patch 8.0.0102
Problem:    Cannot set 'dictionary' to a path.
Solution:   Allow for slash and backslash.  Add a test (partly by Daisuke
            Suzuki, closes #1279, closes #1284)
diff --git a/src/testdir/test_options.vim b/src/testdir/test_options.vim
index 3b6f662..88be8f9 100644
--- a/src/testdir/test_options.vim
+++ b/src/testdir/test_options.vim
@@ -106,3 +106,18 @@
   call assert_fails(":set kmp=trunc\x00name", "E544:")
   call assert_fails(":set kmp=trunc\x00name", "trunc")
 endfunc
+
+func Test_dictionary()
+  " Check that it's possible to set the option.
+  set dictionary=/usr/share/dict/words
+  call assert_equal('/usr/share/dict/words', &dictionary)
+  set dictionary=/usr/share/dict/words,/and/there
+  call assert_equal('/usr/share/dict/words,/and/there', &dictionary)
+  set dictionary=/usr/share/dict\ words
+  call assert_equal('/usr/share/dict words', &dictionary)
+
+  " Check rejecting weird characters.
+  call assert_fails("set dictionary=/not&there", "E474:")
+  call assert_fails("set dictionary=/not>there", "E474:")
+  call assert_fails("set dictionary=/not.*there", "E474:")
+endfunc