remove do expressions

src/expression.js

@@ -281,20 +281,6 @@ pp.parseExprAtom = function(refShorthandDefaultPos) {
   case tt._yield:
     if (this.inGenerator) this.unexpected()
 
-  case tt._do:
-    if (this.options.features["es7.doExpressions"]) {
-      let node = this.startNode()
-      this.next()
-      var oldInFunction = this.inFunction
-      var oldLabels = this.labels
-      this.labels = []
-      this.inFunction = false
-      node.body = this.parseBlock()
-      this.inFunction = oldInFunction
-      this.labels = oldLabels
-      return this.finishNode(node, "DoExpression")
-    }
-
   case tt.name:
     let start = this.markPosition()
     node = this.startNode()