Fix analyzer's treatment of mixin constructors.

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 374e6a3c6f7375b6ad3fe474b075ac5e567c3d54..edbd4e0987b872196447867cd54a33cde11a638d 100644
--- a/pkg/analyzer/lib/src/generated/error_verifier.dart
+++ b/pkg/analyzer/lib/src/generated/error_verifier.dart
@@ -3994,7 +3994,9 @@ class ErrorVerifier extends RecursiveAstVisitor<Object> {
         _errorReporter.reportErrorForNode(CompileTimeErrorCode.NON_GENERATIVE_CONSTRUCTOR, node.name, [superUnnamedConstructor]);
         return true;
       }
-      if (superUnnamedConstructor.isDefaultConstructor) {
+      if (superUnnamedConstructor.isDefaultConstructor &&
+          _enclosingClass.isSuperConstructorAccessible(
+              superUnnamedConstructor)) {
         return true;
       }
     }
@@ -4845,7 +4847,9 @@ class ErrorVerifier extends RecursiveAstVisitor<Object> {
         _errorReporter.reportErrorForNode(CompileTimeErrorCode.NON_GENERATIVE_CONSTRUCTOR, node.returnType, [superUnnamedConstructor]);
         return true;
       }
-      if (!superUnnamedConstructor.isDefaultConstructor) {
+      if (!superUnnamedConstructor.isDefaultConstructor ||
+          !_enclosingClass.isSuperConstructorAccessible(
+              superUnnamedConstructor)) {
         int offset;
         int length;
         {