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Immutable record types are not treated as immutable #777
Description
C# 9.0 syntax allows now to declare reference types as 'records' which is a nice syntax sugar for (immutable) data-container classes. There's a way to declare a record type as 'immutable':
public sealed record MyRecord(
string property1,
int property2,
object propertyEtc
)
{}This would actually generate a following class:
public sealed class MyRecord
{
public string property1 {get; init;}
public int property2 {get; init;}
public object propertyEtc {get; init}
public MyRecord(string property1, int property2, object propertyEtc)
{
this.property1 = property1;
this.property2 = property2;
this.propertyEtc = propertyEtc;
}
//some other code, like Equals()
}The problem is that ParseArguments<MyRecord>() would fail with System.MissingMethodException: No parameterless constructor defined for type 'MyRecord '. (which there's really none).
While I could declare a prarmeterless constructor for such record, it would be really great to have such classes supported as-is.
Activity
mikhail-barg commentedon Sep 23, 2021
As far as I understand, the wiki on immutable types support, the class generally has all that's needed to work as an immutable, and the problem is that it is not regarded as such.
From what I see in
ReflectionExtensions.IsMutable()the culpit is this line:which prevents
init-only properties from being treated as readonly.See for example this post on how to detect for
initproperties.V0ldek commentedon Jan 21, 2022
Just ran into a related issue. I wasn't making a record class, but a regular class with all of its properties readonly, but with
init. That's obviously readonly for all intents and purposes, but CommandLine throws the sameSystem.MissingMethodExceptionas in Mikhail's case.Add test for issue commandlineparser#777.
Implement fix for issue commandlineparser#777.