Emit error on class fields named "constructor"

src/compiler/checker.ts

@@ -31789,6 +31789,9 @@ namespace ts {
 
         function checkGrammarProperty(node: PropertyDeclaration | PropertySignature) {
             if (isClassLike(node.parent)) {
+                if (isStringLiteral(node.name) && node.name.text === "constructor") {
+                    return grammarErrorOnNode(node.name, Diagnostics.Classes_may_not_have_a_field_named_constructor);
+                }
                 if (checkGrammarForInvalidDynamicName(node.name, Diagnostics.A_computed_property_name_in_a_class_property_declaration_must_refer_to_an_expression_whose_type_is_a_literal_type_or_a_unique_symbol_type)) {
                     return true;
                 }

src/compiler/diagnosticMessages.json

@@ -4958,5 +4958,9 @@
     "Quoted constructors have previously been interpreted as methods, which is incorrect. In TypeScript 3.6, they will be correctly parsed as constructors. In the meantime, consider using 'constructor()' to write a constructor, or '[\"constructor\"]()' to write a method.": {
         "category": "Error",
         "code": 18005
+    },
+    "Classes may not have a field named 'constructor'.": {
+        "category": "Error",
+        "code": 18006
     }
 }