From d8595269f4d4b50eed332e10f269eca48b8229df Mon Sep 17 00:00:00 2001
From: Anna Kozlova <anna.kozlova@jetbrains.com>
Date: Thu, 15 Jun 2017 11:42:09 +0300
Subject: [PATCH] extract method: show conflict for same parameter names
 (IDEA-174452)

---
 .../extractMethod/ExtractMethodDialog.java        | 15 +++++++++++++++
 .../IntroduceFunctionalVariableHandler.java       |  6 ++++++
 2 files changed, 21 insertions(+)

diff --git a/java/java-impl/src/com/intellij/refactoring/extractMethod/ExtractMethodDialog.java b/java/java-impl/src/com/intellij/refactoring/extractMethod/ExtractMethodDialog.java
index 083df697eb10..ff020302affe 100644
--- a/java/java-impl/src/com/intellij/refactoring/extractMethod/ExtractMethodDialog.java
+++ b/java/java-impl/src/com/intellij/refactoring/extractMethod/ExtractMethodDialog.java
@@ -54,6 +54,8 @@ import javax.swing.border.Border;
 import java.awt.*;
 import java.awt.event.FocusAdapter;
 import java.awt.event.FocusEvent;
+import java.util.HashSet;
+import java.util.Set;
 
 
 /**
@@ -607,11 +609,13 @@ public class ExtractMethodDialog extends DialogWrapper implements AbstractExtrac
   }
 
   protected void checkMethodConflicts(MultiMap<PsiElement, String> conflicts) {
+    checkParametersConflicts(conflicts);
     PsiMethod prototype;
     try {
       PsiElementFactory factory = JavaPsiFacade.getInstance(myProject).getElementFactory();
       prototype = factory.createMethod(myNameField.getEnteredName().trim(), myReturnType);
       if (myTypeParameterList != null) prototype.getTypeParameterList().replace(myTypeParameterList);
+      Set<String> usedNames = new HashSet<>(); 
       for (VariableData data : myInputVariables) {
         if (data.passAsParameter) {
           prototype.getParameterList().add(factory.createParameter(data.name, data.type));
@@ -626,6 +630,17 @@ public class ExtractMethodDialog extends DialogWrapper implements AbstractExtrac
     ConflictsUtil.checkMethodConflicts(myTargetClass, null, prototype, conflicts);
   }
 
+  protected void checkParametersConflicts(MultiMap<PsiElement, String> conflicts) {
+    Set<String> usedNames = new HashSet<>();
+    for (VariableData data : myInputVariables) {
+      if (data.passAsParameter) {
+        if (!usedNames.add(data.name)) {
+          conflicts.putValue(null, "Conflicting parameter name: " + data.name);
+        }
+      }
+    }
+  }
+
   @Override
   public PsiType getReturnType() {
     return mySelector != null ? mySelector.getSelectedType() : myReturnType;
diff --git a/java/java-impl/src/com/intellij/refactoring/introduceVariable/IntroduceFunctionalVariableHandler.java b/java/java-impl/src/com/intellij/refactoring/introduceVariable/IntroduceFunctionalVariableHandler.java
index c907f87d3337..7bfc7722d493 100644
--- a/java/java-impl/src/com/intellij/refactoring/introduceVariable/IntroduceFunctionalVariableHandler.java
+++ b/java/java-impl/src/com/intellij/refactoring/introduceVariable/IntroduceFunctionalVariableHandler.java
@@ -43,6 +43,7 @@ import com.intellij.refactoring.util.RefactoringChangeUtil;
 import com.intellij.refactoring.util.RefactoringUtil;
 import com.intellij.refactoring.util.VariableData;
 import com.intellij.util.containers.ContainerUtil;
+import com.intellij.util.containers.MultiMap;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
@@ -274,6 +275,11 @@ public class IntroduceFunctionalVariableHandler extends IntroduceVariableHandler
           return "(" + parametersList + ") -> " + returnTypeString;
         }
 
+        @Override
+        protected void checkMethodConflicts(MultiMap<PsiElement, String> conflicts) {
+          checkParametersConflicts(conflicts);
+        }
+
         @NotNull
         @Override
         public String getVisibility() {