fix finding lambdas implementing JDK interfaces

java/java-indexing-impl/java-indexing-impl.iml

@@ -14,6 +14,6 @@
     <orderEntry type="module" module-name="projectModel-api" exported="" />
     <orderEntry type="module" module-name="projectModel-impl" />
     <orderEntry type="module" module-name="java-indexing-api" exported="" />
+    <orderEntry type="library" name="Guava" level="project" />
   </component>
-</module>
-
+</module>

java/java-indexing-impl/src/com/intellij/psi/impl/search/JavaFunctionalExpressionSearcher.java

@@ -15,11 +15,11 @@
  */
 package com.intellij.psi.impl.search;
 
+import com.google.common.annotations.VisibleForTesting;
 import com.intellij.openapi.application.*;
 import com.intellij.openapi.diagnostic.Logger;
 import com.intellij.openapi.module.Module;
 import com.intellij.openapi.module.ModuleManager;
-import com.intellij.openapi.module.impl.scopes.ModulesScope;
 import com.intellij.openapi.project.Project;
 import com.intellij.openapi.roots.LanguageLevelModuleExtension;
 import com.intellij.openapi.roots.ModuleRootManager;
@@ -53,6 +53,13 @@ import static com.intellij.util.containers.ContainerUtilRt.newHashSet;
 
 public class JavaFunctionalExpressionSearcher extends QueryExecutorBase<PsiFunctionalExpression, FunctionalExpressionSearch.SearchParameters> {
   private static final Logger LOG = Logger.getInstance("#" + JavaFunctionalExpressionSearcher.class.getName());
+  /**
+   * The least number of candidate files with functional expressions that directly scanning them becomes expensive
+   * and more advanced ways of searching become necessary: e.g. first searching for methods where the functional interface class is used
+   * and then for their usages,
+    */
+  @VisibleForTesting
+  public static final int SMART_SEARCH_THRESHOLD = 5;
 
   @Override
   public void processQuery(@NotNull FunctionalExpressionSearch.SearchParameters queryParameters,
@@ -71,7 +78,7 @@ public class JavaFunctionalExpressionSearcher extends QueryExecutorBase<PsiFunct
       final Set<Module> highLevelModules = getJava8Modules(project);
       if (highLevelModules.isEmpty()) return;
 
-      useScope = new JavaSourceFilterScope(new ModulesScope(highLevelModules, project).intersectWith(convertToGlobalScope(project, queryParameters.getEffectiveSearchScope())));
+      useScope = convertToGlobalScope(project, queryParameters.getEffectiveSearchScope());
 
       final MethodSignature functionalInterfaceMethod = LambdaUtil.getFunction(aClass);
       LOG.assertTrue(functionalInterfaceMethod != null);
@@ -81,8 +88,8 @@ public class JavaFunctionalExpressionSearcher extends QueryExecutorBase<PsiFunct
     }
 
     //collect all files with '::' and '->' in useScope
-    Set<VirtualFile> candidateFiles = getFilesWithFunctionalExpressionsScope(project, useScope);
-    if (candidateFiles.size() < 5) {
+    Set<VirtualFile> candidateFiles = getFilesWithFunctionalExpressionsScope(project, new JavaSourceFilterScope(useScope));
+    if (candidateFiles.size() < SMART_SEARCH_THRESHOLD) {
       searchInFiles(aClass, consumer, candidateFiles, expectedFunExprParamsCount);
       return;
     }

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/findUsages/ClassFromJdk.java

@@ -0,0 +1,6 @@
+class Test{
+
+  public static void main(java.util.List<String> list) {
+    list.stream().filter((e) -> true)
+  }
+}

java/java-tests/testSrc/com/intellij/codeInsight/daemon/lambda/FindFunctionalInterfaceTest.java

@@ -17,6 +17,8 @@ package com.intellij.codeInsight.daemon.lambda;
 
 import com.intellij.JavaTestUtil;
 import com.intellij.psi.*;
+import com.intellij.psi.impl.search.JavaFunctionalExpressionSearcher;
+import com.intellij.psi.search.GlobalSearchScope;
 import com.intellij.psi.search.searches.FunctionalExpressionSearch;
 import com.intellij.psi.search.searches.ReferencesSearch;
 import com.intellij.psi.util.PsiTreeUtil;
@@ -25,6 +27,7 @@ import com.intellij.testFramework.fixtures.LightCodeInsightFixtureTestCase;
 import org.jetbrains.annotations.NotNull;
 
 import java.util.Collection;
+import java.util.function.Predicate;
 
 public class FindFunctionalInterfaceTest extends LightCodeInsightFixtureTestCase {
   public void testMethodArgument() throws Exception {
@@ -66,6 +69,19 @@ public class FindFunctionalInterfaceTest extends LightCodeInsightFixtureTestCase
     assertEquals(1, references.size());
   }
 
+  public void testClassFromJdk() {
+    myFixture.configureByFile(getTestName(false) + ".java");
+
+    for (int i = 0; i < JavaFunctionalExpressionSearcher.SMART_SEARCH_THRESHOLD + 5; i++) {
+      myFixture.addFileToProject("a" + i + ".java", "class Goo {{ Runnable r = () -> {} }}");
+    }
+
+    PsiClass predicate = JavaPsiFacade.getInstance(getProject()).findClass(Predicate.class.getName(), GlobalSearchScope.allScope(getProject()));
+    assert predicate != null;
+    final PsiFunctionalExpression next = assertOneElement(FunctionalExpressionSearch.search(predicate).findAll());
+    assertEquals("(e) -> true", next.getText());
+  }
+
   @Override
   protected String getBasePath() {
     return JavaTestUtil.getRelativeJavaTestDataPath() + "/codeInsight/daemonCodeAnalyzer/lambda/findUsages/";