Improve binding patterns for arrow functions

test/compress/arrays.js

@@ -1,3 +1,5 @@
+// NOTE trailing comma doesn't contribute to length of an array
+// That also means the array changes length if previous element is a hole too and got cut off
 holes_and_undefined: {
     input: {
         w = [1,,];

test/compress/arrow.js

@@ -90,3 +90,39 @@ arrow_function_with_single_parameter_with_default: {
     }
     expect_exact: "var foo=(a=0)=>doSomething(a);"
 }
+
+arrow_binding_pattern: {
+    input: {
+        var foo = ([]) => "foo";
+        var bar = ({}) => "bar";
+        var with_default = (foo = "default") => foo;
+        var object_with_default = ({foo = "default", bar: baz = "default"}) => foo;
+        var array_after_spread = (...[foo]) => foo;
+        var array_after_spread = (...{foo}) => foo;
+        var computed = ({ [compute()]: x }) => {};
+        var array_hole = ([, , ...x] = [1, 2]) => {};
+        var object_trailing_elision = ({foo,}) => {};
+        var spread_empty_array = (...[]) => "foo";
+        var spread_empty_object = (...{}) => "foo";
+    }
+    expect: {
+        var foo = ([]) => "foo";
+        var bar = ({}) => "bar";
+        var with_default = (foo = "default") => foo;
+        var object_with_default = ({foo = "default", bar: baz = "default"}) => foo;
+        var array_after_spread = (...[foo]) => foo;
+        var array_after_spread = (...{foo}) => foo;
+        var computed = ({ [compute()]: x }) => {};
+        var array_hole = ([, , ...x] = [1, 2]) => {};
+        var object_trailing_elision = ({foo,}) => {};
+        var spread_empty_array = (...[]) => "foo";
+        var spread_empty_object = (...{}) => "foo";
+    }
+}
+
+arrow_binding_pattern_strict: {
+    input: {
+        var foo = ([,]) => "foo";
+    }
+    expect_exact: 'var foo=([,])=>"foo";'
+}

test/compress/destructuring.js

@@ -6,7 +6,8 @@ destructuring_arrays: {
         {let [aa, [bb, cc]] = dd;}
         var [aa, bb] = cc;
         var [aa, [bb, cc]] = dd;
-        var [,[,,,,,],,,zz,] = xx;
+        var [,[,,,,,],,,zz,] = xx; // Trailing comma
+        var [,,zzz,,] = xxx; // Trailing comma after hole
     }
     expect: {
         {const [aa, bb] = cc;}
@@ -15,10 +16,20 @@ destructuring_arrays: {
         {let [aa, [bb, cc]] = dd;}
         var [aa, bb] = cc;
         var [aa, [bb, cc]] = dd;
-        var [,[,,,,,],,,zz,] = xx;
+        var [,[,,,,,],,,zz] = xx;
+        var [,,zzz,,] = xxx;
     }
 }
 
+destructuring_arrays_holes: {
+    input: {
+        var [,,,,] = a;
+        var [,,b,] = c;
+        var [d,,]  = e;
+    }
+    expect_exact: "var[,,,,]=a;var[,,b]=c;var[d,,]=e;"
+}
+
 destructuring_objects: {
     input: {
         {const {aa, bb} = {aa:1, bb:2};}
@@ -82,6 +93,9 @@ destructuring_vardef_in_loops: {
 }
 
 destructuring_expressions: {
+    beautify = {
+        ecma: 6
+    }
     input: {
         ({a, b});
         [{a}];

test/compress/object.js

@@ -89,6 +89,9 @@ getter_setter: {
 
 getter_setter_mangler: {
     mangle = {}
+    beautify = {
+        ecma: 6
+    }
     input: {
         function f(get,set) {
             return {
@@ -102,7 +105,18 @@ getter_setter_mangler: {
             };
         }
     }
-    expect_exact: "function f(t,e){return{get:t,set:e,get g(){},set s(t){},c,a:1,m(){}}}"
+    expect_exact: "function f(n,t){return{get:n,set:t,get g(){},set s(n){},c,a:1,m(){}}}"
+}
+
+use_shorthand_opportunity: {
+    beautify = {
+        ecma: 6
+    }
+    input: {
+        var foo = 123;
+        var obj = {foo: foo};
+    }
+    expect_exact: "var foo=123;var obj={foo};"
 }
 
 computed_property_names: {
@@ -468,3 +482,12 @@ methods_and_getters_with_keep_quoted_props_enabled: {
     }
     expect_exact: 'var obj={a(){},"b"(){},get c(){return"c"},get"d"(){return"d"},set e(a){doSomething(a)},set f(a){doSomething(b)}};'
 }
+
+allow_assignments_to_property_values: {
+    input: {
+        var foo = {123: foo = 123} = {foo: "456"};
+    }
+    expect: {
+        var foo = {123: foo = 123} = {foo: "456"};
+    }
+}