fix param types on methods in _EmptyVersion

pkgs/pub_semver/.gitignore

diff --git a/pkgs/pub_semver/.gitignore b/pkgs/pub_semver/.gitignore
index 7178642..98fed01 100644
--- a/pkgs/pub_semver/.gitignore
+++ b/pkgs/pub_semver/.gitignore
@@ -1,3 +1,4 @@
+.packages
 packages
 pubspec.lock
 

pkgs/pub_semver/CHANGELOG.md

diff --git a/pkgs/pub_semver/CHANGELOG.md b/pkgs/pub_semver/CHANGELOG.md
index 58190a8..7dca24c 100644
--- a/pkgs/pub_semver/CHANGELOG.md
+++ b/pkgs/pub_semver/CHANGELOG.md
@@ -1,3 +1,9 @@
+# 1.2.2
+
+* Make the package analyze under strong mode and compile with the DDC (Dart Dev
+  Compiler). Fix two issues with a private subclass of `VersionConstraint`
+  having different types for overridden methods.
+
 # 1.2.1
 
 * Allow version ranges like `>=1.2.3-dev.1 <1.2.3` to match pre-release versions

pkgs/pub_semver/lib/src/version_constraint.dart

diff --git a/pkgs/pub_semver/lib/src/version_constraint.dart b/pkgs/pub_semver/lib/src/version_constraint.dart
index 3f4d5b8..dbd0aa5 100644
--- a/pkgs/pub_semver/lib/src/version_constraint.dart
+++ b/pkgs/pub_semver/lib/src/version_constraint.dart
@@ -209,8 +209,8 @@
   bool get isEmpty => true;
   bool get isAny => false;
   bool allows(Version other) => false;
-  bool allowsAll(Version other) => other.isEmpty;
-  bool allowsAny(Version other) => false;
+  bool allowsAll(VersionConstraint other) => other.isEmpty;
+  bool allowsAny(VersionConstraint other) => false;
   VersionConstraint intersect(VersionConstraint other) => this;
   VersionConstraint union(VersionConstraint other) => other;
   String toString() => '<empty>';

pkgs/pub_semver/pubspec.yaml

diff --git a/pkgs/pub_semver/pubspec.yaml b/pkgs/pub_semver/pubspec.yaml
index 33545a3..530a4ce 100644
--- a/pkgs/pub_semver/pubspec.yaml
+++ b/pkgs/pub_semver/pubspec.yaml
@@ -1,5 +1,5 @@
 name: pub_semver
-version: 1.2.1
+version: 1.2.2
 author: Dart Team <misc@dartlang.org>
 description: >
  Versions and version constraints implementing pub's versioning policy. This