feat(core): Add "AbstractType<T>" interface (#29295)

This new interface will match classes whether they are abstract or
concrete. Casting as `AbstractType<MyConcrete>` will return a type that
isn't newable. This type will be used to match abstract classes in the
`get()` functions of `Injector` and `TestBed`.
Type isn't used yet so this isn't a breaking change.

Issue #26491

PR Close #29295

packages/core/src/interface/type.ts

@@ -22,6 +22,16 @@ export function isType(v: any): v is Type<any> {
   return typeof v === 'function';
 }
 
+/**
+ * @description
+ *
+ * Represents an abstract class `T`, if applied to a concrete class it would stop being
+ * instantiatable.
+ *
+ * @publicApi
+ */
+export interface AbstractType<T> extends Function { prototype: T; }
+
 export interface Type<T> extends Function { new (...args: any[]): T; }
 
 export type Mutable<T extends{[x: string]: any}, K extends string> = {