Rationalize coercions

test/dart_codegen/expect/convert/ascii.dart

Index: test/dart_codegen/expect/convert/ascii.dart
diff --git a/test/dart_codegen/expect/convert/ascii.dart b/test/dart_codegen/expect/convert/ascii.dart
index f16cc5a793d4081516a3000149544b8e38aa5bc6..0de37e85a27f1490c8dcd13ab4436bd79163398b 100644
--- a/test/dart_codegen/expect/convert/ascii.dart
+++ b/test/dart_codegen/expect/convert/ascii.dart
@@ -39,7 +39,7 @@ int stringLength = string.length;
   }
 ), DEVC$RT.type((List<int> _) {
   }
-), "CastDynamic", """line 96, column 12 of dart:convert/ascii.dart: """, result is List<int>, false);
+), "CompositeCast", """line 96, column 12 of dart:convert/ascii.dart: """, result is List<int>, false);
 }
  StringConversionSink startChunkedConversion(Sink<List<int>> sink) {
 if (sink is! ByteConversionSink) {
@@ -47,13 +47,13 @@ if (sink is! ByteConversionSink) {
   }
  return new _UnicodeSubsetEncoderSink(_subsetMask, DEVC$RT.cast(sink, DEVC$RT.type((Sink<List<int>> _) {
   }
-), ByteConversionSink, "CastGeneral", """line 109, column 55 of dart:convert/ascii.dart: """, sink is ByteConversionSink, true));
+), ByteConversionSink, "ImplicitCast", """line 109, column 55 of dart:convert/ascii.dart: """, sink is ByteConversionSink, true));
 }
  Stream<List<int>> bind(Stream<String> stream) => ((__x0) => DEVC$RT.cast(__x0, DEVC$RT.type((DDC$async$.Stream<dynamic> _) {
 }
 ), DEVC$RT.type((DDC$async$.Stream<List<int>> _) {
 }
-), "CastDynamic", """line 113, column 52 of dart:convert/ascii.dart: """, __x0 is DDC$async$.Stream<List<int>>, false))(super.bind(stream));
+), "CompositeCast", """line 113, column 52 of dart:convert/ascii.dart: """, __x0 is DDC$async$.Stream<List<int>>, false))(super.bind(stream));
 }
  class AsciiEncoder extends _UnicodeSubsetEncoder {const AsciiEncoder() : super(_ASCII_MASK);
 }
@@ -110,7 +110,7 @@ int value = bytes[i];
 }
 ), DEVC$RT.type((DDC$async$.Stream<String> _) {
 }
-), "CastDynamic", """line 221, column 52 of dart:convert/ascii.dart: """, __x1 is DDC$async$.Stream<String>, false))(super.bind(stream));
+), "CompositeCast", """line 221, column 52 of dart:convert/ascii.dart: """, __x1 is DDC$async$.Stream<String>, false))(super.bind(stream));
 }
  class AsciiDecoder extends _UnicodeSubsetDecoder {const AsciiDecoder({
 bool allowInvalid : false}