S3257 FP: when explicit array types in conjunction with c#9 target-typed new

[tomdegoede]

Description

The S3257 RedundantDeclaration analyzer is currently reporting a false positive: error S3257: Remove the array type; it is redundant when an explicit array type is provided and C#9 target-typed new is used for it's elements.

Repro steps

new DataEntityFieldDefinition[]
{
  new(BackEndTypes.Guid, FrontEndDataTypeName.guid, "InstanceId", "InstanceId"),
  new(BackEndTypes.String, FrontEndDataTypeName.text, "EMailadres", "EMailadres"),
  new(BackEndTypes.String, FrontEndDataTypeName.text, "Voorletters", "Voorletters"),
  new(BackEndTypes.String, FrontEndDataTypeName.text, "Roepnaam", "Roepnaam"),
  new(BackEndTypes.String, FrontEndDataTypeName.text, "Geboortenaam", "Geboortenaam"),
}

Expected behavior

The explicit type is actually required for the target-typed new logic to kick in.

Actual behavior

error S3257: Remove the array type; it is redundant is raised.

Known workarounds

Do not use target-typed new.

new []
{
  new DataEntityFieldDefinition(BackEndTypes.Guid, FrontEndDataTypeName.guid, "InstanceId", "InstanceId"),
  new DataEntityFieldDefinition(BackEndTypes.String, FrontEndDataTypeName.text, "EMailadres", "EMailadres"),
  new DataEntityFieldDefinition(BackEndTypes.String, FrontEndDataTypeName.text, "Voorletters", "Voorletters"),
  new DataEntityFieldDefinition(BackEndTypes.String, FrontEndDataTypeName.text, "Roepnaam", "Roepnaam"),
  new DataEntityFieldDefinition(BackEndTypes.String, FrontEndDataTypeName.text, "Geboortenaam", "Geboortenaam"),
}

Related information

Tested using SonarAnalyzer.CSharp 8.29.0.36737.

[costin-zaharia-sonarsource]

Hi @tomdegoede, thanks for reporting this. I can confirm the false positive.

[melix-dev]

Any news on this issue? I'm running into the same issue atm