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Fix dts emit for type params for object methods in const context #3265

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Merged
jakebailey merged 1 commit into from
Mar 30, 2026
Merged

Fix dts emit for type params for object methods in const context #3265

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12 changes: 10 additions & 2 deletions internal/checker/pseudotypenodebuilder.go
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Original file line number Diff line number Diff line change
Expand Up @@ -168,13 +168,21 @@ func (b *NodeBuilderImpl) pseudoTypeToNode(t *pseudochecker.PseudoType) *ast.Nod
switch e.Kind {
case pseudochecker.PseudoObjectElementKindMethod:
d := e.AsPseudoObjectMethod()
var typeParams *ast.NodeList
if len(d.TypeParameters) > 0 {
res := make([]*ast.Node, 0, len(d.TypeParameters))
for _, tp := range d.TypeParameters {
res = append(res, b.reuseNode(tp.AsNode()))
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@jakebailey jakebailey Mar 27, 2026

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I was suspicious of this, but it's the same thing we do for pseudochecker.PseudoTypeKindSingleCallSignature just above here.

I do wonder what would happen if you had a type parameter that say extends typeof local. Do we handle that in general?

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@Andarist Andarist Mar 30, 2026

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I do wonder what would happen if you had a type parameter that say extends typeof local. Do we handle that in general?

Yeah, that's handled in general - unless you have some specific weird edge in mind that could break things with ID or without it.

typeof x is nice because it has to refer to an existing entity name and the declaration emitter also preserves the referenced name (and emits its type ofc) when needed even if that name is not exported otherwise. Local-local names in closures are usually just replaced with their types. In ID it's also kinda hard to even somehow try to "leak" a local-local to the top-level scope because of:

Function must have an explicit return type annotation with --isolatedDeclarations.

}
typeParams = b.f.NewNodeList(res)
}
if isConst {
newProp = b.f.NewPropertySignatureDeclaration(
modifiers,
b.reuseName(e.Name),
nil,
b.f.NewFunctionTypeNode(
nil,
typeParams,
b.pseudoParametersToNodeList(d.Parameters),
b.pseudoTypeToNode(d.ReturnType),
),
Expand All @@ -186,7 +194,7 @@ func (b *NodeBuilderImpl) pseudoTypeToNode(t *pseudochecker.PseudoType) *ast.Nod
modifiers,
b.reuseName(e.Name),
nil,
nil,
typeParams,
b.pseudoParametersToNodeList(d.Parameters),
b.pseudoTypeToNode(d.ReturnType),
)
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1 change: 1 addition & 0 deletions internal/pseudochecker/lookup.go
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Expand Up @@ -346,6 +346,7 @@ func (ch *PseudoChecker) typeFromObjectLiteral(node *ast.ObjectLiteralExpression
e,
e.Name(),
optional,
ch.cloneTypeParameters(e.AsMethodDeclaration().TypeParameters),
ch.cloneParameters(e.ParameterList()),
ch.createReturnFromSignature(e),
))
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16 changes: 9 additions & 7 deletions internal/pseudochecker/type.go
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Expand Up @@ -253,16 +253,18 @@ func newPseudoObjectElement(kind PseudoObjectElementKind, name *ast.Node, option

type PseudoObjectMethod struct {
PseudoObjectElement
Signature *ast.Node
Parameters []*PseudoParameter
ReturnType *PseudoType
Signature *ast.Node
TypeParameters []*ast.TypeParameterDeclaration
Parameters []*PseudoParameter
ReturnType *PseudoType
}

func NewPseudoObjectMethod(signature *ast.Node, name *ast.Node, optional bool, parameters []*PseudoParameter, returnType *PseudoType) *PseudoObjectElement {
func NewPseudoObjectMethod(signature *ast.Node, name *ast.Node, optional bool, typeParameters []*ast.TypeParameterDeclaration, parameters []*PseudoParameter, returnType *PseudoType) *PseudoObjectElement {
return newPseudoObjectElement(PseudoObjectElementKindMethod, name, optional, &PseudoObjectMethod{
Signature: signature,
Parameters: parameters,
ReturnType: returnType,
Signature: signature,
TypeParameters: typeParameters,
Parameters: parameters,
ReturnType: returnType,
})
}

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29 changes: 29 additions & 0 deletions testdata/baselines/reference/compiler/declarationEmitConstObjectLiteralGenericMethod1.js
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@@ -0,0 +1,29 @@
//// [tests/cases/compiler/declarationEmitConstObjectLiteralGenericMethod1.ts] ////

//// [declarationEmitConstObjectLiteralGenericMethod1.ts]
export const obj1 = {
id<T>(value: T) {
return value;
},
pair<T>(left: T, right: T) {
return [left, right];
},
} as const;


//// [declarationEmitConstObjectLiteralGenericMethod1.js]
export const obj1 = {
id(value) {
return value;
},
pair(left, right) {
return [left, right];
},
};


//// [declarationEmitConstObjectLiteralGenericMethod1.d.ts]
export declare const obj1: {
id<T>(value: T): T;
pair<T_1>(left: T_1, right: T_1): T_1[];
};
32 changes: 32 additions & 0 deletions ...data/baselines/reference/compiler/declarationEmitConstObjectLiteralGenericMethod1.symbols
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@@ -0,0 +1,32 @@
//// [tests/cases/compiler/declarationEmitConstObjectLiteralGenericMethod1.ts] ////

=== declarationEmitConstObjectLiteralGenericMethod1.ts ===
export const obj1 = {
>obj1 : Symbol(obj1, Decl(declarationEmitConstObjectLiteralGenericMethod1.ts, 0, 12))

id<T>(value: T) {
>id : Symbol(id, Decl(declarationEmitConstObjectLiteralGenericMethod1.ts, 0, 21))
>T : Symbol(T, Decl(declarationEmitConstObjectLiteralGenericMethod1.ts, 1, 7))
>value : Symbol(value, Decl(declarationEmitConstObjectLiteralGenericMethod1.ts, 1, 10))
>T : Symbol(T, Decl(declarationEmitConstObjectLiteralGenericMethod1.ts, 1, 7))

return value;
>value : Symbol(value, Decl(declarationEmitConstObjectLiteralGenericMethod1.ts, 1, 10))

},
pair<T>(left: T, right: T) {
>pair : Symbol(pair, Decl(declarationEmitConstObjectLiteralGenericMethod1.ts, 3, 6))
>T : Symbol(T, Decl(declarationEmitConstObjectLiteralGenericMethod1.ts, 4, 9))
>left : Symbol(left, Decl(declarationEmitConstObjectLiteralGenericMethod1.ts, 4, 12))
>T : Symbol(T, Decl(declarationEmitConstObjectLiteralGenericMethod1.ts, 4, 9))
>right : Symbol(right, Decl(declarationEmitConstObjectLiteralGenericMethod1.ts, 4, 20))
>T : Symbol(T, Decl(declarationEmitConstObjectLiteralGenericMethod1.ts, 4, 9))

return [left, right];
>left : Symbol(left, Decl(declarationEmitConstObjectLiteralGenericMethod1.ts, 4, 12))
>right : Symbol(right, Decl(declarationEmitConstObjectLiteralGenericMethod1.ts, 4, 20))

},
} as const;
>const : Symbol(const)

29 changes: 29 additions & 0 deletions testdata/baselines/reference/compiler/declarationEmitConstObjectLiteralGenericMethod1.types
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@@ -0,0 +1,29 @@
//// [tests/cases/compiler/declarationEmitConstObjectLiteralGenericMethod1.ts] ////

=== declarationEmitConstObjectLiteralGenericMethod1.ts ===
export const obj1 = {
>obj1 : { readonly id: <T>(value: T) => T; readonly pair: <T>(left: T, right: T) => T[]; }
>{ id<T>(value: T) { return value; }, pair<T>(left: T, right: T) { return [left, right]; },} as const : { readonly id: <T>(value: T) => T; readonly pair: <T>(left: T, right: T) => T[]; }
>{ id<T>(value: T) { return value; }, pair<T>(left: T, right: T) { return [left, right]; },} : { readonly id: <T>(value: T) => T; readonly pair: <T>(left: T, right: T) => T[]; }

id<T>(value: T) {
>id : <T>(value: T) => T
>value : T

return value;
>value : T

},
pair<T>(left: T, right: T) {
>pair : <T>(left: T, right: T) => T[]
>left : T
>right : T

return [left, right];
>[left, right] : T[]
>left : T
>right : T

},
} as const;

10 changes: 10 additions & 0 deletions testdata/tests/cases/compiler/declarationEmitConstObjectLiteralGenericMethod1.ts
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@@ -0,0 +1,10 @@
// @declaration: true

export const obj1 = {
id<T>(value: T) {
return value;
},
pair<T>(left: T, right: T) {
return [left, right];
},
} as const;
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