fix corner case in ie (#5652)

fixes #5651

Author: alexlamsl

lib/scope.js

@@ -369,8 +369,9 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options) {
     // pass 3: fix up any scoping issue with IE8
     if (options.ie) self.walk(new TreeWalker(function(node) {
         if (node instanceof AST_SymbolCatch) {
-            var scope = node.thedef.defun;
-            if (scope.name instanceof AST_SymbolLambda && scope.name.name == node.name) {
+            var def = node.thedef;
+            var scope = def.defun;
+            if (def.name != "arguments" && scope.name instanceof AST_SymbolLambda && scope.name.name == def.name) {
                 scope = scope.parent_scope.resolve();
             }
             redefine(node, scope);

test/compress/default-values.js

@@ -3044,3 +3044,28 @@ issue_5566_5: {
     expect_stdout: "foo bar"
     node_version: ">=6"
 }
+
+issue_5651: {
+    options = {
+        ie: true,
+        unused: true,
+    }
+    input: {
+        console.log(function arguments(a = "FAIL") {
+            try {} catch (arguments) {
+                var arguments;
+            }
+            return arguments[0];
+        }());
+    }
+    expect: {
+        console.log(function arguments(a = "FAIL") {
+            try {} catch (arguments) {
+                var arguments;
+            }
+            return arguments[0];
+        }());
+    }
+    expect_stdout: true
+    node_version: ">=6"
+}

test/compress/destructured.js

@@ -3844,3 +3844,28 @@ issue_5573: {
     ]
     node_version: ">=6"
 }
+
+issue_5651: {
+    options = {
+        ie: true,
+        unused: true,
+    }
+    input: {
+        console.log(function arguments({}) {
+            try {} catch (arguments) {
+                var arguments;
+            }
+            return arguments[0];
+        }("PASS"));
+    }
+    expect: {
+        console.log(function arguments({}) {
+            try {} catch (arguments) {
+                var arguments;
+            }
+            return arguments[0];
+        }("PASS"));
+    }
+    expect_stdout: true
+    node_version: ">=6"
+}