[vm] Remove use of CastError

`CastError` is replaced by `TypeError`.

Also makes the fields of TypeError nullable. See:
https://github.com/dart-lang/sdk/issues/49279

TEST=build SDK and run default suites.

Bug: https://github.com/dart-lang/sdk/issues/49529
Change-Id: I7e880ff2d8b18c4bffdd7a942efd743244a12734
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/274381
Reviewed-by: Tess Strickland <sstrickl@google.com>
Commit-Queue: Daco Harkes <dacoharkes@google.com>

runtime/lib/errors.cc

@@ -144,7 +144,7 @@ DEFINE_NATIVE_ENTRY(AssertionError_throwNewSource, 0, 4) {
   return Object::null();
 }
 
-// Allocate and throw a new TypeError or CastError.
+// Allocate and throw a new TypeError.
 // Arg0: index of the token of the failed type check.
 // Arg1: src value.
 // Arg2: dst type.

runtime/vm/exceptions.cc

@@ -865,8 +865,7 @@ InstancePtr Exceptions::NewInstance(const char* class_name) {
   return Instance::New(cls);
 }
 
-// Allocate, initialize, and throw a TypeError or CastError.
-// If error_msg is not null, throw a TypeError, even for a type cast.
+// Allocate, initialize, and throw a TypeError.
 void Exceptions::CreateAndThrowTypeError(TokenPosition location,
                                          const AbstractType& src_type,
                                          const AbstractType& dst_type,
@@ -876,8 +875,7 @@ void Exceptions::CreateAndThrowTypeError(TokenPosition location,
   Zone* zone = thread->zone();
   const Array& args = Array::Handle(zone, Array::New(4));
 
-  ExceptionType exception_type =
-      (dst_name.ptr() == Symbols::InTypeCast().ptr()) ? kCast : kType;
+  ExceptionType exception_type = kType;
 
   DartFrameIterator iterator(thread,
                              StackFrameIterator::kNoCrossThreadIteration);
@@ -908,9 +906,7 @@ void Exceptions::CreateAndThrowTypeError(TokenPosition location,
     pieces.Add(Symbols::TypeQuote());
     pieces.Add(String::Handle(zone, dst_type.UserVisibleName()));
     pieces.Add(Symbols::SingleQuote());
-    if (exception_type == kCast) {
-      pieces.Add(dst_name);
-    } else if (dst_name.Length() > 0) {
+    if (dst_name.Length() > 0) {
       pieces.Add(Symbols::SpaceOfSpace());
       pieces.Add(Symbols::SingleQuote());
       pieces.Add(dst_name);
@@ -944,7 +940,7 @@ void Exceptions::CreateAndThrowTypeError(TokenPosition location,
     THR_Print("%s\n", error_msg.ToCString());
   }
 
-  // Throw TypeError or CastError instance.
+  // Throw TypeError instance.
   Exceptions::ThrowByType(exception_type, args);
   UNREACHABLE();
 }
@@ -1151,11 +1147,6 @@ ObjectPtr Exceptions::Create(ExceptionType type, const Array& arguments) {
       class_name = &Symbols::AssertionError();
       constructor_name = &Symbols::DotCreate();
       break;
-    case kCast:
-      library = Library::CoreLibrary();
-      class_name = &Symbols::CastError();
-      constructor_name = &Symbols::DotCreate();
-      break;
     case kType:
       library = Library::CoreLibrary();
       class_name = &Symbols::TypeError();

runtime/vm/exceptions.h

@@ -64,7 +64,6 @@ class Exceptions : AllStatic {
     kNullThrown,
     kIsolateSpawn,
     kAssertion,
-    kCast,
     kType,
     kAbstractClassInstantiation,
     kCyclicInitializationError,

runtime/vm/object.cc

@@ -20019,11 +20019,11 @@ Instance checks (e is T) in strong checking mode in a legacy or opted-in lib:
 
 Casts (e as T) in weak checking mode in a legacy or opted-in library:
   If LEGACY_SUBTYPE(S, T) then e as T evaluates to v.
-  Otherwise a CastError is thrown.
+  Otherwise a TypeError is thrown.
 
 Casts (e as T) in strong checking mode in a legacy or opted-in library:
   If NNBD_SUBTYPE(S, T) then e as T evaluates to v.
-  Otherwise a CastError is thrown.
+  Otherwise a TypeError is thrown.
 */
 
 bool Instance::IsInstanceOf(

runtime/vm/runtime_entry.cc

@@ -169,7 +169,7 @@ static void NullErrorHelper(Zone* zone,
     args.SetAt(
         3, String::Handle(
                zone, String::New("Null check operator used on a null value")));
-    Exceptions::ThrowByType(Exceptions::kCast, args);
+    Exceptions::ThrowByType(Exceptions::kType, args);
     return;
   }
 

runtime/vm/symbols.h

@@ -32,7 +32,6 @@ class ObjectPointerVisitor;
   V(BoundsCheckForPartialInstantiation, "_boundsCheckForPartialInstantiation") \
   V(ByteData, "ByteData")                                                      \
   V(Capability, "Capability")                                                  \
-  V(CastError, "_CastError")                                                   \
   V(CheckLoaded, "_checkLoaded")                                               \
   V(Class, "Class")                                                            \
   V(ClassID, "ClassID")                                                        \

sdk/lib/_internal/vm/lib/errors_patch.dart

@@ -106,9 +106,9 @@ class _TypeError extends Error implements TypeError, CastError {
 
   String toString() => _message;
 
-  final String _url;
-  final int _line;
-  final int _column;
+  final String? _url;
+  final int? _line;
+  final int? _column;
   final String _message;
 }