patch 8.2.4946: Vim9: some code not covered by tests

Problem:    Vim9: some code not covered by tests.
Solution:   Add a few more test cases.  Remove dead code.

src/testdir/test_vim9_expr.vim

@@ -2151,6 +2151,9 @@ def Test_expr8_string()
   vv = $'other {val}'
   assert_equal('other val', vv)
 
+  v9.CheckDefAndScriptFailure(['var x = $"foo'], 'E114:', 1)
+  v9.CheckDefAndScriptFailure(['var x = $"foo{xxx}"'], ['E1001: Variable not found: xxx', 'E121: Undefined variable: xxx'], 1)
+
   var x = 'x'
   var vl = 'foo xxx bar xxx baz'
               ->split($'x{x}x')
@@ -2818,6 +2821,7 @@ def Test_expr8_dict()
   g:key = 'x'
   v9.CheckDefExecAndScriptFailure(["var x = {[g:key]: 'text', [g:key]: 'text'}"], 'E721:', 1)
   unlet g:key
+  v9.CheckDefExecAndScriptFailure(["var x = {[notexists]: 'text'}"], ['E1001:', 'E121: Undefined variable: notexists'], 1)
   v9.CheckDefExecAndScriptFailure(["var x = g:anint.member"], ['E715:', 'E488:'], 1)
   v9.CheckDefExecAndScriptFailure(["var x = g:dict_empty.member"], 'E716:', 1)
 
@@ -3370,6 +3374,9 @@ def Test_expr8_parens()
       assert_equal('onetwo', s)
   END
   v9.CheckDefAndScriptSuccess(lines)
+
+  v9.CheckDefAndScriptFailure(['echo ('], ['E1097: Line incomplete', 'E15: Invalid expression: "("'])
+  v9.CheckDefAndScriptFailure(['echo (123]'], "E110: Missing ')'", 1)
 enddef
 
 def Test_expr8_negate_add()
@@ -3480,6 +3487,7 @@ def Test_expr8_call()
        "var x = substitute ('x', 'x', 'x', 'x')"
        ], ['E1001:', 'E121:'], 1)
   v9.CheckDefAndScriptFailure(["var Ref = function('len' [1, 2])"], ['E1123:', 'E116:'], 1)
+  v9.CheckDefAndScriptFailure(["echo match(['foo'] , 'foo')"], 'E1068:', 1)
 enddef
 
 def g:ExistingGlobal(): string
@@ -4000,6 +4008,16 @@ def Test_expr8_blob_subscript()
   v9.CheckDefAndScriptSuccess(lines)
 enddef
 
+def Test_expr8_funcref_subscript()
+  var lines =<< trim END
+      var l = function('len')("abc")
+      assert_equal(3, l)
+  END
+  v9.CheckDefAndScriptSuccess(lines)
+
+  v9.CheckDefAndScriptFailure(["var l = function('len')(xxx)"], ['E1001: Variable not found: xxx', 'E121: Undefined variable: xxx'], 1)
+enddef
+
 def Test_expr8_subscript_linebreak()
   var lines =<< trim END
       var range = range(