MethodReturnTypeFix: do not suggest when type refers to type parameter not available at method declaration

java/java-impl/src/com/intellij/codeInsight/daemon/impl/quickfix/MethodReturnTypeFix.java

@@ -22,10 +22,7 @@ import com.intellij.psi.controlFlow.AnalysisCanceledException;
 import com.intellij.psi.controlFlow.ControlFlow;
 import com.intellij.psi.controlFlow.ControlFlowUtil;
 import com.intellij.psi.search.LocalSearchScope;
-import com.intellij.psi.util.InheritanceUtil;
-import com.intellij.psi.util.PsiTypesUtil;
-import com.intellij.psi.util.PsiUtil;
-import com.intellij.psi.util.TypeConversionUtil;
+import com.intellij.psi.util.*;
 import com.intellij.refactoring.changeSignature.ChangeSignatureProcessor;
 import com.intellij.refactoring.changeSignature.OverriderUsageInfo;
 import com.intellij.refactoring.changeSignature.ParameterInfoImpl;
@@ -36,7 +33,10 @@ import com.intellij.util.IncorrectOperationException;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
-import java.util.*;
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Set;
 
 public class MethodReturnTypeFix extends LocalQuickFixAndIntentionActionOnPsiElement implements HighPriorityAction {
   private static final Logger LOG = Logger.getInstance("#com.intellij.codeInsight.daemon.impl.quickfix.MethodReturnBooleanFix");
@@ -81,7 +81,26 @@ public class MethodReturnTypeFix extends LocalQuickFixAndIntentionActionOnPsiEle
         myReturnType.isValid() &&
         !TypeConversionUtil.isNullType(myReturnType)) {
       final PsiType returnType = myMethod.getReturnType();
-      if (returnType != null && returnType.isValid() && !Comparing.equal(myReturnType, returnType)) return true;
+      if (returnType != null && returnType.isValid() && !Comparing.equal(myReturnType, returnType)) {
+        return allTypeParametersResolved(myMethod, myReturnType);
+      }
+    }
+    return false;
+  }
+
+  private static boolean allTypeParametersResolved(PsiMethod myMethod, PsiType myReturnType) {
+    PsiTypesUtil.TypeParameterSearcher searcher = new PsiTypesUtil.TypeParameterSearcher();
+    myReturnType.accept(searcher);
+    Set<PsiTypeParameter> parameters = searcher.getTypeParameters();
+    return parameters.stream().allMatch(parameter -> isAccessibleAt(parameter, myMethod));
+  }
+
+  private static boolean isAccessibleAt(PsiTypeParameter parameter, PsiMethod method) {
+    PsiTypeParameterListOwner owner = parameter.getOwner();
+    if(owner == method) return true;
+    if(owner instanceof PsiClass) {
+      return PsiTreeUtil.isAncestor(owner, method, true) &&
+             InheritanceUtil.hasEnclosingInstanceInScope((PsiClass)owner, method, false, false);
     }
     return false;
   }
@@ -188,7 +207,7 @@ public class MethodReturnTypeFix extends LocalQuickFixAndIntentionActionOnPsiEle
     return editor;
   }
 
-  @Nullable
+  @NotNull
   private PsiMethod[] getChangeRoots(final PsiMethod method, @NotNull PsiType returnType) {
     if (!myFixWholeHierarchy) return new PsiMethod[]{method};
 
@@ -209,10 +228,6 @@ public class MethodReturnTypeFix extends LocalQuickFixAndIntentionActionOnPsiEle
   @NotNull
   private List<PsiMethod> changeReturnType(final PsiMethod method, @NotNull final PsiType returnType) {
     final PsiMethod[] methods = getChangeRoots(method, returnType);
-    if (methods == null) {
-      // canceled
-      return Collections.emptyList();
-    }
 
     final MethodSignatureChangeVisitor methodSignatureChangeVisitor = new MethodSignatureChangeVisitor();
     for (PsiMethod targetMethod : methods) {

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/methodReturn/afterGenericVar.java

@@ -0,0 +1,14 @@
+// "Make 'method' return 'java.util.List<T>'" "true"
+import java.util.*;
+
+public class Test {
+  class Inner<T> {
+    List<T> method() {
+        return null;
+    }
+
+    void test() {
+      List<T> t = method();
+    }
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/methodReturn/beforeGenericVar.java

@@ -0,0 +1,12 @@
+// "Make 'method' return 'java.util.List<T>'" "true"
+import java.util.*;
+
+public class Test {
+  class Inner<T> {
+    void method() {}
+
+    void test() {
+      List<T> t = met<caret>hod();
+    }
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/methodReturn/beforeGenericVarOutOfScope.java

@@ -0,0 +1,13 @@
+// "Make 'method' return 'java.util.List<T>'" "false"
+import java.util.*;
+
+public class Test {
+  void method() {}
+
+  class Inner<T> {
+
+    void test() {
+      List<T> t = met<caret>hod();
+    }
+  }
+}

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/quickFix/methodReturn/beforeGenericVarStatic.java

@@ -0,0 +1,12 @@
+// "Make 'method' return 'java.util.List<T>'" "false"
+import java.util.*;
+
+public class Test {
+  static class Inner<T> {
+    static void method() {}
+
+    void test() {
+      List<T> t = met<caret>hod();
+    }
+  }
+}