support default values (#4442)

1 files changed, 91 insertions, 18 deletions

diff --git a/lib/parse.js b/lib/parse.js
index 87293cab..c8ad531f 100644
--- a/lib/parse.js
+++ b/lib/parse.js
@@ -1041,11 +1041,30 @@ function parse($TEXT, options) {
     function to_funarg(node) {
         if (node instanceof AST_Array) return new AST_DestructuredArray({
             start: node.start,
-            elements: node.elements.map(function(node) {
-                return node instanceof AST_Hole ? node : to_funarg(node);
-            }),
+            elements: node.elements.map(to_funarg),
+            end: node.end,
+        });
+        if (node instanceof AST_Assign) return new AST_DefaultValue({
+            start: node.start,
+            name: to_funarg(node.left),
+            value: node.right,
             end: node.end,
         });
+        if (node instanceof AST_DefaultValue) {
+            node.name = to_funarg(node.name);
+            return node;
+        }
+        if (node instanceof AST_DestructuredArray) {
+            node.elements = node.elements.map(to_funarg);
+            return node;
+        }
+        if (node instanceof AST_DestructuredObject) {
+            node.properties.forEach(function(prop) {
+                prop.value = to_funarg(prop.value);
+            });
+            return node;
+        }
+        if (node instanceof AST_Hole) return node;
         if (node instanceof AST_Object) return new AST_DestructuredObject({
             start: node.start,
             properties: node.properties.map(function(prop) {
@@ -1122,7 +1141,7 @@ function parse($TEXT, options) {
         var was_funarg = S.in_funarg;
         S.in_funarg = S.in_function;
         var argnames = expr_list(")", !options.strict, false, function() {
-            return maybe_destructured(AST_SymbolFunarg);
+            return maybe_default(AST_SymbolFunarg);
         });
         S.in_funarg = was_funarg;
         var loop = S.in_loop;
@@ -1468,6 +1487,32 @@ function parse($TEXT, options) {
                 }));
                 continue;
             }
+            if (is_token(peek(), "operator", "=")) {
+                var name = as_symbol(AST_SymbolRef);
+                next();
+                a.push(new AST_ObjectKeyVal({
+                    start: start,
+                    key: start.value,
+                    value: new AST_Assign({
+                        start: start,
+                        left: name,
+                        operator: "=",
+                        right: maybe_assign(),
+                        end: prev(),
+                    }),
+                    end: prev(),
+                }));
+                continue;
+            }
+            if (is_token(peek(), "punc", ",") || is_token(peek(), "punc", "}")) {
+                a.push(new AST_ObjectKeyVal({
+                    start: start,
+                    key: start.value,
+                    value: as_symbol(AST_SymbolRef),
+                    end: prev(),
+                }));
+                continue;
+            }
             var key = as_property_key();
             if (is("punc", "(")) {
                 var func_start = S.token;
@@ -1492,15 +1537,6 @@ function parse($TEXT, options) {
                 }));
                 continue;
             }
-            if (is("punc", ",") || is("punc", "}")) {
-                a.push(new AST_ObjectKeyVal({
-                    start: start,
-                    key: key,
-                    value: _make_symbol(AST_SymbolRef, start),
-                    end: prev(),
-                }));
-                continue;
-            }
             if (start.type == "name") switch (key) {
               case "async":
                 key = as_property_key();
@@ -1601,7 +1637,7 @@ function parse($TEXT, options) {
             return new AST_DestructuredArray({
                 start: start,
                 elements: expr_list("]", !options.strict, true, function() {
-                    return maybe_destructured(type);
+                    return maybe_default(type);
                 }),
                 end: prev(),
             });
@@ -1620,15 +1656,25 @@ function parse($TEXT, options) {
                     a.push(new AST_DestructuredKeyVal({
                         start: key_start,
                         key: key,
-                        value: maybe_destructured(type),
+                        value: maybe_default(type),
                         end: prev(),
                     }));
                     continue;
                 }
+                var name = as_symbol(type);
+                if (is("operator", "=")) {
+                    next();
+                    name = new AST_DefaultValue({
+                        start: name.start,
+                        name: name,
+                        value: maybe_assign(),
+                        end: prev(),
+                    });
+                }
                 a.push(new AST_DestructuredKeyVal({
                     start: key_start,
                     key: key_start.value,
-                    value: as_symbol(type),
+                    value: name,
                     end: prev(),
                 }));
             }
@@ -1642,6 +1688,19 @@ function parse($TEXT, options) {
         return as_symbol(type);
     }
 
+    function maybe_default(type) {
+        var start = S.token;
+        var name = maybe_destructured(type);
+        if (!is("operator", "=")) return name;
+        next();
+        return new AST_DefaultValue({
+            start: start,
+            name: name,
+            value: maybe_assign(),
+            end: prev(),
+        });
+    }
+
     function mark_pure(call) {
         var start = call.start;
         var comments = start.comments_before;
@@ -1788,20 +1847,34 @@ function parse($TEXT, options) {
         if (node instanceof AST_Array) {
             var elements = node.elements.map(to_destructured);
             return all(elements, function(node) {
-                return node instanceof AST_Destructured || node instanceof AST_Hole || is_assignable(node);
+                return node instanceof AST_DefaultValue
+                    || node instanceof AST_Destructured
+                    || node instanceof AST_Hole
+                    || is_assignable(node);
             }) ? new AST_DestructuredArray({
                 start: node.start,
                 elements: elements,
                 end: node.end,
             }) : node;
         }
+        if (node instanceof AST_Assign) {
+            var name = to_destructured(node.left);
+            return name instanceof AST_Destructured || is_assignable(name) ? new AST_DefaultValue({
+                start: node.start,
+                name: name,
+                value: node.right,
+                end: node.end,
+            }) : node;
+        }
         if (!(node instanceof AST_Object)) return node;
         var props = [];
         for (var i = 0; i < node.properties.length; i++) {
             var prop = node.properties[i];
             if (!(prop instanceof AST_ObjectKeyVal)) return node;
             var value = to_destructured(prop.value);
-            if (!(value instanceof AST_Destructured || is_assignable(value))) return node;
+            if (!(value instanceof AST_DefaultValue || value instanceof AST_Destructured || is_assignable(value))) {
+                return node;
+            }
             props.push(new AST_DestructuredKeyVal({
                 start: prop.start,
                 key: prop.key,