (forward-line 1))
+        (if (and (< (point) startpos)
+                 (/= startpos
+                     (save-excursion
+                       (goto-char (1+ open-bracket-pos))
+                       (forward-comment (point-max))
+                       (point))))
+            ;; again mimic the first list item
+            (current-indentation)
+          ;; else they're about to enter the first item
+
+          ;; NOTE[gastove|2019-10-25] Okay, this is all really hard to follow, but
+          ;; I *think* what's going on here is:
+          ;; - We go to the position of the opening bracket we're trying to compute indentation against.
+          ;; - We set placeholder to point (meaning we set `placeholder' to `open-bracket-pos')
+          ;; - We call a function that claims to go to the first line of a statement
+          ;; - We call a function that I *believe* tries to take us to the opening delimiter of a matched pair
+          ;; - We return the current indentation of *that*, plus indent offset
+          ;; ... holy moly.
+          (goto-char open-bracket-pos)
+          (setq placeholder (point))
+          (fsharp-goto-initial-line)
+          (fsharp-goto-beginning-of-tqs
+           (save-excursion (nth 3 (parse-partial-sexp
+                                   placeholder (point)))))
+          (+ (current-indentation) fsharp-indent-offset))))))
 
 
 (defun fsharp--compute-indentation-continuation-line ()