Newtype for `decimal` fails to build

[LWEdslev]

This fails to build

using newtype;

Id foo = new(5);
Console.WriteLine(foo);

[newtype<decimal>]
public readonly partial struct Id;

with the following message

/home/lasse-edslev/csharp/Playground/NewType.Generator/newtype.generator.AliasGenerator/Id.g.cs(121,56): error CS0191: A readonly field cannot be assigned to (except in a constructor or init-only setter of the type in which the field is defined or a variable initializer) [/home/lasse-edslev/csharp/Playground/Playground.csproj]
/home/lasse-edslev/csharp/Playground/NewType.Generator/newtype.generator.AliasGenerator/Id.g.cs(124,56): error CS0191: A readonly field cannot be assigned to (except in a constructor or init-only setter of the type in which the field is defined or a variable initializer) [/home/lasse-edslev/csharp/Playground/Playground.csproj]

It works if I use double