Fixing #442: Impossible to define static 'length' function on class

src/compiler/checker.ts

@@ -2160,24 +2160,25 @@ namespace ts {
             return type.flags & TypeFlags.StringLiteral ? `"${escapeString((<LiteralType>type).text)}"` : (<LiteralType>type).text;
         }
 
-        function getSymbolDisplayBuilder(): SymbolDisplayBuilder {
 
-            function getNameOfSymbol(symbol: Symbol): string {
-                if (symbol.declarations && symbol.declarations.length) {
-                    const declaration = symbol.declarations[0];
-                    if (declaration.name) {
-                        return declarationNameToString(declaration.name);
-                    }
-                    switch (declaration.kind) {
-                        case SyntaxKind.ClassExpression:
-                            return "(Anonymous class)";
-                        case SyntaxKind.FunctionExpression:
-                        case SyntaxKind.ArrowFunction:
-                            return "(Anonymous function)";
-                    }
+        function getNameOfSymbol(symbol: Symbol): string {
+            if (symbol.declarations && symbol.declarations.length) {
+                const declaration = symbol.declarations[0];
+                if (declaration.name) {
+                    return declarationNameToString(declaration.name);
+                }
+                switch (declaration.kind) {
+                    case SyntaxKind.ClassExpression:
+                        return "(Anonymous class)";
+                    case SyntaxKind.FunctionExpression:
+                    case SyntaxKind.ArrowFunction:
+                        return "(Anonymous function)";
                 }
-                return symbol.name;
             }
+            return symbol.name;
+        }
+
+        function getSymbolDisplayBuilder(): SymbolDisplayBuilder {
 
             /**
              * Writes only the name of the symbol out to the writer. Uses the original source text
@@ -15654,7 +15655,7 @@ namespace ts {
                     }
                 }
                 else {
-                    const isStatic = forEach(member.modifiers, m => m.kind === SyntaxKind.StaticKeyword);
+                    const isStatic = getModifierFlags(member) & ModifierFlags.Static;
                     const names = isStatic ? staticNames : instanceNames;
 
                     const memberName = member.name && getPropertyNameForPropertyNameNode(member.name);
@@ -15692,6 +15693,38 @@ namespace ts {
             }
         }
 
+        /** 
+         * Static members being set on a constructor function may conflict with built-in properties
+         * of Function. Esp. in ECMAScript 5 there are non-configurable and non-writable 
+         * built-in properties. This check issues a transpile error when a class has a static 
+         * member with the same name as a non-writable built-in property.
+         * 
+         * @see http://www.ecma-international.org/ecma-262/5.1/#sec-15.3.3
+         * @see http://www.ecma-international.org/ecma-262/5.1/#sec-15.3.5
+         * @see http://www.ecma-international.org/ecma-262/6.0/#sec-properties-of-the-function-constructor
+         * @see http://www.ecma-international.org/ecma-262/6.0/#sec-function-instances
+         */
+        function checkClassForStaticPropertyNameConflicts(node: ClassLikeDeclaration) {
+            for (const member of node.members) {
+                const memberNameNode = member.name;
+                const isStatic = getModifierFlags(member) & ModifierFlags.Static;
+                if (isStatic && memberNameNode) {
+                    const memberName = getPropertyNameForPropertyNameNode(memberNameNode);
+                    switch (memberName) {
+                        case "name":
+                        case "length":
+                        case "caller":
+                        case "arguments":
+                        case "prototype":
+                            const message = Diagnostics.Static_property_0_conflicts_with_built_in_property_Function_0_of_constructor_function_1;
+                            const className = getNameOfSymbol(getSymbolOfNode(node));
+                            error(memberNameNode, message, memberName, className);
+                            break;
+                    }
+                }
+            }
+        }
+
         function checkObjectTypeForDuplicateDeclarations(node: TypeLiteralNode | InterfaceDeclaration) {
             const names = createMap<boolean>();
             for (const member of node.members) {
@@ -18267,6 +18300,7 @@ namespace ts {
             const staticType = <ObjectType>getTypeOfSymbol(symbol);
             checkTypeParameterListsIdentical(node, symbol);
             checkClassForDuplicateDeclarations(node);
+            checkClassForStaticPropertyNameConflicts(node);
 
             const baseTypeNode = getClassExtendsHeritageClauseElement(node);
             if (baseTypeNode) {

src/compiler/diagnosticMessages.json

@@ -2015,6 +2015,10 @@
         "category": "Error",
         "code": 2698
     },
+    "Static property '{0}' conflicts with built-in property 'Function.{0}' of constructor function '{1}'.": {
+        "category": "Error",
+        "code": 2699
+    },
     "Rest types may only be created from object types.": {
         "category": "Error",
         "code": 2700

tests/baselines/reference/propertyNamedPrototype.errors.txt

@@ -0,0 +1,10 @@
+tests/cases/conformance/classes/propertyMemberDeclarations/propertyNamedPrototype.ts(3,12): error TS2699: Static property 'prototype' conflicts with built-in property 'Function.prototype' of constructor function 'C'.
+
+
+==== tests/cases/conformance/classes/propertyMemberDeclarations/propertyNamedPrototype.ts (1 errors) ====
+    class C {
+        prototype: number; // ok
+        static prototype: C; // error
+               ~~~~~~~~~
+!!! error TS2699: Static property 'prototype' conflicts with built-in property 'Function.prototype' of constructor function 'C'.
+    }

tests/baselines/reference/staticMemberOfClassAndPublicMemberOfAnotherClassAssignment.errors.txt

@@ -1,43 +1,43 @@
 tests/cases/compiler/staticMemberOfClassAndPublicMemberOfAnotherClassAssignment.ts(12,1): error TS2322: Type 'C' is not assignable to type 'A'.
-  Property 'name' is missing in type 'C'.
+  Property 'prop' is missing in type 'C'.
 tests/cases/compiler/staticMemberOfClassAndPublicMemberOfAnotherClassAssignment.ts(13,1): error TS2322: Type 'typeof B' is not assignable to type 'A'.
-  Property 'name' is missing in type 'typeof B'.
+  Property 'prop' is missing in type 'typeof B'.
 tests/cases/compiler/staticMemberOfClassAndPublicMemberOfAnotherClassAssignment.ts(16,5): error TS2322: Type 'C' is not assignable to type 'B'.
-  Property 'name' is missing in type 'C'.
+  Property 'prop' is missing in type 'C'.
 tests/cases/compiler/staticMemberOfClassAndPublicMemberOfAnotherClassAssignment.ts(17,1): error TS2322: Type 'typeof B' is not assignable to type 'B'.
-  Property 'name' is missing in type 'typeof B'.
+  Property 'prop' is missing in type 'typeof B'.
 
 
 ==== tests/cases/compiler/staticMemberOfClassAndPublicMemberOfAnotherClassAssignment.ts (4 errors) ====
     interface A {
-        name();
+        prop();
     }
     class B {
-        public name() { }
+        public prop() { }
     }
     class C {
-        public static name() { }
+        public static prop() { }
     }
 
     var a: A = new B();
-    a = new C(); // error name is missing
+    a = new C(); // error prop is missing
     ~
 !!! error TS2322: Type 'C' is not assignable to type 'A'.
-!!! error TS2322:   Property 'name' is missing in type 'C'.
-    a = B; // error name is missing
+!!! error TS2322:   Property 'prop' is missing in type 'C'.
+    a = B; // error prop is missing
     ~
 !!! error TS2322: Type 'typeof B' is not assignable to type 'A'.
-!!! error TS2322:   Property 'name' is missing in type 'typeof B'.
+!!! error TS2322:   Property 'prop' is missing in type 'typeof B'.
     a = C;
 
-    var b: B = new C(); // error name is missing
+    var b: B = new C(); // error prop is missing
         ~
 !!! error TS2322: Type 'C' is not assignable to type 'B'.
-!!! error TS2322:   Property 'name' is missing in type 'C'.
-    b = B; // error name is missing
+!!! error TS2322:   Property 'prop' is missing in type 'C'.
+    b = B; // error prop is missing
     ~
 !!! error TS2322: Type 'typeof B' is not assignable to type 'B'.
-!!! error TS2322:   Property 'name' is missing in type 'typeof B'.
+!!! error TS2322:   Property 'prop' is missing in type 'typeof B'.
     b = C;
     b = a;
 

tests/baselines/reference/staticMemberOfClassAndPublicMemberOfAnotherClassAssignment.js

@@ -1,21 +1,21 @@
 //// [staticMemberOfClassAndPublicMemberOfAnotherClassAssignment.ts]
 interface A {
-    name();
+    prop();
 }
 class B {
-    public name() { }
+    public prop() { }
 }
 class C {
-    public static name() { }
+    public static prop() { }
 }
 
 var a: A = new B();
-a = new C(); // error name is missing
-a = B; // error name is missing
+a = new C(); // error prop is missing
+a = B; // error prop is missing
 a = C;
 
-var b: B = new C(); // error name is missing
-b = B; // error name is missing
+var b: B = new C(); // error prop is missing
+b = B; // error prop is missing
 b = C;
 b = a;
 
@@ -29,21 +29,21 @@ c = a;
 var B = (function () {
     function B() {
     }
-    B.prototype.name = function () { };
+    B.prototype.prop = function () { };
     return B;
 }());
 var C = (function () {
     function C() {
     }
-    C.name = function () { };
+    C.prop = function () { };
     return C;
 }());
 var a = new B();
-a = new C(); // error name is missing
-a = B; // error name is missing
+a = new C(); // error prop is missing
+a = B; // error prop is missing
 a = C;
-var b = new C(); // error name is missing
-b = B; // error name is missing
+var b = new C(); // error prop is missing
+b = B; // error prop is missing
 b = C;
 b = a;
 var c = new B();