Roll to pickup pool changes

packages/matcher/CHANGELOG.md

+## 0.12.1+4
+
+* Fixed SDK constraint to allow edge builds.
+
+## 0.12.1+3
+
+* Make `predicate` and `pairwiseCompare` generic methods to allow typed
+ functions to be passed to them as arguments.
+
+* Make internal implementations take better advantage of type promotion to avoid
+  dynamic call overhead.
+
+## 0.12.1+2
+
+* Fixed small documentation issues.
+
+* Fixed small issue in `StringEqualsMatcher`.
+
+* Update to support future Dart language changes.
+
 ## 0.12.1+1
 
 * Produce a better error message when a `CustomMatcher`'s feature throws.
 
 ## 0.12.1
 
 * Add containsAllInOrder matcher for Iterables
 
 ## 0.12.0+2
 
@@ skipping 103 matching lines @@
 * Matchers related to bad language use have been removed. These represent code
 structure that should rarely or never be validated in tests.
     * `isAbstractClassInstantiationError`
     * `throwsAbstractClassInstantiationError`
     * `isFallThroughError`
     * `throwsFallThroughError`
 
 * Added types to a number of method arguments.
 
 * The structure of the library and test code has been updated.