Make dart:math strong mode clean.

sdk/lib/math/rectangle.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 part of dart.math;
 
 /**
  * A base class for representing two-dimensional axis-aligned rectangles.
  *
  * This rectangle uses a left-handed Cartesian coordinate system, with x
  * directed to the right and y directed down, as per the convention in 2D
@@ skipping 191 matching lines @@
    * with x-coordinate between `left` and `left + width`, and
    * with y-coordinate between `top` and `top + height`, both inclusive.
    *
    * The `width` and `height` should be non-negative.
    * If `width` or `height` are negative, they are clamped to zero.
    *
    * If `width` and `height` are zero, the "rectangle" comprises only the single
    * point `(left, top)`.
    */
   MutableRectangle(this.left, this.top, T width, T height)
-      : this._width = (width < 0) ? _clampToZero(width) : width,
-        this._height = (height < 0) ? _clampToZero(height) : height;
+      : this._width = (width < 0) ? _clampToZero/*<T>*/(width) : width,
+        this._height = (height < 0) ? _clampToZero/*<T>*/(height) : height;
 
   /**
    * Create a mutable rectangle spanned by the points [a] and [b];
    *
    * The rectangle contains the points
    * with x-coordinate between `a.x` and `b.x`, and
    * with y-coordinate between `a.y` and `b.y`, both inclusive.
    *
    * If the distance between `a.x` and `b.x` is not representable
    * (which can happen if one or both is a double),
@@ skipping 13 matching lines @@
  /**
    * Sets the width of the rectangle.
    *
    * The width must be non-negative.
    * If a negative width is supplied, it is clamped to zero.
    *
    * Setting the value will change the right edge of the rectangle,
    * but will not change [left].
    */
   void set width(T width) {
-    if (width < 0) width = _clampToZero(width);
+    if (width < 0) width = _clampToZero/*<T>*/(width);
     _width = width;
   }
 
   T get height => _height;
 
   /**
    * Sets the height of the rectangle.
    *
    * The height must be non-negative.
    * If a negative height is supplied, it is clamped to zero.
    *
    * Setting the value will change the bottom edge of the rectangle,
    * but will not change [top].
    */
   void set height(T height) {
-    if (height < 0) height = _clampToZero(height);
+    if (height < 0) height = _clampToZero/*<T>*/(height);
     _height = height;
   }
 }
 
 /**
  * Converts a negative [int] or [double] to a zero-value of the same type.
  *
  * Returns `0` if value is int, `0.0` if value is double.
  */
-num _clampToZero(num value) {
+num/*=T*/ _clampToZero/*<T extends num>*/(num/*=T*/ value) {
   assert(value < 0);
   return -value * 0;
 }