Make DefaultEquality<Null> work at runtime (flutter#73)

Works around dart-lang/sdk#32415

CHANGELOG.md

@@ -1,3 +1,13 @@
+## 1.14.6
+
+* Make `DefaultEquality`'s `equals()` and `hash()` methods take any `Object`
+  rather than objects of type `E`. This makes `const DefaultEquality<Null>()`
+  usable as `Equality<E>` for any `E`, which means it can be used in a const
+  context which expects `Equality<E>`.
+
+  This makes the default arguments of various other const equality constructors
+  work in strong mode.
+
 ## 1.14.5
 
 * Fix issue with `EmptyUnmodifiableSet`'s stubs that were introduced in 1.14.4.

lib/src/equality.dart

@@ -76,10 +76,14 @@ class EqualityBy<E, F> implements Equality<E> {
 ///
 /// This equality uses the objects' own [Object.==] and [Object.hashCode] for
 /// the equality.
+///
+/// Note that [equals] and [hash] take `Object`s rather than `E`s. This allows
+/// `E` to be inferred as `Null` in const contexts where `E` wouldn't be a
+/// compile-time constant, while still allowing the class to be used at runtime.
 class DefaultEquality<E> implements Equality<E> {
   const DefaultEquality();
-  bool equals(E e1, E e2) => e1 == e2;
-  int hash(E e) => e.hashCode;
+  bool equals(Object e1, Object e2) => e1 == e2;
+  int hash(Object e) => e.hashCode;
   bool isValidKey(Object o) => true;
 }
 

pubspec.yaml

@@ -1,5 +1,5 @@
 name: collection
-version: 1.14.5
+version: 1.14.6
 author: Dart Team <[email protected]>
 description: Collections and utilities functions and classes related to collections.
 homepage: https://www.github.com/dart-lang/collection