patch 8.2.2881: various pieces of code not covered by tests

Problem:    Various pieces of code not covered by tests.
Solution:   Add a few more tests. (Yegappan Lakshmanan, closes #8245)
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index 7eca709..2ac97d0 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -887,6 +887,12 @@
   END
   CheckDefAndScriptFailure(lines, 'E1157:', 1)
 
+  # no space before the return type
+  lines =<< trim END
+    var Ref = (x):number => x + 1
+  END
+  CheckDefAndScriptFailure(lines, 'E1069:', 1)
+
   # this works
   for x in ['foo', 'boo']
     echo FilterWithCond(x, (v) => v =~ '^b')
@@ -1318,6 +1324,7 @@
     enddef
   END
   CheckScriptFailure(lines, 'E1068:')
+  call assert_fails('vim9cmd echo stridx("a" .. "b" , "a")', 'E1068:')
 enddef
 
 def Test_white_space_after_comma()