Make type system changes backwards compatible

pkg/analyzer/lib/src/generated/error_verifier.dart

Index: pkg/analyzer/lib/src/generated/error_verifier.dart
diff --git a/pkg/analyzer/lib/src/generated/error_verifier.dart b/pkg/analyzer/lib/src/generated/error_verifier.dart
index a165b228ef78833a01d42067f355fe5b85e219f5..912f3641cb1f8d68c792528bec5c84234c027e8d 100644
--- a/pkg/analyzer/lib/src/generated/error_verifier.dart
+++ b/pkg/analyzer/lib/src/generated/error_verifier.dart
@@ -269,7 +269,7 @@ class ErrorVerifier extends RecursiveAstVisitor<Object> {
    * Initialize a newly created error verifier.
    */
   ErrorVerifier(this._errorReporter, this._currentLibrary, this._typeProvider,
-      this._typeSystem, this._inheritanceManager, this.enableSuperMixins) {
+      this._inheritanceManager, this.enableSuperMixins) {
     this._isInSystemLibrary = _currentLibrary.source.isInSystemLibrary;
     this._hasExtUri = _currentLibrary.hasExtUri;
     _isEnclosingConstructorConst = false;
@@ -282,6 +282,7 @@ class ErrorVerifier extends RecursiveAstVisitor<Object> {
     _boolType = _typeProvider.boolType;
     _intType = _typeProvider.intType;
     _DISALLOWED_TYPES_TO_EXTEND_OR_IMPLEMENT = _typeProvider.nonSubtypableTypes;
+    _typeSystem = _currentLibrary.context.typeSystem;
   }
 
   @override