lambda: accept intersection type when exactly one conjunct is functional

java/java-psi-api/src/com/intellij/psi/LambdaHighlightingUtil.java

@@ -97,18 +97,17 @@ public class LambdaHighlightingUtil {
   @Nullable
   public static String checkInterfaceFunctional(PsiType functionalInterfaceType) {
     if (functionalInterfaceType instanceof PsiIntersectionType) {
-      if (!LambdaUtil.isFunctionalType(functionalInterfaceType)) {
-        int count = 0;
-        for (PsiType type : ((PsiIntersectionType)functionalInterfaceType).getConjuncts()) {
-          if (checkInterfaceFunctional(type) == null) {
-            count++;
-          }
-        }
-
-        if (count > 1) {
-          return "Multiple non-overriding abstract methods found in " + functionalInterfaceType.getPresentableText();
+      int count = 0;
+      for (PsiType type : ((PsiIntersectionType)functionalInterfaceType).getConjuncts()) {
+        if (checkInterfaceFunctional(type) == null) {
+          count++;
         }
       }
+
+      if (count > 1) {
+        return "Multiple non-overriding abstract methods found in " + functionalInterfaceType.getPresentableText();
+      }
+      return null;
     }
     final PsiClassType.ClassResolveResult resolveResult = PsiUtil.resolveGenericsClassInType(functionalInterfaceType);
     final PsiClass aClass = resolveResult.getElement();

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/lambda/highlighting/Intersection.java

@@ -18,3 +18,18 @@ class Test {
     Object o5 = (Runnable & A) <error descr="Multiple non-overriding abstract methods found in Runnable & A">() -> {}</error>;
   }
 }
+
+class Test1 {
+
+  interface A {
+    <X> void foo();
+  }
+
+  interface B {
+    void foo();
+  }
+
+  {
+    Object c0 = (A & B) ()->{};
+  }
+}