dotnet/roslyn - Issue 69700

Link to the PR

In my recent work on the dotnet/roslyn repository, I encountered an interesting issue related to the diagnostic message for missing attribute types. The Roslyn repository is the home of the .NET Compiler Platform, which provides open-source C# and Visual Basic compilers with rich code analysis APIs.

The Issue

The problem was with the diagnostic message for missing attribute types. When an attribute type was missing, the error message was not clear enough. It would say:

• The type or namespace name 'SomeAttribute<>Attribute' could not be found (are you missing a using directive or an assembly reference?)

The expected behavior was for the error message to be more specific and helpful:

• The type or namespace name 'SomeAttributeAttribute<>' could not be found (are you missing a using directive or an assembly reference?)

The Solution

To solve this issue, I added a check on arity in the construction of the message. Here's the code change I made:

Before:

if (options.IsAttributeTypeLookup() && !options.IsVerbatimNameAttributeTypeLookup())
{
    // just recurse one level, so cheat and OR verbatim name option :)
    NotFound(where, simpleName, arity, whereText + "Attribute", diagnostics, aliasOpt, qualifierOpt, options | LookupOptions.VerbatimNameAttributeTypeOnly);
}

After:

if (options.IsAttributeTypeLookup() && !options.IsVerbatimNameAttributeTypeLookup())
{
    string attributeName = arity > 0 ? $"{simpleName}Attribute<>" : $"{simpleName}Attribute";

    NotFound(where, simpleName, arity, attributeName, diagnostics, aliasOpt, qualifierOpt, options | LookupOptions.VerbatimNameAttributeTypeOnly);
}

This change ensures that the diagnostic message is more specific and helpful, improving the developer experience when working with attributes in C#.