compress apply() & call() of function (#2613)

- `fn.apply(a, [ ... ])` => `fn.call(a, ...)`
- `fn.call(a, ... )` => `a, fn(...)`

where `fn` can be `function` literal or symbol reference linked through `reduce_vars`

lib/compress.js

@@ -3857,6 +3857,34 @@ merge(Compressor.prototype, {
                     }
                 }
                 break;
+              case "apply":
+                if (self.args.length == 2 && self.args[1] instanceof AST_Array) {
+                    var args = self.args[1].elements.slice();
+                    args.unshift(self.args[0]);
+                    return make_node(AST_Call, self, {
+                        expression: make_node(AST_Dot, exp, {
+                            expression: exp.expression,
+                            property: "call"
+                        }),
+                        args: args
+                    }).optimize(compressor);
+                }
+                break;
+              case "call":
+                var func = exp.expression;
+                if (func instanceof AST_SymbolRef) {
+                    func = func.fixed_value();
+                }
+                if (func instanceof AST_Function && !func.contains_this()) {
+                    return make_sequence(this, [
+                        self.args[0],
+                        make_node(AST_Call, self, {
+                            expression: exp.expression,
+                            args: self.args.slice(1)
+                        })
+                    ]).optimize(compressor);
+                }
+                break;
             }
         }
         if (compressor.option("unsafe_Func")

test/compress/functions.js

@@ -923,3 +923,129 @@ issue_2604_2: {
     }
     expect_stdout: "PASS"
 }
+
+unsafe_apply_1: {
+    options = {
+        inline: true,
+        passes: 2,
+        reduce_vars: true,
+        side_effects: true,
+        unsafe: true,
+        unused: true,
+    }
+    input: {
+        (function(a, b) {
+            console.log(a, b);
+        }).apply("foo", [ "bar" ]);
+        (function(a, b) {
+            console.log(this, a, b);
+        }).apply("foo", [ "bar" ]);
+        (function(a, b) {
+            console.log(a, b);
+        }).apply("foo", [ "bar" ], "baz");
+    }
+    expect: {
+        console.log("bar", void 0);
+        (function(a, b) {
+            console.log(this, a, b);
+        }).call("foo", "bar");
+        (function(a, b) {
+            console.log(a, b);
+        }).apply("foo", [ "bar" ], "baz");
+    }
+    expect_stdout: true
+}
+
+unsafe_apply_2: {
+    options = {
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unsafe: true,
+    }
+    input: {
+        function foo() {
+            console.log(a, b);
+        }
+        var bar = function(a, b) {
+            console.log(this, a, b);
+        }
+        (function() {
+            foo.apply("foo", [ "bar" ]);
+            bar.apply("foo", [ "bar" ]);
+        })();
+    }
+    expect: {
+        function foo() {
+            console.log(a, b);
+        }
+        var bar = function(a, b) {
+            console.log(this, a, b);
+        }
+        (function() {
+            foo("bar");
+            bar.call("foo", "bar");
+        })();
+    }
+    expect_stdout: true
+}
+
+unsafe_call_1: {
+    options = {
+        inline: true,
+        passes: 2,
+        reduce_vars: true,
+        side_effects: true,
+        unsafe: true,
+        unused: true,
+    }
+    input: {
+        (function(a, b) {
+            console.log(a, b);
+        }).call("foo", "bar");
+        (function(a, b) {
+            console.log(this, a, b);
+        }).call("foo", "bar");
+    }
+    expect: {
+        console.log("bar", void 0);
+        (function(a, b) {
+            console.log(this, a, b);
+        }).call("foo", "bar");
+    }
+    expect_stdout: true
+}
+
+unsafe_call_2: {
+    options = {
+        reduce_vars: true,
+        side_effects: true,
+        toplevel: true,
+        unsafe: true,
+    }
+    input: {
+        function foo() {
+            console.log(a, b);
+        }
+        var bar = function(a, b) {
+            console.log(this, a, b);
+        }
+        (function() {
+            foo.call("foo", "bar");
+            bar.call("foo", "bar");
+        })();
+    }
+    expect: {
+        function foo() {
+            console.log(a, b);
+        }
+        var bar = function(a, b) {
+            console.log(this, a, b);
+        }
+        (function() {
+            foo("bar");
+            bar.call("foo", "bar");
+        })();
+    }
+    expect_stdout: true
+}