fix `pure_funcs` & improve `side_effects`

- only drops side-effect-free arguments
- drop side-effect-free parts with discarded value from `AST_Seq` & `AST_SimpleStatement`

closes #1494

2 files changed, 353 insertions, 0 deletions

diff --git a/test/compress/drop-unused.js b/test/compress/drop-unused.js
index 5a09c6cd..f5a88f21 100644
--- a/test/compress/drop-unused.js
+++ b/test/compress/drop-unused.js
@@ -590,3 +590,61 @@ drop_fnames: {
         }
     }
 }
+
+global_var: {
+    options = {
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        var a;
+        function foo(b) {
+            a;
+            b;
+            c;
+            typeof c === "undefined";
+            c + b + a;
+            b && b.ar();
+            return b;
+        }
+    }
+    expect: {
+        var a;
+        function foo(b) {
+            c;
+            c;
+            b && b.ar();
+            return b;
+        }
+    }
+}
+
+iife: {
+    options = {
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            var a;
+            ~function() {}(b);
+        }
+    }
+    expect: {
+        function f() {
+            ~function() {}(b);
+        }
+    }
+}
+
+drop_value: {
+    options = {
+        side_effects: true,
+    }
+    input: {
+        (1, [2, foo()], 3, {a:1, b:bar()});
+    }
+    expect: {
+        foo(), bar();
+    }
+}
diff --git a/test/compress/pure_funcs.js b/test/compress/pure_funcs.js
new file mode 100644
index 00000000..3cc529a8
--- /dev/null
+++ b/test/compress/pure_funcs.js
@@ -0,0 +1,295 @@
+array: {
+    options = {
+        pure_funcs: [ "Math.floor" ],
+        side_effects: true,
+    }
+    input: {
+        var a;
+        function f(b) {
+            Math.floor(a / b);
+            Math.floor(c / b);
+        }
+    }
+    expect: {
+        var a;
+        function f(b) {
+            c;
+        }
+    }
+}
+
+func: {
+    options = {
+        pure_funcs: function(node) {
+            return !~node.args[0].print_to_string().indexOf("a");
+        },
+        side_effects: true,
+    }
+    input: {
+        function f(a, b) {
+            Math.floor(a / b);
+            Math.floor(c / b);
+        }
+    }
+    expect: {
+        function f(a, b) {
+            Math.floor(c / b);
+        }
+    }
+}
+
+side_effects: {
+    options = {
+        pure_funcs: [ "console.log" ],
+        side_effects: true,
+    }
+    input: {
+        function f(a, b) {
+            console.log(a());
+            console.log(b);
+        }
+    }
+    expect: {
+        function f(a, b) {
+            a();
+        }
+    }
+}
+
+unused: {
+    options = {
+        pure_funcs: [ "pure" ],
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        function foo() {
+            var u = pure(1);
+            var x = pure(2);
+            var y = pure(x);
+            var z = pure(pure(side_effects()));
+            return pure(3);
+        }
+    }
+    expect: {
+        function foo() {
+            side_effects();
+            return pure(3);
+        }
+    }
+}
+
+babel: {
+    options = {
+        pure_funcs: [ "_classCallCheck" ],
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        function _classCallCheck(instance, Constructor) {
+            if (!(instance instanceof Constructor))
+                throw new TypeError("Cannot call a class as a function");
+        }
+        var Foo = function Foo() {
+            _classCallCheck(this, Foo);
+        };
+    }
+    expect: {
+        function _classCallCheck(instance, Constructor) {
+            if (!(instance instanceof Constructor))
+                throw new TypeError("Cannot call a class as a function");
+        }
+        var Foo = function() {
+        };
+    }
+}
+
+conditional: {
+    options = {
+        pure_funcs: [ "pure" ],
+        side_effects: true,
+    }
+    input: {
+        pure(1 | a() ? 2 & b() : 7 ^ c());
+        pure(1 | a() ? 2 & b() : 5);
+        pure(1 | a() ? 4 : 7 ^ c());
+        pure(1 | a() ? 4 : 5);
+        pure(3 ? 2 & b() : 7 ^ c());
+        pure(3 ? 2 & b() : 5);
+        pure(3 ? 4 : 7 ^ c());
+        pure(3 ? 4 : 5);
+    }
+    expect: {
+        1 | a() ? b() : c();
+        1 | a() && b();
+        1 | a() || c();
+        a();
+        3 ? b() : c();
+        3 && b();
+        3 || c();
+    }
+}
+
+relational: {
+    options = {
+        pure_funcs: [ "foo" ],
+        side_effects :true,
+    }
+    input: {
+        foo() in foo();
+        foo() instanceof bar();
+        foo() < "bar";
+        bar() > foo();
+        bar() != bar();
+        bar() !== "bar";
+        "bar" == foo();
+        "bar" === bar();
+        "bar" >= "bar";
+    }
+    expect: {
+        bar();
+        bar();
+        bar(), bar();
+        bar();
+        bar();
+    }
+}
+
+arithmetic: {
+    options = {
+        pure_funcs: [ "foo" ],
+        side_effects :true,
+    }
+    input: {
+        foo() + foo();
+        foo() - bar();
+        foo() * "bar";
+        bar() / foo();
+        bar() & bar();
+        bar() | "bar";
+        "bar" >> foo();
+        "bar" << bar();
+        "bar" >>> "bar";
+    }
+    expect: {
+        bar();
+        bar();
+        bar(), bar();
+        bar();
+        bar();
+    }
+}
+
+boolean_and: {
+    options = {
+        pure_funcs: [ "foo" ],
+        side_effects :true,
+    }
+    input: {
+        foo() && foo();
+        foo() && bar();
+        foo() && "bar";
+        bar() && foo();
+        bar() && bar();
+        bar() && "bar";
+        "bar" && foo();
+        "bar" && bar();
+        "bar" && "bar";
+    }
+    expect: {
+        foo() && bar();
+        bar();
+        bar() && bar();
+        bar();
+        "bar" && bar();
+    }
+}
+
+boolean_or: {
+    options = {
+        pure_funcs: [ "foo" ],
+        side_effects :true,
+    }
+    input: {
+        foo() || foo();
+        foo() || bar();
+        foo() || "bar";
+        bar() || foo();
+        bar() || bar();
+        bar() || "bar";
+        "bar" || foo();
+        "bar" || bar();
+        "bar" || "bar";
+    }
+    expect: {
+        foo() || bar();
+        bar();
+        bar() || bar();
+        bar();
+        "bar" || bar();
+    }
+}
+
+assign: {
+    options = {
+        pure_funcs: [ "foo" ],
+        side_effects :true,
+    }
+    input: {
+        var a;
+        function f(b) {
+            a = foo();
+            b *= 4 + foo();
+            c >>= 0 | foo();
+        }
+    }
+    expect: {
+        var a;
+        function f(b) {
+            a = foo();
+            b *= 4 + foo();
+            c >>= 0 | foo();
+        }
+    }
+}
+
+unary: {
+    options = {
+        pure_funcs: [ "foo" ],
+        side_effects :true,
+    }
+    input: {
+        typeof foo();
+        typeof bar();
+        typeof "bar";
+        void foo();
+        void bar();
+        void "bar";
+        delete a[foo()];
+        delete a[bar()];
+        delete a["bar"];
+        a[foo()]++;
+        a[bar()]++;
+        a["bar"]++;
+        --a[foo()];
+        --a[bar()];
+        --a["bar"];
+        ~foo();
+        ~bar();
+        ~"bar";
+    }
+    expect: {
+        bar();
+        bar();
+        delete a[foo()];
+        delete a[bar()];
+        delete a["bar"];
+        a[foo()]++;
+        a[bar()]++;
+        a["bar"]++;
+        --a[foo()];
+        --a[bar()];
+        --a["bar"];
+        bar();
+    }
+}