dotnet/roslyn
View on GitHubIncorrect "Nullability doesn't match the target delegate" when tuple element names don't explicitly match
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#74,493 opened on Jul 23, 2024
Area-CompilersBugFeature - Nullable Reference Typeshelp wanted
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Description
Version Used: 17.11.0 Preview 3.0
The following code erroneously causes this warning to appear for each lambda in the Error List and at the command line, though squiggles are not shown:
⚠️ CS8621 Nullability of reference types in return type of 'lambda expression' doesn't match the target delegate 'Func<(string, object?), ?>' (possibly because of nullability attributes).
class C
{
void M((string Name, object? Value)[] parameters)
{
_ = parameters.Append(("A", "A")).ToDictionary(
tuple => tuple.Name,
tuple => tuple.Value);
}
}
If you name the elements in the tuple expression to exactly match the tuple element names in the collection, the warning goes away.
class C
{
void M((string Name, object? Value)[] parameters)
{
_ = parameters.Append((Name: "A", Value: "A")).ToDictionary(
tuple => tuple.Name,
tuple => tuple.Value);
}
}
For each element where a name is missing or does not exactly match, a nullability warning returns.