Simplify parseBindingAtom

This way it's clearer that ES6 only adds specific features instead of
completely altering this behavior. Also, this provides better error messages
in ES6+ for keywords as lvalues.

src/lval.js

@@ -110,23 +110,19 @@ pp.parseRestBinding = function() {
 // Parses lvalue (assignable) atom.
 
 pp.parseBindingAtom = function() {
-  if (this.options.ecmaVersion < 6) return this.parseIdent()
-  switch (this.type) {
-  case tt.name:
-    return this.parseIdent()
-
-  case tt.bracketL:
-    let node = this.startNode()
-    this.next()
-    node.elements = this.parseBindingList(tt.bracketR, true, true)
-    return this.finishNode(node, "ArrayPattern")
-
-  case tt.braceL:
-    return this.parseObj(true)
-
-  default:
-    this.unexpected()
+  if (this.options.ecmaVersion >= 6) {
+    switch (this.type) {
+    case tt.bracketL:
+      let node = this.startNode()
+      this.next()
+      node.elements = this.parseBindingList(tt.bracketR, true, true)
+      return this.finishNode(node, "ArrayPattern")
+
+    case tt.braceL:
+      return this.parseObj(true)
+    }
   }
+  return this.parseIdent()
 }
 
 pp.parseBindingList = function(close, allowEmpty, allowTrailingComma) {

test/tests-harmony.js

@@ -12692,13 +12692,13 @@ testFail("function hello() {'use strict'; ({ i: 10, s(eval) { } }); }", "Binding
 
 testFail("function a() { \"use strict\"; ({ b(t, t) { } }); }", "Argument name clash (1:37)", {ecmaVersion: 6});
 
-testFail("var super", "Unexpected token (1:4)", {ecmaVersion: 6});
+testFail("var super", "Unexpected keyword 'super' (1:4)", {ecmaVersion: 6});
 
-testFail("var default", "Unexpected token (1:4)", {ecmaVersion: 6});
+testFail("var default", "Unexpected keyword 'default' (1:4)", {ecmaVersion: 6});
 
 testFail("let default", "Unexpected token (1:4)", {ecmaVersion: 6});
 
-testFail("const default", "Unexpected token (1:6)", {ecmaVersion: 6});
+testFail("const default", "Unexpected keyword 'default' (1:6)", {ecmaVersion: 6});
 
 testFail("\"use strict\"; ({ v: eval } = obj)", "Assigning to eval in strict mode (1:20)", {ecmaVersion: 6});
 
@@ -12750,10 +12750,10 @@ testFail("yield 10", "Unexpected token (1:6)", {ecmaVersion: 6});
 
 testFail("void { [1, 2]: 3 };", "Unexpected token (1:9)", {ecmaVersion: 6});
 
-testFail("let [this] = [10]", "Unexpected token (1:5)", {ecmaVersion: 6});
+testFail("let [this] = [10]", "Unexpected keyword 'this' (1:5)", {ecmaVersion: 6});
 testFail("let {this} = x", "Unexpected keyword 'this' (1:5)", {ecmaVersion: 6});
-testFail("let [function] = [10]", "Unexpected token (1:5)", {ecmaVersion: 6});
-testFail("let [function] = x", "Unexpected token (1:5)", {ecmaVersion: 6});
+testFail("let [function] = [10]", "Unexpected keyword 'function' (1:5)", {ecmaVersion: 6});
+testFail("let [function] = x", "Unexpected keyword 'function' (1:5)", {ecmaVersion: 6});
 testFail("([function] = [10])", "Unexpected token (1:10)", {ecmaVersion: 6});
 testFail("([this] = [10])", "Assigning to rvalue (1:2)", {ecmaVersion: 6});
 testFail("({this} = x)", "Unexpected keyword 'this' (1:2)", {ecmaVersion: 6});