patch 8.2.0772: Vim9: some variable initializations not tested

Problem:    Vim9: some variable initializations not tested.
Solution:   Add a few more tests

src/testdir/test_vim9_script.vim

@@ -1736,6 +1736,8 @@ def Test_let_func_call()
       return 'this'
     endfunc
     let val: string = GetValue() 
+    " env var is always a string
+    let env = $TERM
   END
   writefile(lines, 'Xfinished')
   source Xfinished
@@ -1758,7 +1760,34 @@ def Test_let_missing_type()
 
   lines =<< trim END
     vim9script
-    let var = g:unkown
+    func GetValue()
+      return 'this'
+    endfunc
+    let val = [GetValue()]
+  END
+  CheckScriptFailure(lines, 'E1091:')
+
+  lines =<< trim END
+    vim9script
+    func GetValue()
+      return 'this'
+    endfunc
+    let val = {GetValue(): 123}
+  END
+  CheckScriptFailure(lines, 'E1091:')
+
+  lines =<< trim END
+    vim9script
+    func GetValue()
+      return 'this'
+    endfunc
+    let val = {'a': GetValue()}
+  END
+  CheckScriptFailure(lines, 'E1091:')
+
+  lines =<< trim END
+    vim9script
+    let var = g:unknown
   END
   CheckScriptFailure(lines, 'E1091:')
 

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    772,
 /**/
     771,
 /**/