Inferred function return type is different from TS 5.9.3

[In3luki]

Steps to reproduce

This is a contrived reproduction from a larger codebase. It looks like the error happens on line 24 where the inferred type of getItem(options.uuid) is always the same type as options.item as far as I can tell.

https://www.typescriptlang.org/play/?#code/MYGwhgzhAEDiCmA7eAnAlsAkgF3gW2gG8AoaM6RMPeaAXmgCIBzJVDBgbmIF9jjRIMAMoAHeMDQAzDDnzR4AD1yIAJjATJ0WXARLloAewBuqdCpqVqdRhDETpwTjz6SAromDY0BxNBbZZPAAeABUAEQNgV2pEbHklJDU4Vi1AgD4AClJyAH1XVzQVAC5oCGx0RCYAGmIAShLwyOikOIAfClcQECJsshR4bFcUX0IKKngS5hT2aG5oSGhGqJjsLl5iNw8vHz8B0XEpGR0M+uh9+yO5PXJ+weGiMepJ2wOHBlm1vmAfMsMRbcQEBK1zI+UKAH4SmUKkwuPo0DpIWc7IdtHJ2ohOiA1tZCNwuPwfnEEXJ6AZ-t5AQA6EkEcHg6AZckAiBUsEqaAM-yBJkUn5sgoqWrQEr+c6onm1WoEqSMgCEGVp0DQgOwYA88AMkmSmkueClPX02AAFigDAB3aAAURQZpQGQYADkDHF1cqdHKGNKePIQBAaLKMgqlSqyurgJrteKHIEDSDoN9AQYQPAqeawMNFToqZZ4N7eEA

Behavior with typescript@5.9

The type of item is correctly narrowed to GenericItem at the end of the if block and no errors are shown.

Behavior with tsgo

The type of item becomes never and the error Property 'name' does not exist on type 'never' is shown.

[Andarist]

This boils down to "Improved inference from return types (old code base is inconsistent here)." introduced by #244

declare const obj: {
  prop: number | undefined;
};

declare function returnTypeInference<T>(): T;
const result1 = obj.prop ?? returnTypeInference();
//                          ^? Strada: function returnTypeInference<number | undefined>(): number | undefined
//                             Corsa: function returnTypeInference<number | undefined>(): number | undefined

declare function nonNullableReturnTypeInference<T extends {}>(): T;
const result2 = obj.prop ?? nonNullableReturnTypeInference();
//                         ^? Strada: function nonNullableReturnTypeInference<{}>(): {}
//                            Corsa: function nonNullableReturnTypeInference<number>(): number

There is an old PR of mine that implements basically the same thing in Strada here. By landing it, we could at least make versions behave the same way 😉