patch 8.2.4116: Vim9: cannot use a method with a complex expression in :def

Problem:    Vim9: cannot use a method with a complex expression in a :def
            function.
Solution:   Implement compiling the expression.
diff --git a/src/testdir/test_vim9_expr.vim b/src/testdir/test_vim9_expr.vim
index 263b6d3..3ea3a0b 100644
--- a/src/testdir/test_vim9_expr.vim
+++ b/src/testdir/test_vim9_expr.vim
@@ -3140,7 +3140,6 @@
   CheckDefAndScriptSuccess(lines)
 
   lines =<< trim END
-      vim9script
       def SetNumber(n: number)
         g:number = n
       enddef
@@ -3166,7 +3165,7 @@
 
       unlet g:number
   END
-  CheckScriptSuccess(lines)  # TODO: CheckDefAndScriptSuccess()
+  CheckDefAndScriptSuccess(lines)
 
   lines =<< trim END
     def RetVoid()