Fix spurious _N suffix on type parameters of sibling object-literal methods in declaration emit (#3969)

Copilot · jakebailey · web-flow · commit 431937b86273 · 2026-05-19T16:33:28.000Z
Co-authored-by: copilot-swe-agent[bot] &lt;198982749+Copilot@users.noreply.github.com&gt;
Co-authored-by: jakebailey &lt;5341706+jakebailey@users.noreply.github.com&gt;
diff --git a/internal/checker/pseudotypenodebuilder.go b/internal/checker/pseudotypenodebuilder.go
@@ -203,11 +203,11 @@ func (b *NodeBuilderImpl) pseudoTypeToNode(t *pseudochecker.PseudoType) *ast.Nod
 			if isConst || (e.Kind == pseudochecker.PseudoObjectElementKindPropertyAssignment && e.AsPseudoPropertyAssignment().Readonly) {
 				modifiers = b.f.NewModifierList([]*ast.Node{b.f.NewModifier(ast.KindReadonlyKeyword)})
 			}
+			var cleanup func()
 			if e.Kind != pseudochecker.PseudoObjectElementKindPropertyAssignment {
 				signature := b.ch.getSignatureFromDeclaration(e.Signature())
 				expandedParams := b.ch.getExpandedParameters(signature, true /*skipUnionExpanding*/)[0]
-				cleanup := b.enterNewScope(e.Signature(), expandedParams, signature.typeParameters, signature.parameters, signature.mapper)
-				defer cleanup()
+				cleanup = b.enterNewScope(e.Signature(), expandedParams, signature.typeParameters, signature.parameters, signature.mapper)
 			}
 			var newProp *ast.Node
 			switch e.Kind {
@@ -279,6 +279,9 @@ func (b *NodeBuilderImpl) pseudoTypeToNode(t *pseudochecker.PseudoType) *ast.Nod
 				b.e.SetCommentRange(newProp, e.Name.Parent.Loc)
 			}
 			newElements = append(newElements, newProp)
+			if cleanup != nil {
+				cleanup()
+			}
 		}
 		result := b.f.NewTypeLiteralNode(b.f.NewNodeList(newElements))
 		if b.ctx.flags&nodebuilder.FlagsMultilineObjectLiterals == 0 {
diff --git a/testdata/baselines/reference/compiler/declarationEmitConstObjectLiteralGenericMethod1.js b/testdata/baselines/reference/compiler/declarationEmitConstObjectLiteralGenericMethod1.js
@@ -25,5 +25,5 @@ export const obj1 = {
 //// [declarationEmitConstObjectLiteralGenericMethod1.d.ts]
 export declare const obj1: {
     id<T>(value: T): T;
-    pair<T_1>(left: T_1, right: T_1): T_1[];
+    pair<T>(left: T, right: T): T[];
 };
diff --git a/testdata/baselines/reference/compiler/declarationEmitObjectLiteralMethodGenericNoSuffix.js b/testdata/baselines/reference/compiler/declarationEmitObjectLiteralMethodGenericNoSuffix.js
@@ -0,0 +1,37 @@
+//// [tests/cases/compiler/declarationEmitObjectLiteralMethodGenericNoSuffix.ts] ////
+
+//// [declarationEmitObjectLiteralMethodGenericNoSuffix.ts]
+export const o = {
+    foo<M extends string>(): void { },
+    bar<M extends string>(): void { },
+};
+
+export const o2 = {
+    foo<T>(value: T): T { return value; },
+    bar<T>(value: T): T { return value; },
+    baz<T, U>(a: T, b: U): [T, U] { return [a, b]; },
+};
+
+
+//// [declarationEmitObjectLiteralMethodGenericNoSuffix.js]
+export const o = {
+    foo() { },
+    bar() { },
+};
+export const o2 = {
+    foo(value) { return value; },
+    bar(value) { return value; },
+    baz(a, b) { return [a, b]; },
+};
+
+
+//// [declarationEmitObjectLiteralMethodGenericNoSuffix.d.ts]
+export declare const o: {
+    foo<M extends string>(): void;
+    bar<M extends string>(): void;
+};
+export declare const o2: {
+    foo<T>(value: T): T;
+    bar<T>(value: T): T;
+    baz<T, U>(a: T, b: U): [T, U];
+};
diff --git a/testdata/baselines/reference/compiler/declarationEmitObjectLiteralMethodGenericNoSuffix.symbols b/testdata/baselines/reference/compiler/declarationEmitObjectLiteralMethodGenericNoSuffix.symbols
@@ -0,0 +1,50 @@
+//// [tests/cases/compiler/declarationEmitObjectLiteralMethodGenericNoSuffix.ts] ////
+
+=== declarationEmitObjectLiteralMethodGenericNoSuffix.ts ===
+export const o = {
+>o : Symbol(o, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 0, 12))
+
+    foo<M extends string>(): void { },
+>foo : Symbol(foo, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 0, 18))
+>M : Symbol(M, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 1, 8))
+
+    bar<M extends string>(): void { },
+>bar : Symbol(bar, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 1, 38))
+>M : Symbol(M, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 2, 8))
+
+};
+
+export const o2 = {
+>o2 : Symbol(o2, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 5, 12))
+
+    foo<T>(value: T): T { return value; },
+>foo : Symbol(foo, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 5, 19))
+>T : Symbol(T, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 6, 8))
+>value : Symbol(value, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 6, 11))
+>T : Symbol(T, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 6, 8))
+>T : Symbol(T, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 6, 8))
+>value : Symbol(value, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 6, 11))
+
+    bar<T>(value: T): T { return value; },
+>bar : Symbol(bar, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 6, 42))
+>T : Symbol(T, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 7, 8))
+>value : Symbol(value, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 7, 11))
+>T : Symbol(T, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 7, 8))
+>T : Symbol(T, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 7, 8))
+>value : Symbol(value, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 7, 11))
+
+    baz<T, U>(a: T, b: U): [T, U] { return [a, b]; },
+>baz : Symbol(baz, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 7, 42))
+>T : Symbol(T, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 8, 8))
+>U : Symbol(U, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 8, 10))
+>a : Symbol(a, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 8, 14))
+>T : Symbol(T, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 8, 8))
+>b : Symbol(b, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 8, 19))
+>U : Symbol(U, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 8, 10))
+>T : Symbol(T, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 8, 8))
+>U : Symbol(U, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 8, 10))
+>a : Symbol(a, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 8, 14))
+>b : Symbol(b, Decl(declarationEmitObjectLiteralMethodGenericNoSuffix.ts, 8, 19))
+
+};
+
diff --git a/testdata/baselines/reference/compiler/declarationEmitObjectLiteralMethodGenericNoSuffix.types b/testdata/baselines/reference/compiler/declarationEmitObjectLiteralMethodGenericNoSuffix.types
@@ -0,0 +1,39 @@
+//// [tests/cases/compiler/declarationEmitObjectLiteralMethodGenericNoSuffix.ts] ////
+
+=== declarationEmitObjectLiteralMethodGenericNoSuffix.ts ===
+export const o = {
+>o : { foo<M extends string>(): void; bar<M extends string>(): void; }
+>{    foo<M extends string>(): void { },    bar<M extends string>(): void { },} : { foo<M extends string>(): void; bar<M extends string>(): void; }
+
+    foo<M extends string>(): void { },
+>foo : <M extends string>() => void
+
+    bar<M extends string>(): void { },
+>bar : <M extends string>() => void
+
+};
+
+export const o2 = {
+>o2 : { foo<T>(value: T): T; bar<T>(value: T): T; baz<T, U>(a: T, b: U): [T, U]; }
+>{    foo<T>(value: T): T { return value; },    bar<T>(value: T): T { return value; },    baz<T, U>(a: T, b: U): [T, U] { return [a, b]; },} : { foo<T>(value: T): T; bar<T>(value: T): T; baz<T, U>(a: T, b: U): [T, U]; }
+
+    foo<T>(value: T): T { return value; },
+>foo : <T>(value: T) => T
+>value : T
+>value : T
+
+    bar<T>(value: T): T { return value; },
+>bar : <T>(value: T) => T
+>value : T
+>value : T
+
+    baz<T, U>(a: T, b: U): [T, U] { return [a, b]; },
+>baz : <T, U>(a: T, b: U) => [T, U]
+>a : T
+>b : U
+>[a, b] : [T, U]
+>a : T
+>b : U
+
+};
+
diff --git a/testdata/tests/cases/compiler/declarationEmitObjectLiteralMethodGenericNoSuffix.ts b/testdata/tests/cases/compiler/declarationEmitObjectLiteralMethodGenericNoSuffix.ts
@@ -0,0 +1,12 @@
+// @declaration: true
+
+export const o = {
+    foo<M extends string>(): void { },
+    bar<M extends string>(): void { },
+};
+
+export const o2 = {
+    foo<T>(value: T): T { return value; },
+    bar<T>(value: T): T { return value; },
+    baz<T, U>(a: T, b: U): [T, U] { return [a, b]; },
+};

Original file line number	Diff line number	Diff line change
`@@ -203,11 +203,11 @@ func (b NodeBuilderImpl) pseudoTypeToNode(t pseudochecker.PseudoType) *ast.Nod`
`203`	`203`	`if isConst \|\| (e.Kind == pseudochecker.PseudoObjectElementKindPropertyAssignment && e.AsPseudoPropertyAssignment().Readonly) {`
`204`	`204`	`modifiers = b.f.NewModifierList([]*ast.Node{b.f.NewModifier(ast.KindReadonlyKeyword)})`
`205`	`205`	`}`
	`206`	`+ var cleanup func()`
`206`	`207`	`if e.Kind != pseudochecker.PseudoObjectElementKindPropertyAssignment {`
`207`	`208`	`signature := b.ch.getSignatureFromDeclaration(e.Signature())`
`208`	`209`	`expandedParams := b.ch.getExpandedParameters(signature, true /skipUnionExpanding/)[0]`
`209`		`- cleanup := b.enterNewScope(e.Signature(), expandedParams, signature.typeParameters, signature.parameters, signature.mapper)`
`210`		`- defer cleanup()`
	`210`	`+ cleanup = b.enterNewScope(e.Signature(), expandedParams, signature.typeParameters, signature.parameters, signature.mapper)`
`211`	`211`	`}`
`212`	`212`	`var newProp *ast.Node`
`213`	`213`	`switch e.Kind {`
`@@ -279,6 +279,9 @@ func (b NodeBuilderImpl) pseudoTypeToNode(t pseudochecker.PseudoType) *ast.Nod`
`279`	`279`	`b.e.SetCommentRange(newProp, e.Name.Parent.Loc)`
`280`	`280`	`}`
`281`	`281`	`newElements = append(newElements, newProp)`
	`282`	`+ if cleanup != nil {`
	`283`	`+ cleanup()`
	`284`	`+ }`
`282`	`285`	`}`
`283`	`286`	`result := b.f.NewTypeLiteralNode(b.f.NewNodeList(newElements))`
`284`	`287`	`if b.ctx.flags&nodebuilder.FlagsMultilineObjectLiterals == 0 {`