extract method: suggested names for folded params should be unique (IDEA-120974)

java/java-analysis-impl/src/com/intellij/refactoring/extractMethod/ParametersFolder.java

@@ -140,7 +140,7 @@ public class ParametersFolder {
       if (nameInfo.names.length > 0) {
         data.name = nameInfo.names[0];
       }
-      setUniqueName(data);
+      setUniqueName(data, scope, mostRanked);
     }
 
     return mostRanked != null;
@@ -165,12 +165,19 @@ public class ParametersFolder {
     return false;
   }
 
-  private void setUniqueName(VariableData data) {
+  private void setUniqueName(VariableData data, LocalSearchScope scope, PsiExpression expr) {
+    String name = data.name;
     int idx = 1;
-    while (myUsedNames.contains(data.name)) {
-      data.name += idx;
+    while (true) {
+      if (myUsedNames.add(name)) {
+        final PsiVariable definedVariable = PsiResolveHelper.SERVICE.getInstance(expr.getProject()).resolveReferencedVariable(name, expr);
+        if (definedVariable == null || !scope.containsRange(expr.getContainingFile(), definedVariable.getTextRange())) {
+          data.name = name;
+          break;
+        }
+      }
+      name = data.name + idx++;
     }
-    myUsedNames.add(data.name);
   }
 
   private static Set<PsiVariable> findUsedVariables(VariableData data, final List<? extends PsiVariable> inputVariables,

java/java-tests/testData/refactoring/extractMethod/FoldedParamNameSuggestion.java

@@ -0,0 +1,6 @@
+class Test {
+    String get(String[] args) {
+        <selection>String arg = args[0];
+        return arg;</selection>
+    }
+}

java/java-tests/testData/refactoring/extractMethod/FoldedParamNameSuggestion_after.java

@@ -0,0 +1,10 @@
+class Test {
+    String get(String[] args) {
+        return newMethod(args[0]);
+    }
+
+    private String newMethod(String arg1) {
+        String arg = arg1;
+        return arg;
+    }
+}

java/java-tests/testSrc/com/intellij/refactoring/ExtractMethodTest.java

@@ -523,6 +523,10 @@ public class ExtractMethodTest extends LightCodeInsightTestCase {
     doTest();
   }
 
+  public void testFoldedParamNameSuggestion() throws Exception {
+    doTest();
+  }
+
   public void testNonFoldInIfBody() throws Exception {
     doTest();
   }