Add async gen templates for dstr-binding

src/dstr-binding/default/async-gen-func-decl-dflt.template

+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+path: language/statements/async-generator/dstr-dflt-
+name: async generator function declaration (default parameter)
+esid: sec-asyncgenerator-definitions-instantiatefunctionobject
+features: [async-iteration]
+info: |
+    AsyncGeneratorDeclaration : async [no LineTerminator here] function * BindingIdentifier
+        ( FormalParameters ) { AsyncGeneratorBody }
+
+        [...]
+        3. Let F be ! AsyncGeneratorFunctionCreate(Normal, FormalParameters, AsyncGeneratorBody,
+            scope, strict).
+        [...]
+flags: [async]
+---*/
+
+var callCount = 0;
+async function* f(/*{ elems }*/ = /*{ vals }*/) {
+  /*{ body }*/
+  callCount = callCount + 1;
+};
+f().next().then(() => {
+    assert.sameValue(callCount, 1, 'invoked exactly once');
+}).then($DONE, $DONE);

src/dstr-binding/default/async-gen-func-decl.template

+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+path: language/statements/async-generator/dstr-
+name: async generator function declaration
+esid: sec-asyncgenerator-definitions-instantiatefunctionobject
+features: [async-iteration]
+info: |
+    AsyncGeneratorDeclaration : async [no LineTerminator here] function * BindingIdentifier
+        ( FormalParameters ) { AsyncGeneratorBody }
+
+        [...]
+        3. Let F be ! AsyncGeneratorFunctionCreate(Normal, FormalParameters, AsyncGeneratorBody,
+            scope, strict).
+        [...]
+flags: [async]
+---*/
+
+var callCount = 0;
+async function* f(/*{ elems }*/) {
+  /*{ body }*/
+  callCount = callCount + 1;
+};
+f(/*{ vals }*/).next().then(() => {
+    assert.sameValue(callCount, 1, 'invoked exactly once');
+}).then($DONE, $DONE);

src/dstr-binding/default/async-gen-func-expr-dflt.template

+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+path: language/expressions/async-generator/dstr-dflt-
+name: async generator function expression (default parameter)
+esid: sec-asyncgenerator-definitions-evaluation
+features: [async-iteration]
+info: |
+    AsyncGeneratorExpression : async [no LineTerminator here] function * ( FormalParameters ) {
+        AsyncGeneratorBody }
+    
+        [...]
+        3. Let closure be ! AsyncGeneratorFunctionCreate(Normal, FormalParameters,
+           AsyncGeneratorBody, scope, strict).
+        [...]
+flags: [async]
+---*/
+
+var callCount = 0;
+var f;
+f = async function*(/*{ elems }*/ = /*{ vals }*/) {
+  /*{ body }*/
+  callCount = callCount + 1;
+};
+
+f().next().then(() => {
+    assert.sameValue(callCount, 1, 'invoked exactly once');
+}).then($DONE, $DONE);

src/dstr-binding/default/async-gen-func-expr.template

+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+path: language/expressions/async-generator/dstr-
+name: async generator function expression
+esid: sec-asyncgenerator-definitions-evaluation
+features: [async-iteration]
+info: |
+    AsyncGeneratorExpression : async [no LineTerminator here] function * ( FormalParameters ) {
+        AsyncGeneratorBody }
+    
+        [...]
+        3. Let closure be ! AsyncGeneratorFunctionCreate(Normal, FormalParameters,
+           AsyncGeneratorBody, scope, strict).
+        [...]
+flags: [async]
+---*/
+
+var callCount = 0;
+var f;
+f = async function*(/*{ elems }*/) {
+  /*{ body }*/
+  callCount = callCount + 1;
+};
+
+f(/*{ vals }*/).next().then(() => {
+    assert.sameValue(callCount, 1, 'invoked exactly once');
+}).then($DONE, $DONE);

src/dstr-binding/default/async-gen-func-named-expr-dflt.template

+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+path: language/expressions/async-generator/dstr-named-dflt-
+name: async generator named function expression (default parameter)
+esid: sec-asyncgenerator-definitions-evaluation
+features: [async-iteration]
+info: |
+    AsyncGeneratorExpression : async [no LineTerminator here] function * BindingIdentifier
+        ( FormalParameters ) { AsyncGeneratorBody }
+    
+        [...]
+        7. Let closure be ! AsyncGeneratorFunctionCreate(Normal, FormalParameters,
+           AsyncGeneratorBody, funcEnv, strict).
+        [...]
+flags: [async]
+---*/
+
+var callCount = 0;
+var f;
+f = async function* g(/*{ elems }*/ = /*{ vals }*/) {
+  /*{ body }*/
+  callCount = callCount + 1;
+};
+
+f().next().then(() => {
+    assert.sameValue(callCount, 1, 'invoked exactly once');
+}).then($DONE, $DONE);

src/dstr-binding/default/async-gen-func-named-expr.template

+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+path: language/expressions/async-generator/dstr-named-
+name: async generator named function expression
+esid: sec-asyncgenerator-definitions-evaluation
+features: [async-iteration]
+info: |
+    AsyncGeneratorExpression : async [no LineTerminator here] function * BindingIdentifier
+        ( FormalParameters ) { AsyncGeneratorBody }
+    
+        [...]
+        7. Let closure be ! AsyncGeneratorFunctionCreate(Normal, FormalParameters,
+           AsyncGeneratorBody, funcEnv, strict).
+        [...]
+flags: [async]
+---*/
+
+var callCount = 0;
+var f;
+f = async function* g(/*{ elems }*/) {
+  /*{ body }*/
+  callCount = callCount + 1;
+};
+
+f(/*{ vals }*/).next().then(() => {
+    assert.sameValue(callCount, 1, 'invoked exactly once');
+}).then($DONE, $DONE);

src/dstr-binding/default/async-gen-meth.template

+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+path: language/expressions/object/dstr-async-gen-meth-
+name: async generator method
+esid: sec-asyncgenerator-definitions-propertydefinitionevaluation
+features: [async-iteration]
+info: |
+    AsyncGeneratorMethod :
+        async [no LineTerminator here] * PropertyName ( UniqueFormalParameters )
+            { AsyncGeneratorBody }
+
+    1. Let propKey be the result of evaluating PropertyName.
+    2. ReturnIfAbrupt(propKey).
+    3. If the function code for this AsyncGeneratorMethod is strict mode code, let strict be true.
+       Otherwise let strict be false.
+    4. Let scope be the running execution context's LexicalEnvironment.
+    5. Let closure be ! AsyncGeneratorFunctionCreate(Method, UniqueFormalParameters,
+       AsyncGeneratorBody, scope, strict).
+    [...]
+flags: [async]
+---*/
+
+var callCount = 0;
+var obj = {
+  async *method(/*{ elems }*/) {
+    /*{ body }*/
+    callCount = callCount + 1;
+  }
+};
+
+obj.method(/*{ vals }*/).next().then(() => {
+    assert.sameValue(callCount, 1, 'invoked exactly once');
+}).then($DONE, $DONE);

src/dstr-binding/default/async-gen-method-dflt.template

+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+path: language/expressions/object/dstr-async-gen-meth-dflt-
+name: async generator method (default parameter)
+esid: sec-asyncgenerator-definitions-propertydefinitionevaluation
+features: [async-iteration]
+info: |
+    AsyncGeneratorMethod :
+        async [no LineTerminator here] * PropertyName ( UniqueFormalParameters )
+            { AsyncGeneratorBody }
+
+    1. Let propKey be the result of evaluating PropertyName.
+    2. ReturnIfAbrupt(propKey).
+    3. If the function code for this AsyncGeneratorMethod is strict mode code, let strict be true.
+       Otherwise let strict be false.
+    4. Let scope be the running execution context's LexicalEnvironment.
+    5. Let closure be ! AsyncGeneratorFunctionCreate(Method, UniqueFormalParameters,
+       AsyncGeneratorBody, scope, strict).
+    [...]
+flags: [async]
+---*/
+
+var callCount = 0;
+var obj = {
+  async *method(/*{ elems }*/ = /*{ vals }*/) {
+    /*{ body }*/
+    callCount = callCount + 1;
+  }
+};
+
+obj.method().next().then(() => {
+    assert.sameValue(callCount, 1, 'invoked exactly once');
+}).then($DONE, $DONE);

src/dstr-binding/default/cls-decl-async-gen-meth-dflt.template

+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+path: language/statements/class/dstr-async-gen-meth-dflt-
+name: class expression async generator method (default parameters)
+esid: sec-class-definitions-runtime-semantics-evaluation
+features: [async-iteration]
+info: |
+    ClassDeclaration : class BindingIdentifier ClassTail
+
+    1. Let className be StringValue of BindingIdentifier.
+    2. Let value be the result of ClassDefinitionEvaluation of ClassTail with
+       argument className.
+    [...]
+
+    14.5.14 Runtime Semantics: ClassDefinitionEvaluation
+
+    21. For each ClassElement m in order from methods
+        a. If IsStatic of m is false, then
+           i. Let status be the result of performing
+              PropertyDefinitionEvaluation for m with arguments proto and
+              false.
+        [...]
+
+    Runtime Semantics: PropertyDefinitionEvaluation
+
+    AsyncGeneratorMethod :
+        async [no LineTerminator here] * PropertyName ( UniqueFormalParameters )
+            { AsyncGeneratorBody }
+
+    1. Let propKey be the result of evaluating PropertyName.
+    2. ReturnIfAbrupt(propKey).
+    3. If the function code for this AsyncGeneratorMethod is strict mode code, let strict be true.
+       Otherwise let strict be false.
+    4. Let scope be the running execution context's LexicalEnvironment.
+    5. Let closure be ! AsyncGeneratorFunctionCreate(Method, UniqueFormalParameters,
+       AsyncGeneratorBody, scope, strict).
+    [...]
+flags: [async]
+---*/
+
+var callCount = 0;
+class C {
+  async *method(/*{ elems }*/ = /*{ vals }*/) {
+    /*{ body }*/
+    callCount = callCount + 1;
+  }
+};
+
+new C().method().next().then(() => {
+    assert.sameValue(callCount, 1, 'invoked exactly once');    
+}).then($DONE, $DONE);

src/dstr-binding/default/cls-decl-async-gen-meth-static-dflt.template

+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+path: language/statements/class/dstr-async-gen-meth-static-dflt-
+name: static class expression async generator method (default parameter)
+esid: sec-runtime-semantics-bindingclassdeclarationevaluation
+features: [async-iteration]
+info: |
+    ClassDeclaration : class BindingIdentifier ClassTail
+
+    1. Let className be StringValue of BindingIdentifier.
+    2. Let value be the result of ClassDefinitionEvaluation of ClassTail with
+       argument className.
+    [...]
+
+    14.5.14 Runtime Semantics: ClassDefinitionEvaluation
+
+    21. For each ClassElement m in order from methods
+        a. If IsStatic of m is false, then
+        b. Else,
+           Let status be the result of performing PropertyDefinitionEvaluation for
+           m with arguments F and false.
+    [...]
+
+    Runtime Semantics: PropertyDefinitionEvaluation
+
+    AsyncGeneratorMethod :
+        async [no LineTerminator here] * PropertyName ( UniqueFormalParameters )
+            { AsyncGeneratorBody }
+
+    1. Let propKey be the result of evaluating PropertyName.
+    2. ReturnIfAbrupt(propKey).
+    3. If the function code for this AsyncGeneratorMethod is strict mode code, let strict be true.
+       Otherwise let strict be false.
+    4. Let scope be the running execution context's LexicalEnvironment.
+    5. Let closure be ! AsyncGeneratorFunctionCreate(Method, UniqueFormalParameters,
+       AsyncGeneratorBody, scope, strict).
+    [...]
+flags: [async]
+---*/
+
+var callCount = 0;
+class C {
+  static async *method(/*{ elems }*/ = /*{ vals }*/) {
+    /*{ body }*/
+    callCount = callCount + 1;
+  }
+};
+
+C.method().next().then(() => {
+    assert.sameValue(callCount, 1, 'invoked exactly once');    
+}).then($DONE, $DONE);

src/dstr-binding/default/cls-decl-async-gen-meth-static.template

+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+path: language/statements/class/dstr-async-gen-meth-static-
+name: static class expression async generator method
+esid: sec-runtime-semantics-bindingclassdeclarationevaluation
+features: [async-iteration]
+info: |
+    ClassDeclaration : class BindingIdentifier ClassTail
+
+    1. Let className be StringValue of BindingIdentifier.
+    2. Let value be the result of ClassDefinitionEvaluation of ClassTail with
+       argument className.
+    [...]
+
+    14.5.14 Runtime Semantics: ClassDefinitionEvaluation
+
+    21. For each ClassElement m in order from methods
+        a. If IsStatic of m is false, then
+        b. Else,
+           Let status be the result of performing PropertyDefinitionEvaluation for
+           m with arguments F and false.
+    [...]
+
+    Runtime Semantics: PropertyDefinitionEvaluation
+
+    AsyncGeneratorMethod :
+        async [no LineTerminator here] * PropertyName ( UniqueFormalParameters )
+            { AsyncGeneratorBody }
+
+    1. Let propKey be the result of evaluating PropertyName.
+    2. ReturnIfAbrupt(propKey).
+    3. If the function code for this AsyncGeneratorMethod is strict mode code, let strict be true.
+       Otherwise let strict be false.
+    4. Let scope be the running execution context's LexicalEnvironment.
+    5. Let closure be ! AsyncGeneratorFunctionCreate(Method, UniqueFormalParameters,
+       AsyncGeneratorBody, scope, strict).
+    [...]
+flags: [async]
+---*/
+
+var callCount = 0;
+class C {
+  static async *method(/*{ elems }*/) {
+    /*{ body }*/
+    callCount = callCount + 1;
+  }
+};
+
+C.method(/*{ vals }*/).next().then(() => {
+    assert.sameValue(callCount, 1, 'invoked exactly once');    
+}).then($DONE, $DONE);

src/dstr-binding/default/cls-decl-async-gen-meth.template

+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+path: language/statements/class/dstr-async-gen-meth-
+name: class expression method
+esid: sec-class-definitions-runtime-semantics-evaluation
+features: [async-iteration]
+info: |
+    ClassDeclaration : class BindingIdentifier ClassTail
+
+    1. Let className be StringValue of BindingIdentifier.
+    2. Let value be the result of ClassDefinitionEvaluation of ClassTail with
+       argument className.
+    [...]
+
+    14.5.14 Runtime Semantics: ClassDefinitionEvaluation
+
+    21. For each ClassElement m in order from methods
+        a. If IsStatic of m is false, then
+           i. Let status be the result of performing
+              PropertyDefinitionEvaluation for m with arguments proto and
+              false.
+        [...]
+
+    Runtime Semantics: PropertyDefinitionEvaluation
+
+    AsyncGeneratorMethod :
+        async [no LineTerminator here] * PropertyName ( UniqueFormalParameters )
+            { AsyncGeneratorBody }
+
+    1. Let propKey be the result of evaluating PropertyName.
+    2. ReturnIfAbrupt(propKey).
+    3. If the function code for this AsyncGeneratorMethod is strict mode code, let strict be true.
+       Otherwise let strict be false.
+    4. Let scope be the running execution context's LexicalEnvironment.
+    5. Let closure be ! AsyncGeneratorFunctionCreate(Method, UniqueFormalParameters,
+       AsyncGeneratorBody, scope, strict).
+    [...]
+flags: [async]
+---*/
+
+var callCount = 0;
+class C {
+  async *method(/*{ elems }*/) {
+    /*{ body }*/
+    callCount = callCount + 1;
+  }
+};
+
+new C().method(/*{ vals }*/).then(() => {
+    assert.sameValue(callCount, 1, 'invoked exactly once');    
+}).then($DONE, $DONE);

src/dstr-binding/default/cls-expr-async-gen-meth-dflt.template

+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+path: language/expressions/class/dstr-async-gen-meth-dflt-
+name: class expression async generator method (default parameter)
+esid: sec-class-definitions-runtime-semantics-evaluation
+features: [async-iteration]
+info: |
+    ClassExpression : class BindingIdentifieropt ClassTail
+
+    1. If BindingIdentifieropt is not present, let className be undefined.
+    2. Else, let className be StringValue of BindingIdentifier.
+    3. Let value be the result of ClassDefinitionEvaluation of ClassTail
+       with argument className.
+    [...]
+
+    14.5.14 Runtime Semantics: ClassDefinitionEvaluation
+
+    21. For each ClassElement m in order from methods
+        a. If IsStatic of m is false, then
+           i. Let status be the result of performing
+              PropertyDefinitionEvaluation for m with arguments proto and
+              false.
+        [...]
+
+    Runtime Semantics: PropertyDefinitionEvaluation
+
+    AsyncGeneratorMethod :
+        async [no LineTerminator here] * PropertyName ( UniqueFormalParameters )
+            { AsyncGeneratorBody }
+
+    1. Let propKey be the result of evaluating PropertyName.
+    2. ReturnIfAbrupt(propKey).
+    3. If the function code for this AsyncGeneratorMethod is strict mode code, let strict be true.
+       Otherwise let strict be false.
+    4. Let scope be the running execution context's LexicalEnvironment.
+    5. Let closure be ! AsyncGeneratorFunctionCreate(Method, UniqueFormalParameters,
+       AsyncGeneratorBody, scope, strict).
+    [...]
+flags: [async]
+---*/
+
+var callCount = 0;
+var C = class {
+  async *method(/*{ elems }*/ = /*{ vals }*/) {
+    /*{ body }*/
+    callCount = callCount + 1;
+  }
+};
+
+new C().method().next().then(() => {
+    assert.sameValue(callCount, 1, 'invoked exactly once');    
+}).then($DONE, $DONE);

src/dstr-binding/default/cls-expr-async-gen-meth-static-dflt.template

+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+path: language/expressions/class/dstr-async-gen-meth-static-dflt-
+name: static class expression async generator method (default parameter)
+esid: sec-class-definitions-runtime-semantics-evaluation
+features: [async-iteration]
+info: |
+    ClassExpression : class BindingIdentifieropt ClassTail
+
+    1. If BindingIdentifieropt is not present, let className be undefined.
+    2. Else, let className be StringValue of BindingIdentifier.
+    3. Let value be the result of ClassDefinitionEvaluation of ClassTail
+       with argument className.
+    [...]
+
+    14.5.14 Runtime Semantics: ClassDefinitionEvaluation
+
+    21. For each ClassElement m in order from methods
+        a. If IsStatic of m is false, then
+        b. Else,
+           Let status be the result of performing PropertyDefinitionEvaluation
+           for m with arguments F and false.
+    [...]
+
+    Runtime Semantics: PropertyDefinitionEvaluation
+
+    AsyncGeneratorMethod :
+        async [no LineTerminator here] * PropertyName ( UniqueFormalParameters )
+            { AsyncGeneratorBody }
+
+    1. Let propKey be the result of evaluating PropertyName.
+    2. ReturnIfAbrupt(propKey).
+    3. If the function code for this AsyncGeneratorMethod is strict mode code, let strict be true.
+       Otherwise let strict be false.
+    4. Let scope be the running execution context's LexicalEnvironment.
+    5. Let closure be ! AsyncGeneratorFunctionCreate(Method, UniqueFormalParameters,
+       AsyncGeneratorBody, scope, strict).
+    [...]
+flags: [async]
+---*/
+
+var callCount = 0;
+var C = class {
+  static async *method(/*{ elems }*/ = /*{ vals }*/) {
+    /*{ body }*/
+    callCount = callCount + 1;
+  }
+};
+
+C.method().next().then(() => {
+    assert.sameValue(callCount, 1, 'invoked exactly once');    
+}).then($DONE, $DONE);

src/dstr-binding/default/cls-expr-async-gen-meth-static.template

+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+path: language/expressions/class/dstr-async-gen-meth-static-
+name: static class expression async generator method
+esid: sec-class-definitions-runtime-semantics-evaluation
+features: [async-iteration]
+info: |
+    ClassExpression : class BindingIdentifieropt ClassTail
+
+    1. If BindingIdentifieropt is not present, let className be undefined.
+    2. Else, let className be StringValue of BindingIdentifier.
+    3. Let value be the result of ClassDefinitionEvaluation of ClassTail
+       with argument className.
+    [...]
+
+    14.5.14 Runtime Semantics: ClassDefinitionEvaluation
+
+    21. For each ClassElement m in order from methods
+        a. If IsStatic of m is false, then
+        b. Else,
+           Let status be the result of performing PropertyDefinitionEvaluation
+           for m with arguments F and false.
+    [...]
+
+    Runtime Semantics: PropertyDefinitionEvaluation
+
+    AsyncGeneratorMethod :
+        async [no LineTerminator here] * PropertyName ( UniqueFormalParameters )
+            { AsyncGeneratorBody }
+
+    1. Let propKey be the result of evaluating PropertyName.
+    2. ReturnIfAbrupt(propKey).
+    3. If the function code for this AsyncGeneratorMethod is strict mode code, let strict be true.
+       Otherwise let strict be false.
+    4. Let scope be the running execution context's LexicalEnvironment.
+    5. Let closure be ! AsyncGeneratorFunctionCreate(Method, UniqueFormalParameters,
+       AsyncGeneratorBody, scope, strict).
+    [...]
+flags: [async]
+---*/
+
+var callCount = 0;
+var C = class {
+  static async *method(/*{ elems }*/) {
+    /*{ body }*/
+    callCount = callCount + 1;
+  }
+};
+
+C.method(/*{ vals }*/).next().then(() => {
+    assert.sameValue(callCount, 1, 'invoked exactly once');    
+}).then($DONE, $DONE);

src/dstr-binding/default/cls-expr-async-gen-meth.template

+// Copyright (C) 2017 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+path: language/expressions/class/dstr-async-gen-meth-
+name: class expression method
+esid: sec-class-definitions-runtime-semantics-evaluation
+features: [async-iteration]
+info: |
+    ClassExpression : class BindingIdentifieropt ClassTail
+
+    1. If BindingIdentifieropt is not present, let className be undefined.
+    2. Else, let className be StringValue of BindingIdentifier.
+    3. Let value be the result of ClassDefinitionEvaluation of ClassTail
+       with argument className.
+    [...]
+
+    14.5.14 Runtime Semantics: ClassDefinitionEvaluation
+
+    21. For each ClassElement m in order from methods
+        a. If IsStatic of m is false, then
+           i. Let status be the result of performing
+              PropertyDefinitionEvaluation for m with arguments proto and
+              false.
+        [...]
+
+    Runtime Semantics: PropertyDefinitionEvaluation
+
+    AsyncGeneratorMethod :
+        async [no LineTerminator here] * PropertyName ( UniqueFormalParameters )
+            { AsyncGeneratorBody }
+
+    1. Let propKey be the result of evaluating PropertyName.
+    2. ReturnIfAbrupt(propKey).
+    3. If the function code for this AsyncGeneratorMethod is strict mode code, let strict be true.
+       Otherwise let strict be false.
+    4. Let scope be the running execution context's LexicalEnvironment.
+    5. Let closure be ! AsyncGeneratorFunctionCreate(Method, UniqueFormalParameters,
+       AsyncGeneratorBody, scope, strict).
+    [...]
+flags: [async]
+---*/
+
+var callCount = 0;
+var C = class {
+  async *method(/*{ elems }*/) {
+    /*{ body }*/
+    callCount = callCount + 1;
+  }
+};
+
+new C().method(/*{ vals }*/).next().then(() => {
+    assert.sameValue(callCount, 1, 'invoked exactly once');    
+}).then($DONE, $DONE);