Add tests for private method/fields unnescapable token

src/class-elements/private-async-generator-cannot-escape-token.case

+// Copyright (C) 2018 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+desc: The pound signal in the private async generator cannot be escaped
+template: syntax/invalid
+info: |
+  PrivateName::
+    # IdentifierName
+
+  U+0023 is the escape sequence for #
+features: [class-methods-private, async-iteration]
+---*/
+
+//- elements
+async * \u0023m() { return 42; }

src/class-elements/private-async-method-cannot-escape-token.case

+// Copyright (C) 2018 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+desc: The pound signal in the private async method cannot be escaped
+template: syntax/invalid
+info: |
+  PrivateName::
+    # IdentifierName
+
+  U+0023 is the escape sequence for #
+features: [class-methods-private, async-functions]
+---*/
+
+//- elements
+async \u0023m() { return 42; }

src/class-elements/private-call-exp-cannot-escape-token.case

+// Copyright (C) 2018 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+desc: The pound signal in the private reference cannot be escaped
+template: syntax/invalid
+info: |
+  PrivateName ::
+    # IdentifierName
+
+  MemberExpression :
+    MemberExpression . PrivateName
+
+  CallExpression :
+    CallExpression . PrivateName
+
+  U+0023 is the escape sequence for #
+features: [class-fields-private]
+---*/
+
+//- elements
+method() {
+  foo().\u0023field;
+}

src/class-elements/private-field-cannot-escape-token.case

+// Copyright (C) 2018 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+desc: The pound signal in the private field cannot be escaped
+template: syntax/invalid
+info: |
+  PrivateName::
+    # IdentifierName
+
+  U+0023 is the escape sequence for #
+features: [class-fields-private]
+---*/
+
+//- elements
+\u0023field;

src/class-elements/private-generator-cannot-escape-token.case

+// Copyright (C) 2018 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+desc: The pound signal in the private generator cannot be escaped
+template: syntax/invalid
+info: |
+  PrivateName::
+    # IdentifierName
+
+  U+0023 is the escape sequence for #
+features: [class-methods-private, generators]
+---*/
+
+//- elements
+* \u0023m() { return 42; }

src/class-elements/private-member-exp-cannot-escape-token.case

+// Copyright (C) 2018 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+desc: The pound signal in the private reference cannot be escaped
+template: syntax/invalid
+info: |
+  PrivateName ::
+    # IdentifierName
+
+  MemberExpression :
+    MemberExpression . PrivateName
+
+  CallExpression :
+    CallExpression . PrivateName
+
+  U+0023 is the escape sequence for #
+features: [class-fields-private]
+---*/
+
+//- elements
+method() {
+  this.\u0023field;
+}

src/class-elements/private-method-cannot-escape-token.case

+// Copyright (C) 2018 Leo Balter. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+desc: The pound signal in the private method cannot be escaped
+template: syntax/invalid
+info: |
+  PrivateName::
+    # IdentifierName
+
+  U+0023 is the escape sequence for #
+features: [class-methods-private]
+---*/
+
+//- elements
+\u0023m() { return 42; }