method refs: missed qualifier substitution for return type (IDEA-140539)

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

@@ -184,7 +184,7 @@ public class PsiMethodReferenceCompatibilityConstraint implements ConstraintForm
           //the constraint reduces to the bound set B3 which would be used to determine the method reference's invocation type 
           //when targeting the return type of the function type, as defined in 18.5.2.
           session.collectApplicabilityConstraints(myExpression, ((MethodCandidateInfo)resolve), groundTargetType);
-          session.registerReturnTypeConstraints(referencedMethodReturnType, returnType);
+          session.registerReturnTypeConstraints(psiSubstitutor.substitute(referencedMethodReturnType), returnType);
           return true;
         }
       }

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

@@ -0,0 +1,10 @@
+import java.util.function.Function;
+
+class Test {
+
+  private void foo(final Function<String, String> steps) {
+    map(steps::compose);
+  }
+
+  <U> void map(Function<Function<String, String>,  U> mapper) {}
+}

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

@@ -402,6 +402,10 @@ public class NewMethodRefHighlightingTest extends LightDaemonAnalyzerTestCase {
     doTest();
   }
 
+  public void testSubstitutionForReturnTypeConstraintsForTargetGenericMethod() throws Exception {
+    doTest();
+  }
+
   private void doTest() {
     doTest(false);
   }