Bug fix for issue #14696, things changed are;

- Empty class type will now throw an error,
- Trailing comma in class type will also throw an error,
- Added tests for empty class type parameter,
- Updated tests for class type parameters with trailing comma

This behavior is consistently following function or method like when its type parameter is either empty or has trailing comma.

src/compiler/checker.ts

@@ -19559,7 +19559,7 @@ namespace ts {
         }
 
         function checkClassLikeDeclaration(node: ClassLikeDeclaration) {
-            checkGrammarClassDeclarationHeritageClauses(node);
+            checkGrammarClassLikeDeclaration(node);
             checkDecorators(node);
             if (node.name) {
                 checkTypeNameIsReserved(node.name, Diagnostics.Class_name_cannot_be_0);
@@ -22520,6 +22520,11 @@ namespace ts {
                 checkGrammarParameterList(node.parameters) || checkGrammarArrowFunction(node, file);
         }
 
+        function checkGrammarClassLikeDeclaration(node: ClassLikeDeclaration): boolean {
+            const file = getSourceFileOfNode(node);
+            return checkGrammarClassDeclarationHeritageClauses(node) || checkGrammarTypeParameterList(node.typeParameters, file);
+        }
+
         function checkGrammarArrowFunction(node: FunctionLikeDeclaration, file: SourceFile): boolean {
             if (node.kind === SyntaxKind.ArrowFunction) {
                 const arrowFunction = <ArrowFunction>node;