From 48f74fdf808c2efa2c101bca2624485b09f177ee Mon Sep 17 00:00:00 2001
From: Andrew Branch <andrew@wheream.io>
Date: Fri, 14 Jun 2019 17:29:39 -0700
Subject: [PATCH 1/3] Consider non-public literal members in index type of
 constrained type parameters

---
 src/compiler/checker.ts                          | 16 ++++++++--------
 ...exedAccessPrivateMemberOfGenericConstraint.js | 14 ++++++++++++++
 ...ccessPrivateMemberOfGenericConstraint.symbols | 14 ++++++++++++++
 ...dAccessPrivateMemberOfGenericConstraint.types | 11 +++++++++++
 ...exedAccessPrivateMemberOfGenericConstraint.ts |  5 +++++
 5 files changed, 52 insertions(+), 8 deletions(-)
 create mode 100644 tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.js
 create mode 100644 tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.symbols
 create mode 100644 tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.types
 create mode 100644 tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index a4ad3af7d9..65076aefa2 100644
--- a/src/compiler/checker.ts
+++ b/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) {
diff --git a/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.js b/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.js
new file mode 100644
index 0000000000..0e8877479c
--- /dev/null
+++ b/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;
+}());
diff --git a/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.symbols b/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.symbols
new file mode 100644
index 0000000000..a687739758
--- /dev/null
+++ b/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))
+
diff --git a/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.types b/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.types
new file mode 100644
index 0000000000..3f59d71914
--- /dev/null
+++ b/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"]
+
diff --git a/tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts b/tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts
new file mode 100644
index 0000000000..a2f2bb8c47
--- /dev/null
+++ b/tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts
@@ -0,0 +1,5 @@
+class A {
+  private a: number;
+}
+
+type B<T extends A> = T["a"];

From 1ad32857010671e82a77cd629750e097edf6f449 Mon Sep 17 00:00:00 2001
From: Andrew Branch <andrew@wheream.io>
Date: Mon, 17 Jun 2019 09:45:09 -0700
Subject: [PATCH 2/3] Add test cases for union and intersection constraints

---
 ...dAccessPrivateMemberOfGenericConstraint.js | 14 ++++++++-
 ...ssPrivateMemberOfGenericConstraint.symbols | 30 ++++++++++++++++---
 ...cessPrivateMemberOfGenericConstraint.types | 18 +++++++++--
 ...dAccessPrivateMemberOfGenericConstraint.ts |  9 +++++-
 4 files changed, 63 insertions(+), 8 deletions(-)

diff --git a/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.js b/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.js
index 0e8877479c..bd10676fab 100644
--- a/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.js
+++ b/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.js
@@ -3,7 +3,14 @@ class A {
   private a: number;
 }
 
-type B<T extends A> = T["a"];
+class B {
+  private a: string;
+}
+
+type X<T extends A> = T["a"];
+type Y<T extends A | B> = T["a"];
+type Z<T extends A & B> = T["a"];
+
 
 
 //// [indexedAccessPrivateMemberOfGenericConstraint.js]
@@ -12,3 +19,8 @@ var A = /** @class */ (function () {
     }
     return A;
 }());
+var B = /** @class */ (function () {
+    function B() {
+    }
+    return B;
+}());
diff --git a/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.symbols b/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.symbols
index a687739758..9a57021cff 100644
--- a/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.symbols
+++ b/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.symbols
@@ -6,9 +6,31 @@ class A {
 >a : Symbol(A.a, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 0, 9))
 }
 
-type B<T extends A> = T["a"];
+class B {
 >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))
+
+  private a: string;
+>a : Symbol(B.a, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 4, 9))
+}
+
+type X<T extends A> = T["a"];
+>X : Symbol(X, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 6, 1))
+>T : Symbol(T, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 8, 7))
+>A : Symbol(A, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 0, 0))
+>T : Symbol(T, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 8, 7))
+
+type Y<T extends A | B> = T["a"];
+>Y : Symbol(Y, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 8, 29))
+>T : Symbol(T, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 9, 7))
+>A : Symbol(A, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 0, 0))
+>B : Symbol(B, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 2, 1))
+>T : Symbol(T, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 9, 7))
+
+type Z<T extends A & B> = T["a"];
+>Z : Symbol(Z, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 9, 33))
+>T : Symbol(T, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 10, 7))
+>A : Symbol(A, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 0, 0))
+>B : Symbol(B, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 2, 1))
+>T : Symbol(T, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 10, 7))
+
 
diff --git a/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.types b/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.types
index 3f59d71914..3e1e668499 100644
--- a/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.types
+++ b/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.types
@@ -6,6 +6,20 @@ class A {
 >a : number
 }
 
-type B<T extends A> = T["a"];
->B : T["a"]
+class B {
+>B : B
+
+  private a: string;
+>a : string
+}
+
+type X<T extends A> = T["a"];
+>X : T["a"]
+
+type Y<T extends A | B> = T["a"];
+>Y : T["a"]
+
+type Z<T extends A & B> = T["a"];
+>Z : T["a"]
+
 
diff --git a/tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts b/tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts
index a2f2bb8c47..77823cccef 100644
--- a/tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts
+++ b/tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts
@@ -2,4 +2,11 @@ class A {
   private a: number;
 }
 
-type B<T extends A> = T["a"];
+class B {
+  private a: string;
+}
+
+type X<T extends A> = T["a"];
+type Y<T extends A | B> = T["a"];
+type Z<T extends A & B> = T["a"];
+

From 04fbd93bf8f0ab6b743c230232c2ae47429e08d9 Mon Sep 17 00:00:00 2001
From: Andrew Branch <andrew@wheream.io>
Date: Mon, 17 Jun 2019 15:21:21 -0700
Subject: [PATCH 3/3] Revert previous fix and improve error message instead

---
 src/compiler/checker.ts                       | 40 +++++++++++++------
 src/compiler/diagnosticMessages.json          |  4 ++
 ...rivateMemberOfGenericConstraint.errors.txt | 27 +++++++++++++
 ...dAccessPrivateMemberOfGenericConstraint.js |  3 +-
 ...ssPrivateMemberOfGenericConstraint.symbols |  7 ++--
 ...cessPrivateMemberOfGenericConstraint.types |  5 +--
 ...dAccessPrivateMemberOfGenericConstraint.ts |  3 +-
 7 files changed, 67 insertions(+), 22 deletions(-)
 create mode 100644 tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.errors.txt

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 65076aefa2..4f8f09e51e 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -9987,8 +9987,8 @@ namespace ts {
             });
         }
 
-        function getLiteralTypeFromProperty(prop: Symbol, include: TypeFlags, includeNonPublic?: boolean) {
-            if (includeNonPublic || !(getDeclarationModifierFlagsFromSymbol(prop) & ModifierFlags.NonPublicAccessibilityModifier)) {
+        function getLiteralTypeFromProperty(prop: Symbol, include: TypeFlags) {
+            if (!(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, includeNonPublic?: boolean) {
-            return getUnionType(map(getPropertiesOfType(type), p => getLiteralTypeFromProperty(p, include, includeNonPublic)));
+        function getLiteralTypeFromProperties(type: Type, include: TypeFlags) {
+            return getUnionType(map(getPropertiesOfType(type), p => getLiteralTypeFromProperty(p, include)));
         }
 
         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, /*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);
+                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);
         }
 
         function getExtractStringType(type: Type) {
@@ -10097,9 +10097,9 @@ namespace ts {
             return false;
         }
 
-        function getPropertyTypeForIndexType(originalObjectType: Type, objectType: Type, indexType: Type, fullIndexType: Type, suppressNoImplicitAnyError: boolean, accessNode: ElementAccessExpression | IndexedAccessTypeNode | PropertyName | BindingName | SyntheticExpression | undefined, accessFlags: AccessFlags) {
+        function getPropertyNameFromIndex(indexType: Type, accessNode: StringLiteral | Identifier | ObjectBindingPattern | ArrayBindingPattern | ComputedPropertyName | NumericLiteral | IndexedAccessTypeNode | ElementAccessExpression | SyntheticExpression | undefined) {
             const accessExpression = accessNode && accessNode.kind === SyntaxKind.ElementAccessExpression ? accessNode : undefined;
-            const propName = isTypeUsableAsPropertyName(indexType) ?
+            return isTypeUsableAsPropertyName(indexType) ?
                 getPropertyNameFromType(indexType) :
                 accessExpression && checkThatExpressionIsProperSymbolReference(accessExpression.argumentExpression, indexType, /*reportError*/ false) ?
                     getPropertyNameForKnownSymbolName(idText((<PropertyAccessExpression>accessExpression.argumentExpression).name)) :
@@ -10107,6 +10107,11 @@ namespace ts {
                         // late bound names are handled in the first branch, so here we only need to handle normal names
                         getPropertyNameForPropertyNameNode(accessNode) :
                         undefined;
+        }
+
+        function getPropertyTypeForIndexType(originalObjectType: Type, objectType: Type, indexType: Type, fullIndexType: Type, suppressNoImplicitAnyError: boolean, accessNode: ElementAccessExpression | IndexedAccessTypeNode | PropertyName | BindingName | SyntheticExpression | undefined, accessFlags: AccessFlags) {
+            const accessExpression = accessNode && accessNode.kind === SyntaxKind.ElementAccessExpression ? accessNode : undefined;
+            const propName = getPropertyNameFromIndex(indexType, accessNode);
             if (propName !== undefined) {
                 const prop = getPropertyOfType(objectType, propName);
                 if (prop) {
@@ -25292,7 +25297,7 @@ namespace ts {
             forEach(node.types, checkSourceElement);
         }
 
-        function checkIndexedAccessIndexType(type: Type, accessNode: Node) {
+        function checkIndexedAccessIndexType(type: Type, accessNode: IndexedAccessTypeNode | ElementAccessExpression) {
             if (!(type.flags & TypeFlags.IndexedAccess)) {
                 return type;
             }
@@ -25308,9 +25313,20 @@ namespace ts {
             }
             // Check if we're indexing with a numeric type and if either object or index types
             // is a generic type with a constraint that has a numeric index signature.
-            if (getIndexInfoOfType(getApparentType(objectType), IndexKind.Number) && isTypeAssignableToKind(indexType, TypeFlags.NumberLike)) {
+            const apparentObjectType = getApparentType(objectType);
+            if (getIndexInfoOfType(apparentObjectType, IndexKind.Number) && isTypeAssignableToKind(indexType, TypeFlags.NumberLike)) {
                 return type;
             }
+            if (isGenericObjectType(objectType)) {
+                const propertyName = getPropertyNameFromIndex(indexType, accessNode);
+                if (propertyName) {
+                    const propertySymbol = forEachType(apparentObjectType, 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;
         }
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index b209a87880..061c242e26 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -2963,6 +2963,10 @@
         "category": "Error",
         "code": 4104
     },
+    "Private or protected member '{0}' cannot be accessed on a type parameter.": {
+        "category": "Error",
+        "code": 4105
+    },
 
     "The current host does not support the '{0}' option.": {
         "category": "Error",
diff --git a/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.errors.txt b/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.errors.txt
new file mode 100644
index 0000000000..56bf43e77a
--- /dev/null
+++ b/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.errors.txt
@@ -0,0 +1,27 @@
+tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts(9,24): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts(9,32): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts(10,27): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts(11,27): error TS4105: Private or protected member 'a' cannot be accessed on a type parameter.
+
+
+==== tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts (4 errors) ====
+    class A {
+      private a: number;
+    }
+    
+    class B {
+      private a: string;
+    }
+    
+    type X<T extends A> = [T["a"], (T | B)["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 Y<T extends A | B> = T["a"];
+                              ~~~~~~
+!!! 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.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.js b/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.js
index bd10676fab..5d2bfc5891 100644
--- a/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.js
+++ b/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.js
@@ -7,10 +7,9 @@ class B {
   private a: string;
 }
 
-type X<T extends A> = T["a"];
+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"];
-
 
 
 //// [indexedAccessPrivateMemberOfGenericConstraint.js]
diff --git a/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.symbols b/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.symbols
index 9a57021cff..69c433b16d 100644
--- a/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.symbols
+++ b/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.symbols
@@ -13,14 +13,16 @@ class B {
 >a : Symbol(B.a, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 4, 9))
 }
 
-type X<T extends A> = T["a"];
+type X<T extends A> = [T["a"], (T | B)["a"]];
 >X : Symbol(X, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 6, 1))
 >T : Symbol(T, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 8, 7))
 >A : Symbol(A, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 0, 0))
 >T : Symbol(T, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 8, 7))
+>T : Symbol(T, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 8, 7))
+>B : Symbol(B, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 2, 1))
 
 type Y<T extends A | B> = T["a"];
->Y : Symbol(Y, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 8, 29))
+>Y : Symbol(Y, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 8, 45))
 >T : Symbol(T, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 9, 7))
 >A : Symbol(A, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 0, 0))
 >B : Symbol(B, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 2, 1))
@@ -33,4 +35,3 @@ type Z<T extends A & B> = T["a"];
 >B : Symbol(B, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 2, 1))
 >T : Symbol(T, Decl(indexedAccessPrivateMemberOfGenericConstraint.ts, 10, 7))
 
-
diff --git a/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.types b/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.types
index 3e1e668499..abdbaa8486 100644
--- a/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.types
+++ b/tests/baselines/reference/indexedAccessPrivateMemberOfGenericConstraint.types
@@ -13,8 +13,8 @@ class B {
 >a : string
 }
 
-type X<T extends A> = T["a"];
->X : T["a"]
+type X<T extends A> = [T["a"], (T | B)["a"]];
+>X : [T["a"], (B | T)["a"]]
 
 type Y<T extends A | B> = T["a"];
 >Y : T["a"]
@@ -22,4 +22,3 @@ type Y<T extends A | B> = T["a"];
 type Z<T extends A & B> = T["a"];
 >Z : T["a"]
 
-
diff --git a/tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts b/tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts
index 77823cccef..a2fa8f4a46 100644
--- a/tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts
+++ b/tests/cases/compiler/indexedAccessPrivateMemberOfGenericConstraint.ts
@@ -6,7 +6,6 @@ class B {
   private a: string;
 }
 
-type X<T extends A> = T["a"];
+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"];
-