patch 8.0.1518: error messages suppressed after ":silent! try"

Problem:    Error messages suppressed after ":silent! try". (Ben Reilly)
Solution:   Restore emsg_silent before executing :try. (closes #2531)

src/ex_docmd.c

@@ -2880,8 +2880,18 @@ do_one_cmd(
     }
 #endif
 
+    /* The :try command saves the emsg_silent flag, reset it here when
+     * ":silent! try" was used, it should only apply to :try itself. */
+    if (ea.cmdidx == CMD_try && did_esilent > 0)
+    {
+	emsg_silent -= did_esilent;
+	if (emsg_silent < 0)
+	    emsg_silent = 0;
+	did_esilent = 0;
+    }
+
 /*
- * 7. Switch on command name.
+ * 7. Execute the command.
  *
  * The "ea" structure holds the arguments that can be used.
  */

src/testdir/test_eval_stuff.vim

@@ -11,3 +11,17 @@ endfunction
 func Test_catch_return_with_error()
   call assert_equal(1, s:foo())
 endfunc
+
+func Test_nocatch_restore_silent_emsg()
+  silent! try
+    throw 1
+  catch
+  endtry
+  echoerr 'wrong'
+  let c1 = nr2char(screenchar(&lines, 1))
+  let c2 = nr2char(screenchar(&lines, 2))
+  let c3 = nr2char(screenchar(&lines, 3))
+  let c4 = nr2char(screenchar(&lines, 4))
+  let c5 = nr2char(screenchar(&lines, 5))
+  call assert_equal('wrong', c1 . c2 . c3 . c4 . c5)
+endfunc

src/version.c

@@ -771,6 +771,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1518,
 /**/
     1517,
 /**/