add new arrows compress option (#2154)

Convert ES5 style anonymous function expressions
to arrow functions if permissible by language semantics.

Note: `arrows` requires that the `ecma` compress option
is set to `6` or greater.

fixes #2150

test/compress/arrow.js

@@ -210,3 +210,73 @@ no_leading_parentheses: {
     }
     expect_exact: "(x,y)=>x(y);async(x,y)=>await x(y);"
 }
+
+async_identifiers: {
+    options = {
+        arrows: true,
+        ecma: 6,
+    }
+    input: {
+        var async = function(x){ console.log("async", x); };
+        var await = function(x){ console.log("await", x); };
+        async(1);
+        await(2);
+    }
+    expect: {
+        var async = x => { console.log("async", x); };
+        var await = x => { console.log("await", x); };
+        async(1);
+        await(2);
+    }
+    expect_stdout: [
+        "async 1",
+        "await 2",
+    ]
+    node_version: ">=4"
+}
+
+async_function_expression: {
+    options = {
+        arrows: true,
+        ecma: 6,
+        evaluate: true,
+        side_effects: true,
+    }
+    input: {
+        var named = async function foo() {
+            await bar(1 + 0) + (2 + 0);
+        }
+        var anon = async function() {
+            await (1 + 0) + bar(2 + 0);
+        }
+    }
+    expect: {
+        var named = async function foo() {
+            await bar(1);
+        };
+        var anon = async () => {
+            await 1, bar(2);
+        };
+    }
+}
+
+issue_27: {
+    options = {
+        arrows: true,
+        collapse_vars: true,
+        ecma: 6,
+        unused: true,
+    }
+    input: {
+        (function(jQuery) {
+            var $;
+            $ = jQuery;
+            $("body").addClass("foo");
+        })(jQuery);
+    }
+    expect: {
+        (jQuery => {
+            jQuery("body").addClass("foo");
+        })(jQuery);
+    }
+}

test/compress/async.js

@@ -167,14 +167,14 @@ async_inline: {
 
 async_identifiers: {
     input: {
-        let async = function(x){ console.log("async", x); };
-        let await = function(x){ console.log("await", x); };
+        var async = function(x){ console.log("async", x); };
+        var await = function(x){ console.log("await", x); };
         async(1);
         await(2);
     }
     expect: {
-        let async = function(x){ console.log("async", x); };
-        let await = function(x){ console.log("await", x); };
+        var async = function(x){ console.log("async", x); };
+        var await = function(x){ console.log("await", x); };
         async(1);
         await(2);
     }
@@ -182,7 +182,6 @@ async_identifiers: {
         "async 1",
         "await 2",
     ]
-    node_version: ">=8"
 }
 
 async_shorthand_property: {

test/compress/issue-203.js

@@ -32,3 +32,25 @@ compress_new_function_with_destruct: {
         Function("[[a]]", "[{bb:b}]", 'return a');
     }
 }
+
+compress_new_function_with_destruct_arrows: {
+    options = {
+        arrows: true,
+        unsafe: true,
+        unsafe_Func: true,
+        ecma: 6
+    }
+    beautify = {
+        ecma: 6
+    }
+    input: {
+        new Function("aa, [bb]", 'return aa;');
+        new Function("aa, {bb}", 'return aa;');
+        new Function("[[aa]], [{bb}]", 'return aa;');
+    }
+    expect: {
+        Function("aa, [bb]", 'return aa;');
+        Function("aa, {bb}", 'return aa;');
+        Function("[[aa]], [{bb}]", 'return aa;');
+    }
+}

test/compress/parameters.js

@@ -1,4 +1,7 @@
 arrow_functions: {
+    options = {
+        arrows: true,
+    }
     input: {
         (a) => b;  // 1 args
         (a, b) => c;  // n args
@@ -13,6 +16,9 @@ arrow_functions: {
 }
 
 arrow_return: {
+    options = {
+        arrows: true,
+    }
     input: {
         () => {};
         () => { return; };