introduce `functions` (#3360)

`var f = function() {};` => `function f() {}`

7 files changed, 268 insertions, 46 deletions

diff --git a/README.md b/README.md
index 1be2d2e8..bf8fbd23 100644
--- a/README.md
+++ b/README.md
@@ -636,6 +636,9 @@ If you're using the `X-SourceMap` header instead, you can just omit `sourceMap.u
 - `expression` (default: `false`) -- Pass `true` to preserve completion values
   from terminal statements without `return`, e.g. in bookmarklets.
 
+- `functions` (default: `true`) -- convert declarations from `var`to `function`
+  whenever possible.
+
 - `global_defs` (default: `{}`) -- see [conditional compilation](#conditional-compilation)
 
 - `hoist_funs` (default: `false`) -- hoist function declarations
diff --git a/lib/compress.js b/lib/compress.js
index 6c12d2bd..2fdfc89e 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -60,6 +60,7 @@ function Compressor(options, false_by_default) {
         drop_debugger   : !false_by_default,
         evaluate        : !false_by_default,
         expression      : false,
+        functions       : !false_by_default,
         global_defs     : false,
         hoist_funs      : false,
         hoist_props     : !false_by_default,
@@ -150,7 +151,7 @@ Compressor.prototype = new TreeTransformer;
 merge(Compressor.prototype, {
     option: function(key) { return this.options[key] },
     exposed: function(def) {
-        if (def.global) for (var i = 0, len = def.orig.length; i < len; i++)
+        if (def.global) for (var i = 0; i < def.orig.length; i++)
             if (!this.toplevel[def.orig[i] instanceof AST_SymbolDefun ? "funcs" : "vars"])
                 return true;
         return false;
@@ -1241,7 +1242,7 @@ merge(Compressor.prototype, {
                 // Scan case expressions first in a switch statement
                 if (node instanceof AST_Switch) {
                     node.expression = node.expression.transform(scanner);
-                    for (var i = 0, len = node.body.length; !abort && i < len; i++) {
+                    for (var i = 0; !abort && i < node.body.length; i++) {
                         var branch = node.body[i];
                         if (branch instanceof AST_Case) {
                             if (!hit) {
@@ -1887,7 +1888,7 @@ merge(Compressor.prototype, {
             }
 
             function next_index(i) {
-                for (var j = i + 1, len = statements.length; j < len; j++) {
+                for (var j = i + 1; j < statements.length; j++) {
                     var stat = statements[j];
                     if (!(stat instanceof AST_Var && declarations_only(stat))) {
                         break;
@@ -1978,7 +1979,7 @@ merge(Compressor.prototype, {
         function to_simple_statement(block, decls) {
             if (!(block instanceof AST_BlockStatement)) return block;
             var stat = null;
-            for (var i = 0, len = block.body.length; i < len; i++) {
+            for (var i = 0; i < block.body.length; i++) {
                 var line = block.body[i];
                 if (line instanceof AST_Var && declarations_only(line)) {
                     decls.push(line);
@@ -2118,7 +2119,7 @@ merge(Compressor.prototype, {
 
         function join_consecutive_vars(statements) {
             var defs;
-            for (var i = 0, j = -1, len = statements.length; i < len; i++) {
+            for (var i = 0, j = -1; i < statements.length; i++) {
                 var stat = statements[i];
                 var prev = statements[j];
                 if (stat instanceof AST_Definitions) {
@@ -2719,7 +2720,7 @@ merge(Compressor.prototype, {
         def(AST_Array, function(compressor, cached, depth) {
             if (compressor.option("unsafe")) {
                 var elements = [];
-                for (var i = 0, len = this.elements.length; i < len; i++) {
+                for (var i = 0; i < this.elements.length; i++) {
                     var element = this.elements[i];
                     var value = element._eval(compressor, cached, depth);
                     if (element === value) return this;
@@ -2732,7 +2733,7 @@ merge(Compressor.prototype, {
         def(AST_Object, function(compressor, cached, depth) {
             if (compressor.option("unsafe")) {
                 var val = {};
-                for (var i = 0, len = this.properties.length; i < len; i++) {
+                for (var i = 0; i < this.properties.length; i++) {
                     var prop = this.properties[i];
                     var key = prop.key;
                     if (key instanceof AST_Symbol) {
@@ -2927,7 +2928,7 @@ merge(Compressor.prototype, {
                     if (!native_fn || !native_fn[key]) return this;
                 }
                 var args = [];
-                for (var i = 0, len = this.args.length; i < len; i++) {
+                for (var i = 0; i < this.args.length; i++) {
                     var arg = this.args[i];
                     var value = arg._eval(compressor, cached, depth);
                     if (arg === value) return this;
@@ -3463,9 +3464,7 @@ merge(Compressor.prototype, {
             if (node instanceof AST_Definitions && scope === self) {
                 node.definitions.forEach(function(def) {
                     var node_def = def.name.definition();
-                    if (def.name instanceof AST_SymbolVar) {
-                        var_defs_by_id.add(node_def.id, def);
-                    }
+                    var_defs_by_id.add(node_def.id, def);
                     if (!drop_vars) {
                         if (!(node_def.id in in_use_ids)) {
                             in_use_ids[node_def.id] = true;
@@ -3572,29 +3571,40 @@ merge(Compressor.prototype, {
                         if (def.value && sym.id in fixed_ids && fixed_ids[sym.id] !== def) {
                             def.value = def.value.drop_side_effect_free(compressor);
                         }
-                        if (def.name instanceof AST_SymbolVar) {
-                            var var_defs = var_defs_by_id.get(sym.id);
-                            if (var_defs.length > 1 && (!def.value || sym.orig.indexOf(def.name) > sym.eliminated)) {
-                                compressor.warn("Dropping duplicated definition of variable {name} [{file}:{line},{col}]", template(def.name));
-                                if (def.value) {
-                                    var ref = make_node(AST_SymbolRef, def.name, def.name);
-                                    sym.references.push(ref);
-                                    var assign = make_node(AST_Assign, def, {
-                                        operator: "=",
-                                        left: ref,
-                                        right: def.value
-                                    });
-                                    if (fixed_ids[sym.id] === def) {
-                                        fixed_ids[sym.id] = assign;
-                                    }
-                                    side_effects.push(assign.transform(tt));
+                        var var_defs = var_defs_by_id.get(sym.id);
+                        if (var_defs.length > 1 && (!def.value || sym.orig.indexOf(def.name) > sym.eliminated)) {
+                            compressor.warn("Dropping duplicated definition of variable {name} [{file}:{line},{col}]", template(def.name));
+                            if (def.value) {
+                                var ref = make_node(AST_SymbolRef, def.name, def.name);
+                                sym.references.push(ref);
+                                var assign = make_node(AST_Assign, def, {
+                                    operator: "=",
+                                    left: ref,
+                                    right: def.value
+                                });
+                                if (fixed_ids[sym.id] === def) {
+                                    fixed_ids[sym.id] = assign;
                                 }
-                                remove(var_defs, def);
-                                sym.eliminated++;
-                                return;
+                                side_effects.push(assign.transform(tt));
                             }
+                            remove(var_defs, def);
+                            sym.eliminated++;
+                            return;
                         }
-                        if (def.value) {
+                        if (!def.value) {
+                            head.push(def);
+                        } else if (compressor.option("functions")
+                            && def.value === def.name.fixed_value()
+                            && def.value instanceof AST_Function
+                            && !def.value.name
+                            && !def.value.variables.get(def.name.name)
+                            && (!compressor.has_directive("use strict") || parent instanceof AST_Scope)) {
+                            compressor.warn("Declaring {name} as function [{file}:{line},{col}]", template(def.name));
+                            var defun = make_node(AST_Defun, def, def.value);
+                            defun.name = make_node(AST_SymbolDefun, def.name, def.name);
+                            self.def_function(defun.name);
+                            body.push(defun);
+                        } else {
                             if (side_effects.length > 0) {
                                 if (tail.length > 0) {
                                     side_effects.push(def.value);
@@ -3607,8 +3617,6 @@ merge(Compressor.prototype, {
                                 side_effects = [];
                             }
                             tail.push(def);
-                        } else {
-                            head.push(def);
                         }
                     } else if (sym.orig[0] instanceof AST_SymbolCatch) {
                         var value = def.value && def.value.drop_side_effect_free(compressor);
@@ -4669,7 +4677,7 @@ merge(Compressor.prototype, {
             && !fn.uses_arguments
             && !fn.pinned()) {
             var pos = 0, last = 0;
-            for (var i = 0, len = self.args.length; i < len; i++) {
+            for (var i = 0; i < self.args.length; i++) {
                 var trim = i >= fn.argnames.length;
                 if (trim || fn.argnames[i].__unused) {
                     var node = self.args[i].drop_side_effect_free(compressor);
@@ -5047,7 +5055,7 @@ merge(Compressor.prototype, {
         }
 
         function can_inject_args(catches, safe_to_inject) {
-            for (var i = 0, len = fn.argnames.length; i < len; i++) {
+            for (var i = 0; i < fn.argnames.length; i++) {
                 var arg = fn.argnames[i];
                 if (arg.__unused) continue;
                 if (!safe_to_inject
@@ -5062,7 +5070,7 @@ merge(Compressor.prototype, {
         }
 
         function can_inject_vars(catches, safe_to_inject) {
-            for (var i = 0, len = fn.body.length; i < len; i++) {
+            for (var i = 0; i < fn.body.length; i++) {
                 var stat = fn.body[i];
                 if (!(stat instanceof AST_Var)) continue;
                 if (!safe_to_inject) return false;
@@ -5142,10 +5150,10 @@ merge(Compressor.prototype, {
 
         function flatten_vars(decls, expressions) {
             var pos = expressions.length;
-            for (var i = 0, lines = fn.body.length; i < lines; i++) {
+            for (var i = 0; i < fn.body.length; i++) {
                 var stat = fn.body[i];
                 if (!(stat instanceof AST_Var)) continue;
-                for (var j = 0, defs = stat.definitions.length; j < defs; j++) {
+                for (var j = 0; j < stat.definitions.length; j++) {
                     var var_def = stat.definitions[j];
                     var name = var_def.name;
                     var redef = name.definition().redefined();
diff --git a/lib/output.js b/lib/output.js
index 7f7e74df..4b1ae949 100644
--- a/lib/output.js
+++ b/lib/output.js
@@ -123,7 +123,7 @@ function OutputStream(options) {
         });
     } : function(str) {
         var s = "";
-        for (var i = 0, len = str.length; i < len; i++) {
+        for (var i = 0; i < str.length; i++) {
             if (is_surrogate_pair_head(str[i]) && !is_surrogate_pair_tail(str[i + 1])
                 || is_surrogate_pair_tail(str[i]) && !is_surrogate_pair_head(str[i - 1])) {
                 s += "\\u" + str.charCodeAt(i).toString(16);
diff --git a/lib/parse.js b/lib/parse.js
index a58557dd..f7c5d11b 100644
--- a/lib/parse.js
+++ b/lib/parse.js
@@ -272,10 +272,8 @@ function tokenizer($TEXT, filename, html5_comments, shebang) {
 
     function find_eol() {
         var text = S.text;
-        for (var i = S.pos, n = S.text.length; i < n; ++i) {
-            var ch = text[i];
-            if (NEWLINE_CHARS[ch])
-                return i;
+        for (var i = S.pos; i < S.text.length; ++i) {
+            if (NEWLINE_CHARS[text[i]]) return i;
         }
         return -1;
     }
diff --git a/lib/scope.js b/lib/scope.js
index f78b4c5e..b6bfe1a8 100644
--- a/lib/scope.js
+++ b/lib/scope.js
@@ -333,7 +333,7 @@ function next_mangled_name(scope, options, def) {
         } while (scope = scope.parent_scope);
     });
     var name;
-    for (var i = 0, len = holes.length; i < len; i++) {
+    for (var i = 0; i < holes.length; i++) {
         name = base54(holes[i]);
         if (names[name]) continue;
         holes.splice(i, 1);
@@ -555,7 +555,7 @@ var base54 = (function() {
     var freq = Object.create(null);
     function init(chars) {
         var array = [];
-        for (var i = 0, len = chars.length; i < len; i++) {
+        for (var i = 0; i < chars.length; i++) {
             var ch = chars[i];
             array.push(ch);
             freq[ch] = -1e-2 * i;
diff --git a/test/compress/functions.js b/test/compress/functions.js
index cb7a1b86..2d00c594 100644
--- a/test/compress/functions.js
+++ b/test/compress/functions.js
@@ -2703,3 +2703,216 @@ loop_inline: {
     }
     expect_stdout: "undefined"
 }
+
+functions: {
+    options = {
+        functions: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        !function() {
+            var a = function() {
+                return "a";
+            };
+            var b = function x() {
+                return !!x;
+            };
+            var c = function(c) {
+                return c;
+            };
+            if (c(b(a()))) {
+                var d = function() {};
+                var e = function y() {
+                    return typeof y;
+                };
+                var f = function(f) {
+                    return f;
+                };
+                console.log(a(d()), b(e()), c(f(42)), typeof d, e(), typeof f);
+            }
+        }();
+    }
+    expect: {
+        !function() {
+            function a() {
+                return "a";
+            }
+            var b = function x() {
+                return !!x;
+            };
+            var c = function(c) {
+                return c;
+            };
+            if (c(b(a()))) {
+                function d() {}
+                var e = function y() {
+                    return typeof y;
+                };
+                var f = function(f) {
+                    return f;
+                };
+                console.log(a(d()), b(e()), c(f(42)), typeof d, e(), typeof f);
+            }
+        }();
+    }
+    expect_stdout: "a true 42 function function function"
+}
+
+functions_use_strict: {
+    options = {
+        functions: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        "use strict";
+        !function() {
+            var a = function() {
+                return "a";
+            };
+            var b = function x() {
+                return !!x;
+            };
+            var c = function(c) {
+                return c;
+            };
+            if (c(b(a()))) {
+                var d = function() {};
+                var e = function y() {
+                    return typeof y;
+                };
+                var f = function(f) {
+                    return f;
+                };
+                console.log(a(d()), b(e()), c(f(42)), typeof d, e(), typeof f);
+            }
+        }();
+    }
+    expect: {
+        "use strict";
+        !function() {
+            function a() {
+                return "a";
+            }
+            var b = function x() {
+                return !!x;
+            };
+            var c = function(c) {
+                return c;
+            };
+            if (c(b(a()))) {
+                var d = function() {};
+                var e = function y() {
+                    return typeof y;
+                };
+                var f = function(f) {
+                    return f;
+                };
+                console.log(a(d()), b(e()), c(f(42)), typeof d, e(), typeof f);
+            }
+        }();
+    }
+    expect_stdout: "a true 42 function function function"
+}
+
+issue_2437: {
+    options = {
+        collapse_vars: true,
+        conditionals: true,
+        functions: true,
+        inline: true,
+        join_vars: true,
+        passes: 2,
+        reduce_funcs: true,
+        reduce_vars: true,
+        sequences: true,
+        side_effects: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        function foo() {
+            return bar();
+        }
+        function bar() {
+            if (xhrDesc) {
+                var req = new XMLHttpRequest();
+                var result = !!req.onreadystatechange;
+                Object.defineProperty(XMLHttpRequest.prototype, 'onreadystatechange', xhrDesc || {});
+                return result;
+            } else {
+                var req = new XMLHttpRequest();
+                var detectFunc = function(){};
+                req.onreadystatechange = detectFunc;
+                var result = req[SYMBOL_FAKE_ONREADYSTATECHANGE_1] === detectFunc;
+                req.onreadystatechange = null;
+                return result;
+            }
+        }
+        console.log(foo());
+    }
+    expect: {
+        console.log(function() {
+            if (xhrDesc) {
+                var result = !!(req = new XMLHttpRequest()).onreadystatechange;
+                return Object.defineProperty(XMLHttpRequest.prototype, "onreadystatechange", xhrDesc || {}),
+                    result;
+            }
+            function detectFunc() {}
+            var req;
+            (req = new XMLHttpRequest()).onreadystatechange = detectFunc;
+            result = req[SYMBOL_FAKE_ONREADYSTATECHANGE_1] === detectFunc;
+            return req.onreadystatechange = null, result;
+        }());
+    }
+}
+
+issue_2485: {
+    options = {
+        functions: true,
+        reduce_funcs: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        var foo = function(bar) {
+            var n = function(a, b) {
+                return a + b;
+            };
+            var sumAll = function(arg) {
+                return arg.reduce(n, 0);
+            };
+            var runSumAll = function(arg) {
+                return sumAll(arg);
+            };
+            bar.baz = function(arg) {
+                var n = runSumAll(arg);
+                return (n.get = 1), n;
+            };
+            return bar;
+        };
+        var bar = foo({});
+        console.log(bar.baz([1, 2, 3]));
+    }
+    expect: {
+        var foo = function(bar) {
+            function n(a, b) {
+                return a + b;
+            }
+            function runSumAll(arg) {
+                return function(arg) {
+                    return arg.reduce(n, 0);
+                }(arg);
+            }
+            bar.baz = function(arg) {
+                var n = runSumAll(arg);
+                return (n.get = 1), n;
+            };
+            return bar;
+        };
+        var bar = foo({});
+        console.log(bar.baz([1, 2, 3]));
+    }
+    expect_stdout: "6"
+}
diff --git a/test/jetstream.js b/test/jetstream.js
index 9545784b..2d85dfdd 100644
--- a/test/jetstream.js
+++ b/test/jetstream.js
@@ -3,7 +3,7 @@
 
 "use strict";
 
-var site = "https://browserbench.org/JetStream";
+var site = "https://browserbench.org/JetStream1.1";
 if (typeof phantom == "undefined") {
     require("../tools/exit");
     var args = process.argv.slice(2);