Give test-completion's PREDICATE full alist entry

Since 2016-06-26 "Fix test-completion with completion-regexp-list", when
calling test-completion with an alist collection, the predicate was
recieving the string value instead of the alist entry (Bug#24966).

* src/minibuf.c (Ftest_completion): Don't modify the found element, just
test STRING against `completion-regexp-list'.
* test/src/minibuf-tests.el: New tests for `try-completion',
`all-completions', and `test-completion'.

1 files changed, 3 insertions, 5 deletions

diff --git a/src/minibuf.c b/src/minibuf.c
index 57eea05b0fc..6c694cb3123 100644
--- a/src/minibuf.c
+++ b/src/minibuf.c
@@ -1686,8 +1686,6 @@ the values STRING, PREDICATE and `lambda'.  */)
       tem = Fassoc_string (string, collection, completion_ignore_case ? Qt : Qnil);
       if (NILP (tem))
         return Qnil;
-      else if (CONSP (tem))
-        tem = XCAR (tem);
     }
   else if (VECTORP (collection))
     {
@@ -1770,9 +1768,9 @@ the values STRING, PREDICATE and `lambda'.  */)
       for (regexps = Vcompletion_regexp_list; CONSP (regexps);
            regexps = XCDR (regexps))
         {
-          if (NILP (Fstring_match (XCAR (regexps),
-                                   SYMBOLP (tem) ? string : tem,
-                                   Qnil)))
+          /* We can test against STRING, because if we got here, then
+             the element is equivalent to it.  */
+          if (NILP (Fstring_match (XCAR (regexps), string, Qnil)))
             return unbind_to (count, Qnil);
         }
       unbind_to (count, Qnil);