Typecheck constructor initializers properly

test/dart_codegen/expect/core/exceptions.dart

 part of dart.core;
  abstract class Exception {factory Exception([var message]) => new _ExceptionImplementation(message);
 }
  class _ExceptionImplementation implements Exception {final message;
  _ExceptionImplementation([this.message]);
  String toString() {
 if (message == null) return "Exception";
  return "Exception: $message";
 }
 }
@@ skipping 10 matching lines @@
  if (source is! String) {
 if (offset != -1) {
   report += " (at offset $offset)";
   }
  return report;
 }
  if (offset != -1 && (offset < 0 || offset > source.length)) {
 offset = -1;
 }
  if (offset == -1) {
-String source = ((__x3) => DDC$RT.cast(__x3, dynamic, String, "CastGeneral", """line 113, column 23 of dart:core/exceptions.dart: """, __x3 is String, true))(this.source);
+String source = ((__x4) => DDC$RT.cast(__x4, dynamic, String, "CastGeneral", """line 113, column 23 of dart:core/exceptions.dart: """, __x4 is String, true))(this.source);
  if (source.length > 78) {
   source = source.substring(0, 75) + "...";
   }
  return "$report\n$source";
 }
  int lineNum = 1;
  int lineStart = 0;
  bool lastWasCR;
  for (int i = 0;
  i < offset;
  i++) {
-int char = ((__x4) => DDC$RT.cast(__x4, dynamic, int, "CastGeneral", """line 123, column 18 of dart:core/exceptions.dart: """, __x4 is int, true))(source.codeUnitAt(i));
+int char = ((__x5) => DDC$RT.cast(__x5, dynamic, int, "CastGeneral", """line 123, column 18 of dart:core/exceptions.dart: """, __x5 is int, true))(source.codeUnitAt(i));
  if (char == 0x0a) {
   if (lineStart != i || !lastWasCR) {
     lineNum++;
     }
    lineStart = i + 1;
    lastWasCR = false;
   }
  else if (char == 0x0d) {
   lineNum++;
    lineStart = i + 1;
    lastWasCR = true;
   }
 }
  if (lineNum > 1) {
 report += " (at line $lineNum, character ${offset - lineStart + 1}
 )\n";
 }
  else {
 report += " (at character ${offset + 1}
 )\n";
 }
  int lineEnd = DDC$RT.cast(source.length, dynamic, int, "CastGeneral", """line 141, column 19 of dart:core/exceptions.dart: """, source.length is int, true);
  for (int i = offset;
  i < source.length;
  i++) {
-int char = ((__x5) => DDC$RT.cast(__x5, dynamic, int, "CastGeneral", """line 143, column 18 of dart:core/exceptions.dart: """, __x5 is int, true))(source.codeUnitAt(i));
+int char = ((__x6) => DDC$RT.cast(__x6, dynamic, int, "CastGeneral", """line 143, column 18 of dart:core/exceptions.dart: """, __x6 is int, true))(source.codeUnitAt(i));
  if (char == 0x0a || char == 0x0d) {
 lineEnd = i;
  break;
 }
 }
  int length = lineEnd - lineStart;
  int start = lineStart;
  int end = lineEnd;
  String prefix = "";
  String postfix = "";
  if (length > 78) {
 int index = offset - lineStart;
  if (index < 75) {
 end = start + 75;
  postfix = "...";
 }
  else if (end - offset < 75) {
 start = end - 75;
  prefix = "...";
 }
  else {
 start = offset - 36;
  end = offset + 36;
  prefix = postfix = "...";
 }
 }
- String slice = ((__x6) => DDC$RT.cast(__x6, dynamic, String, "CastGeneral", """line 171, column 20 of dart:core/exceptions.dart: """, __x6 is String, true))(source.substring(start, end));
+ String slice = ((__x7) => DDC$RT.cast(__x7, dynamic, String, "CastGeneral", """line 171, column 20 of dart:core/exceptions.dart: """, __x7 is String, true))(source.substring(start, end));
  int markOffset = offset - start + prefix.length;
  return "$report$prefix$slice$postfix\n${" " * markOffset}
 ^\n";
 }
 }
  class IntegerDivisionByZeroException implements Exception {const IntegerDivisionByZeroException();
  String toString() => "IntegerDivisionByZeroException";
 }