evaluate elisp header args at original call site

* lisp/ob-core.el (org-babel-execute-src-block): Ensure that the
  location is set before anything else is done.
* lisp/ob-ref.el (org-babel-ref-parse): Evaluate Emacs Lisp values in
  header arguments at the location of the original code block.
* testing/lisp/test-ob.el (test-ob/location-of-header-arg-eval): Test
  defending the new header argument evaluation behavior.

lisp/ob-core.el

@@ -562,7 +562,11 @@ Optionally supply a value for PARAMS which will be merged with
 the header arguments specified at the front of the source code
 block."
   (interactive)
-  (let* ((info (if info
+  (let* ((org-babel-current-src-block-location
+	  (or org-babel-current-src-block-location
+	      (nth 6 info)
+	      (org-babel-where-is-src-block-head)))
+	 (info (if info
 		   (copy-tree info)
 		 (org-babel-get-src-block-info)))
 	 (merged-params (org-babel-merge-params (nth 2 info) params)))
@@ -571,8 +575,6 @@ block."
       (let* ((params (if params
 			 (org-babel-process-params merged-params)
 		       (nth 2 info)))
-	     (org-babel-current-src-block-location
-	      (or org-babel-current-src-block-location (nth 6 info)))
 	     (cachep (and (not arg) (cdr (assoc :cache params))
 			   (string= "yes" (cdr (assoc :cache params)))))
 	     (new-hash (when cachep (org-babel-sha1-hash info)))

lisp/ob-ref.el

@@ -83,7 +83,10 @@ the variable."
     (let ((var (match-string 1 assignment))
 	  (ref (match-string 2 assignment)))
       (cons (intern var)
-	    (let ((out (org-babel-read ref)))
+	    (let ((out (save-excursion
+			 (when org-babel-current-src-block-location
+			   (goto-char org-babel-current-src-block-location))
+			 (org-babel-read ref))))
 	      (if (equal out ref)
 		  (if (string-match "^\".*\"$" ref)
 		      (read ref)

testing/lisp/test-ob.el

@@ -1144,6 +1144,29 @@ echo \"$data\"
 	    (org-babel-execute-src-block)
 	    (buffer-string)))))
 
+(ert-deftest test-ob/location-of-header-arg-eval ()
+  "Test location of header argument evaluation."
+  (org-test-with-temp-text "
+#+name: top-block
+#+begin_src emacs-lisp :var pt=(point)
+  pt
+#+end_src
+
+#+name: bottom-block
+#+begin_src emacs-lisp :var pt=top-block()
+  pt
+#+end_src
+"
+    ;; the value of the second block should be greater than the first
+    (should
+     (< (progn (re-search-forward org-babel-src-block-regexp nil t)
+	       (goto-char (match-beginning 0))
+	       (prog1 (save-match-data (org-babel-execute-src-block))
+		 (goto-char (match-end 0))))
+	(progn (re-search-forward org-babel-src-block-regexp nil t)
+	       (goto-char (match-beginning 0))
+	       (org-babel-execute-src-block))))))
+
 (provide 'test-ob)
 
 ;;; test-ob ends here