Consider non-public literal members in index type of constrained type parameters

Author: andrewbranch

src/compiler/checker.ts

@@ -9987,8 +9987,8 @@ namespace ts {
             });
         }
 
-        function getLiteralTypeFromProperty(prop: Symbol, include: TypeFlags) {
-            if (!(getDeclarationModifierFlagsFromSymbol(prop) & ModifierFlags.NonPublicAccessibilityModifier)) {
+        function getLiteralTypeFromProperty(prop: Symbol, include: TypeFlags, includeNonPublic?: boolean) {
+            if (includeNonPublic || !(getDeclarationModifierFlagsFromSymbol(prop) & ModifierFlags.NonPublicAccessibilityModifier)) {
                 let type = getLateBoundSymbol(prop).nameType;
                 if (!type && !isKnownSymbol(prop)) {
                     if (prop.escapedName === InternalSymbolName.Default) {
@@ -10006,8 +10006,8 @@ namespace ts {
             return neverType;
         }
 
-        function getLiteralTypeFromProperties(type: Type, include: TypeFlags) {
-            return getUnionType(map(getPropertiesOfType(type), p => getLiteralTypeFromProperty(p, include)));
+        function getLiteralTypeFromProperties(type: Type, include: TypeFlags, includeNonPublic?: boolean) {
+            return getUnionType(map(getPropertiesOfType(type), p => getLiteralTypeFromProperty(p, include, includeNonPublic)));
         }
 
         function getNonEnumNumberIndexInfo(type: Type) {
@@ -10023,10 +10023,10 @@ namespace ts {
                 type === wildcardType ? wildcardType :
                 type.flags & TypeFlags.Unknown ? neverType :
                 type.flags & (TypeFlags.Any | TypeFlags.Never) ? keyofConstraintType :
-                stringsOnly ? !noIndexSignatures && getIndexInfoOfType(type, IndexKind.String) ? stringType : getLiteralTypeFromProperties(type, TypeFlags.StringLiteral) :
-                !noIndexSignatures && getIndexInfoOfType(type, IndexKind.String) ? getUnionType([stringType, numberType, getLiteralTypeFromProperties(type, TypeFlags.UniqueESSymbol)]) :
-                getNonEnumNumberIndexInfo(type) ? getUnionType([numberType, getLiteralTypeFromProperties(type, TypeFlags.StringLiteral | TypeFlags.UniqueESSymbol)]) :
-                getLiteralTypeFromProperties(type, TypeFlags.StringOrNumberLiteralOrUnique);
+                stringsOnly ? !noIndexSignatures && getIndexInfoOfType(type, IndexKind.String) ? stringType : getLiteralTypeFromProperties(type, TypeFlags.StringLiteral, /*includeNonPublic*/ true) :
+                !noIndexSignatures && getIndexInfoOfType(type, IndexKind.String) ? getUnionType([stringType, numberType, getLiteralTypeFromProperties(type, TypeFlags.UniqueESSymbol, /*includeNonPublic*/ true)]) :
+                getNonEnumNumberIndexInfo(type) ? getUnionType([numberType, getLiteralTypeFromProperties(type, TypeFlags.StringLiteral | TypeFlags.UniqueESSymbol, /*includeNonPublic*/ true)]) :
+                getLiteralTypeFromProperties(type, TypeFlags.StringOrNumberLiteralOrUnique, /*includeNonPublic*/ true);
         }
 
         function getExtractStringType(type: Type) {

tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.js

@@ -0,0 +1,14 @@
+//// [indexedAccessPrivateMemberOfGenericConstraint.ts]
+class A {
+  private a: number;
+}
+
+type B<T extends A> = T["a"];
+
+
+//// [indexedAccessPrivateMemberOfGenericConstraint.js]
+var A = /** @class */ (function () {
+    function A() {
+    }
+    return A;
+}());

tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.symbols

@@ -0,0 +1,14 @@
+=== tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts ===
+class A {
+>A : Symbol(A, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 0, 0))
+
+  private a: number;
+>a : Symbol(A.a, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 0, 9))
+}
+
+type B<T extends A> = T["a"];
+>B : Symbol(B, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 2, 1))
+>T : Symbol(T, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 4, 7))
+>A : Symbol(A, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 0, 0))
+>T : Symbol(T, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 4, 7))
+

tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.types

@@ -0,0 +1,11 @@
+=== tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts ===
+class A {
+>A : A
+
+  private a: number;
+>a : number
+}
+
+type B<T extends A> = T["a"];
+>B : T["a"]
+

tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts

@@ -0,0 +1,5 @@
+class A {
+  private a: number;
+}
+
+type B<T extends A> = T["a"];