Fix requalifying type variable uses during viewpoint adaptation

framework/src/main/java/org/checkerframework/framework/type/AbstractViewpointAdapter.java

@@ -8,6 +8,7 @@
 import org.checkerframework.framework.type.AnnotatedTypeMirror.AnnotatedPrimitiveType;
 import org.checkerframework.framework.type.AnnotatedTypeMirror.AnnotatedTypeVariable;
 import org.checkerframework.framework.type.AnnotatedTypeMirror.AnnotatedWildcardType;
+import org.checkerframework.javacutil.AnnotationUtils;
 import org.checkerframework.javacutil.BugInCF;
 import org.checkerframework.javacutil.ElementUtils;
 import org.plumelib.util.IPair;
@@ -285,7 +286,12 @@ protected AnnotatedTypeMirror combineAnnotationWithType(
                 AnnotatedTypeMirror resLower =
                         combineAnnotationWithType(receiverAnnotation, atv.getLowerBound());
                 mappings.put(atv.getLowerBound(), resLower);
-
+                // The values of the mappings are the viewpoint adapted lower and upper bounds,
+                // and we wish to replace the old bounds of atv with the new mappings.
+                // However, we need to first remove the primary annotations of atv, otherwise
+                // in later replacement, the primary annotations would override our computed
+                // new mappings (see method fixupBoundAnnotations).
+                atv.clearAnnotations();
                 AnnotatedTypeMirror result =
                         AnnotatedTypeCopierWithReplacement.replace(atv, mappings);
 
@@ -408,6 +414,25 @@ private AnnotatedTypeMirror substituteTVars(AnnotatedTypeMirror lhs, AnnotatedTy
             // Base case where actual type argument is extracted
             if (lhs.getKind() == TypeKind.DECLARED) {
                 rhs = getTypeVariableSubstitution((AnnotatedDeclaredType) lhs, atv);
+                // When substituting an annotated type variable use (e.g., fields, return type), we
+                // don't want to replace the type qualifier of it with the qualifier on the
+                // type argument, as specified in
+                // https://checkerframework.org/manual/#type-variable-use. However, method
+                // getTypeVariableSubstitution will replace the annotated type qualifier as well.
+                // We fix up the substitution by checking if the types of the lower and upper bound
+                // are the same. If they are the same: (1) either the type variable use is
+                // annotated, and we need to fix up the
+                // primary annotation of the substituted result (rhs) by replacing it with the
+                // previous annotated type qualifier (from atv); (2) or the use is not annotated,
+                // but
+                // the type parameter is declared with the same upper and lower bounds, and it's no
+                // harm doing the same replacement as (1) because the qualifiers of the substituted
+                // result (rhs) and the old type variable use (atv) must be the same.
+                if (AnnotationUtils.areSame(
+                        atv.getLowerBound().getAnnotations(),
+                        atv.getUpperBound().getAnnotations())) {
+                    rhs.replaceAnnotations(atv.getLowerBound().getAnnotations());
+                }
             }
         } else if (rhs.getKind() == TypeKind.DECLARED) {
             AnnotatedDeclaredType adt = (AnnotatedDeclaredType) rhs.shallowCopy();

framework/tests/viewpointtest/AnnoOnTypeVariableUse.java

@@ -0,0 +1,17 @@
+import viewpointtest.quals.*;
+
+@SuppressWarnings("cast.unsafe.constructor.invocation")
+class AnnoOnTypeVariableUse<E> {
+    @ReceiverDependentQual E element;
+
+    static void test() {
+        AnnoOnTypeVariableUse<@B Element> d = new @A AnnoOnTypeVariableUse<@B Element>();
+        // d.element = @A |> @RDQ = @A
+        // thus expects no error here
+        d.element = new @A Element();
+    }
+}
+
+class Element {
+    int f = 1;
+}