Merge pull request #872 from fabiosantoscode/feature/harmony-defaults

Feature/harmony defaults

lib/ast.js

@@ -384,7 +384,7 @@ var AST_ArrowParametersOrSeq = DEFNODE("ArrowParametersOrSeq", "expressions", {
     as_params: function (croak) {
         // We don't want anything which doesn't belong in a destructuring
         var root = this;
-        return this.expressions.map(function to_fun_args(ex) {
+        return this.expressions.map(function to_fun_args(ex, _, __, default_seen_above) {
             if (ex instanceof AST_Object) {
                 if (ex.properties.length == 0)
                     croak("Invalid destructuring function parameter", ex.start.line, ex.start.col);
@@ -392,6 +392,7 @@ var AST_ArrowParametersOrSeq = DEFNODE("ArrowParametersOrSeq", "expressions", {
                     start: ex.start,
                     end: ex.end,
                     is_array: false,
+                    default: default_seen_above,
                     names: ex.properties.map(to_fun_args)
                 });
             } else if (ex instanceof AST_ObjectSymbol) {
@@ -408,6 +409,7 @@ var AST_ArrowParametersOrSeq = DEFNODE("ArrowParametersOrSeq", "expressions", {
             } else if (ex instanceof AST_SymbolRef) {
                 return new AST_SymbolFunarg({
                     name: ex.name,
+                    default: default_seen_above,
                     start: ex.start,
                     end: ex.end
                 });
@@ -420,8 +422,11 @@ var AST_ArrowParametersOrSeq = DEFNODE("ArrowParametersOrSeq", "expressions", {
                     start: ex.start,
                     end: ex.end,
                     is_array: true,
+                    default: default_seen_above,
                     names: ex.elements.map(to_fun_args)
                 });
+            } else if (ex instanceof AST_Assign) {
+                return to_fun_args(ex.left, undefined, undefined, ex.right);
             } else {
                 croak("Invalid function parameter", ex.start.line, ex.start.col);
             }
@@ -485,7 +490,7 @@ var AST_Defun = DEFNODE("Defun", null, {
 }, AST_Lambda);
 
 /* -----[ DESTRUCTURING ]----- */
-var AST_Destructuring = DEFNODE("Destructuring", "names is_array", {
+var AST_Destructuring = DEFNODE("Destructuring", "names is_array default", {
     $documentation: "A destructuring of several names. Used in destructuring assignment and with destructuring function argument names",
     _walk: function(visitor) {
         return visitor._visit(this, function(){
@@ -1011,10 +1016,16 @@ var AST_SymbolAccessor = DEFNODE("SymbolAccessor", null, {
     $documentation: "The name of a property accessor (setter/getter function)"
 }, AST_Symbol);
 
-var AST_SymbolDeclaration = DEFNODE("SymbolDeclaration", "init", {
+var AST_SymbolDeclaration = DEFNODE("SymbolDeclaration", "init default", {
     $documentation: "A declaration symbol (symbol in var/const, function name or argument, symbol in catch)",
     $propdoc: {
-        init: "[AST_Node*/S] array of initializers for this declaration."
+        init: "[AST_Node*/S] array of initializers for this declaration.",
+        default: "[AST_Expression] The default for this parameter. For example, `= 6`"
+    },
+    _walk: function (visitor) {
+        return visitor._visit(this, function() {
+            if (this.default) this.default._walk(visitor);
+        });
     }
 }, AST_Symbol);
 

lib/output.js

@@ -639,6 +639,12 @@ function OutputStream(options) {
             name.print(output);
         })
         output.print(self.is_array ? "]" : "}");
+        if (self.default) {
+            output.space();
+            output.print('=');
+            output.space();
+            self.default.print(output)
+        }
     })
 
     DEFPRINT(AST_Debugger, function(self, output){
@@ -1275,9 +1281,21 @@ function OutputStream(options) {
         output.space();
         self.value.print(output);
     });
-    DEFPRINT(AST_Symbol, function(self, output){
-        var def = self.definition();
-        output.print_name(def ? def.mangled_name || def.name : self.name);
+    AST_Symbol.DEFMETHOD("_do_print", function(output){
+        var def = this.definition();
+        output.print_name(def ? def.mangled_name || def.name : this.name);
+    });
+    DEFPRINT(AST_Symbol, function (self, output) {
+        self._do_print(output);
+    });
+    DEFPRINT(AST_SymbolDeclaration, function(self, output){
+        self._do_print(output);
+        if (self.default) {
+            output.space();
+            output.print('=');
+            output.space();
+            self.default.print(output)
+        }
     });
     DEFPRINT(AST_ObjectSymbol, function(self, output){
         var name = self.mangled_key || self.symbol.name;

lib/parse.js

@@ -1255,8 +1255,12 @@ function parse($TEXT, options) {
                 }));
                 next();
             } else if (is("name")) {
-                children.push(_make_symbol(sym_type));
-                next();
+                children.push(new (sym_type)({
+                    name  : String(S.token.value),
+                    start : S.token,
+                    default: (next(), is("operator", "=")) ? (next(), expression(false)) : undefined,
+                    end   : S.token
+                }));
             } else {
                 children.push(expression());
             }
@@ -1483,7 +1487,21 @@ function parse($TEXT, options) {
                 continue;
             }
             
-            if (!is("punc", ":")) {
+            if (is("operator", "=")) {
+                next();
+                a.push(new AST_Assign({
+                    start: start,
+                    // Symbol class doesn't matter. This is only meant to carry the symbol name into .as_params() since this is not normally valid.
+                    left: new AST_SymbolRef({
+                        start: start,
+                        end: start,
+                        name: name
+                    }),
+                    operator: "=",
+                    right: expression(false),
+                    end: prev()
+                }));
+            } else if (!is("punc", ":")) {
                 // It's one of those object destructurings, the value is its own name
                 a.push(new AST_ObjectSymbol({
                     start: start,