Clean up multi-line in haskell-interactive a bit

* Using indent-relative explicitly disables some unwanted heuristics
  that indent-according-to-mode uses. I've found that this way is
  better, but it could certainly use improvement.

* Make haskell-interactive-mode-multi-line properly indent the
  expression.

* haskell-interactive-mode-cleanup-response is now useless as far as I
  can tell.

Author: fice-t

haskell-interactive-mode.el

@@ -167,7 +167,8 @@ be nil.")
   "Make newline and indent."
   (interactive)
   (newline)
-  (indent-according-to-mode))
+  (indent-to (length haskell-interactive-prompt))
+  (indent-relative))
 
 (defun haskell-interactive-mode-kill-whole-line ()
   "Kill the whole REPL line."
@@ -236,22 +237,6 @@ be nil.")
                                   (point-min))
                              end))))))))
 
-(defun haskell-interactive-mode-cleanup-response (expr response)
-  "Ignore the mess that GHCi outputs on multi-line input."
-  (if (not (string-match "\n" expr))
-      response
-    (let ((i 0)
-          (out "")
-          (lines (length (split-string expr "\n"))))
-      (cl-loop for part in (split-string response "| ")
-               do (setq out
-                        (concat out
-                                (if (> i lines)
-                                    (concat (if (or (= i 0) (= i (1+ lines))) "" "| ") part)
-                                  "")))
-               do (setq i (1+ i)))
-      out)))
-
 (defun haskell-interactive-mode-multi-line (expr)
   "If a multi-line expression EXPR has been entered, then reformat it to be:
 
@@ -260,21 +245,18 @@ do the
    multi-liner
    expr
 :}"
-  (if (not (string-match "\n" expr))
+  (if (not (string-match-p "\n" expr))
       expr
-    (let* ((i 0)
-           (lines (split-string expr "\n"))
-           (len (length lines)))
-      (mapconcat 'identity
-                 (cl-loop for line in lines
-                          collect (cond ((= i 0)
-                                         (concat ":{" "\n" line))
-                                        ((= i (1- len))
-                                         (concat line "\n" ":}"))
-                                        (t
-                                         line))
-                          do (setq i (1+ i)))
-                 "\n"))))
+    (let ((len (length haskell-interactive-prompt))
+          (lines (split-string expr "\n")))
+      (cl-loop for elt on (cdr lines) do
+               (setcar elt (substring (car elt) len)))
+      ;; Temporarily set prompt2 to be empty to avoid unwanted output
+      (concat ":set prompt2 \"\"\n"
+              ":{\n"
+              (mapconcat #'identity lines "\n")
+              "\n:}\n"
+              (format ":set prompt2 \"%s\"" haskell-interactive-prompt2)))))
 
 (defun haskell-interactive-trim (line)
   "Trim indentation off of LINE in the REPL."

haskell-repl.el

@@ -101,8 +101,7 @@
   "Print the result of evaluating the expression."
   (let ((response
          (with-temp-buffer
-           (insert (haskell-interactive-mode-cleanup-response
-                    (cl-caddr state) response))
+           (insert response)
            (haskell-interactive-mode-handle-h)
            (buffer-string))))
     (when haskell-interactive-mode-eval-mode