introduce variable from lambda expression

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

@@ -117,7 +117,8 @@ public class LambdaUtil {
       final int parameterIndex = ((PsiParameterList)paramParent).getParameterIndex(param);
       if (parameterIndex > -1) {
         final PsiLambdaExpression lambdaExpression = PsiTreeUtil.getParentOfType(param, PsiLambdaExpression.class);
-        final PsiClassType.ClassResolveResult resolveResult = getFunctionInterfaceType(lambdaExpression);
+        final PsiType type = getFunctionInterfaceType(lambdaExpression);
+        final PsiClassType.ClassResolveResult resolveResult = type instanceof PsiClassType ? ((PsiClassType)type).resolveGenerics() : null;
         if (resolveResult != null) {
           final MethodSignature methodSignature = getFunction(resolveResult.getElement());
           if (methodSignature != null) {
@@ -140,7 +141,7 @@ public class LambdaUtil {
   }
 
   @Nullable
-  public static PsiClassType.ClassResolveResult getFunctionInterfaceType(@Nullable PsiLambdaExpression lambdaExpression) {
+  public static PsiType getFunctionInterfaceType(@Nullable PsiLambdaExpression lambdaExpression) {
     if (lambdaExpression != null) {
       final PsiElement parent = lambdaExpression.getParent();
       PsiType type = null;
@@ -177,10 +178,7 @@ public class LambdaUtil {
           type = method.getReturnType();
         }
       }
-
-      if (type instanceof PsiClassType) {
-        return ((PsiClassType)type).resolveGenerics();
-      }
+      return type;
     }
     return null;
   }

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

@@ -57,7 +57,7 @@ public class PsiLambdaExpressionType extends PsiType {
 
   @Override
   public <A> A accept(@NotNull final PsiTypeVisitor<A> visitor) {
-    return visitor.visitType(this);
+    return visitor.visitLambdaExpressionType(this);
   }
 
   @Override

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

@@ -67,4 +67,9 @@ public class PsiTypeVisitor<A> {
   public A visitDiamondType(PsiDiamondType diamondType) {
     return visitType(diamondType);
   }
+  
+  @Nullable
+  public A visitLambdaExpressionType(PsiLambdaExpressionType lambdaExpressionType) {
+    return visitType(LambdaUtil.getFunctionInterfaceType(lambdaExpressionType.getExpression()));
+  }
 }