Correct finding type variables of enclosing classes.

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

@@ -211,33 +211,58 @@ public List<AnnotatedDeclaredType> visitDeclared(AnnotatedDeclaredType type, Voi
      * type parameters of {@code type}, its enclosing types, and all super types of all {@code
      * type}'s enclosing types.
      *
+     * <p>It does not get the type parameters of the supertypes of {@code type} because the result
+     * of this method is used to substitute the type arguments of the supertypes of {@code type}.
+     *
      * @param type a type
      * @return a mapping from each type parameter to its corresponding annotated type argument
      */
     private Map<TypeVariable, AnnotatedTypeMirror> getTypeVarToTypeArg(AnnotatedDeclaredType type) {
       Map<TypeVariable, AnnotatedTypeMirror> mapping = new HashMap<>();
-      AnnotatedDeclaredType enclosing = type;
-      while (enclosing != null) {
-        TypeElement enclosingTypeElement = (TypeElement) enclosing.getUnderlyingType().asElement();
-        List<? extends TypeParameterElement> typeParams = enclosingTypeElement.getTypeParameters();
-        List<AnnotatedTypeMirror> typeArgs = enclosing.getTypeArguments();
-        for (int i = 0; i < enclosing.getTypeArguments().size(); ++i) {
-          AnnotatedTypeMirror typArg = typeArgs.get(i);
-          TypeParameterElement ele = typeParams.get(i);
-          mapping.put((TypeVariable) ele.asType(), typArg);
-        }
+      // addTypeVarsFromEnclosingTypes can't be called with `type` because it calls
+      // `directSupertypes(types)`, which then calls this method. Add the type variables from `type`
+      // and then call addTypeVarsFromEnclosingTypes on the enclosing type.
+      addTypeVariablesToMapping(type, mapping);
+      addTypeVarsFromEnclosingTypes(type.getEnclosingType(), mapping);
+      return mapping;
+    }
 
-        @SuppressWarnings("interning:not.interned") // First time through type == enclosing.
-        boolean notType = enclosing != type;
-        if (notType) {
-          for (AnnotatedDeclaredType enclSuper : directSupertypes(enclosing)) {
-            mapping.putAll(getTypeVarToTypeArg(enclSuper));
-          }
-        }
+    /**
+     * Adds a mapping from a type parameter to its corresponding annotated type argument for all
+     * type parameters of {@code type}.
+     *
+     * @param type a type
+     * @param mapping type variable to type argument map; side-effected by this method
+     */
+    private void addTypeVariablesToMapping(
+        AnnotatedDeclaredType type, Map<TypeVariable, AnnotatedTypeMirror> mapping) {
+      TypeElement enclosingTypeElement = (TypeElement) type.getUnderlyingType().asElement();
+      List<? extends TypeParameterElement> typeParams = enclosingTypeElement.getTypeParameters();
+      List<AnnotatedTypeMirror> typeArgs = type.getTypeArguments();
+      for (int i = 0; i < type.getTypeArguments().size(); ++i) {
+        AnnotatedTypeMirror typArg = typeArgs.get(i);
+        TypeParameterElement ele = typeParams.get(i);
+        mapping.put((TypeVariable) ele.asType(), typArg);
+      }
+    }
 
+    /**
+     * Adds a mapping from a type parameter to its corresponding annotated type argument for all
+     * type parameters of {@code enclosing} and its enclosing types. This method recurs on all the
+     * super types of {@code enclosing}.
+     *
+     * @param mapping type variable to type argument map; side-effected by this method
+     * @param enclosing a type
+     */
+    private void addTypeVarsFromEnclosingTypes(
+        AnnotatedDeclaredType enclosing, Map<TypeVariable, AnnotatedTypeMirror> mapping) {
+      while (enclosing != null) {
+        addTypeVariablesToMapping(enclosing, mapping);
+        for (AnnotatedDeclaredType enclSuper : directSupertypes(enclosing)) {
+          addTypeVarsFromEnclosingTypes(enclSuper, mapping);
+        }
         enclosing = enclosing.getEnclosingType();
       }
-      return mapping;
     }
 
     private List<AnnotatedDeclaredType> supertypesFromElement(

framework/tests/all-systems/Issue4924.java

@@ -0,0 +1,15 @@
+public class Issue4924 {
+  interface Callback<A> {}
+
+  static class Template<B> {
+    class Adapter implements Callback<B> {}
+  }
+
+  static class Super<C> extends Template<C> {}
+
+  static class Issue extends Super<String> {
+    void foo() {
+      Callback<String> f = new Adapter();
+    }
+  }
+}