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
     }
 }

tests/baselines/reference/propertyNamedConstructor.errors.txt

@@ -0,0 +1,14 @@
+tests/cases/conformance/classes/propertyMemberDeclarations/propertyNamedConstructor.ts(2,3): error TS18006: Classes may not have a field named 'constructor'.
+
+
+==== tests/cases/conformance/classes/propertyMemberDeclarations/propertyNamedConstructor.ts (1 errors) ====
+    class X1 {
+      "constructor" = 3; // Error
+      ~~~~~~~~~~~~~
+!!! error TS18006: Classes may not have a field named 'constructor'.
+    }
+    
+    class X2 {
+      ["constructor"] = 3;
+    }
+    

tests/baselines/reference/propertyNamedConstructor.js

@@ -0,0 +1,23 @@
+//// [propertyNamedConstructor.ts]
+class X1 {
+  "constructor" = 3; // Error
+}
+
+class X2 {
+  ["constructor"] = 3;
+}
+
+
+//// [propertyNamedConstructor.js]
+var X1 = /** @class */ (function () {
+    function X1() {
+        this["constructor"] = 3; // Error
+    }
+    return X1;
+}());
+var X2 = /** @class */ (function () {
+    function X2() {
+        this["constructor"] = 3;
+    }
+    return X2;
+}());

tests/baselines/reference/propertyNamedConstructor.symbols

@@ -0,0 +1,16 @@
+=== tests/cases/conformance/classes/propertyMemberDeclarations/propertyNamedConstructor.ts ===
+class X1 {
+>X1 : Symbol(X1, Decl(propertyNamedConstructor.ts, 0, 0))
+
+  "constructor" = 3; // Error
+>"constructor" : Symbol(X1["constructor"], Decl(propertyNamedConstructor.ts, 0, 10))
+}
+
+class X2 {
+>X2 : Symbol(X2, Decl(propertyNamedConstructor.ts, 2, 1))
+
+  ["constructor"] = 3;
+>["constructor"] : Symbol(X2["constructor"], Decl(propertyNamedConstructor.ts, 4, 10))
+>"constructor" : Symbol(X2["constructor"], Decl(propertyNamedConstructor.ts, 4, 10))
+}
+

tests/baselines/reference/propertyNamedConstructor.types

@@ -0,0 +1,18 @@
+=== tests/cases/conformance/classes/propertyMemberDeclarations/propertyNamedConstructor.ts ===
+class X1 {
+>X1 : X1
+
+  "constructor" = 3; // Error
+>"constructor" : number
+>3 : 3
+}
+
+class X2 {
+>X2 : X2
+
+  ["constructor"] = 3;
+>["constructor"] : number
+>"constructor" : "constructor"
+>3 : 3
+}
+

tests/cases/conformance/classes/propertyMemberDeclarations/propertyNamedConstructor.ts

@@ -0,0 +1,7 @@
+class X1 {
+  "constructor" = 3; // Error
+}
+
+class X2 {
+  ["constructor"] = 3;
+}