Don't drop unused if scope uses with statement

Fix provided by @kzc

lib/compress.js

@@ -1326,6 +1326,7 @@ merge(Compressor.prototype, {
         if (compressor.option("unused")
             && !(self instanceof AST_Toplevel)
             && !self.uses_eval
+            && !self.uses_with
            ) {
             var in_use = [];
             var in_use_ids = {}; // avoid expensive linear scans of in_use

test/compress/issue-1105.js

@@ -0,0 +1,147 @@
+with_in_global_scope: {
+    options = {
+        unused: true
+    }
+    input: {
+        var o = 42;
+        with(o) {
+            var foo = 'something'
+        }
+        doSomething(o);
+    }
+    expect: {
+        var o=42;
+        with(o)
+            var foo = "something";
+        doSomething(o);
+    }
+}
+with_in_function_scope: {
+    options = {
+        unused: true
+    }
+    input: {
+        function foo() {
+            var o = 42;
+            with(o) {
+                var foo = "something"
+            }
+            doSomething(o);
+        }
+    }
+    expect: {
+        function foo() {
+            var o=42;
+            with(o)
+                var foo = "something";
+            doSomething(o)
+        }
+    }
+}
+compress_with_with_in_other_scope: {
+    options = {
+        unused: true
+    }
+    input: {
+        function foo() {
+            var o = 42;
+            with(o) {
+                var foo = "something"
+            }
+            doSomething(o);
+        }
+        function bar() {
+            var unused = 42;
+            return something();
+        }
+    }
+    expect: {
+        function foo() {
+            var o = 42;
+            with(o)
+                var foo = "something";
+            doSomething(o)
+        }
+        function bar() {
+            return something()
+        }
+    }
+}
+with_using_existing_variable_outside_scope: {
+    options = {
+        unused: true
+    }
+    input: {
+        function f() {
+            var o = {};
+            var unused = {}; // Doesn't get removed because upper scope uses with
+            function foo() {
+                with(o) {
+                    var foo = "something"
+                }
+                doSomething(o);
+            }
+            foo()
+        }
+    }
+    expect: {
+        function f() {
+            var o = {};
+            var unused = {};
+            function foo() {
+                with(o)
+                    var foo = "something";
+                doSomething(o)
+            }
+            foo()
+        }
+    }
+}
+check_drop_unused_in_peer_function: {
+    options = {
+        unused: true
+    }
+    input: {
+        function outer() {
+            var o = {};
+            var unused = {};     // should be kept
+            function foo() {     // should be kept
+                function not_in_use() {
+                    var nested_unused = "foo"; // should be dropped
+                    return 24;
+                }
+                var unused = {}; // should be kept
+                with (o) {
+                    var foo = "something";
+                }
+                doSomething(o);
+            }
+            function bar() {
+                var unused = {}; // should be dropped
+                doSomethingElse();
+            }
+            foo();
+            bar();
+        }
+    }
+    expect: {
+        function outer() {
+            var o = {};
+            var unused = {};     // should be kept
+            function foo() {     // should be kept
+                function not_in_use() {
+                    return 24;
+                }
+                var unused = {}; // should be kept
+                with (o)
+                    var foo = "something";
+                doSomething(o);
+            }
+            function bar() {
+                doSomethingElse();
+            }
+            foo();
+            bar();
+        }
+    }
+}