Constructor Visibility

src/compiler/checker.ts

@@ -1711,6 +1711,16 @@ namespace ts {
             return result;
         }
 
+        function visibilityToString(flags: NodeFlags) {
+            if (flags === NodeFlags.Private) {
+                return "private";
+            }
+            if (flags === NodeFlags.Protected) {
+                return "protected";
+            }
+            return "public";
+        }
+
         function getTypeAliasForTypeLiteral(type: Type): Symbol {
             if (type.symbol && type.symbol.flags & SymbolFlags.TypeLiteral) {
                 let node = type.symbol.declarations[0].parent;
@@ -5889,16 +5899,20 @@ namespace ts {
 
                 const sourceSignatures = getSignaturesOfType(source, kind);
                 const targetSignatures = getSignaturesOfType(target, kind);
-                if (kind === SignatureKind.Construct && sourceSignatures.length && targetSignatures.length &&
-                    isAbstractConstructorType(source) && !isAbstractConstructorType(target)) {
-                    // An abstract constructor type is not assignable to a non-abstract constructor type
-                    // as it would otherwise be possible to new an abstract class. Note that the assignablity
-                    // check we perform for an extends clause excludes construct signatures from the target,
-                    // so this check never proceeds.
-                    if (reportErrors) {
-                        reportError(Diagnostics.Cannot_assign_an_abstract_constructor_type_to_a_non_abstract_constructor_type);
+                if (kind === SignatureKind.Construct && sourceSignatures.length && targetSignatures.length) {
+                    if (isAbstractConstructorType(source) && !isAbstractConstructorType(target)) {
+                        // An abstract constructor type is not assignable to a non-abstract constructor type
+                        // as it would otherwise be possible to new an abstract class. Note that the assignablity
+                        // check we perform for an extends clause excludes construct signatures from the target,
+                        // so this check never proceeds.
+                        if (reportErrors) {
+                            reportError(Diagnostics.Cannot_assign_an_abstract_constructor_type_to_a_non_abstract_constructor_type);
+                        }
+                        return Ternary.False;
+                    }
+                    if (!constructorVisibilitiesAreCompatible(sourceSignatures[0], targetSignatures[0], reportErrors)) {
+                        return Ternary.False;
                     }
-                    return Ternary.False;
                 }
 
                 let result = Ternary.True;
@@ -6052,6 +6066,36 @@ namespace ts {
                 }
                 return Ternary.True;
             }
+
+            function constructorVisibilitiesAreCompatible(sourceSignature: Signature, targetSignature: Signature, reportErrors: boolean) {
+                if (!sourceSignature.declaration || !targetSignature.declaration) {
+                    return true;
+                }
+
+                const sourceAccessibility = sourceSignature.declaration.flags & (NodeFlags.Private | NodeFlags.Protected);
+                const targetAccessibility = targetSignature.declaration.flags & (NodeFlags.Private | NodeFlags.Protected);
+
+                // A public, protected and private signature is assignable to a private signature.
+                if (targetAccessibility === NodeFlags.Private) {
+                    return true;
+                }
+
+                // A public and protected signature is assignable to a protected signature.
+                if (targetAccessibility === NodeFlags.Protected && sourceAccessibility !== NodeFlags.Private) {
+                    return true;
+                }
+
+                // Only a public signature is assignable to public signature.
+                if (targetAccessibility !== NodeFlags.Protected && !sourceAccessibility) {
+                    return true;
+                }
+
+                if (reportErrors) {
+                    reportError(Diagnostics.Cannot_assign_a_0_constructor_type_to_a_1_constructor_type, visibilityToString(sourceAccessibility), visibilityToString(targetAccessibility));
+                }
+
+                return false;
+            }
         }
 
         // Return true if the given type is the constructor type for an abstract class
@@ -10103,6 +10147,9 @@ namespace ts {
             // that the user will not add any.
             const constructSignatures = getSignaturesOfType(expressionType, SignatureKind.Construct);
             if (constructSignatures.length) {
+                if (!isConstructorAccessible(node, constructSignatures[0])) {
+                    return resolveErrorCall(node);
+                }
                 return resolveCall(node, constructSignatures, candidatesOutArray);
             }
 
@@ -10123,6 +10170,37 @@ namespace ts {
             return resolveErrorCall(node);
         }
 
+        function isConstructorAccessible(node: NewExpression, signature: Signature) {
+            if (!signature || !signature.declaration) {
+                return true;
+            }
+
+            const declaration = signature.declaration;
+            const flags = declaration.flags;
+
+            // Public constructor is accessible.
+            if (!(flags & (NodeFlags.Private | NodeFlags.Protected))) {
+                return true;
+            }
+
+            const declaringClass = <InterfaceType>getDeclaredTypeOfSymbol(declaration.parent.symbol);
+            const enclosingClassDeclaration = getContainingClass(node);
+            const enclosingClass = enclosingClassDeclaration ? <InterfaceType>getDeclaredTypeOfSymbol(getSymbolOfNode(enclosingClassDeclaration)) : undefined;
+
+            // A private or protected constructor can only be instantiated within it's own class 
+            if (declaringClass !== enclosingClass) {
+                if (flags & NodeFlags.Private) {
+                    error(node, Diagnostics.Constructor_of_class_0_is_private_and_only_accessible_within_the_class_declaration, typeToString(declaringClass));
+                }
+                if (flags & NodeFlags.Protected) {
+                    error(node, Diagnostics.Constructor_of_class_0_is_protected_and_only_accessible_within_the_class_declaration, typeToString(declaringClass));
+                }
+                return false;
+            }
+
+            return true;
+        }
+
         function resolveTaggedTemplateExpression(node: TaggedTemplateExpression, candidatesOutArray: Signature[]): Signature {
             const tagType = checkExpression(node.tag);
             const apparentType = getApparentType(tagType);
@@ -12059,7 +12137,7 @@ namespace ts {
                             error(o.name, Diagnostics.Overload_signatures_must_all_be_ambient_or_non_ambient);
                         }
                         else if (deviation & (NodeFlags.Private | NodeFlags.Protected)) {
-                            error(o.name, Diagnostics.Overload_signatures_must_all_be_public_private_or_protected);
+                            error(o.name || o, Diagnostics.Overload_signatures_must_all_be_public_private_or_protected);
                         }
                         else if (deviation & NodeFlags.Abstract) {
                             error(o.name, Diagnostics.Overload_signatures_must_all_be_abstract_or_not_abstract);
@@ -13928,6 +14006,7 @@ namespace ts {
                 if (baseTypes.length && produceDiagnostics) {
                     const baseType = baseTypes[0];
                     const staticBaseType = getBaseConstructorTypeOfClass(type);
+                    checkBaseTypeAccessibility(staticBaseType, baseTypeNode);
                     checkSourceElement(baseTypeNode.expression);
                     if (baseTypeNode.typeArguments) {
                         forEach(baseTypeNode.typeArguments, checkSourceElement);
@@ -13983,6 +14062,16 @@ namespace ts {
             }
         }
 
+        function checkBaseTypeAccessibility(type: ObjectType, node: ExpressionWithTypeArguments) {
+            const signatures = getSignaturesOfType(type, SignatureKind.Construct);
+            if (signatures.length) {
+                const declaration = signatures[0].declaration;
+                if (declaration && declaration.flags & NodeFlags.Private) {
+                    error(node, Diagnostics.Cannot_extend_a_class_0_Class_constructor_is_marked_as_private, (<Identifier>node.expression).text);
+                }
+            }
+        }
+
         function getTargetSymbol(s: Symbol) {
             // if symbol is instantiated its flags are not copied from the 'target'
             // so we'll need to get back original 'target' symbol to work with correct set of flags
@@ -16188,16 +16277,12 @@ namespace ts {
                     case SyntaxKind.PublicKeyword:
                     case SyntaxKind.ProtectedKeyword:
                     case SyntaxKind.PrivateKeyword:
-                        let text: string;
-                        if (modifier.kind === SyntaxKind.PublicKeyword) {
-                            text = "public";
-                        }
-                        else if (modifier.kind === SyntaxKind.ProtectedKeyword) {
-                            text = "protected";
+                        let text = visibilityToString(modifierToFlag(modifier.kind));
+
+                        if (modifier.kind === SyntaxKind.ProtectedKeyword) {
                             lastProtected = modifier;
                         }
-                        else {
-                            text = "private";
+                        else if (modifier.kind === SyntaxKind.PrivateKeyword) {
                             lastPrivate = modifier;
                         }
 
@@ -16348,12 +16433,6 @@ namespace ts {
                 if (flags & NodeFlags.Abstract) {
                     return grammarErrorOnNode(lastStatic, Diagnostics._0_modifier_cannot_appear_on_a_constructor_declaration, "abstract");
                 }
-                else if (flags & NodeFlags.Protected) {
-                    return grammarErrorOnNode(lastProtected, Diagnostics._0_modifier_cannot_appear_on_a_constructor_declaration, "protected");
-                }
-                else if (flags & NodeFlags.Private) {
-                    return grammarErrorOnNode(lastPrivate, Diagnostics._0_modifier_cannot_appear_on_a_constructor_declaration, "private");
-                }
                 else if (flags & NodeFlags.Async) {
                     return grammarErrorOnNode(lastAsync, Diagnostics._0_modifier_cannot_appear_on_a_constructor_declaration, "async");
                 }

src/compiler/declarationEmitter.ts

@@ -1316,7 +1316,7 @@ namespace ts {
                 if (node.kind === SyntaxKind.FunctionDeclaration) {
                     emitModuleElementDeclarationFlags(node);
                 }
-                else if (node.kind === SyntaxKind.MethodDeclaration) {
+                else if (node.kind === SyntaxKind.MethodDeclaration || node.kind === SyntaxKind.Constructor) {
                     emitClassMemberDeclarationFlags(node.flags);
                 }
                 if (node.kind === SyntaxKind.FunctionDeclaration) {

src/compiler/diagnosticMessages.json

@@ -1823,6 +1823,22 @@
         "category": "Error",
         "code": 2671
     },
+    "Cannot assign a '{0}' constructor type to a '{1}' constructor type.": {
+        "category": "Error",
+        "code": 2672
+    },
+    "Constructor of class '{0}' is private and only accessible within the class declaration.": {
+        "category": "Error",
+        "code": 2673
+    },
+    "Constructor of class '{0}' is protected and only accessible within the class declaration.": {
+        "category": "Error",
+        "code": 2674
+    },
+    "Cannot extend a class '{0}'. Class constructor is marked as private.": {
+        "category": "Error",
+        "code": 2675
+    },
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",
         "code": 4000

tests/baselines/reference/Protected3.symbols

@@ -0,0 +1,6 @@
+=== tests/cases/conformance/parser/ecmascript5/Protected/Protected3.ts ===
+class C {
+>C : Symbol(C, Decl(Protected3.ts, 0, 0))
+
+  protected constructor() { }
+}

tests/baselines/reference/Protected3.types

@@ -0,0 +1,6 @@
+=== tests/cases/conformance/parser/ecmascript5/Protected/Protected3.ts ===
+class C {
+>C : C
+
+  protected constructor() { }
+}

tests/baselines/reference/classConstructorAccessibility.errors.txt

@@ -1,49 +1,50 @@
-tests/cases/conformance/classes/constructorDeclarations/classConstructorAccessibility.ts(6,5): error TS1089: 'private' modifier cannot appear on a constructor declaration.
-tests/cases/conformance/classes/constructorDeclarations/classConstructorAccessibility.ts(10,5): error TS1089: 'protected' modifier cannot appear on a constructor declaration.
-tests/cases/conformance/classes/constructorDeclarations/classConstructorAccessibility.ts(23,9): error TS1089: 'private' modifier cannot appear on a constructor declaration.
-tests/cases/conformance/classes/constructorDeclarations/classConstructorAccessibility.ts(27,9): error TS1089: 'protected' modifier cannot appear on a constructor declaration.
+tests/cases/conformance/classes/constructorDeclarations/classConstructorAccessibility.ts(15,9): error TS2673: Constructor of class 'D' is private and only accessible within the class declaration.
+tests/cases/conformance/classes/constructorDeclarations/classConstructorAccessibility.ts(16,9): error TS2674: Constructor of class 'E' is protected and only accessible within the class declaration.
+tests/cases/conformance/classes/constructorDeclarations/classConstructorAccessibility.ts(32,13): error TS2673: Constructor of class 'D<T>' is private and only accessible within the class declaration.
+tests/cases/conformance/classes/constructorDeclarations/classConstructorAccessibility.ts(33,13): error TS2674: Constructor of class 'E<T>' is protected and only accessible within the class declaration.
 
 
 ==== tests/cases/conformance/classes/constructorDeclarations/classConstructorAccessibility.ts (4 errors) ====
+
     class C {
         public constructor(public x: number) { }
     }
 
     class D {
-        private constructor(public x: number) { } // error
-        ~~~~~~~
-!!! error TS1089: 'private' modifier cannot appear on a constructor declaration.
+        private constructor(public x: number) { }
     }
 
     class E {
-        protected constructor(public x: number) { } // error
-        ~~~~~~~~~
-!!! error TS1089: 'protected' modifier cannot appear on a constructor declaration.
+        protected constructor(public x: number) { }
     }
 
     var c = new C(1);
-    var d = new D(1);
-    var e = new E(1);
+    var d = new D(1); // error
+            ~~~~~~~~
+!!! error TS2673: Constructor of class 'D' is private and only accessible within the class declaration.
+    var e = new E(1); // error
+            ~~~~~~~~
+!!! error TS2674: Constructor of class 'E' is protected and only accessible within the class declaration.
 
     module Generic {
         class C<T> {
             public constructor(public x: T) { }
         }
 
         class D<T> {
-            private constructor(public x: T) { } // error
-            ~~~~~~~
-!!! error TS1089: 'private' modifier cannot appear on a constructor declaration.
+            private constructor(public x: T) { }
         }
 
         class E<T> {
-            protected constructor(public x: T) { } // error
-            ~~~~~~~~~
-!!! error TS1089: 'protected' modifier cannot appear on a constructor declaration.
+            protected constructor(public x: T) { }
         }
 
         var c = new C(1);
-        var d = new D(1);
-        var e = new E(1);
+        var d = new D(1); // error
+                ~~~~~~~~
+!!! error TS2673: Constructor of class 'D<T>' is private and only accessible within the class declaration.
+        var e = new E(1); // error
+                ~~~~~~~~
+!!! error TS2674: Constructor of class 'E<T>' is protected and only accessible within the class declaration.
     }