Description
Description
I had a bug report for my open source source generator project:
SteveDunn/Vogen#622
I looked at the emitted code and can see that it emits value == null rather than value is null. This caused a compilation error because the type in question has overloaded == operators, so the C# compiler reports:
CS0034: Operator '==' is ambiguous on operands of type 'Foo' and '<null>'
The line in question in STJ is here: https://github.com/dotnet/runtime/blob/main/src/libraries/System.Text.Json/gen/JsonSourceGenerator.Emitter.cs#L977
Reproduction Steps
[JsonSourceGenerationOptions(WriteIndented = true)]
[JsonSerializable(typeof(Foo))]
internal partial class JsonSourceGenerationContext : JsonSerializerContext;
internal class Foo
{
public Foo(string value) => Value = value;
public string Value { get; }
public bool Equals(string primitive) => Value.Equals(primitive);
public override bool Equals(Object obj) => Equals(obj as Foo);
public bool Equals(Foo foo) => Value == foo.Value;
public static bool operator ==(Foo left, Foo right) => Equals(left, right);
public static bool operator !=(Foo left, Foo right) => !Equals(left, right);
public static bool operator ==(Foo left, string right) => Equals(left.Value, right);
public static bool operator !=(Foo left, string right) => !Equals(left.Value, right);
public override int GetHashCode()
{
unchecked // Overflow is fine, just wrap
{
int hash = (int)2166136261;
hash = (hash * 16777619) ^ GetType().GetHashCode();
hash = (hash * 16777619) ^ EqualityComparer<string>.Default.GetHashCode(Value);
return hash;
}
}
}This should compile, but doesn't. Instead, the compiler reports:
CS0034: Operator '==' is ambiguous on operands of type 'Foo' and '<null>'
Expected behavior
For it to compile
Actual behavior
Emits error CS0034: Operator '==' is ambiguous on operands of type 'Foo' and '<null>'
Regression?
No, I think the source generator stuff in STJ is fairly new
Known Workarounds
If I change my type from a class to a struct, then the null check isn't emitted.
Configuration
.NET 8, Windows 11, X64, not specific to any particular configuration.
Other information
I plan on doing a fix and a PR