Fixes palantir#372 -- remove additonal false positives

Skip method signatures and catch clause variable declarations

src/rules/noDuplicateVariableRule.ts

@@ -46,6 +46,16 @@ class NoDuplicateVariableWalker extends Lint.ScopeAwareRuleWalker<ScopeInfo> {
         // don't call super, we don't want to walk the inside of type nodes
     }
 
+    public visitMethodSignature(node: ts.SignatureDeclaration): void {
+        // don't call super, we don't want to walk method signatures either
+    }
+
+    public visitCatchClause(node: ts.CatchClause): void {
+        // don't visit the catch clause variable declaration, just visit the block
+        // the catch clause variable declaration has its own special scoping rules
+        this.visitBlock(node.block);
+    }
+
     public visitVariableDeclaration(node: ts.VariableDeclaration): void {
         var propertyName = <ts.Identifier> node.name;
         var variableName = propertyName.text;

test/files/rules/duplicate-variable.test.ts

@@ -109,3 +109,23 @@ var dependents: {[vertex: string]: any};
 
 function blah(arg1: {[key: string]: any, arg2: {[key:string]: any}) {
 }
+
+export interface IClipboard {
+    copy(key: string, state: any): void;
+    paste(key: string): any;
+    findMaxOrMin(values: any[], defaultValue: number, operation: (...values: any[]) => number)
+}
+
+try {
+    //
+} catch (e) {
+    e.blah();
+    //
+}
+
+try {
+    //
+} catch (e) {
+    e.blah();
+    //
+}