Typecheck constructor initializers properly

test/dart_codegen/expect/math/rectangle.dart

 part of dart.math;
  abstract class _RectangleBase<T extends num> {const _RectangleBase();
  T get left;
  T get top;
  T get width;
  T get height;
  T get right => ((__x1) => DDC$RT.cast(__x1, num, T, "CastGeneral", """line 33, column 18 of dart:math/rectangle.dart: """, __x1 is T, false))(left + width);
  T get bottom => ((__x2) => DDC$RT.cast(__x2, num, T, "CastGeneral", """line 35, column 19 of dart:math/rectangle.dart: """, __x2 is T, false))(top + height);
  String toString() {
   return 'Rectangle ($left, $top) $width x $height';
@@ skipping 46 matching lines @@
  T width = ((__x4) => DDC$RT.cast(__x4, num, T, "CastGeneral", """line 168, column 15 of dart:math/rectangle.dart: """, __x4 is T, false))(max(a.x, b.x) - left);
  T top = ((__x5) => DDC$RT.cast(__x5, num, T, "CastGeneral", """line 169, column 13 of dart:math/rectangle.dart: """, __x5 is T, false))(min(a.y, b.y));
  T height = ((__x6) => DDC$RT.cast(__x6, num, T, "CastGeneral", """line 170, column 16 of dart:math/rectangle.dart: """, __x6 is T, false))(max(a.y, b.y) - top);
  return new Rectangle<T>(left, top, width, height);
 }
 }
  class MutableRectangle<T extends num> extends _RectangleBase<T> implements Rectangle<T> {T left;
  T top;
  T _width;
  T _height;
- MutableRectangle(this.left, this.top, T width, T height) : this._width = (width < 0) ? _clampToZero(width) : width, this._height = (height < 0) ? _clampToZero(height) : height;
+ MutableRectangle(this.left, this.top, T width, T height) : this._width = ((__x7) => DDC$RT.cast(__x7, dynamic, T, "CastGeneral", """line 212, column 23 of dart:math/rectangle.dart: """, __x7 is T, false))((width < 0) ? _clampToZero(width) : width), this._height = ((__x8) => DDC$RT.cast(__x8, dynamic, T, "CastGeneral", """line 213, column 24 of dart:math/rectangle.dart: """, __x8 is T, false))((height < 0) ? _clampToZero(height) : height);
  factory MutableRectangle.fromPoints(Point<T> a, Point<T> b) {
-T left = ((__x7) => DDC$RT.cast(__x7, num, T, "CastGeneral", """line 228, column 14 of dart:math/rectangle.dart: """, __x7 is T, false))(min(a.x, b.x));
- T width = ((__x8) => DDC$RT.cast(__x8, num, T, "CastGeneral", """line 229, column 15 of dart:math/rectangle.dart: """, __x8 is T, false))(max(a.x, b.x) - left);
- T top = ((__x9) => DDC$RT.cast(__x9, num, T, "CastGeneral", """line 230, column 13 of dart:math/rectangle.dart: """, __x9 is T, false))(min(a.y, b.y));
- T height = ((__x10) => DDC$RT.cast(__x10, num, T, "CastGeneral", """line 231, column 16 of dart:math/rectangle.dart: """, __x10 is T, false))(max(a.y, b.y) - top);
+T left = ((__x9) => DDC$RT.cast(__x9, num, T, "CastGeneral", """line 228, column 14 of dart:math/rectangle.dart: """, __x9 is T, false))(min(a.x, b.x));
+ T width = ((__x10) => DDC$RT.cast(__x10, num, T, "CastGeneral", """line 229, column 15 of dart:math/rectangle.dart: """, __x10 is T, false))(max(a.x, b.x) - left);
+ T top = ((__x11) => DDC$RT.cast(__x11, num, T, "CastGeneral", """line 230, column 13 of dart:math/rectangle.dart: """, __x11 is T, false))(min(a.y, b.y));
+ T height = ((__x12) => DDC$RT.cast(__x12, num, T, "CastGeneral", """line 231, column 16 of dart:math/rectangle.dart: """, __x12 is T, false))(max(a.y, b.y) - top);
  return new MutableRectangle<T>(left, top, width, height);
 }
  T get width => _width;
  void set width(T width) {
-if (width < 0) width = ((__x11) => DDC$RT.cast(__x11, num, T, "CastGeneral", """line 247, column 28 of dart:math/rectangle.dart: """, __x11 is T, false))(_clampToZero(width));
+if (width < 0) width = ((__x13) => DDC$RT.cast(__x13, num, T, "CastGeneral", """line 247, column 28 of dart:math/rectangle.dart: """, __x13 is T, false))(_clampToZero(width));
  _width = width;
 }
  T get height => _height;
  void set height(T height) {
-if (height < 0) height = ((__x12) => DDC$RT.cast(__x12, num, T, "CastGeneral", """line 263, column 30 of dart:math/rectangle.dart: """, __x12 is T, false))(_clampToZero(height));
+if (height < 0) height = ((__x14) => DDC$RT.cast(__x14, num, T, "CastGeneral", """line 263, column 30 of dart:math/rectangle.dart: """, __x14 is T, false))(_clampToZero(height));
  _height = height;
 }
 }
  num _clampToZero(num value) {
 assert (value < 0); return -value * 0;
 }