Added error message for private identifiers used with static decorators. There is no spec to go with this behavior as of yet.

Author: dragomirtitian

src/compiler/checker.ts

@@ -35993,6 +35993,9 @@ namespace ts {
         }
 
         function checkClassDeclaration(node: ClassDeclaration) {
+            if (some(node.decorators) && some(node.members, p => hasStaticModifier(p) && isPrivateIdentifierClassElementDeclaration(p))) {
+                grammarErrorOnNode(node.decorators[0], Diagnostics.Class_decorators_can_t_be_used_with_static_private_identifier_Consider_removing_the_experimental_decorator);
+            }
             if (!node.name && !hasSyntacticModifier(node, ModifierFlags.Default)) {
                 grammarErrorOnFirstToken(node, Diagnostics.A_class_declaration_without_the_default_modifier_must_have_a_name);
             }

src/compiler/diagnosticMessages.json

@@ -6350,5 +6350,9 @@
     "Invalid value for 'jsxFragmentFactory'. '{0}' is not a valid identifier or qualified-name.": {
         "category": "Error",
         "code": 18035
+    },
+    "Class decorators can't be used with static private identifier. Consider removing the experimental decorator.": {
+        "category": "Error",
+        "code": 18036
     }
 }