Fix for inheriting covariance from a resynthesyzed parameter.

pkg/analyzer/lib/src/summary/link.dart

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /**
  * This library is capable of producing linked summaries from unlinked
  * ones (or prelinked ones).  It functions by building a miniature
  * element model to represent the contents of the summaries, and then
  * scanning the element model to gather linked information and adding
  * it to the summary data structures.
@@ skipping 1416 matching lines @@
  * Element representing a compilation unit which is depended upon
  * (either directly or indirectly) by the build unit being linked.
  *
  * TODO(paulberry): ensure that inferred types in dependencies are properly
  * resynthesized.
  */
 class CompilationUnitElementInDependency extends CompilationUnitElementForLink {
   @override
   final LinkedUnit _linkedUnit;
 
+  /**
+   * Set of slot ids corresponding to parameters that inherit `covariant`.
+   */
+  Set<int> parametersInheritingCovariant;
+
   List<EntityRef> _linkedTypeRefs;
 
   @override
   final LibraryElementInDependency enclosingElement;
 
   CompilationUnitElementInDependency(
       this.enclosingElement,
       UnlinkedUnit unlinkedUnit,
       LinkedUnit linkedUnit,
       int unitNum,
       String absoluteUri)
       : _linkedUnit = linkedUnit,
         super(
             unlinkedUnit, unitNum, linkedUnit.references.length, absoluteUri) {
+    parametersInheritingCovariant =
+        _linkedUnit.parametersInheritingCovariant.toSet();
     // Make one pass through the linked types to determine the lengths for
     // _linkedTypeRefs and _linkedTypes.  TODO(paulberry): add an int to the
     // summary to make this unnecessary.
     int maxLinkedTypeSlot = 0;
     for (EntityRef ref in _linkedUnit.types) {
       if (ref.slot > maxLinkedTypeSlot) {
         maxLinkedTypeSlot = ref.slot;
       }
     }
     // Initialize _linkedTypeRefs.
@@ skipping 2829 matching lines @@
   DartType _inferredType;
   TopLevelInferenceErrorBuilder _inferenceError;
   DartType _declaredType;
   bool _inheritsCovariant = false;
 
   ParameterElementForLink(this.enclosingElement, this._unlinkedParam,
       this._typeParameterContext, this.compilationUnit, this._parameterIndex) {
     if (_unlinkedParam.initializer?.bodyExpr != null) {
       _constNode = new ConstParameterNode(this);
     }
+    if (compilationUnit is CompilationUnitElementInDependency) {
+      _inheritsCovariant =
+          (compilationUnit as CompilationUnitElementInDependency)
+              .parametersInheritingCovariant
+              .contains(_unlinkedParam.inheritsCovariantSlot);
+    }
   }
 
   factory ParameterElementForLink.forFactory(
       ParameterParentElementForLink enclosingElement,
       UnlinkedParam unlinkedParameter,
       TypeParameterizedElementMixin typeParameterContext,
       CompilationUnitElementForLink compilationUnit,
       int parameterIndex) {
     if (unlinkedParameter.isInitializingFormal) {
       return new FieldFormalParameterElementForLink(
@@ skipping 1192 matching lines @@
    * there are no type parameters in scope.
    */
   TypeParameterizedElementMixin get _typeParameterContext;
 
   @override
   noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);
 
   @override
   String toString() => '$enclosingElement.$name';
 }