add generic method comments to a few SDK methods

sdk/lib/math/math.dart

Index: sdk/lib/math/math.dart
diff --git a/sdk/lib/math/math.dart b/sdk/lib/math/math.dart
index d167d80f86a07823fbf6134be43ca104b04a090c..91352d75bed49dc770cc9359230556186a35ff86 100644
--- a/sdk/lib/math/math.dart
+++ b/sdk/lib/math/math.dart
@@ -63,7 +63,7 @@ const double SQRT2 = 1.4142135623730951;
   * same mathematical value) then it is unspecified which of the two arguments
   * is returned.
   */
-num min(num a, num b) {
+num/*=T*/ max/*<T extends num>*/(num/*=T*/ a, num/*=T*/ b) {

[Lasse Reichstein Nielsen, 2015/11/19 06:58:32]

Is this a way to say that max of two doubles is a double, and max of two
integers is an integer, while max of an int and a double is only known to be a
num?

If so, should you do the same to num.+ (etc)? Or is that already special cased
by the spec?

[Jennifer Messerly, 2015/11/20 17:41:18]

Exactly.
Yup, they're covered by "16.27 Additive Expressions" page 96 of the 3rd edition:
http://www.ecma-international.org/publications/files/ECMA-ST/ECMA-408.pdf :

   // These partially redundant type checks improve code quality for dart2js.
   // Most of the improvement is at call sites from the inferred non-null num
   // return type.
@@ -98,7 +98,7 @@ num min(num a, num b) {
   * otherwise equal (including int and doubles with the same mathematical value)
   * then it is unspecified which of the two arguments is returned.
   */
-num max(num a, num b) {
+num/*=T*/ max/*<T extends num>*/(num/*=T*/ a, num/*=T*/ b) {
   // These partially redundant type checks improve code quality for dart2js.
   // Most of the improvement is at call sites from the inferred non-null num
   // return type.