fixes #52, fields shadowing getters/setters or other fields

lib/runtime/dart/math.js

Index: lib/runtime/dart/math.js
diff --git a/lib/runtime/dart/math.js b/lib/runtime/dart/math.js
index ad6a382788c631272f5522865eea3cd80bf41e33..565e5fff110c366ed670fa7edf425fde58f78399 100644
--- a/lib/runtime/dart/math.js
+++ b/lib/runtime/dart/math.js
@@ -19,11 +19,19 @@ var math;
       return _JenkinsSmiHash.finish(_JenkinsSmiHash.combine(_JenkinsSmiHash.combine(_JenkinsSmiHash.combine(_JenkinsSmiHash.combine(0, dart.as(a, core.int)), dart.as(b, core.int)), dart.as(c, core.int)), dart.as(d, core.int)));
     }
   }
+  let x$ = Symbol('x');
+  let y$ = Symbol('y');
   let Point$ = dart.generic(function(T) {
     class Point extends core.Object {
+      get x() {
+        return this[x$];
+      }
+      get y() {
+        return this[y$];
+      }
       Point(x, y) {
-        this.x = x;
-        this.y = y;
+        this[x$] = x;
+        this[y$] = y;
       }
       toString() {
         return `Point(${this.x}, ${this.y})`;
@@ -134,13 +142,29 @@ var math;
     return _RectangleBase;
   });
   let _RectangleBase = _RectangleBase$();
+  let left$ = Symbol('left');
+  let top$ = Symbol('top');
+  let width$ = Symbol('width');
+  let height$ = Symbol('height');
   let Rectangle$ = dart.generic(function(T) {
     class Rectangle extends _RectangleBase$(T) {
+      get left() {
+        return this[left$];
+      }
+      get top() {
+        return this[top$];
+      }
+      get width() {
+        return this[width$];
+      }
+      get height() {
+        return this[height$];
+      }
       Rectangle(left, top, width, height) {
-        this.left = left;
-        this.top = top;
-        this.width = dart.as(width['<'](0) ? dart.notNull(width['unary-']()) * 0 : width, T);
-        this.height = dart.as(height['<'](0) ? dart.notNull(height['unary-']()) * 0 : height, T);
+        this[left$] = left;
+        this[top$] = top;
+        this[width$] = dart.as(width['<'](0) ? dart.notNull(width['unary-']()) * 0 : width, T);
+        this[height$] = dart.as(height['<'](0) ? dart.notNull(height['unary-']()) * 0 : height, T);
         super._RectangleBase();
       }
       fromPoints(a, b) {
@@ -155,13 +179,27 @@ var math;
     return Rectangle;
   });
   let Rectangle = Rectangle$();
+  let left$0 = Symbol('left');
+  let top$0 = Symbol('top');
   let _width = Symbol('_width');
   let _height = Symbol('_height');
   let MutableRectangle$ = dart.generic(function(T) {
     class MutableRectangle extends _RectangleBase$(T) {
+      get left() {
+        return this[left$0];
+      }
+      set left(value) {
+        this[left$0] = value;
+      }
+      get top() {
+        return this[top$0];
+      }
+      set top(value) {
+        this[top$0] = value;
+      }
       MutableRectangle(left, top, width, height) {
-        this.left = left;
-        this.top = top;
+        this[left$0] = left;
+        this[top$0] = top;
         this[_width] = dart.as(width['<'](0) ? _clampToZero(width) : width, T);
         this[_height] = dart.as(height['<'](0) ? _clampToZero(height) : height, T);
         super._RectangleBase();