fix #30330, don't ignore cast failures in DDC for language/lib tests

tests/language_strong/language_strong.status

 # Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 # Skip entire suite if not running in strong mode.
 [ ! $strong ]
 *: SkipByDesign
 
 # Skip tests that are not yet strong-mode clean.
 [ $strong ]
@@ skipping 700 matching lines @@
 canonical_const2_test: RuntimeError # Ints and doubles are unified.
 canonical_const_test: RuntimeError # Ints and doubles are unified.
 call_closurization_test: RuntimeError # Issue 29920
 compile_time_constant_a_test: RuntimeError # Allows mutating const map.
 compile_time_constant_b_test: RuntimeError # Issue 29920
 compile_time_constant_d_test: RuntimeError # Issue 29920
 const_evaluation_test/01: RuntimeError # Issue 29920
 const_switch_test/02: RuntimeError # Issue 29920
 const_switch_test/04: RuntimeError # Ints and doubles are unified.
 constructor12_test: RuntimeError # Issue 29920
-covariant_subtyping_test: RuntimeError # Issue 29920
 custom_await_stack_trace_test: RuntimeError # Issue 29920
 cyclic_type2_test: RuntimeError # Issue 29920
 cyclic_type_test/02: RuntimeError # Issue 29920
 cyclic_type_test/03: RuntimeError # Issue 29920
 cyclic_type_test/04: RuntimeError # Issue 29920
 deferred_call_empty_before_load_test: RuntimeError # Issue 27777
 deferred_load_library_wrong_args_test/01: MissingRuntimeError, RuntimeError # Issue 29920
 deferred_not_loaded_check_test: RuntimeError # Issue 27777
 deferred_redirecting_factory_test: RuntimeError # Issue 27777
 deferred_static_seperate_test: RuntimeError # Issue 27777
 double_int_to_string_test: RuntimeError # Issue 29920
 dynamic_test: RuntimeError # Strong mode is-check failure: M1 does not soundly subtype Iface<dynamic, num>
 exception_test: RuntimeError # DDC doesn't implement NullThrownError?
 execute_finally6_test: RuntimeError # Issue 29920
 expect_test: RuntimeError # Issue 29920
 f_bounded_quantification3_test: RuntimeError # Issue 29920
 field_increment_bailout_test: RuntimeError # Issue 29920
 field_optimization3_test: RuntimeError # Issue 29920
 first_class_types_test: RuntimeError, OK # Strong mode reifies inferred type argument.
 flatten_test/05: MissingRuntimeError # Issue 29920
 flatten_test/08: MissingRuntimeError # Issue 29920
 flatten_test/09: MissingRuntimeError # Issue 29920
 flatten_test/12: MissingRuntimeError # Issue 29920
 for_variable_capture_test: RuntimeError # Issue 29920
-function_subtype_cast0_test: RuntimeError # Issue 29920
-function_subtype_cast1_test: RuntimeError # Issue 29920
-function_subtype_cast2_test: RuntimeError # Issue 29920
-function_subtype_cast3_test: RuntimeError # Issue 29920
 function_subtype_named1_test: RuntimeError # Issue 29920
 function_subtype_named2_test: RuntimeError # Issue 29920
 function_subtype_optional1_test: RuntimeError # Issue 29920
 function_subtype_optional2_test: RuntimeError # Issue 29920
 function_subtype_typearg2_test: RuntimeError # Issue 29920
 function_subtype_typearg4_test: RuntimeError # Issue 29920
 function_type_alias3_test: RuntimeError # Issue 29920
 generic_instanceof2_test: RuntimeError # Issue 29920
 generic_instanceof_test: RuntimeError # Issue 29920
 generic_is_check_test: RuntimeError # Issue 29920
@@ skipping 40 matching lines @@
 # not behave correctly at runtime. We cannot record this as "Fail" without
 # confusing the DDC travis bot (as "Fail" is normally used for compile time
 # failures of _negative_tests). Remove "Skip" once we have the DDC travis bot
 # running on test.dart, OR when we fix dartanalyzer/dartdevc CommandOutput
 # classes to invert negative test status in the same way our other tools do.
 prefix10_negative_test: Skip # Issue 29920
 
 [ $compiler == dartdevc && $system == windows ]
 multiline_strings_test: RuntimeError # Issue 30336
 raw_string_test: RuntimeError # Issue 30336