method refs: ensure inference from captured return type (IDEA-145152)

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

@@ -197,8 +197,9 @@ public class PsiMethodReferenceCompatibilityConstraint implements ConstraintForm
         }
       }
 
-      constraints.add(new TypeCompatibilityConstraint(returnType,
-                                                      session.substituteWithInferenceVariables(psiSubstitutor.substitute(referencedMethodReturnType))));
+      final PsiType capturedReturnType = PsiImplUtil.normalizeWildcardTypeByPosition(psiSubstitutor.substitute(referencedMethodReturnType),
+                                                                                     myExpression);
+      constraints.add(new TypeCompatibilityConstraint(returnType, session.substituteWithInferenceVariables(capturedReturnType)));
     }
     
     return true;

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/newMethodRef/CapturedReturnTypeOfMethodReference.java

@@ -0,0 +1,12 @@
+import java.util.stream.Stream;
+class Test {
+
+  void foo(final Stream<StubElement<?>> inStream){
+    inStream.map(StubElement::getPsi)
+      .map(s -> s.length());
+  }
+
+  class StubElement<T extends String> {
+    T getPsi() {return null;}
+  }
+}

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

@@ -426,6 +426,10 @@ public class NewMethodRefHighlightingTest extends LightDaemonAnalyzerTestCase {
     doTest();
   }
 
+  public void testCapturedReturnTypeOfMethodReference() throws Exception {
+    doTest();
+  }
+
   private void doTest() {
     doTest(false);
   }