inference: skip standalone expressions in lambda returns (IDEA-171922)

java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/ExpressionCompatibilityConstraint.java

@@ -129,6 +129,9 @@ public class ExpressionCompatibilityConstraint extends InputOutputConstraintForm
                                                                          PsiExpression expression,
                                                                          PsiType targetType,
                                                                          boolean registerErrorOnFailure) {
+    if (!PsiPolyExpressionUtil.isPolyExpression(expression)) {
+      return session;
+    }
     final PsiExpressionList argumentList = ((PsiCall)expression).getArgumentList();
     if (argumentList != null) {
       final MethodCandidateInfo.CurrentCandidateProperties candidateProperties = MethodCandidateInfo.getCurrentMethod(argumentList);

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/newLambda/IgnoreStandaloneExpressionsInLambdaReturnForNestedCalls.java

@@ -0,0 +1,14 @@
+
+import java.util.ArrayList;
+import java.util.Map;
+import java.util.function.Function;
+import java.util.stream.Collector;
+import java.util.stream.Collectors;
+
+
+class Foo {
+  private static void foo(final Function<String, ?> compose) {
+    Collector<String, ?, ? extends Map<?, ArrayList<String>>> stringMapCollector =
+      Collectors.groupingBy(compose, Collector.of(() -> new ArrayList<String>(), null, null, s -> new ArrayList<>(s)));
+  }
+}

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

@@ -155,6 +155,7 @@ public class NewLambdaHighlightingTest extends LightDaemonAnalyzerTestCase {
   public void testGroundTargetTypeWhenAbstractMethodInSuperclass() { doTest(); }
   public void testNestedLambdasWithInferenceOfReturnTypeInTheLatestLambda() { doTest(); }
   public void testCapturedWildcardNotOpenedDuringInference() { doTest(); }
+  public void testIgnoreStandaloneExpressionsInLambdaReturnForNestedCalls() { doTest(); }
 
   private void doTest() {
     IdeaTestUtil.setTestVersion(JavaSdkVersion.JDK_1_8, getModule(), getTestRootDisposable());