better async contextual identifiers

acorn.js

@@ -2079,15 +2079,6 @@
     next();
     return parseFunction(node, true, false);
   }
-
-  function eatAsync() {
-    if (tokType === _name && tokVal === "async") {
-      next();
-      return true;
-    } else {
-      return false;
-    }
-  }
   
   function parseIfStatement(node) {
     next();
@@ -2727,23 +2718,28 @@
       } else first = false;
 
       var prop = startNode(), isGenerator, isAsync;
-      if (options.ecmaVersion >= 7) {
-        isAsync = eatAsync();
-        if (isAsync && tokType === _star) unexpected();
+      if (options.ecmaVersion >= 7 && tokType === _ellipsis) {
+        prop = parseMaybeUnary();
+        prop.type = "SpreadProperty";
+        node.properties.push(prop);
+        continue;
       }
       if (options.ecmaVersion >= 6) {
         prop.method = false;
         prop.shorthand = false;
         isGenerator = eat(_star);
       }
-      if (options.ecmaVersion >= 7 && tokType === _ellipsis) {
-        if (isAsync || isGenerator) unexpected();
-        prop = parseMaybeUnary();
-        prop.type = "SpreadProperty";
-        node.properties.push(prop);
-        continue;
+      if (options.ecmaVersion >= 7 && !isGenerator && tokType === _name && tokVal === "async") {
+        var asyncId = parseIdent();
+        if (tokType === _colon || tokType === _parenL) {
+          prop.key = asyncId;
+        } else {
+          isAsync = true;
+          parsePropertyName(prop);
+        }
+      } else {
+        parsePropertyName(prop);
       }
-      parsePropertyName(prop);
       if (eat(_colon)) {
         prop.value = parseExpression(true);
         prop.kind = "init";
@@ -2953,12 +2949,18 @@
         method['static'] = false;
         }
       var isAsync = false;
-      if (options.ecmaVersion >= 7) {
-        isAsync = eatAsync();
-        if (isAsync && tokType === _star) unexpected();
-      }
       var isGenerator = eat(_star);
-      parsePropertyName(method);
+       if (options.ecmaVersion >= 7 && !isGenerator && tokType === _name && tokVal === "async") {
+        var asyncId = parseIdent();
+        if (tokType === _colon || tokType === _parenL) {
+          method.key = asyncId;
+        } else {
+          isAsync = true;
+          parsePropertyName(method);
+        }
+      } else {
+        parsePropertyName(method);
+      }
       if (tokType !== _parenL && !method.computed && method.key.type === "Identifier" &&
           (method.key.name === "get" || method.key.name === "set" || (options.playground && method.key.name === "memo"))) {
         if (isGenerator || isAsync) unexpected();

test/tests-6to5.js

@@ -1733,6 +1733,174 @@ test('(function() { var async; async = 10 })', {
   ranges: true
 });
 
+test('class Test { async() {} }', {
+  type: "Program",
+  start: 0,
+  end: 25,
+  body: [{
+    type: "ClassDeclaration",
+    start: 0,
+    end: 25,
+    id: {
+      type: "Identifier",
+      start: 6,
+      end: 10,
+      name: "Test"
+    },
+    superClass: null,
+    body: {
+      type: "ClassBody",
+      start: 11,
+      end: 25,
+      body: [{
+        type: "MethodDefinition",
+        start: 13,
+        end: 23,
+        static: false,
+        key: {
+          type: "Identifier",
+          start: 13,
+          end: 18,
+          name: "async"
+        },
+        kind: "",
+        value: {
+          type: "FunctionExpression",
+          start: 18,
+          end: 23,
+          id: null,
+          params: [],
+          defaults: [],
+          rest: null,
+          generator: false,
+          async: false,
+          body: {
+            type: "BlockStatement",
+            start: 21,
+            end: 23,
+            body: []
+          },
+          expression: false
+        }
+      }]
+    }
+  }]
+}, {
+  ecmaVersion: 7
+});
+
+test('var obj = { async: "test" };', {
+  type: "Program",
+  start: 0,
+  end: 28,
+  body: [{
+    type: "VariableDeclaration",
+    start: 0,
+    end: 28,
+    declarations: [{
+      type: "VariableDeclarator",
+      start: 4,
+      end: 27,
+      id: {
+        type: "Identifier",
+        start: 4,
+        end: 7,
+        name: "obj"
+      },
+      init: {
+        type: "ObjectExpression",
+        start: 10,
+        end: 27,
+        properties: [{
+          type: "Property",
+          start: 12,
+          end: 25,
+          method: false,
+          shorthand: false,
+          key: {
+            type: "Identifier",
+            start: 12,
+            end: 17,
+            name: "async"
+          },
+          value: {
+            type: "Literal",
+            start: 19,
+            end: 25,
+            value: "test",
+            raw: "\"test\""
+          },
+          kind: "init"
+        }]
+      }
+    }],
+    kind: "var"
+  }]
+}, {
+  ecmaVersion: 7
+});
+
+test('var obj = { async() {} };', {
+  type: "Program",
+  start: 0,
+  end: 25,
+  body: [{
+    type: "VariableDeclaration",
+    start: 0,
+    end: 25,
+    declarations: [{
+      type: "VariableDeclarator",
+      start: 4,
+      end: 24,
+      id: {
+        type: "Identifier",
+        start: 4,
+        end: 7,
+        name: "obj"
+      },
+      init: {
+        type: "ObjectExpression",
+        start: 10,
+        end: 24,
+        properties: [{
+          type: "Property",
+          start: 12,
+          end: 22,
+          method: true,
+          shorthand: false,
+          key: {
+            type: "Identifier",
+            start: 12,
+            end: 17,
+            name: "async"
+          },
+          kind: "init",
+          value: {
+            type: "FunctionExpression",
+            start: 17,
+            end: 22,
+            id: null,
+            params: [],
+            defaults: [],
+            rest: null,
+            generator: false,
+            body: {
+              type: "BlockStatement",
+              start: 20,
+              end: 22,
+              body: []
+            },
+            expression: false
+          }
+        }]
+      }
+    }],
+    kind: "var"
+  }]
+}, {
+  ecmaVersion: 7
+});
+
 // ES7: Abstract references
 
 test('foo::bar;', {