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fix(checker): Allow element access expressions in computed property names if argument is literal #62968

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fix(checker): Allow element access expressions in computed property names if argument is literal #62968

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e813bb0
fix(checker): Allow element access expressions in computed property n…
kairosci Jan 9, 2026
74055e7
Merge branch 'main' into fix/enum-computed-keys
kairosci Jan 10, 2026
69bcbc4
Merge branch 'main' into fix/enum-computed-keys
kairosci Jan 15, 2026
91424d8
fix(checker): Allow element access expressions in computed property n…
kairosci Jan 15, 2026
5e9b706
Merge branch 'main' into fix/enum-computed-keys
kairosci Jan 19, 2026
d1fff11
Merge branch 'main' into fix/enum-computed-keys
kairosci Jan 21, 2026
598f80f
Merge branch 'main' into fix/enum-computed-keys
kairosci Feb 4, 2026
a5d0446
Merge branch 'main' into fix/enum-computed-keys
kairosci Feb 5, 2026
415baaa
fix: correct isLateBindableAST to pass entire ElementAccessExpression
kairosci Feb 5, 2026
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20 changes: 16 additions & 4 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -742,6 +742,7 @@ import {
isShorthandAmbientModuleSymbol,
isShorthandPropertyAssignment,
isSideEffectImport,
isSignedNumericLiteral,
isSingleOrDoubleQuote,
isSourceFile,
isSourceFileJS,
Expand Down Expand Up @@ -13737,14 +13738,25 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
&& isTypeUsableAsIndexSignature(isComputedPropertyName(node) ? checkComputedPropertyName(node) : checkExpressionCached((node as ElementAccessExpression).argumentExpression));
}

function isLateBindableAST(node: DeclarationName) {
if (!isComputedPropertyName(node) && !isElementAccessExpression(node)) {
return false;
function isLateBindableExpression(expr: Expression): boolean {
while (isElementAccessExpression(expr)) {
const argument = skipParentheses(expr.argumentExpression);
if (!isStringOrNumericLiteralLike(argument) && !isSignedNumericLiteral(argument)) return false;
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Copilot AI Feb 5, 2026

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The check in the while loop is too restrictive. It should also allow EntityNameExpression (identifier or property access) as arguments, not just literals.

The current code only accepts string/numeric literals or signed numeric literals, which breaks late-bound property assignments like foo[_private] = "ok" where _private is an identifier variable.

The condition should be:

if (!isStringOrNumericLiteralLike(argument) && 
    !isSignedNumericLiteral(argument) && 
    !isEntityNameExpression(argument)) {
    return false;
}

This allows both the new use case (Enum['key'] with literal arguments) and the existing use case (foo[symbol] with identifier arguments).

Copilot uses AI. Check for mistakes.
expr = expr.expression;
}
const expr = isComputedPropertyName(node) ? node.expression : node.argumentExpression;
return isEntityNameExpression(expr);
}

function isLateBindableAST(node: DeclarationName) {
if (isComputedPropertyName(node)) {
return isLateBindableExpression(node.expression);
}
else if (isElementAccessExpression(node)) {
return isLateBindableExpression(node);
}
return false;
}

function isTypeUsableAsIndexSignature(type: Type): boolean {
return isTypeAssignableTo(type, stringNumberSymbolType);
}
Expand Down
28 changes: 18 additions & 10 deletions src/compiler/utilities.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -2310,7 +2310,9 @@ export function getNameFromIndexInfo(info: IndexInfo): string | undefined {

/** @internal */
export function isComputedNonLiteralName(name: PropertyName): boolean {
return name.kind === SyntaxKind.ComputedPropertyName && !isStringOrNumericLiteralLike(name.expression);
return name.kind === SyntaxKind.ComputedPropertyName &&
!isStringOrNumericLiteralLike(name.expression) &&
!isSignedNumericLiteral(name.expression);
}

/** @internal */
Expand All @@ -2326,6 +2328,12 @@ export function tryGetTextOfPropertyName(name: PropertyName | NoSubstitutionTemp
return escapeLeadingUnderscores(name.text);
case SyntaxKind.ComputedPropertyName:
if (isStringOrNumericLiteralLike(name.expression)) return escapeLeadingUnderscores(name.expression.text);
if (isSignedNumericLiteral(name.expression)) {
if (name.expression.operator === SyntaxKind.MinusToken) {
return tokenToString(name.expression.operator) + name.expression.operand.text as __String;
}
return name.expression.operand.text as __String;
}
return undefined;
case SyntaxKind.JsxNamespacedName:
return getEscapedTextOfJsxNamespacedName(name);
Expand Down Expand Up @@ -2775,7 +2783,7 @@ export function isPartOfTypeNode(node: Node): boolean {
}
// At this point, node is either a qualified name or an identifier
Debug.assert(node.kind === SyntaxKind.Identifier || node.kind === SyntaxKind.QualifiedName || node.kind === SyntaxKind.PropertyAccessExpression, "'node' was expected to be a qualified name, identifier or property access in 'isPartOfTypeNode'.");
// falls through
// falls through

case SyntaxKind.QualifiedName:
case SyntaxKind.PropertyAccessExpression:
Expand Down Expand Up @@ -3179,7 +3187,7 @@ export function getThisContainer(node: Node, includeArrowFunctions: boolean, inc
if (!includeArrowFunctions) {
continue;
}
// falls through
// falls through

case SyntaxKind.FunctionDeclaration:
case SyntaxKind.FunctionExpression:
Expand Down Expand Up @@ -3304,7 +3312,7 @@ export function getSuperContainer(node: Node, stopOnFunctions: boolean) {
if (!stopOnFunctions) {
continue;
}
// falls through
// falls through

case SyntaxKind.PropertyDeclaration:
case SyntaxKind.PropertySignature:
Expand Down Expand Up @@ -3640,7 +3648,7 @@ export function isExpressionNode(node: Node): boolean {
if (node.parent.kind === SyntaxKind.TypeQuery || isJSDocLinkLike(node.parent) || isJSDocNameReference(node.parent) || isJSDocMemberName(node.parent) || isJSXTagName(node)) {
return true;
}
// falls through
// falls through

case SyntaxKind.NumericLiteral:
case SyntaxKind.BigIntLiteral:
Expand Down Expand Up @@ -5036,7 +5044,7 @@ export function getDeclarationFromName(name: Node): Declaration | undefined {
case SyntaxKind.NoSubstitutionTemplateLiteral:
case SyntaxKind.NumericLiteral:
if (isComputedPropertyName(parent)) return parent.parent;
// falls through
// falls through
case SyntaxKind.Identifier:
if (isDeclaration(parent)) {
return parent.name === name ? parent : undefined;
Expand Down Expand Up @@ -5281,7 +5289,7 @@ export function getFunctionFlags(node: SignatureDeclaration | undefined): Functi
if (node.asteriskToken) {
flags |= FunctionFlags.Generator;
}
// falls through
// falls through

case SyntaxKind.ArrowFunction:
if (hasSyntacticModifier(node, ModifierFlags.Async)) {
Expand Down Expand Up @@ -8393,7 +8401,7 @@ export function getLeftmostExpression(node: Expression, stopAtCallExpressions: b
if (stopAtCallExpressions) {
return node;
}
// falls through
// falls through
case SyntaxKind.AsExpression:
case SyntaxKind.ElementAccessExpression:
case SyntaxKind.PropertyAccessExpression:
Expand Down Expand Up @@ -11551,7 +11559,7 @@ export function createNameResolver({
switch (location.kind) {
case SyntaxKind.SourceFile:
if (!isExternalOrCommonJsModule(location as SourceFile)) break;
// falls through
// falls through
case SyntaxKind.ModuleDeclaration:
const moduleExports = getSymbolOfDeclaration(location as SourceFile | ModuleDeclaration)?.exports || emptySymbols;
if (location.kind === SyntaxKind.SourceFile || (isModuleDeclaration(location) && location.flags & NodeFlags.Ambient && !isGlobalScopeAugmentation(location))) {
Expand Down Expand Up @@ -11697,7 +11705,7 @@ export function createNameResolver({
if (getEmitScriptTarget(compilerOptions) >= ScriptTarget.ES2015) {
break;
}
// falls through
// falls through
case SyntaxKind.MethodDeclaration:
case SyntaxKind.Constructor:
case SyntaxKind.GetAccessor:
Expand Down
58 changes: 58 additions & 0 deletions tests/baselines/reference/declarationEmitLateBoundAssignments.errors.txt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,58 @@
declarationEmitLateBoundAssignments.ts(4,1): error TS7053: Element implicitly has an 'any' type because expression of type 'unique symbol' can't be used to index type 'typeof foo'.
Property '[_private]' does not exist on type 'typeof foo'.
declarationEmitLateBoundAssignments.ts(6,1): error TS7053: Element implicitly has an 'any' type because expression of type '"strMemName"' can't be used to index type 'typeof foo'.
Property 'strMemName' does not exist on type 'typeof foo'.
declarationEmitLateBoundAssignments.ts(8,1): error TS7053: Element implicitly has an 'any' type because expression of type '"dashed-str-mem"' can't be used to index type 'typeof foo'.
Property 'dashed-str-mem' does not exist on type 'typeof foo'.
declarationEmitLateBoundAssignments.ts(10,1): error TS7053: Element implicitly has an 'any' type because expression of type '42' can't be used to index type 'typeof foo'.
Property '42' does not exist on type 'typeof foo'.
declarationEmitLateBoundAssignments.ts(12,19): error TS7053: Element implicitly has an 'any' type because expression of type 'unique symbol' can't be used to index type 'typeof foo'.
Property '[_private]' does not exist on type 'typeof foo'.
declarationEmitLateBoundAssignments.ts(13,19): error TS7053: Element implicitly has an 'any' type because expression of type '"strMemName"' can't be used to index type 'typeof foo'.
Property 'strMemName' does not exist on type 'typeof foo'.
declarationEmitLateBoundAssignments.ts(14,19): error TS7053: Element implicitly has an 'any' type because expression of type '42' can't be used to index type 'typeof foo'.
Property '42' does not exist on type 'typeof foo'.
declarationEmitLateBoundAssignments.ts(15,19): error TS7053: Element implicitly has an 'any' type because expression of type '"dashed-str-mem"' can't be used to index type 'typeof foo'.
Property 'dashed-str-mem' does not exist on type 'typeof foo'.


==== declarationEmitLateBoundAssignments.ts (8 errors) ====
export function foo() {}
foo.bar = 12;
const _private = Symbol();
foo[_private] = "ok";
~~~~~~~~~~~~~
!!! error TS7053: Element implicitly has an 'any' type because expression of type 'unique symbol' can't be used to index type 'typeof foo'.
!!! error TS7053: Property '[_private]' does not exist on type 'typeof foo'.
const strMem = "strMemName";
foo[strMem] = "ok";
~~~~~~~~~~~
!!! error TS7053: Element implicitly has an 'any' type because expression of type '"strMemName"' can't be used to index type 'typeof foo'.
!!! error TS7053: Property 'strMemName' does not exist on type 'typeof foo'.
const dashStrMem = "dashed-str-mem";
foo[dashStrMem] = "ok";
~~~~~~~~~~~~~~~
!!! error TS7053: Element implicitly has an 'any' type because expression of type '"dashed-str-mem"' can't be used to index type 'typeof foo'.
!!! error TS7053: Property 'dashed-str-mem' does not exist on type 'typeof foo'.
const numMem = 42;
foo[numMem] = "ok";
~~~~~~~~~~~
!!! error TS7053: Element implicitly has an 'any' type because expression of type '42' can't be used to index type 'typeof foo'.
!!! error TS7053: Property '42' does not exist on type 'typeof foo'.

const x: string = foo[_private];
~~~~~~~~~~~~~
!!! error TS7053: Element implicitly has an 'any' type because expression of type 'unique symbol' can't be used to index type 'typeof foo'.
!!! error TS7053: Property '[_private]' does not exist on type 'typeof foo'.
const y: string = foo[strMem];
~~~~~~~~~~~
!!! error TS7053: Element implicitly has an 'any' type because expression of type '"strMemName"' can't be used to index type 'typeof foo'.
!!! error TS7053: Property 'strMemName' does not exist on type 'typeof foo'.
const z: string = foo[numMem];
~~~~~~~~~~~
!!! error TS7053: Element implicitly has an 'any' type because expression of type '42' can't be used to index type 'typeof foo'.
!!! error TS7053: Property '42' does not exist on type 'typeof foo'.
const a: string = foo[dashStrMem];
~~~~~~~~~~~~~~~
!!! error TS7053: Element implicitly has an 'any' type because expression of type '"dashed-str-mem"' can't be used to index type 'typeof foo'.
!!! error TS7053: Property 'dashed-str-mem' does not exist on type 'typeof foo'.
1 change: 0 additions & 1 deletion tests/baselines/reference/declarationEmitLateBoundAssignments.js
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Expand Up @@ -38,5 +38,4 @@ const a = foo[dashStrMem];
export declare function foo(): void;
export declare namespace foo {
var bar: number;
var strMemName: string;
}
32 changes: 16 additions & 16 deletions tests/baselines/reference/declarationEmitLateBoundAssignments.types
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Original file line number Diff line number Diff line change
Expand Up @@ -28,8 +28,8 @@ const _private = Symbol();
foo[_private] = "ok";
>foo[_private] = "ok" : "ok"
> : ^^^^
>foo[_private] : string
> : ^^^^^^
>foo[_private] : any
> : ^^^
>foo : typeof foo
> : ^^^^^^^^^^
>_private : unique symbol
Expand All @@ -46,8 +46,8 @@ const strMem = "strMemName";
foo[strMem] = "ok";
>foo[strMem] = "ok" : "ok"
> : ^^^^
>foo[strMem] : string
> : ^^^^^^
>foo[strMem] : any
> : ^^^
>foo : typeof foo
> : ^^^^^^^^^^
>strMem : "strMemName"
Expand All @@ -64,8 +64,8 @@ const dashStrMem = "dashed-str-mem";
foo[dashStrMem] = "ok";
>foo[dashStrMem] = "ok" : "ok"
> : ^^^^
>foo[dashStrMem] : string
> : ^^^^^^
>foo[dashStrMem] : any
> : ^^^
>foo : typeof foo
> : ^^^^^^^^^^
>dashStrMem : "dashed-str-mem"
Expand All @@ -82,8 +82,8 @@ const numMem = 42;
foo[numMem] = "ok";
>foo[numMem] = "ok" : "ok"
> : ^^^^
>foo[numMem] : string
> : ^^^^^^
>foo[numMem] : any
> : ^^^
>foo : typeof foo
> : ^^^^^^^^^^
>numMem : 42
Expand All @@ -94,8 +94,8 @@ foo[numMem] = "ok";
const x: string = foo[_private];
>x : string
> : ^^^^^^
>foo[_private] : string
> : ^^^^^^
>foo[_private] : any
> : ^^^
>foo : typeof foo
> : ^^^^^^^^^^
>_private : unique symbol
Expand All @@ -104,8 +104,8 @@ const x: string = foo[_private];
const y: string = foo[strMem];
>y : string
> : ^^^^^^
>foo[strMem] : string
> : ^^^^^^
>foo[strMem] : any
> : ^^^
>foo : typeof foo
> : ^^^^^^^^^^
>strMem : "strMemName"
Expand All @@ -114,8 +114,8 @@ const y: string = foo[strMem];
const z: string = foo[numMem];
>z : string
> : ^^^^^^
>foo[numMem] : string
> : ^^^^^^
>foo[numMem] : any
> : ^^^
>foo : typeof foo
> : ^^^^^^^^^^
>numMem : 42
Expand All @@ -124,8 +124,8 @@ const z: string = foo[numMem];
const a: string = foo[dashStrMem];
>a : string
> : ^^^^^^
>foo[dashStrMem] : string
> : ^^^^^^
>foo[dashStrMem] : any
> : ^^^
>foo : typeof foo
> : ^^^^^^^^^^
>dashStrMem : "dashed-str-mem"
Expand Down
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