[ES9] implement object rest/spread

lib/parse.js

@@ -1547,18 +1547,33 @@ function parse($TEXT, options) {
                 } else {
                     expect(",");
                 }
+                if (is("expand", "...")) {
+                    is_expand = true;
+                    expand_token = S.token;
+                    used_parameters.mark_spread(S.token);
+                    next();
+                }
                 if (is("name") && (is_token(peek(), "punc") || is_token(peek(), "operator")) && [",", "}", "="].indexOf(peek().value) !== -1) {
                     used_parameters.add_parameter(S.token);
+                    var value = new symbol_type({
+                        start: S.token,
+                        name: S.token.value,
+                        end: S.token,
+                    });
+                    if (is_expand) {
+                        elements.push(new AST_Expansion({
+                            start: expand_token,
+                            expression: value,
+                            end: value.end,
+                        }));
+                    } else {
                         elements.push(new AST_ObjectKeyVal({
                             start: prev(),
                             key: S.token.value,
-                        value: new symbol_type({
-                            start: S.token,
-                            name: S.token.value,
-                            end: S.token
-                        }),
-                        end: prev()
+                            value: value,
+                            end: value.end,
                         }));
+                    }
                     next();
                 } else if (is("punc", "}")) {
                     continue; // Allow trailing hole
@@ -1589,7 +1604,12 @@ function parse($TEXT, options) {
                         }));
                     }
                 }
-                if (is("operator", "=")) {
+                if (is_expand) {
+                    if (!is("punc", "}")) {
+                        unexpected(); // Must be last element
+                    }
+                }
+                else if (is("operator", "=")) {
                     used_parameters.mark_default_assignment(S.token);
                     next();
                     elements[elements.length - 1].value = new AST_DefaultAssign({
@@ -2143,7 +2163,18 @@ function parse($TEXT, options) {
             if (!options.strict && is("punc", "}"))
                 // allow trailing comma
                 break;
+
             start = S.token;
+            if (start.type == "expand") {
+                next();
+                a.push(new AST_Expansion({
+                    start: start,
+                    expression: expression(false),
+                    end: prev(),
+                }));
+                continue;
+            }
+
             var name = as_property_name();
             var value;
 

test/compress/harmony.js

@@ -695,3 +695,37 @@ export_default_class_decl: {
     }
     expect_exact: "export default class Car{};export class Cab{};"
 }
+
+object_rest_spread: {
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        var   { w: w1, ...V } = { w: 7, x: 1, y: 2 }; console.log(w1, V);
+        let   { w: w2, ...L } = { w: 8, x: 3, y: 4 }; console.log(w2, L);
+        const { w: w3, ...C } = { w: 9, x: 5, y: 6 }; console.log(w3, C);
+
+        let b;
+        ({ b, ...V } = { a: 1, b: 2, c: 3 }); console.log(V);
+        ({ b, ...L } = { a: 4, b: 5, c: 6 }); console.log(L);
+
+        (function({ y, ...p }){ console.log(p); })({ x: 1, y: 2, z: 3 });
+        (({ y, ...p }) =>     { console.log(p); })({ x: 4, y: 5, z: 6 });
+
+        const T = { a: 1, b: 2 }; console.log({ ...T, w: 0, ...{}, ...L, ...{K: 9} });
+    }
+    expect: {
+        var   { w: o, ...l } = { w: 7, x: 1, y: 2 }; console.log(o, l);
+        let   { w: c, ...n } = { w: 8, x: 3, y: 4 }; console.log(c, n);
+        const { w: e, ...s } = { w: 9, x: 5, y: 6 }; console.log(e, s);
+
+        let g;
+        ({ b: g, ...l } = { a: 1, b: 2, c: 3 }); console.log(l);
+        ({ b: g, ...n } = { a: 4, b: 5, c: 6 }); console.log(n);
+
+        (function({ y: o, ...l }) { console.log(l); })({ x: 1, y: 2, z: 3 });
+        (({ y: o, ...l }) =>      { console.log(l); })({ x: 4, y: 5, z: 6 });
+
+        const w = { a: 1, b: 2 }; console.log({ ...w, w: 0, ...{}, ...n, ...{ K: 9 } });
+    }
+}

test/mocha/lhs-expressions.js

@@ -253,13 +253,13 @@ describe("Left-hand side expressions", function () {
         // Multiple spreads are not allowed in destructuring array
         expect("[...a, ...b] = [1, 2, 3, 4]", "Spread must the be last element in destructuring array");
 
-        // Spread in obvious object pattern
-        expect("({...a} = foo)", "Unexpected token: expand (...)");
-
         // Spread in block should not be allowed
         expect("{...a} = foo", "Unexpected token: expand (...)");
 
-        // Not in standard yet
-        expect("let foo = {bar: 42}, bar; bar = {...foo}", "Unexpected token: expand (...)");
+        // Object spread must be last in destructuring declaration
+        expect("let { ...x, a } = o;", "Unexpected token: punc (,)");
+
+        // Only one spread per destructuring declaration
+        expect("let { a, ...x, ...y } = o;", "Unexpected token: punc (,)");
     });
 });