Add fallback for Idris2 to use :type-of for eldoc-lookup

Why:
Idris2 IDE mode is lacking implementation of `doc-overview`
attribute used in Idris 1 to display the short doc in minibuffer.

This may be temporary until Idris2 implementation is updated.

Author: keram

idris-commands.el

@@ -502,7 +502,23 @@ Considered as a global variable"
 
 (defun idris-eldoc-lookup ()
   "Return Eldoc string associated with the thing at point."
-  (get-char-property (point) 'idris-eldoc))
+  (let ((prop-val (get-char-property (point) 'idris-eldoc)))
+    ;; Idris2 temporary hack to make eldoc bit useful
+    (if (and (stringp prop-val) (string-suffix-p ": " prop-val) (>=-protocol-version 2 1))
+        (let* ((thing (idris-name-at-point))
+               (ty (idris-eval (list :type-of thing) t))
+               ;; (ty (idris-eval (list :docs-for thing) t))
+               (result (car ty))
+               (formatting (cdr ty))
+               (result-colour (idris-propertize-str (idris-repl-semantic-text-props formatting)
+                                                    result)))
+          ;; memoize result
+          (dolist (overlay (overlays-at (point)))
+            (when (overlay-get overlay 'idris-source-highlight)
+              (overlay-put overlay 'idris-eldoc result-colour)))
+          result-colour)
+      ;; Idris 1 using :doc-overview semantic properties extracted from highlights
+      prop-val)))
 
 (defun idris-pretty-print ()
   "Get a term or definition pretty-printed by Idris.

idris-common-utils.el

@@ -123,6 +123,13 @@ inserted text (that is, relative to point prior to insertion)."
                                           (+ ,start begin length)
                                           props))))))
 
+(defun idris-propertize-str (spans text)
+  "Add properties indicated by SPANS to the TEXT.
+SPANS is a list of (BEGIN LENGTH PROPERTIES) elements."
+  (dolist (span spans text)
+    (cl-destructuring-bind (begin length props) span
+      (set-text-properties begin (+ begin length) props text))))
+
 ;;; TODO: Take care of circular dependency issue
 (autoload 'idris-eval "inferior-idris.el")
 
@@ -224,7 +231,6 @@ inserted text (that is, relative to point prior to insertion)."
                            (cadr namespace)))
           (t nil))))
 
-
 (defun idris-semantic-properties-help-echo (props)
   (let* ((name (assoc :name props))
          (decor (assoc :decor props))