Consistently error on attempts to access private properties on generic objects

src/compiler/checker.ts

@@ -19584,6 +19584,15 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         if (objectType === wildcardType || indexType === wildcardType) {
             return wildcardType;
         }
+        if (isGenericObjectType(objectType)) {
+            const propertyName = getPropertyNameFromIndex(indexType, accessNode);
+            if (propertyName) {
+                if (someType(getApparentType(objectType), t => isNonPublicPropertyOfType(t, propertyName))) {
+                    error(accessNode, Diagnostics.Private_or_protected_member_0_cannot_be_accessed_on_a_type_parameter, unescapeLeadingUnderscores(propertyName));
+                    return errorType;
+                }
+            }
+        }
         objectType = getReducedType(objectType);
         // If the object type has a string index signature and no other members we know that the result will
         // always be the type of that index signature and we can simplify accordingly.
@@ -19646,6 +19655,14 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 : getUnionType(propTypes, UnionReduction.Literal, aliasSymbol, aliasTypeArguments);
         }
         return getPropertyTypeForIndexType(objectType, apparentObjectType, indexType, indexType, accessNode, accessFlags | AccessFlags.CacheSymbol | AccessFlags.ReportDeprecated);
+
+        function isNonPublicPropertyOfType(type: Type, propertyName: __String): boolean {
+            if (type.flags & TypeFlags.Intersection) {
+                return some((type as IntersectionType).types, t => isNonPublicPropertyOfType(t, propertyName));
+            }
+            const propertySymbol = getPropertyOfType(type, propertyName);
+            return !!(propertySymbol && getDeclarationModifierFlagsFromSymbol(propertySymbol) & ModifierFlags.NonPublicAccessibilityModifier);
+        }
     }
 
     function getTypeFromIndexedAccessTypeNode(node: IndexedAccessTypeNode) {
@@ -42754,16 +42771,6 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             }
             return type;
         }
-        if (isGenericObjectType(objectType)) {
-            const propertyName = getPropertyNameFromIndex(indexType, accessNode);
-            if (propertyName) {
-                const propertySymbol = forEachType(getApparentType(objectType), t => getPropertyOfType(t, propertyName));
-                if (propertySymbol && getDeclarationModifierFlagsFromSymbol(propertySymbol) & ModifierFlags.NonPublicAccessibilityModifier) {
-                    error(accessNode, Diagnostics.Private_or_protected_member_0_cannot_be_accessed_on_a_type_parameter, unescapeLeadingUnderscores(propertyName));
-                    return errorType;
-                }
-            }
-        }
         error(accessNode, Diagnostics.Type_0_cannot_be_used_to_index_type_1, typeToString(indexType), typeToString(objectType));
         return errorType;
     }

tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.errors.txt

@@ -1,9 +1,41 @@
 indexedAccessPrivateMemberOfGenericConstraint.ts(9,24): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
 indexedAccessPrivateMemberOfGenericConstraint.ts(9,32): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
 indexedAccessPrivateMemberOfGenericConstraint.ts(10,27): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(11,27): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(12,37): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(13,37): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(14,23): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(15,37): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(16,37): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(26,25): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(26,33): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(27,28): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(28,28): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(29,38): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(30,38): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(31,24): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(32,38): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(33,38): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(43,33): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(44,28): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(45,28): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(46,38): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(47,38): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(48,24): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(49,38): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(50,38): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(60,25): error TS2536: Type '"a"' cannot be used to index type 'T'.
+indexedAccessPrivateMemberOfGenericConstraint.ts(60,33): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(61,28): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(62,28): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(63,38): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(64,38): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(65,24): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(66,38): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+indexedAccessPrivateMemberOfGenericConstraint.ts(67,38): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
 
 
-==== indexedAccessPrivateMemberOfGenericConstraint.ts (3 errors) ====
+==== indexedAccessPrivateMemberOfGenericConstraint.ts (35 errors) ====
     class A {
       private a: number;
     }
@@ -21,4 +53,124 @@ indexedAccessPrivateMemberOfGenericConstraint.ts(10,27): error TS4105: Private o
                               ~~~~~~
 !!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
     type Z<T extends A & B> = T["a"];
+                              ~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type R<T extends A, T2 extends B> = (T | T2)["a"];
+                                        ~~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type S<T extends B, T2 extends A> = (T | T2)["a"];
+                                        ~~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type U<T extends A> = (T & B)["a"];
+                          ~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type V<T extends A, T2 extends B> = (T & T2)["a"];
+                                        ~~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type W<T extends B, T2 extends A> = (T & T2)["a"];
+                                        ~~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+
+    class C {
+      declare private a: number;
+    }
+
+    class D {
+      declare a: string;
+    }
+
+    type X2<T extends C> = [T["a"], (T | D)["a"]];
+                            ~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+                                    ~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type Y2<T extends C | D> = T["a"];
+                               ~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type Z2<T extends C & D> = T["a"];
+                               ~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type R2<T extends C, T2 extends D> = (T | T2)["a"];
+                                         ~~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type S2<T extends D, T2 extends C> = (T | T2)["a"];
+                                         ~~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type U2<T extends C> = (T & D)["a"];
+                           ~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type V2<T extends C, T2 extends D> = (T & T2)["a"];
+                                         ~~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type W2<T extends D, T2 extends C> = (T & T2)["a"];
+                                         ~~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+
+    class E {
+      declare a: number;
+    }
+
+    class F {
+      declare private a: string;
+    }
+
+    type X3<T extends E> = [T["a"], (T | F)["a"]];
+                                    ~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type Y3<T extends E | F> = T["a"];
+                               ~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type Z3<T extends E & F> = T["a"];
+                               ~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type R3<T extends E, T2 extends F> = (T | T2)["a"];
+                                         ~~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type S3<T extends F, T2 extends E> = (T | T2)["a"];
+                                         ~~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type U3<T extends E> = (T & F)["a"];
+                           ~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type V3<T extends E, T2 extends F> = (T & T2)["a"];
+                                         ~~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type W3<T extends F, T2 extends E> = (T & T2)["a"];
+                                         ~~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+
+    class G {
+      declare b: number;
+    }
+
+    class H {
+      declare private a: string;
+    }
+
+    type X4<T extends G> = [T["a"], (T | H)["a"]];
+                            ~~~~~~
+!!! error TS2536: Type '"a"' cannot be used to index type 'T'.
+                                    ~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type Y4<T extends G | H> = T["a"];
+                               ~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type Z4<T extends G & H> = T["a"];
+                               ~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type R4<T extends G, T2 extends H> = (T | T2)["a"];
+                                         ~~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type S4<T extends H, T2 extends G> = (T | T2)["a"];
+                                         ~~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type U4<T extends G> = (T & H)["a"];
+                           ~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type V4<T extends G, T2 extends H> = (T & T2)["a"];
+                                         ~~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+    type W4<T extends H, T2 extends G> = (T & T2)["a"];
+                                         ~~~~~~~~~~~~~
+!!! error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
 

tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.js

@@ -12,6 +12,62 @@ class B {
 type X<T extends A> = [T["a"], (T | B)["a"]];
 type Y<T extends A | B> = T["a"];
 type Z<T extends A & B> = T["a"];
+type R<T extends A, T2 extends B> = (T | T2)["a"];
+type S<T extends B, T2 extends A> = (T | T2)["a"];
+type U<T extends A> = (T & B)["a"];
+type V<T extends A, T2 extends B> = (T & T2)["a"];
+type W<T extends B, T2 extends A> = (T & T2)["a"];
+
+class C {
+  declare private a: number;
+}
+
+class D {
+  declare a: string;
+}
+
+type X2<T extends C> = [T["a"], (T | D)["a"]];
+type Y2<T extends C | D> = T["a"];
+type Z2<T extends C & D> = T["a"];
+type R2<T extends C, T2 extends D> = (T | T2)["a"];
+type S2<T extends D, T2 extends C> = (T | T2)["a"];
+type U2<T extends C> = (T & D)["a"];
+type V2<T extends C, T2 extends D> = (T & T2)["a"];
+type W2<T extends D, T2 extends C> = (T & T2)["a"];
+
+class E {
+  declare a: number;
+}
+
+class F {
+  declare private a: string;
+}
+
+type X3<T extends E> = [T["a"], (T | F)["a"]];
+type Y3<T extends E | F> = T["a"];
+type Z3<T extends E & F> = T["a"];
+type R3<T extends E, T2 extends F> = (T | T2)["a"];
+type S3<T extends F, T2 extends E> = (T | T2)["a"];
+type U3<T extends E> = (T & F)["a"];
+type V3<T extends E, T2 extends F> = (T & T2)["a"];
+type W3<T extends F, T2 extends E> = (T & T2)["a"];
+
+class G {
+  declare b: number;
+}
+
+class H {
+  declare private a: string;
+}
+
+type X4<T extends G> = [T["a"], (T | H)["a"]];
+type Y4<T extends G | H> = T["a"];
+type Z4<T extends G & H> = T["a"];
+type R4<T extends G, T2 extends H> = (T | T2)["a"];
+type S4<T extends H, T2 extends G> = (T | T2)["a"];
+type U4<T extends G> = (T & H)["a"];
+type V4<T extends G, T2 extends H> = (T & T2)["a"];
+type W4<T extends H, T2 extends G> = (T & T2)["a"];
 
 
 //// [indexedAccessPrivateMemberOfGenericConstraint.js]
@@ -25,3 +81,33 @@ var B = /** @class */ (function () {
     }
     return B;
 }());
+var C = /** @class */ (function () {
+    function C() {
+    }
+    return C;
+}());
+var D = /** @class */ (function () {
+    function D() {
+    }
+    return D;
+}());
+var E = /** @class */ (function () {
+    function E() {
+    }
+    return E;
+}());
+var F = /** @class */ (function () {
+    function F() {
+    }
+    return F;
+}());
+var G = /** @class */ (function () {
+    function G() {
+    }
+    return G;
+}());
+var H = /** @class */ (function () {
+    function H() {
+    }
+    return H;
+}());