patch 8.2.0753: Vim9: expressions are evaluated in the discovery phase

Problem:    Vim9: expressions are evaluated in the discovery phase.
Solution:   Bail out if an expression is not a constant.  Require a type for
            declared constants.
diff --git a/src/testdir/test_vim9_disassemble.vim b/src/testdir/test_vim9_disassemble.vim
index 7213ee4..2df28e2 100644
--- a/src/testdir/test_vim9_disassemble.vim
+++ b/src/testdir/test_vim9_disassemble.vim
@@ -1054,7 +1054,7 @@
     def FuncTwo(): string
       return 'two'
     enddef
-    let g:res_FuncOne = execute('disass FuncOne')
+    let g:res_FuncOne: string = execute('disass FuncOne')
   END
   writefile(lines, 'Xdisassemble')
   source Xdisassemble