patch 8.2.0519: Vim9: return type not properly checked

Problem:    Vim9: return type not properly checked.
Solution:   Check type properly, also at runtime.
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index c122168..74653b1 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -380,6 +380,10 @@
   return arg
 enddef
 
+def FuncOneArgRetAny(arg: any): any
+  return arg
+enddef
+
 def Test_func_type()
   let Ref1: func()
   funcResult = 0
@@ -417,5 +421,20 @@
   CheckDefFailure(['let Ref1: func()', 'Ref1 = FuncOneArgRetNumber'], 'E1013: type mismatch, expected func() but got func(number): number')
 enddef
 
+def Test_func_return_type()
+  let nr: number
+  nr = FuncNoArgRetNumber()
+  assert_equal(1234, nr)
+
+  nr = FuncOneArgRetAny(122)
+  assert_equal(122, nr)
+
+  let str: string
+  str = FuncOneArgRetAny('yes')
+  assert_equal('yes', str)
+
+  CheckDefFailure(['let str: string', 'str = FuncNoArgRetNumber()'], 'E1013: type mismatch, expected string but got number')
+enddef
+
 
 " vim: ts=8 sw=2 sts=2 expandtab tw=80 fdm=marker