Restore earlier behaviour when parsing non-simple arrow function bodies

Author: caitp

src/compiler/parser.ts

@@ -3038,8 +3038,9 @@ module ts {
 
             // If we have an arrow, then try to parse the body. Even if not, try to parse if we
             // have an opening brace, just in case we're in an error state.
-            arrowFunction.equalsGreaterThanToken = parseExpectedToken(SyntaxKind.EqualsGreaterThanToken, false, Diagnostics._0_expected, "=>");
-            if (arrowFunction.equalsGreaterThanToken.kind === SyntaxKind.EqualsGreaterThanToken || token === SyntaxKind.OpenBraceToken) {
+            var lastToken = token;
+            arrowFunction.equalsGreaterThanToken = parseExpectedToken(SyntaxKind.EqualsGreaterThanToken, /*reportAtCurrentPosition:*/false, Diagnostics._0_expected, "=>");
+            if (lastToken === SyntaxKind.EqualsGreaterThanToken || lastToken === SyntaxKind.OpenBraceToken) {
                 arrowFunction.body = parseArrowFunctionExpressionBody();
             }
             else {