fix corner case with arguments as function name (#2729)

fixes #2728

lib/scope.js

@@ -151,7 +151,7 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
             node.references = [];
         }
         if (node instanceof AST_SymbolLambda) {
-            defun.def_function(node, defun);
+            defun.def_function(node, node.name == "arguments" ? undefined : defun);
         }
         else if (node instanceof AST_SymbolDefun) {
             // Careful here, the scope where this should be defined is

test/compress/typeof.js

@@ -178,3 +178,126 @@ duplicate_lambda_arg_name: {
     }
     expect_stdout: "undefined"
 }
+
+issue_2728_1: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        typeofs: true,
+    }
+    input: {
+        (function arguments() {
+            console.log(typeof arguments);
+        })();
+    }
+    expect: {
+        (function arguments() {
+            console.log(typeof arguments);
+        })();
+    }
+    expect_stdout: "object"
+}
+
+issue_2728_2: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        typeofs: true,
+    }
+    input: {
+        function arguments() {
+            return typeof arguments;
+        }
+        console.log(typeof arguments, arguments());
+    }
+    expect: {
+        function arguments() {
+            return typeof arguments;
+        }
+        console.log(typeof arguments, arguments());
+    }
+    expect_stdout: "function object"
+}
+
+issue_2728_3: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        typeofs: true,
+    }
+    input: {
+        (function() {
+            function arguments() {
+            }
+            console.log(typeof arguments);
+        })();
+    }
+    expect: {
+        (function() {
+            function arguments() {
+            }
+            console.log("function");
+        })();
+    }
+    expect_stdout: "function"
+}
+
+issue_2728_4: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        toplevel: true,
+        typeofs: true,
+    }
+    input: {
+        function arguments() {
+        }
+        console.log(typeof arguments);
+    }
+    expect: {
+        function arguments() {
+        }
+        console.log("function");
+    }
+    expect_stdout: "function"
+}
+
+issue_2728_5: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        typeofs: true,
+    }
+    input: {
+        (function arguments(arguments) {
+            console.log(typeof arguments);
+        })();
+    }
+    expect: {
+        (function arguments(arguments) {
+            console.log(typeof arguments);
+        })();
+    }
+    expect_stdout: "undefined"
+}
+
+issue_2728_6: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        typeofs: true,
+    }
+    input: {
+        function arguments(arguments) {
+            return typeof arguments;
+        }
+        console.log(typeof arguments, arguments());
+    }
+    expect: {
+        function arguments(arguments) {
+            return typeof arguments;
+        }
+        console.log(typeof arguments, arguments());
+    }
+    expect_stdout: "function undefined"
+}