Arrow function

ast/node.go

@@ -128,6 +128,23 @@ type (
 		DeclarationList []*VariableDeclaration
 	}
 
+	ConciseBody interface {
+		Node
+		_conciseBody()
+	}
+
+	ExpressionBody struct {
+		Expression Expression
+	}
+
+	ArrowFunctionLiteral struct {
+		Start           file.Idx
+		ParameterList   *ParameterList
+		Body            ConciseBody
+		Source          string
+		DeclarationList []*VariableDeclaration
+	}
+
 	Identifier struct {
 		Name unistring.String
 		Idx  file.Idx
@@ -238,6 +255,7 @@ func (*CallExpression) _expressionNode()        {}
 func (*ConditionalExpression) _expressionNode() {}
 func (*DotExpression) _expressionNode()         {}
 func (*FunctionLiteral) _expressionNode()       {}
+func (*ArrowFunctionLiteral) _expressionNode()  {}
 func (*Identifier) _expressionNode()            {}
 func (*NewExpression) _expressionNode()         {}
 func (*NullLiteral) _expressionNode()           {}
@@ -497,6 +515,9 @@ func (*SpreadElement) _property() {}
 
 func (*Identifier) _bindingTarget() {}
 
+func (*BlockStatement) _conciseBody() {}
+func (*ExpressionBody) _conciseBody() {}
+
 // ==== //
 // Node //
 // ==== //
@@ -525,6 +546,7 @@ func (self *CallExpression) Idx0() file.Idx        { return self.Callee.Idx0() }
 func (self *ConditionalExpression) Idx0() file.Idx { return self.Test.Idx0() }
 func (self *DotExpression) Idx0() file.Idx         { return self.Left.Idx0() }
 func (self *FunctionLiteral) Idx0() file.Idx       { return self.Function }
+func (self *ArrowFunctionLiteral) Idx0() file.Idx  { return self.Start }
 func (self *Identifier) Idx0() file.Idx            { return self.Idx }
 func (self *NewExpression) Idx0() file.Idx         { return self.New }
 func (self *NullLiteral) Idx0() file.Idx           { return self.Idx }
@@ -566,6 +588,7 @@ func (self *Binding) Idx0() file.Idx             { return self.Target.Idx0() }
 func (self *ForLoopInitializerVarDeclList) Idx0() file.Idx { return self.List[0].Idx0() }
 func (self *PropertyShort) Idx0() file.Idx                 { return self.Name.Idx }
 func (self *PropertyKeyed) Idx0() file.Idx                 { return self.Key.Idx0() }
+func (self *ExpressionBody) Idx0() file.Idx                { return self.Expression.Idx0() }
 
 // ==== //
 // Idx1 //
@@ -582,6 +605,7 @@ func (self *CallExpression) Idx1() file.Idx        { return self.RightParenthesi
 func (self *ConditionalExpression) Idx1() file.Idx { return self.Test.Idx1() }
 func (self *DotExpression) Idx1() file.Idx         { return self.Identifier.Idx1() }
 func (self *FunctionLiteral) Idx1() file.Idx       { return self.Body.Idx1() }
+func (self *ArrowFunctionLiteral) Idx1() file.Idx  { return self.Body.Idx1() }
 func (self *Identifier) Idx1() file.Idx            { return file.Idx(int(self.Idx) + len(self.Name)) }
 func (self *NewExpression) Idx1() file.Idx         { return self.RightParenthesis + 1 }
 func (self *NullLiteral) Idx1() file.Idx           { return file.Idx(int(self.Idx) + 4) } // "null"
@@ -656,3 +680,5 @@ func (self *PropertyShort) Idx1() file.Idx {
 }
 
 func (self *PropertyKeyed) Idx1() file.Idx { return self.Value.Idx1() }
+
+func (self *ExpressionBody) Idx1() file.Idx { return self.Expression.Idx1() }

builtin_function.go

@@ -33,6 +33,8 @@ repeat:
 	switch f := obj.self.(type) {
 	case *funcObject:
 		return newStringValue(f.src)
+	case *arrowFuncObject:
+		return newStringValue(f.src)
 	case *nativeFuncObject:
 		return newStringValue(fmt.Sprintf("function %s() { [native code] }", nilSafe(f.getStr("name", nil)).toString()))
 	case *boundFuncObject:
@@ -46,6 +48,8 @@ repeat:
 		switch c := f.target.self.(type) {
 		case *funcObject:
 			name = c.src
+		case *arrowFuncObject:
+			name = c.src
 		case *nativeFuncObject:
 			name = nilSafe(f.getStr("name", nil)).toString().String()
 		case *boundFuncObject:

compiler.go

@@ -248,6 +248,8 @@ type scope struct {
 
 	// is a function or a top-level lexical environment
 	function bool
+	// is an arrow function's top-level lexical environment (functions only)
+	arrow bool
 	// is a variable environment, i.e. the target for dynamically created var bindings
 	variable bool
 	// a function scope that has at least one direct eval() and non-strict, so the variables can be added dynamically
@@ -365,6 +367,8 @@ func (p *Program) _dumpCode(indent string, logger func(format string, args ...in
 		logger("%s %d: %T(%v)", indent, pc, ins, ins)
 		if f, ok := ins.(*newFunc); ok {
 			f.prg._dumpCode(indent+">", logger)
+		} else if f, ok := ins.(*newArrowFunc); ok {
+			f.prg._dumpCode(indent+">", logger)
 		}
 	}
 }
@@ -395,7 +399,7 @@ func (s *scope) lookupName(name unistring.String) (binding *binding, noDynamics
 				return
 			}
 		}
-		if name == "arguments" && curScope.function {
+		if name == "arguments" && curScope.function && !curScope.arrow {
 			curScope.argsNeeded = true
 			binding, _ = curScope.bindName(name)
 			return