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Fix/indexed access type hover #62677

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Fix/indexed access type hover #62677

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0d0bd10
WIP: Fix indexed access type resolution in hover/quick info
TudorGR Oct 20, 2025
dce4663
Merge remote-tracking branch 'upstream/main' into fix/indexed-access-…
TudorGR Oct 26, 2025
9eb59a8
Remove unused baseline file
TudorGR Oct 26, 2025
07ea18b
Scope indexed access type resolution to QuickInfo only
TudorGR Oct 26, 2025
729c75a
Revert "Merge remote-tracking branch 'upstream/main' into fix/indexed…
TudorGR Oct 27, 2025
07d33dc
Update test baselines to reflect QuickInfo behavior changes
TudorGR Oct 27, 2025
134ed3c
Merge branch 'main' into fix/indexed-access-type-hover
TudorGR Oct 27, 2025
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8 changes: 6 additions & 2 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -6842,7 +6842,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
return factory.createThisTypeNode();
}

if (!inTypeAlias && type.aliasSymbol && (context.flags & NodeBuilderFlags.UseAliasDefinedOutsideCurrentScope || isTypeSymbolAccessible(type.aliasSymbol, context.enclosingDeclaration))) {
// When in an object type literal context, expand type aliases to show resolved types
// for better clarity in hover information and quick info
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Copilot AI Oct 26, 2025

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The comment describes expanding type aliases but the actual condition checks for !(context.flags & NodeBuilderFlags.InObjectTypeLiteral) which means the expansion is avoided when in object type literal context. The comment should clarify that type aliases are expanded unless we're in an object type literal context, or the logic may be inverted from the intended behavior.

Suggested change
// When in an object type literal context, expand type aliases to show resolved types
// for better clarity in hover information and quick info
// Expand type aliases to show resolved types for better clarity in hover information and quick info,
// unless we're in an object type literal context.

Copilot uses AI. Check for mistakes.
if (!inTypeAlias && type.aliasSymbol && !(context.flags & NodeBuilderFlags.InObjectTypeLiteral) && (context.flags & NodeBuilderFlags.UseAliasDefinedOutsideCurrentScope || isTypeSymbolAccessible(type.aliasSymbol, context.enclosingDeclaration))) {
if (!shouldExpandType(type, context, /*isAlias*/ true)) {
const typeArgumentNodes = mapToTypeNodes(type.aliasTypeArguments, context);
if (isReservedMemberName(type.aliasSymbol.escapedName) && !(type.aliasSymbol.flags & SymbolFlags.Class)) return factory.createTypeReferenceNode(factory.createIdentifier(""), typeArgumentNodes);
Expand Down Expand Up @@ -9028,7 +9030,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
let result;
const addUndefinedForParameter = declaration && (isParameter(declaration) || isJSDocParameterTag(declaration)) && requiresAddingImplicitUndefined(declaration, context.enclosingDeclaration);
const decl = declaration ?? symbol.valueDeclaration ?? getDeclarationWithTypeAnnotation(symbol) ?? symbol.declarations?.[0];
if (!canPossiblyExpandType(type, context) && decl) {
// When in an object type literal context, prefer the resolved type over the syntactic form
// to ensure indexed access types and generic type aliases are properly resolved
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Copilot AI Oct 26, 2025

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This comment states we prefer resolved types when in object type literal context, but the code condition !(context.flags & NodeBuilderFlags.InObjectTypeLiteral) means the syntactic form is avoided when we're NOT in object type literal context. The comment contradicts the code logic.

Suggested change
// When in an object type literal context, prefer the resolved type over the syntactic form
// to ensure indexed access types and generic type aliases are properly resolved
// When NOT in an object type literal context, prefer the syntactic form over the resolved type
// to preserve original type annotations where possible

Copilot uses AI. Check for mistakes.
if (!canPossiblyExpandType(type, context) && decl && !(context.flags & NodeBuilderFlags.InObjectTypeLiteral)) {
const restore = addSymbolTypeToContext(context, symbol, type);
if (isAccessor(decl)) {
result = syntacticNodeBuilder.serializeTypeOfAccessor(decl, symbol, context);
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40 changes: 40 additions & 0 deletions tests/cases/fourslash/quickInfoIndexedAccessWithGeneric.ts
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Original file line number Diff line number Diff line change
@@ -0,0 +1,40 @@
/// <reference path='fourslash.ts'/>

// @strict: true

// @Filename: /test.ts
////type Scalars = {
//// Number: number;
////};
////
////type Maybe<T> = T | null;
////
////type TypeA = {
//// a: Scalars["Number"] | null;
//// b: Maybe<number>;
//// c: Scalars["Number"] | null;
////};
////
////type TypeB = {
//// a: Scalars["Number"] | null;
//// b: number | null;
//// c: Scalars["Number"] | null;
////};
////
////const testA: Type/*typeA*/A = null!;
////const testB: Type/*typeB*/B = null!;

// Both types should show fully resolved types (number | null) for all fields
goTo.marker("typeA");
verify.quickInfoIs(`type TypeA = {
a: number | null;
b: number | null;
c: number | null;
}`);

goTo.marker("typeB");
verify.quickInfoIs(`type TypeB = {
a: number | null;
b: number | null;
c: number | null;
}`);
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