FIX for bug 256242: Extract local variable refactoring doesn't avoid variable name collisions by Tom Ball https://bugs.eclipse.org/bugs/show_bug.cgi?id=256242

core/org.eclipse.cdt.ui.tests/resources/refactoring/ExtractLocalVariable.rts

@@ -250,3 +250,68 @@ int A::foo()
     return i;
 }
 
+//!ExtractLocalVariableRefactoringTest proposed name in scope
+//#org.eclipse.cdt.ui.tests.refactoring.extractlocalvariable.ExtractLocalVariableRefactoringTest
+//@A.h
+#ifndef A_H_
+#define A_H_
+
+class A
+{
+public:
+  A();
+  virtual ~A();
+  int foo();
+};
+
+#endif /*A_H_*/
+
+//=
+#ifndef A_H_
+#define A_H_
+
+class A
+{
+public:
+  A();
+  virtual ~A();
+  int foo();
+};
+
+#endif /*A_H_*/
+
+//@A.cpp
+#include "A.h"
+
+A::A()
+{
+}
+
+A::~A()
+{
+}
+
+int A::foo()
+{
+  int x = 3;
+  return /*$*/(x + 2)/*$$*/ * 15;
+}
+
+//=
+#include "A.h"
+
+A::A()
+{
+}
+
+A::~A()
+{
+}
+
+int A::foo()
+{
+  int x = 3;
+    int i = x + 2;
+    return i * 15;
+}
+

core/org.eclipse.cdt.ui/src/org/eclipse/cdt/internal/ui/refactoring/extractlocalvariable/ExtractLocalVariableRefactoring.java

@@ -23,6 +23,8 @@ import org.eclipse.jface.viewers.ISelection;
 import org.eclipse.ltk.core.refactoring.RefactoringStatus;
 import org.eclipse.text.edits.TextEditGroup;
 
+import org.eclipse.cdt.core.dom.ast.DOMException;
+import org.eclipse.cdt.core.dom.ast.IASTCompoundStatement;
 import org.eclipse.cdt.core.dom.ast.IASTDeclSpecifier;
 import org.eclipse.cdt.core.dom.ast.IASTDeclaration;
 import org.eclipse.cdt.core.dom.ast.IASTDeclarationStatement;
@@ -38,6 +40,7 @@ import org.eclipse.cdt.core.dom.ast.IASTSimpleDeclaration;
 import org.eclipse.cdt.core.dom.ast.IASTStatement;
 import org.eclipse.cdt.core.dom.ast.IASTUnaryExpression;
 import org.eclipse.cdt.core.dom.ast.IBinding;
+import org.eclipse.cdt.core.dom.ast.IScope;
 import org.eclipse.cdt.core.dom.ast.cpp.CPPASTVisitor;
 import org.eclipse.cdt.core.dom.ast.cpp.ICPPASTCompositeTypeSpecifier;
 import org.eclipse.cdt.core.dom.rewrite.ASTRewrite;
@@ -49,7 +52,7 @@ import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPASTInitializerExpression;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPASTLiteralExpression;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPASTName;
 import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPASTSimpleDeclaration;
-import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPMethod;
+import org.eclipse.cdt.internal.core.dom.parser.cpp.CPPFunction;
 
 import org.eclipse.cdt.internal.ui.refactoring.CRefactoring;
 import org.eclipse.cdt.internal.ui.refactoring.ModificationCollector;
@@ -149,16 +152,17 @@ public class ExtractLocalVariableRefactoring extends CRefactoring {
 		if (funcDef != null) {
 			IBinding binding = funcDef.getDeclarator().getName()
 					.resolveBinding();
-			if (binding instanceof CPPMethod) {
+			if (binding instanceof CPPFunction) {
 
-				CPPMethod method = (CPPMethod) binding;
+				CPPFunction function = (CPPFunction) binding;
-				IASTNode decl = method.getDeclarations()[0];
+				IASTNode[] decls = function.getDeclarations();
-
+				if (decls != null && decls.length > 0) {
-				IASTNode spec = decl.getParent().getParent();
+					IASTNode spec = decls[0].getParent().getParent();
-				if (spec instanceof ICPPASTCompositeTypeSpecifier) {
+					if (spec instanceof ICPPASTCompositeTypeSpecifier) {
-					ICPPASTCompositeTypeSpecifier compTypeSpec = 
+						ICPPASTCompositeTypeSpecifier compTypeSpec =
-						(ICPPASTCompositeTypeSpecifier) spec;
+							(ICPPASTCompositeTypeSpecifier) spec;
-					return compTypeSpec;
+						return compTypeSpec;
+					}
 				}
 			}
 		}
@@ -310,6 +314,18 @@ public class ExtractLocalVariableRefactoring extends CRefactoring {
 	 */
 	public String[] guessTempNames() {
 		final List<String> guessedTempNames = new ArrayList<String>();
+		final List<String> usedNames = new ArrayList<String>();
+		IASTFunctionDefinition funcDef = NodeHelper
+			.findFunctionDefinitionInAncestors(target);
+		final IScope scope;
+		if (funcDef != null &&
+				funcDef.getBody() instanceof IASTCompoundStatement) {
+			IASTCompoundStatement body = (IASTCompoundStatement)funcDef.getBody();
+			scope = body.getScope();
+		} else {
+			scope = null;
+		}
+
 		if (target != null) {
 			target.accept(new CPPASTVisitor() {
 				{
@@ -366,13 +382,51 @@ public class ExtractLocalVariableRefactoring extends CRefactoring {
 						}
 					}
 					name = new String(tmpName, 0, len);
-					if (name.length() > 0 && !guessedTempNames.contains(name) && 
+					if (name.length() > 0) {
-							!info.getUsedNames().contains(name)) {
+						if (nameAvailable(name, guessedTempNames, scope)) {
 							guessedTempNames.add(name);
+						} else {
+							usedNames.add(name);
+						}
 					}
 				}
 			});
 		}
+		if (guessedTempNames.isEmpty()) {
+			String name = makeTempName(usedNames, scope);
+			if (name != null) {
+				guessedTempNames.add(name);
+			}
+		}
 		return guessedTempNames.toArray(new String[0]);
 	}
+
+	private boolean nameAvailable(String name, List<String> guessedNames, IScope scope) {
+		if (guessedNames.contains(name) ||
+				info.getUsedNames().contains(name)) {
+			return false;
+		}
+		try {
+			if (scope != null) {
+				IBinding[] bindings = scope.find(name);
+				return bindings == null || bindings.length == 0;
+			}
+		} catch (DOMException e) {
+			// fall-through
+		}
+		return true; // no name references found
+	}
+
+	private String makeTempName(List<String> usedNames, IScope scope) {
+		List<String> noNames = new ArrayList<String>();
+		for (int i = 0; i < 10; i++) {
+			for (String used : usedNames) {
+				String name = used + i;   // such as "i2"
+				if (nameAvailable(name, noNames, scope)) {
+					return name;
+				}
+			}
+		}
+		return null;
+	}
 }