patch 9.0.0409: #{g:x} was seen as a curly-braces expression

Problem:    #{g:x} was seen as a curly-braces expression.
Solution:   Do never see #{} as a curly-braces expression. (closes #11075)

src/dict.c

@@ -911,13 +911,15 @@ eval_dict(char_u **arg, typval_T *rettv, evalarg_T *evalarg, int literal)
     int		vim9script = in_vim9script();
     int		had_comma;
 
-    // First check if it's not a curly-braces thing: {expr}.
+    // First check if it's not a curly-braces expression: {expr}.
     // Must do this without evaluating, otherwise a function may be called
     // twice.  Unfortunately this means we need to call eval1() twice for the
     // first item.
-    // But {} is an empty Dictionary.
+    // "{}" is an empty Dictionary.
+    // "#{abc}" is never a curly-braces expression.
     if (!vim9script
 	    && *curly_expr != '}'
+	    && !literal
 	    && eval1(&curly_expr, &tv, NULL) == OK
 	    && *skipwhite(curly_expr) == '}')
 	return NOTDONE;

src/testdir/test_listdict.vim

@@ -321,6 +321,10 @@ func Test_dict()
 
   " allow key starting with number at the start, not a curly expression
   call assert_equal({'1foo': 77}, #{1foo: 77})
+
+  " #{expr} is not a curly expression
+  let x = 'x'
+  call assert_equal(#{g: x}, #{g:x})
 endfunc
 
 " This was allowed in legacy Vim script

src/version.c

@@ -703,6 +703,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    409,
 /**/
     408,
 /**/