support rest parameters (#4515)

5 files changed, 538 insertions, 22 deletions

diff --git a/test/compress/async.js b/test/compress/awaits.js
index 7ae753fb..7ae753fb 100644
--- a/test/compress/async.js
+++ b/test/compress/awaits.js
diff --git a/test/compress/rests.js b/test/compress/rests.js
new file mode 100644
index 00000000..1a27860d
--- /dev/null
+++ b/test/compress/rests.js
@@ -0,0 +1,487 @@
+arrow_1: {
+    input: {
+        console.log.apply(console, ((...a) => a)("PASS", 42));
+    }
+    expect_exact: 'console.log.apply(console,((...a)=>a)("PASS",42));'
+    expect_stdout: "PASS 42"
+    node_version: ">=6"
+}
+
+arrow_2: {
+    input: {
+        console.log.apply(console, ((a, ...b) => b)("FAIL", "PASS", 42));
+    }
+    expect_exact: 'console.log.apply(console,((a,...b)=>b)("FAIL","PASS",42));'
+    expect_stdout: "PASS 42"
+    node_version: ">=6"
+}
+
+arrow_destructured_array_1: {
+    input: {
+        console.log.apply(console, (([ ...a ]) => a)("PASS"));
+    }
+    expect_exact: 'console.log.apply(console,(([...a])=>a)("PASS"));'
+    expect_stdout: "P A S S"
+    node_version: ">=6"
+}
+
+arrow_destructured_array_2: {
+    input: {
+        console.log.apply(console, (([ a, ...b ]) => b)([ "FAIL", "PASS", 42 ]));
+    }
+    expect_exact: 'console.log.apply(console,(([a,...b])=>b)(["FAIL","PASS",42]));'
+    expect_stdout: "PASS 42"
+    node_version: ">=6"
+}
+
+arrow_destructured_array_3: {
+    input: {
+        console.log((([ [ ...a ] = "FAIL" ]) => a)([ "PASS" ]).join("|"));
+    }
+    expect_exact: 'console.log((([[...a]="FAIL"])=>a)(["PASS"]).join("|"));'
+    expect_stdout: "P|A|S|S"
+    node_version: ">=6"
+}
+
+arrow_destructured_object_1: {
+    input: {
+        var f = ({ ...a }) => a, o = f({ PASS: 42 });
+        for (var k in o)
+            console.log(k, o[k]);
+    }
+    expect_exact: "var f=({...a})=>a,o=f({PASS:42});for(var k in o)console.log(k,o[k]);"
+    expect_stdout: "PASS 42"
+    node_version: ">=8"
+}
+
+arrow_destructured_object_2: {
+    input: {
+        var f = ({ FAIL: a, ...b }) => b, o = f({ PASS: 42, FAIL: null });
+        for (var k in o)
+            console.log(k, o[k]);
+    }
+    expect_exact: "var f=({FAIL:a,...b})=>b,o=f({PASS:42,FAIL:null});for(var k in o)console.log(k,o[k]);"
+    expect_stdout: "PASS 42"
+    node_version: ">=8"
+}
+
+arrow_destructured_object_3: {
+    input: {
+        var f = ([ { ...a } = [ "FAIL" ] ]) => a;
+        var o = f([ "PASS" ]);
+        for (var k in o)
+            console.log(k, o[k]);
+    }
+    expect_exact: 'var f=([{...a}=["FAIL"]])=>a;var o=f(["PASS"]);for(var k in o)console.log(k,o[k]);'
+    expect_stdout: [
+        "0 P",
+        "1 A",
+        "2 S",
+        "3 S",
+    ]
+    node_version: ">=8"
+}
+
+funarg_1: {
+    input: {
+        console.log.apply(console, function(...a) {
+            return a;
+        }("PASS", 42));
+    }
+    expect_exact: 'console.log.apply(console,function(...a){return a}("PASS",42));'
+    expect_stdout: "PASS 42"
+    node_version: ">=6"
+}
+
+funarg_2: {
+    input: {
+        console.log.apply(console, function(a, ...b) {
+            return b;
+        }("FAIL", "PASS", 42));
+    }
+    expect_exact: 'console.log.apply(console,function(a,...b){return b}("FAIL","PASS",42));'
+    expect_stdout: "PASS 42"
+    node_version: ">=6"
+}
+
+destructured_array_1: {
+    input: {
+        var [ ...a ] = [ "PASS", 42 ];
+        console.log.apply(console, a);
+    }
+    expect_exact: 'var[...a]=["PASS",42];console.log.apply(console,a);'
+    expect_stdout: "PASS 42"
+    node_version: ">=6"
+}
+
+destructured_array_2: {
+    input: {
+        var [ a, ...b ] = [ "FAIL", "PASS", 42 ];
+        console.log.apply(console, b);
+    }
+    expect_exact: 'var[a,...b]=["FAIL","PASS",42];console.log.apply(console,b);'
+    expect_stdout: "PASS 42"
+    node_version: ">=6"
+}
+
+destructured_object_1: {
+    input: {
+        var { ...a } = [ "FAIL", "PASS", 42 ];
+        console.log(a[1], a[2]);
+    }
+    expect_exact: 'var{...a}=["FAIL","PASS",42];console.log(a[1],a[2]);'
+    expect_stdout: "PASS 42"
+    node_version: ">=8"
+}
+
+destructured_object_2: {
+    input: {
+        var { 0: a, ...b } = [ "FAIL", "PASS", 42 ];
+        console.log(b[1], b[2]);
+    }
+    expect_exact: 'var{0:a,...b}=["FAIL","PASS",42];console.log(b[1],b[2]);'
+    expect_stdout: "PASS 42"
+    node_version: ">=8"
+}
+
+drop_fargs: {
+    options = {
+        keep_fargs: false,
+        rests: true,
+        unused: true,
+    }
+    input: {
+        console.log(function(a, ...b) {
+            return b[0];
+        }("FAIL", "PASS"));
+    }
+    expect: {
+        console.log(function(b) {
+            return b[0];
+        }([ "PASS" ]));
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+inline: {
+    options = {
+        inline: true,
+        toplevel: true,
+    }
+    input: {
+        console.log(function(a, ...[ b, c ]) {
+            return c + b + a;
+        }("SS", "A", "P"));
+    }
+    expect: {
+        console.log(([ a, ...[ b, c ] ] = [ "SS", "A", "P" ], c + b + a));
+        var a, b, c;
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+retain_var: {
+    options = {
+        unused: true,
+    }
+    input: {
+        var [ ...a ] = [ "PASS" ];
+        console.log(a[0]);
+    }
+    expect: {
+        var [ ...a ] = [ "PASS" ];
+        console.log(a[0]);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+reduce_destructured_array: {
+    options = {
+        reduce_vars: true,
+        rests: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var [ ...a ] = [ "PASS" ];
+        console.log(a[0]);
+    }
+    expect: {
+        console.log([ "PASS" ][0]);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+reduce_destructured_object: {
+    options = {
+        reduce_vars: true,
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var { ...a } = [ "PASS" ];
+        console.log(a[0]);
+    }
+    expect: {
+        var { ...a } = [ "PASS" ];
+        console.log(a[0]);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=8"
+}
+
+retain_destructured_array: {
+    options = {
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var [ a, ...b ] = [ "FAIL", "PASS", 42 ];
+        console.log.apply(console, b);
+    }
+    expect: {
+        var [ , ...b ] = [ "FAIL", "PASS", 42 ];
+        console.log.apply(console, b);
+    }
+    expect_stdout: "PASS 42"
+    node_version: ">=6"
+}
+
+retain_destructured_object_1: {
+    options = {
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var { 0: a, ...b } = [ "FAIL", "PASS", 42 ];
+        for (var k in b)
+            console.log(k, b[k]);
+    }
+    expect: {
+        var { 0: a, ...b } = [ "FAIL", "PASS", 42 ];
+        for (var k in b)
+            console.log(k, b[k]);
+    }
+    expect_stdout: [
+        "1 PASS",
+        "2 42",
+    ]
+    node_version: ">=8"
+}
+
+retain_destructured_object_2: {
+    options = {
+        toplevel: true,
+        unused: true,
+    }
+    input: {
+        var { foo: [ a ], ...b } = { foo: [ "FAIL" ], bar: "PASS", baz: 42 };
+        for (var k in b)
+            console.log(k, b[k]);
+    }
+    expect: {
+        var { foo: [], ...b } = { foo: [ "FAIL" ], bar: "PASS", baz: 42 };
+        for (var k in b)
+            console.log(k, b[k]);
+    }
+    expect_stdout: [
+        "bar PASS",
+        "baz 42",
+    ]
+    node_version: ">=8"
+}
+
+retain_funarg_destructured_array_1: {
+    options = {
+        inline: true,
+        keep_fargs: false,
+        pure_getters: "strict",
+        unused: true,
+    }
+    input: {
+        console.log((([ ...a ]) => a)([ "PASS" ])[0]);
+    }
+    expect: {
+        console.log((([ ...a ]) => a)([ "PASS" ])[0]);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
+
+retain_funarg_destructured_array_2: {
+    options = {
+        unused: true,
+    }
+    input: {
+        console.log(function([ a, ...b ]) {
+            return b;
+        }("bar")[1]);
+    }
+    expect: {
+        console.log(function([ , ...b ]) {
+            return b;
+        }("bar")[1]);
+    }
+    expect_stdout: "r"
+    node_version: ">=6"
+}
+
+retain_funarg_destructured_object_1: {
+    options = {
+        inline: true,
+        keep_fargs: false,
+        pure_getters: "strict",
+        unused: true,
+    }
+    input: {
+        console.log((({ ...a }) => a)([ "PASS" ])[0]);
+    }
+    expect: {
+        console.log((({ ...a }) => a)([ "PASS" ])[0]);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=8"
+}
+
+retain_funarg_destructured_object_2: {
+    options = {
+        unused: true,
+    }
+    input: {
+        console.log(function({ p: a, ... b }) {
+            return b;
+        }({ p: "FAIL" }).p || "PASS");
+    }
+    expect: {
+        console.log(function({ p: a, ... b }) {
+            return b;
+        }({ p: "FAIL" }).p || "PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=8"
+}
+
+drop_unused_call_args_1: {
+    options = {
+        rests: true,
+        unused: true,
+    }
+    input: {
+        (function(...a) {
+            console.log(a[0]);
+        })(42, console.log("PASS"));
+    }
+    expect: {
+        (function(a) {
+            console.log(a[0]);
+        })([ 42, console.log("PASS") ]);
+    }
+    expect_stdout: [
+        "PASS",
+        "42",
+    ]
+    node_version: ">=6"
+}
+
+drop_unused_call_args_2: {
+    options = {
+        keep_fargs: false,
+        rests: true,
+        unused: true,
+    }
+    input: {
+        console.log(function(a, ...b) {
+            return b;
+        }(console).length);
+    }
+    expect: {
+        console.log(function(b) {
+            return b;
+        }((console, [])).length);
+    }
+    expect_stdout: "0"
+    node_version: ">=6"
+}
+
+merge_funarg: {
+    options = {
+        merge_vars: true,
+    }
+    input: {
+        (function(...a) {
+            var b = a.length;
+            console.log(b);
+        })();
+    }
+    expect: {
+        (function(...b) {
+            var b = b.length;
+            console.log(b);
+        })();
+    }
+    expect_stdout: "0"
+    node_version: ">=6"
+}
+
+merge_funarg_destructured_array: {
+    options = {
+        merge_vars: true,
+    }
+    input: {
+        (function([ ...a ]) {
+            var b = a.length;
+            console.log(b);
+        })([]);
+    }
+    expect: {
+        (function([ ...b ]) {
+            var b = b.length;
+            console.log(b);
+        })([]);
+    }
+    expect_stdout: "0"
+    node_version: ">=6"
+}
+
+merge_funarg_destructured_object: {
+    options = {
+        merge_vars: true,
+    }
+    input: {
+        (function({ ...a }) {
+            var b = a[0];
+            console.log(b);
+        })([ "PASS" ]);
+    }
+    expect: {
+        (function({ ...b }) {
+            var b = b[0];
+            console.log(b);
+        })([ "PASS" ]);
+    }
+    expect_stdout: "PASS"
+    node_version: ">=8"
+}
+
+keep_arguments: {
+    options = {
+        arguments: true,
+        keep_fargs: false,
+    }
+    input: {
+        (function(...[ {} ]) {
+            console.log(arguments[0]);
+        })("PASS");
+    }
+    expect: {
+        (function(...[ {} ]) {
+            console.log(arguments[0]);
+        })("PASS");
+    }
+    expect_stdout: "PASS"
+    node_version: ">=6"
+}
diff --git a/test/compress/spread.js b/test/compress/spreads.js
index 944915fe..1e4dcbf6 100644
--- a/test/compress/spread.js
+++ b/test/compress/spreads.js
@@ -128,7 +128,7 @@ dont_inline: {
 do_inline: {
     options = {
         inline: true,
-        spread: true,
+        spreads: true,
     }
     input: {
         console.log(function(a) {
@@ -167,7 +167,7 @@ drop_empty_call_1: {
 drop_empty_call_2: {
     options = {
         side_effects: true,
-        spread: true,
+        spreads: true,
     }
     input: {
         (function() {})(...[ console.log("PASS") ]);
@@ -181,7 +181,7 @@ drop_empty_call_2: {
 
 convert_hole: {
     options = {
-        spread: true,
+        spreads: true,
     }
     input: {
         console.log(...[ "PASS", , 42 ]);
@@ -275,7 +275,7 @@ reduce_vars_2: {
 convert_setter: {
     options = {
         objects: true,
-        spread: true,
+        spreads: true,
     }
     input: {
         var o = {
@@ -419,7 +419,7 @@ keep_getter_4: {
 keep_accessor: {
     options = {
         objects: true,
-        spread: true,
+        spreads: true,
     }
     input: {
         var o = {
@@ -467,7 +467,7 @@ keep_accessor: {
 object_key_order_1: {
     options = {
         objects: true,
-        spread: true,
+        spreads: true,
     }
     input: {
         var o = {
@@ -497,7 +497,7 @@ object_key_order_1: {
 object_key_order_2: {
     options = {
         objects: true,
-        spread: true,
+        spreads: true,
     }
     input: {
         var o = {
@@ -527,7 +527,7 @@ object_key_order_2: {
 object_key_order_3: {
     options = {
         objects: true,
-        spread: true,
+        spreads: true,
     }
     input: {
         var o = {
@@ -557,7 +557,7 @@ object_key_order_3: {
 object_key_order_4: {
     options = {
         objects: true,
-        spread: true,
+        spreads: true,
     }
     input: {
         var o = {
@@ -587,7 +587,7 @@ object_key_order_4: {
 object_spread_array: {
     options = {
         objects: true,
-        spread: true,
+        spreads: true,
     }
     input: {
         var o = {
@@ -613,7 +613,7 @@ object_spread_array: {
 object_spread_string: {
     options = {
         objects: true,
-        spread: true,
+        spreads: true,
     }
     input: {
         var o = {
@@ -670,7 +670,7 @@ unused_var_side_effects: {
 issue_4329: {
     options = {
         objects: true,
-        spread: true,
+        spreads: true,
     }
     input: {
         console.log({
@@ -749,7 +749,7 @@ issue_4342: {
 issue_4345: {
     options = {
         objects: true,
-        spread: true,
+        spreads: true,
     }
     input: {
         console.log({
@@ -809,7 +809,7 @@ issue_4361: {
 issue_4363: {
     options = {
         objects: true,
-        spread: true,
+        spreads: true,
     }
     input: {
         ({
diff --git a/test/reduce.js b/test/reduce.js
index 54494c56..cd00d5e9 100644
--- a/test/reduce.js
+++ b/test/reduce.js
@@ -452,6 +452,10 @@ module.exports = function reduce_test(testcase, minify_options, reduce_options)
                     CHANGED = true;
                     return List.skip;
                 }
+            } else if (parent.rest === node) {
+                node.start._permute++;
+                CHANGED = true;
+                return null;
             }
 
             // replace this node
diff --git a/test/ufuzz/index.js b/test/ufuzz/index.js
index 23b3a144..7f2a7d72 100644
--- a/test/ufuzz/index.js
+++ b/test/ufuzz/index.js
@@ -140,6 +140,8 @@ var SUPPORT = function(matrix) {
     default_value: "[ a = 0 ] = [];",
     destructuring: "[] = [];",
     let: "let a;",
+    rest: "var [...a] = [];",
+    rest_object: "var {...a} = {};",
     spread: "[...[]];",
     spread_object: "({...0});",
     trailing_comma: "function f(a,) {}",
@@ -427,9 +429,22 @@ function createAssignmentPairs(recurmax, stmtDepth, canThrow, nameLenBefore, was
     var avoid = [];
     var len = unique_vars.length;
     var pairs = createPairs(recurmax, !nameLenBefore);
+    pairs.has_rest = nameLenBefore && convertToRest(pairs.names);
     unique_vars.length = len;
     return pairs;
 
+    function convertToRest(names) {
+        var last = names.length - 1;
+        if (last >= 0 && SUPPORT.rest && rng(20) == 0) {
+            var name = names[last];
+            if (name && name.indexOf("=") < 0) {
+                if (/^[[{]/.test(name)) name = "[ " + name + " ]";
+                names[last] = "..." + name;
+                return true;
+            }
+        }
+    }
+
     function fill(nameFn, valueFn) {
         var save_async = async;
         if (was_async != null) {
@@ -519,12 +534,13 @@ function createAssignmentPairs(recurmax, stmtDepth, canThrow, nameLenBefore, was
                         if (index < pairs.values.length) {
                             pairs.values.splice(index, 0, rng(2) ? createAssignmentValue(recurmax) : "");
                         } else switch (rng(5)) {
-                        case 0:
+                          case 0:
                             pairs.values[index] = createAssignmentValue(recurmax);
-                        case 1:
+                          case 1:
                             pairs.values.length = index + 1;
                         }
                     }
+                    convertToRest(pairs.names);
                     names.unshift("[ " + pairs.names.join(", ") + " ]" + default_value);
                     values.unshift("[ " + pairs.values.join(", ") + " ]");
                 });
@@ -547,10 +563,17 @@ function createAssignmentPairs(recurmax, stmtDepth, canThrow, nameLenBefore, was
                     }
                 });
                 fill(function() {
-                    names.unshift("{ " + addTrailingComma(pairs.names.map(function(name, index) {
-                        var key = index in keys ? keys[index] : rng(10) && createKey(recurmax, keys);
-                        return key ? key + ": " + name : name;
-                    }).join(", ")) + " }" + createDefaultValue(recurmax, noDefault));
+                    var last = pairs.names.length - 1, has_rest = false;
+                    var s = pairs.names.map(function(name, index) {
+                        if (index in keys) return keys[index] + ": " + name;
+                        if (index == last && SUPPORT.rest_object && rng(20) == 0 && name.indexOf("=") < 0) {
+                            has_rest = true;
+                            return "..." + name;
+                        }
+                        return rng(10) == 0 ? name : createKey(recurmax, keys) + ": " + name;
+                    }).join(", ");
+                    if (!has_rest) s = addTrailingComma(s);
+                    names.unshift("{ " + s + " }" + createDefaultValue(recurmax, noDefault));
                 }, function() {
                     values.unshift("{ " + addTrailingComma(pairs.values.map(function(value, index) {
                         var key = index in keys ? keys[index] : createKey(recurmax, keys);
@@ -677,7 +700,8 @@ function createFunction(recurmax, allowDefun, canThrow, stmtDepth) {
         if (SUPPORT.destructuring && (!allowDefun || !(name in called)) && rng(2)) {
             called[name] = false;
             var pairs = createAssignmentPairs(recurmax, stmtDepth, canThrow, nameLenBefore, save_async);
-            params = addTrailingComma(pairs.names.join(", "));
+            params = pairs.names.join(", ");
+            if (!pairs.has_rest) params = addTrailingComma(params);
             args = addTrailingComma(pairs.values.join(", "));
         } else {
             params = createParams(save_async);
@@ -1037,7 +1061,8 @@ function _createExpression(recurmax, noComma, stmtDepth, canThrow) {
                     var params;
                     if (SUPPORT.destructuring && rng(2)) {
                         var pairs = createAssignmentPairs(recurmax, stmtDepth, canThrow, nameLenBefore, save_async);
-                        params = addTrailingComma(pairs.names.join(", "));
+                        params = pairs.names.join(", ");
+                        if (!pairs.has_rest) params = addTrailingComma(params);
                         args = addTrailingComma(pairs.values.join(", "));
                     } else {
                         params = createParams(save_async, NO_DUPLICATE);