diff --git a/java/java-analysis-impl/src/com/intellij/codeInspection/AnonymousCanBeLambdaInspection.java b/java/java-analysis-impl/src/com/intellij/codeInspection/AnonymousCanBeLambdaInspection.java
index 93e4951fd534..a5558660cbe1 100644
--- a/java/java-analysis-impl/src/com/intellij/codeInspection/AnonymousCanBeLambdaInspection.java
+++ b/java/java-analysis-impl/src/com/intellij/codeInspection/AnonymousCanBeLambdaInspection.java
@@ -77,8 +77,7 @@ public class AnonymousCanBeLambdaInspection extends BaseJavaBatchLocalInspection
         super.visitAnonymousClass(aClass);
         if (PsiUtil.getLanguageLevel(aClass).isAtLeast(LanguageLevel.JDK_1_8)) {
           final PsiClassType baseClassType = aClass.getBaseClassType();
-          final String functionalInterfaceErrorMessage = LambdaHighlightingUtil.checkInterfaceFunctional(baseClassType);
-          if (functionalInterfaceErrorMessage == null) {
+          if (LambdaUtil.isFunctionalType(baseClassType)) {
             final PsiMethod[] methods = aClass.getMethods();
             if (methods.length == 1 && aClass.getFields().length == 0) {
               final PsiCodeBlock body = methods[0].getBody();
@@ -288,9 +287,7 @@ public class AnonymousCanBeLambdaInspection extends BaseJavaBatchLocalInspection
     }
 
     private static boolean isInferred(PsiLambdaExpression lambdaExpression, PsiType interfaceType) {
-      return interfaceType == null || !LambdaUtil.isLambdaFullyInferred(lambdaExpression, interfaceType) || LambdaHighlightingUtil
-                                                                                                              .checkInterfaceFunctional(
-                                                                                                                interfaceType) != null;
+      return interfaceType == null || !LambdaUtil.isLambdaFullyInferred(lambdaExpression, interfaceType) || !LambdaUtil.isFunctionalType(interfaceType);
     }
 
     private static String composeLambdaText(PsiMethod method, final boolean appendType) {
diff --git a/java/java-analysis-impl/src/com/intellij/codeInspection/AnonymousCanBeMethodReferenceInspection.java b/java/java-analysis-impl/src/com/intellij/codeInspection/AnonymousCanBeMethodReferenceInspection.java
index 558c3c0cef43..6ad6d223b5a0 100644
--- a/java/java-analysis-impl/src/com/intellij/codeInspection/AnonymousCanBeMethodReferenceInspection.java
+++ b/java/java-analysis-impl/src/com/intellij/codeInspection/AnonymousCanBeMethodReferenceInspection.java
@@ -67,8 +67,7 @@ public class AnonymousCanBeMethodReferenceInspection extends BaseJavaBatchLocalI
         super.visitAnonymousClass(aClass);
         if (PsiUtil.getLanguageLevel(aClass).isAtLeast(LanguageLevel.JDK_1_8)) {
           final PsiClassType baseClassType = aClass.getBaseClassType();
-          final String functionalInterfaceErrorMessage = LambdaHighlightingUtil.checkInterfaceFunctional(baseClassType);
-          if (functionalInterfaceErrorMessage == null) {
+          if (LambdaUtil.isFunctionalType(baseClassType)) {
             final PsiMethod[] methods = aClass.getMethods();
             if (methods.length == 1 && aClass.getFields().length == 0) {
               final PsiCodeBlock body = methods[0].getBody();
diff --git a/java/java-impl/src/com/intellij/codeInsight/completion/LambdaCompletionProvider.java b/java/java-impl/src/com/intellij/codeInsight/completion/LambdaCompletionProvider.java
index 8073d1b6a270..386c8a2296c6 100644
--- a/java/java-impl/src/com/intellij/codeInsight/completion/LambdaCompletionProvider.java
+++ b/java/java-impl/src/com/intellij/codeInsight/completion/LambdaCompletionProvider.java
@@ -40,7 +40,7 @@ public class LambdaCompletionProvider extends CompletionProvider<CompletionParam
     final ExpectedTypeInfo[] expectedTypes = JavaSmartCompletionContributor.getExpectedTypes(parameters);
     for (ExpectedTypeInfo expectedType : expectedTypes) {
       final PsiType defaultType = expectedType.getDefaultType();
-      if (LambdaHighlightingUtil.checkInterfaceFunctional(defaultType) == null) {
+      if (LambdaUtil.isFunctionalType(defaultType)) {
         final PsiMethod method = LambdaUtil.getFunctionalInterfaceMethod(defaultType);
         if (method != null) {
           final PsiParameter[] params = method.getParameterList().getParameters();
diff --git a/java/java-impl/src/com/intellij/codeInsight/completion/MethodReferenceCompletionProvider.java b/java/java-impl/src/com/intellij/codeInsight/completion/MethodReferenceCompletionProvider.java
index dbd2fc8ef3c6..f0605676005b 100644
--- a/java/java-impl/src/com/intellij/codeInsight/completion/MethodReferenceCompletionProvider.java
+++ b/java/java-impl/src/com/intellij/codeInsight/completion/MethodReferenceCompletionProvider.java
@@ -19,9 +19,8 @@ import com.intellij.codeInsight.ExpectedTypeInfo;
 import com.intellij.codeInsight.ExpectedTypeInfoImpl;
 import com.intellij.codeInsight.TailType;
 import com.intellij.codeInsight.lookup.LookupElement;
-import com.intellij.codeInsight.lookup.LookupElementBuilder;
-import com.intellij.psi.*;
-import com.intellij.psi.filters.ElementFilter;
+import com.intellij.psi.LambdaUtil;
+import com.intellij.psi.PsiType;
 import com.intellij.psi.util.PsiUtil;
 import com.intellij.util.Consumer;
 import com.intellij.util.ProcessingContext;
@@ -36,7 +35,7 @@ public class MethodReferenceCompletionProvider extends CompletionProvider<Comple
     final ExpectedTypeInfo[] expectedTypes = JavaSmartCompletionContributor.getExpectedTypes(parameters);
     for (ExpectedTypeInfo expectedType : expectedTypes) {
       final PsiType defaultType = expectedType.getDefaultType();
-      if (LambdaHighlightingUtil.checkInterfaceFunctional(defaultType) == null) {
+      if (LambdaUtil.isFunctionalType(defaultType)) {
         final PsiType returnType = LambdaUtil.getFunctionalInterfaceReturnType(defaultType);
         if (returnType != null) {
           final ExpectedTypeInfoImpl typeInfo =
diff --git a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/InputOutputConstraintFormula.java b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/InputOutputConstraintFormula.java
index e4090894e124..0a49428722a1 100644
--- a/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/InputOutputConstraintFormula.java
+++ b/java/java-psi-impl/src/com/intellij/psi/impl/source/resolve/graphInference/constraints/InputOutputConstraintFormula.java
@@ -49,7 +49,7 @@ public abstract class InputOutputConstraintFormula implements ConstraintFormula
       if (inferenceVariable != null) {
         return Collections.singleton(inferenceVariable);
       }
-      if (LambdaHighlightingUtil.checkInterfaceFunctional(type) == null) {
+      if (LambdaUtil.isFunctionalType(type)) {
         final PsiType functionType =
           psiExpression instanceof PsiLambdaExpression
           ? FunctionalInterfaceParameterizationUtil.getGroundTargetType(type, (PsiLambdaExpression)psiExpression)
diff --git a/plugins/IntentionPowerPak/src/com/siyeh/ipp/types/ReplaceLambdaWithAnonymousIntention.java b/plugins/IntentionPowerPak/src/com/siyeh/ipp/types/ReplaceLambdaWithAnonymousIntention.java
index 7a31564ca981..fbd948aaf420 100644
--- a/plugins/IntentionPowerPak/src/com/siyeh/ipp/types/ReplaceLambdaWithAnonymousIntention.java
+++ b/plugins/IntentionPowerPak/src/com/siyeh/ipp/types/ReplaceLambdaWithAnonymousIntention.java
@@ -155,7 +155,7 @@ public class ReplaceLambdaWithAnonymousIntention extends Intention {
         return functionalInterfaceType != null &&
                LambdaUtil.getFunctionalInterfaceMethod(functionalInterfaceType) != null &&
                LambdaUtil.isLambdaFullyInferred(lambdaExpression, functionalInterfaceType) &&
-               LambdaHighlightingUtil.checkInterfaceFunctional(functionalInterfaceType) == null;
+               LambdaUtil.isFunctionalType(functionalInterfaceType);
       }
       return false;
     }