Fixed type parameter leak in union calls with mixed type parameter presence

Author: Andarist

src/compiler/checker.ts

@@ -13541,6 +13541,9 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         if (paramMapper) {
             result.mapper = left.compositeKind !== TypeFlags.Intersection && left.mapper && left.compositeSignatures ? combineTypeMappers(left.mapper, paramMapper) : paramMapper;
         }
+        else if (left.compositeKind !== TypeFlags.Intersection && left.mapper && left.compositeSignatures) {
+            result.mapper = left.mapper;
+        }
         return result;
     }
 

tests/baselines/reference/unionCallMixedTypeParameterPresence.symbols

@@ -0,0 +1,45 @@
+//// [tests/cases/compiler/unionCallMixedTypeParameterPresence.ts] ////
+
+=== unionCallMixedTypeParameterPresence.ts ===
+// https://github.com/microsoft/TypeScript/issues/57356
+
+interface Err<T> {
+>Err : Symbol(Err, Decl(unionCallMixedTypeParameterPresence.ts, 0, 0))
+>T : Symbol(T, Decl(unionCallMixedTypeParameterPresence.ts, 2, 14))
+
+  f<U>(a: (err: T) => U): Err<U>;
+>f : Symbol(Err.f, Decl(unionCallMixedTypeParameterPresence.ts, 2, 18))
+>U : Symbol(U, Decl(unionCallMixedTypeParameterPresence.ts, 3, 4))
+>a : Symbol(a, Decl(unionCallMixedTypeParameterPresence.ts, 3, 7))
+>err : Symbol(err, Decl(unionCallMixedTypeParameterPresence.ts, 3, 11))
+>T : Symbol(T, Decl(unionCallMixedTypeParameterPresence.ts, 2, 14))
+>U : Symbol(U, Decl(unionCallMixedTypeParameterPresence.ts, 3, 4))
+>Err : Symbol(Err, Decl(unionCallMixedTypeParameterPresence.ts, 0, 0))
+>U : Symbol(U, Decl(unionCallMixedTypeParameterPresence.ts, 3, 4))
+}
+interface Ok<T> {
+>Ok : Symbol(Ok, Decl(unionCallMixedTypeParameterPresence.ts, 4, 1))
+>T : Symbol(T, Decl(unionCallMixedTypeParameterPresence.ts, 5, 13))
+
+  f(a: (err: T) => unknown): Err<T>;
+>f : Symbol(Ok.f, Decl(unionCallMixedTypeParameterPresence.ts, 5, 17))
+>a : Symbol(a, Decl(unionCallMixedTypeParameterPresence.ts, 6, 4))
+>err : Symbol(err, Decl(unionCallMixedTypeParameterPresence.ts, 6, 8))
+>T : Symbol(T, Decl(unionCallMixedTypeParameterPresence.ts, 5, 13))
+>Err : Symbol(Err, Decl(unionCallMixedTypeParameterPresence.ts, 0, 0))
+>T : Symbol(T, Decl(unionCallMixedTypeParameterPresence.ts, 5, 13))
+}
+declare const e: Err<0> | Err<1> | Ok<2>;
+>e : Symbol(e, Decl(unionCallMixedTypeParameterPresence.ts, 8, 13))
+>Err : Symbol(Err, Decl(unionCallMixedTypeParameterPresence.ts, 0, 0))
+>Err : Symbol(Err, Decl(unionCallMixedTypeParameterPresence.ts, 0, 0))
+>Ok : Symbol(Ok, Decl(unionCallMixedTypeParameterPresence.ts, 4, 1))
+
+const e2 = e.f((e) => e);
+>e2 : Symbol(e2, Decl(unionCallMixedTypeParameterPresence.ts, 9, 5))
+>e.f : Symbol(f, Decl(unionCallMixedTypeParameterPresence.ts, 2, 18), Decl(unionCallMixedTypeParameterPresence.ts, 2, 18), Decl(unionCallMixedTypeParameterPresence.ts, 5, 17))
+>e : Symbol(e, Decl(unionCallMixedTypeParameterPresence.ts, 8, 13))
+>f : Symbol(f, Decl(unionCallMixedTypeParameterPresence.ts, 2, 18), Decl(unionCallMixedTypeParameterPresence.ts, 2, 18), Decl(unionCallMixedTypeParameterPresence.ts, 5, 17))
+>e : Symbol(e, Decl(unionCallMixedTypeParameterPresence.ts, 9, 16))
+>e : Symbol(e, Decl(unionCallMixedTypeParameterPresence.ts, 9, 16))
+

tests/baselines/reference/unionCallMixedTypeParameterPresence.types

@@ -0,0 +1,30 @@
+//// [tests/cases/compiler/unionCallMixedTypeParameterPresence.ts] ////
+
+=== unionCallMixedTypeParameterPresence.ts ===
+// https://github.com/microsoft/TypeScript/issues/57356
+
+interface Err<T> {
+  f<U>(a: (err: T) => U): Err<U>;
+>f : <U>(a: (err: T) => U) => Err<U>
+>a : (err: T) => U
+>err : T
+}
+interface Ok<T> {
+  f(a: (err: T) => unknown): Err<T>;
+>f : (a: (err: T) => unknown) => Err<T>
+>a : (err: T) => unknown
+>err : T
+}
+declare const e: Err<0> | Err<1> | Ok<2>;
+>e : Err<0> | Err<1> | Ok<2>
+
+const e2 = e.f((e) => e);
+>e2 : Err<2> | Err<0 | 1 | 2>
+>e.f((e) => e) : Err<2> | Err<0 | 1 | 2>
+>e.f : (<U>(a: (err: 0) => U) => Err<U>) | (<U_1>(a: (err: 1) => U_1) => Err<U_1>) | ((a: (err: 2) => unknown) => Err<2>)
+>e : Err<0> | Err<1> | Ok<2>
+>f : (<U>(a: (err: 0) => U) => Err<U>) | (<U_1>(a: (err: 1) => U_1) => Err<U_1>) | ((a: (err: 2) => unknown) => Err<2>)
+>(e) => e : (e: 0 | 1 | 2) => 0 | 1 | 2
+>e : 0 | 1 | 2
+>e : 0 | 1 | 2
+

tests/cases/compiler/unionCallMixedTypeParameterPresence.ts

@@ -0,0 +1,13 @@
+// @strict: true
+// @noEmit: true
+
+// https://github.com/microsoft/TypeScript/issues/57356
+
+interface Err<T> {
+  f<U>(a: (err: T) => U): Err<U>;
+}
+interface Ok<T> {
+  f(a: (err: T) => unknown): Err<T>;
+}
+declare const e: Err<0> | Err<1> | Ok<2>;
+const e2 = e.f((e) => e);