patch 8.2.0339: Vim9: function return type may depend on arguments

Problem:    Vim9: function return type may depend on arguments.
Solution:   Instead of a fixed return type use a function to figure out the
            return type.
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index ac8bd75..e5b3b47 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -55,7 +55,12 @@
 
   if has('channel')
     let chan1: channel
+    let job1: job
   endif
+  if has('float')
+    let float1: float = 3.4
+  endif
+  let party: partial = funcref('Test_syntax')
 
   g:newvar = 'new'
   assert_equal('new', g:newvar)