IDEA-135189 (False positive of "Type may be weakened")

plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/abstraction/TypeMayBeWeakenedInspection.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2006-2014 Bas Leijdekkers
+ * Copyright 2006-2015 Bas Leijdekkers
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -18,6 +18,7 @@ package com.siyeh.ig.abstraction;
 import com.intellij.codeInsight.daemon.impl.analysis.JavaHighlightUtil;
 import com.intellij.codeInspection.ProblemDescriptor;
 import com.intellij.codeInspection.ui.MultipleCheckboxOptionsPanel;
+import com.intellij.openapi.application.ApplicationManager;
 import com.intellij.openapi.project.Project;
 import com.intellij.psi.*;
 import com.intellij.psi.codeStyle.JavaCodeStyleManager;
@@ -294,7 +295,7 @@ public class TypeMayBeWeakenedInspection extends BaseInspection {
     @Override
     public void visitMethod(PsiMethod method) {
       super.visitMethod(method);
-      if (isOnTheFly() && !method.hasModifierProperty(PsiModifier.PRIVATE)) {
+      if (isOnTheFly() && !method.hasModifierProperty(PsiModifier.PRIVATE) && !ApplicationManager.getApplication().isUnitTestMode()) {
         // checking methods with greater visibility is too expensive.
         // for error checking in the editor
         return;

plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/psiutils/WeakestTypeFinder.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2008-2014 Bas Leijdekkers
+ * Copyright 2008-2015 Bas Leijdekkers
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -155,11 +155,17 @@ public class WeakestTypeFinder {
         checkClass(javaLangIterableClass, weakestTypeClasses);
       }
       else if (referenceParent instanceof PsiReturnStatement) {
-        final PsiMethod containingMethod = PsiTreeUtil.getParentOfType(referenceParent, PsiMethod.class);
-        if (containingMethod == null) {
+        final PsiElement owner = PsiTreeUtil.getParentOfType(referenceParent, PsiMethod.class, PsiLambdaExpression.class);
+        final PsiType type;
+        if (owner instanceof PsiMethod) {
+          type = ((PsiMethod)owner).getReturnType();
+        }
+        else if (owner instanceof PsiLambdaExpression) {
+          type = LambdaUtil.getFunctionalInterfaceReturnType((PsiLambdaExpression)owner);
+        }
+        else {
           return Collections.emptyList();
         }
-        final PsiType type = containingMethod.getReturnType();
         if (!checkType(type, weakestTypeClasses)) {
           return Collections.emptyList();
         }

plugins/InspectionGadgets/test/com/siyeh/igtest/abstraction/weaken_type/Lambda.java

@@ -0,0 +1,23 @@
+package com.siyeh.igtest.abstraction.weaken_type;
+
+import java.util.function.Supplier;
+
+public interface Lambda {
+
+    int count();
+
+    static Lambda newWeaken(int value) {
+        return new Lambda() {
+            @Override
+            public int count() {
+                return value;
+            }
+        };
+    }
+
+    static Supplier<Lambda> newSupplier() {
+        return () -> {
+            return Lambda.newWeaken(0);
+        };
+    }
+}

plugins/InspectionGadgets/testsrc/com/siyeh/ig/abstraction/TypeMayBeWeakenedInspectionTest.java

@@ -9,6 +9,7 @@ public class TypeMayBeWeakenedInspectionTest extends LightInspectionTestCase {
   public void testTypeMayBeWeakened() { doTest(); }
   public void testNumberAdderDemo() { doTest(); }
   public void testAutoClosableTest() { doTest(); }
+  public void testLambda() { doTest(); }
 
   @Override
   protected String[] getEnvironmentClasses() {
@@ -33,6 +34,11 @@ public class TypeMayBeWeakenedInspectionTest extends LightInspectionTestCase {
       "@FunctionalInterface " +
       "public interface Function<T, R> {" +
       "    R apply(T t);" +
+      "}",
+      "package java.util.function;\n" +
+      "@FunctionalInterface\n" +
+      "public interface Supplier<T> {\n" +
+      "    T get();\n" +
       "}"
     };
   }