Implement handling of arrow functions in the parser

test/mjsunit/harmony/arrow-functions-parsing.js

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --harmony_arrow_functions
+
+
+// Test basic arrow functions syntax.
+
+// Bracketed block body.
+var bracketedEmptyBody = () => {};
+var bracketedNoArgs = () => { return 42; };
+var bracketedIdent = x => { return x; };
+var bracketedIdentParens = (x) => { return x; };
+var bracketedAddTwo = (x, y) => { return x + y; };
+var bracketedAddThree = (x, y, z) => { return x + y + z; };
+
+// Single expression body.
+var noArgs = () => 24;
+var ident = x => x;
+var square = x => x * x;
+var addTwo = (x, y) => x + y;
+var addThree = (x, y, z) => x + y + z;
+var mutateObject = (x, y) => x.a = y;
+var objectLiteral = () => ({"value": 42});
+var returnsArrowFun = x => y => x + y;
+var returnsArrowFun = (x, y) => (u, v) => x*u + y*v;
+
+var yIsUndefined = x => x, y
+assertEquals(y, undefined);
+
+// Parsing arrow functions introduces a return in ParseAssignmentExpression
+// when a closing parenthesis is found. This tests that errors are still
+// raised when closing them incorrectly.
+assertThrows(");", SyntaxError);
+assertThrows(") => 0;", SyntaxError);
+
+assertThrows("=> 0;", SyntaxError);                        // Empty param list not optional
+assertThrows("var f = =>;", SyntaxError);                  // No arguments or body
+assertThrows("var f = () =>;", SyntaxError);               // No body
+assertThrows("var f = => {};", SyntaxError);               // No argument list or single argument
+assertThrows("var f = ) => {};", SyntaxError);             // No opening paren in parameter list
+assertThrows("var f = x, y => {};", SyntaxError);          // Multiple args without parens
+assertThrows("var f = return => {};", SyntaxError);        // Argument name is reserved
+assertThrows("var f = (a,if) => {};", SyntaxError);        // Argument name in list is reserved
+assertThrows("var f = () => {'value': 42};", SyntaxError); // Object literal must be parenthesized
+
+// TODO(aperez): Those cases do not pass because for now it is not possible
+// to know whether expressions have multiple parenthesis nesting levels from
+// the AST.
+//assertThrows("(()) => 0;", SyntaxError);                   // Double-paren not allowed
+//assertThrows("((x)) => 0;", SyntaxError);                  // Double-paren not allowed
+//assertThrows("((x, y)) => 0;", SyntaxError);               // Double-paren not allowed