Readonly properties do not use constant type

[brokenmass]

The following code generates incorrect types when using tsgo as the type of the read only property is not narrowed to its constant value.
This has the negative consequences of breaking discriminated unions of class instances that use readonly props as discriminato.

Steps to reproduce

enum Types {
  'A' = 'A',
  'B' = 'B'
}
export class LiteralA {
  readonly type = 'A';
}
export class LiteralB {
  readonly type = 'B';
}
export class EnumA {
  readonly type = Types.A;
}
export class EnumB {
  readonly type = Types. B;
}

Behavior with typescript@5.9

declare enum Types {
  'A' = "A",
  'B' = "B”
}
export declare class LiteralA {
  readonly type = "A";
}
export declare class LiteralB {
  readonly type = "B";
}
export declare class EnumA {
  readonly type = Types['A'];
}
export declare class EnumB {
  readonly type = Types['B'];
} 

Behavior with tsgo

declare enum Types {
  'A' = "A",
  'B' = "B”
}
export declare class LiteralA {
  readonly type = string;
}
export declare class LiteralB {
  readonly type = string;
}
export declare class EnumA {
  readonly type = Types;
}
export declare class EnumB {
  readonly type = Types;
} 

[ahejlsberg]

This looks to be a problem in emit. The checker infers the correct literal types for the properties.

[brokenmass]

The issue is in util.go , method canHaveLiteralInitializer.

At line 17 it should be == 0, not != 0 :

return host.GetEffectiveDeclarationFlags(node, ast.ModifierFlagsPrivate) == 0

Apologies if in a locked network at the moment and cannot raise a pr.

[jakebailey]

Yes indeed, thanks! #2219

[brokenmass]

I just noticed this issue : #989 it should be a duplicated.