Overload order affects assignability of abstract constructors overloaded with regular constructors in interfaces

🔎 Search Terms

abstract constructors, constructor overloading, overload order, intersection, type aliases, interfaces, assignability

🕗 Version & Regression Information

• This seems like a bug
• This is the behavior in every version I tried since abstract constructors were added (4.2)

⏯ Playground Link

https://www.typescriptlang.org/play/?noUncheckedIndexedAccess=true&ts=5.7.0-dev.20240904#code/C4TwDgpgBAwgjFAvFAhgIwM7AE4oMbBQB2EA7lABQoBcUcAlEgHx0BQoksATEsWZTShdGiFl1asAlkWARsAM3zQAglAgAPWUQAmGWHAA03KAG8AvlAD0lqAFFs2APbZaMFESKPCKDBkkBzIlQg9CxcAig8RyIwgFcCZygOaGBHVGJogFpQnHxCKJiceNTsJPAIADopGTlFPGgAITVNCB09GC4jeFMLaygAeQBrCW0IPAAbFGxocYhvWmVWUYmpmbmoNFoGiT6AFQALCAxoVY2vfbV5eTHgSQA3CHGQVExcglYSchQKBiNP1Aowj+-DQP3owPIoOEEhQvDQVhsQ1Y8OQsL69icLlg7k83l8ARCIVe4Xy0TiCVKySSaVhniI2WJeUiZKKFLKkCq7HKUGUjIIADFJNgsLxugAybhczi8sJ5AAyPkIyA6UAl8BGY0m0ygs28fOAguFwAW+sNWCWmtOupesoICqwJttwHtwB2NgORxO2p8fkC6Fm1LU+AujkO2FYORJZqVNrezsVEf1Lt4kby0YkKNjUaFIvRDmcrhxXlQ+MCwSzTIK5JK7JSNIy9NTESrrJrySqTYNOZj8L6SORKaTioRA2GneTyF7iOGQA

💻 Code

type C1 = abstract new (a: 1) => 1
type C2 = new (a: 2) => 2

interface A extends C1, C2 {} // Error: Cannot assign an abstract constructor type to a non-abstract constructor type.
interface B extends C2, C1 {} // Ok

declare let a: A
declare let b: B

// These are both effectively abstract
new a(1), new a(2), new b(1), new b(2)

a = b // Ok
b = a // Error: Cannot assign an abstract constructor type to a non-abstract constructor type.

type AbstractFirst = C1 & C2
type AbstractLast = C2 & C1

declare let abstractFirst: AbstractFirst
declare let abstractLast: AbstractLast

// These are assignable to each oher
abstractFirst = abstractLast
abstractLast = abstractFirst

b = abstractFirst // Error: Cannot assign an abstract constructor type to a non-abstract constructor type.
abstractFirst = b // Ok

b = abstractLast // Ok
abstractLast = b // Ok

🙁 Actual behavior

It seems that interfaces with both abstract and regular constructor overloads are only assignable from types with non-abstract first constructor overload.

🙂 Expected behavior

I don't expect any difference here.

Additional information about the issue

No response

Start with the linked TypeScript Playground repro and compare assignability for interfaces and intersections containing abstract and regular constructor overloads in both orders. Trace the compiler's constructor overload and assignability checks, then verify that reversing overload order no longer changes the reported errors shown in the example.