Set up structure of prototype assignments

No actual binding happens yet though

src/compiler/binder.ts

@@ -2042,6 +2042,8 @@ namespace ts {
                         case SpecialPropertyAssignmentKind.PrototypeProperty:
                             bindPrototypePropertyAssignment((node as BinaryExpression).left as PropertyAccessEntityNameExpression, node);
                             break;
+                        case SpecialPropertyAssignmentKind.Prototype:
+                            bindPrototypeAssignment(node as BinaryExpression);
                         case SpecialPropertyAssignmentKind.ThisProperty:
                             bindThisPropertyAssignment(node as BinaryExpression);
                             break;
@@ -2361,8 +2363,13 @@ namespace ts {
             }
         }
 
+        /** For `x.prototype = { p, ... }`, declare members p,... if `x` is function/class/{}, or not declared. */
+        function bindPrototypeAssignment(node: BinaryExpression) {
+            return node;
+        }
+
         /**
-         * For 'x.prototype.y = z', declare a 'member' y on x if x is a function or class, or not declared.
+         * For `x.prototype.y = z`, declare a member `y` on `x` if `x` is a function or class, or not declared.
          * Note that jsdoc preceding an ExpressionStatement like `x.prototype.y;` is also treated as a declaration.
          */
         function bindPrototypePropertyAssignment(lhs: PropertyAccessEntityNameExpression, parent: Node) {

src/compiler/checker.ts

@@ -14254,6 +14254,7 @@ namespace ts {
                 case SpecialPropertyAssignmentKind.ModuleExports:
                 case SpecialPropertyAssignmentKind.PrototypeProperty:
                 case SpecialPropertyAssignmentKind.ThisProperty:
+                case SpecialPropertyAssignmentKind.Prototype:
                     return false;
                 default:
                     Debug.assertNever(kind);

src/compiler/types.ts

@@ -3964,7 +3964,9 @@ namespace ts {
         /// this.name = expr
         ThisProperty,
         // F.name = expr
-        Property
+        Property,
+        // F.prototype = { ... }
+        Prototype,
     }
 
     export interface JsFileExtensionInfo {

src/compiler/utilities.ts

@@ -1590,6 +1590,10 @@ namespace ts {
                 return SpecialPropertyAssignmentKind.Property;
             }
         }
+        else if (lhs.name.escapedText === "prototype" && expr.right.kind === SyntaxKind.ObjectLiteralExpression) {
+            // F.prototype = { ... }
+            return SpecialPropertyAssignmentKind.Prototype;
+        }
         else if (lhs.expression.kind === SyntaxKind.ThisKeyword) {
             return SpecialPropertyAssignmentKind.ThisProperty;
         }

src/services/navigationBar.ts

@@ -275,6 +275,7 @@ namespace ts.NavigationBar {
                     case SpecialPropertyAssignmentKind.ExportsProperty:
                     case SpecialPropertyAssignmentKind.ModuleExports:
                     case SpecialPropertyAssignmentKind.PrototypeProperty:
+                    case SpecialPropertyAssignmentKind.Prototype:
                         addNodeWithRecursiveChild(node, (node as BinaryExpression).right);
                         break;
                     case SpecialPropertyAssignmentKind.ThisProperty:

src/services/utilities.ts

@@ -370,6 +370,8 @@ namespace ts {
                     case SpecialPropertyAssignmentKind.Property:
                         // static method / property
                         return isFunctionExpression(right) ? ScriptElementKind.memberFunctionElement : ScriptElementKind.memberVariableElement;
+                    case SpecialPropertyAssignmentKind.Prototype:
+                        return ScriptElementKind.localClassElement;
                     default: {
                         assertTypeIsNever(kind);
                         return ScriptElementKind.unknown;