dotnet/roslyn

Unexpected error CS0146: "Circular base class dependency involving 'A.B' and 'A.B'" in using static directive

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#369 opened on Feb 10, 2015

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 (3 comments) (0 reactions) (0 assignees)C# (20,414 stars) (4,257 forks)batch import
Area-CompilersBugLanguage-C#Pedantic ;)help wanted

Description

using static A.B.B;

class A
{
    public class B : A { }
}

ACTUAL: SourceCode.cs(1,18): error CS0146: Circular base class dependency involving 'A.B' and 'A.B'

EXPECTED: No errors

The problem seems to be in the Microsoft.CodeAnalysis.CSharp.InContainerBinder.LookupSymbolsInSingleBinder method (%Roslyn%\src\Compilers\CSharp\Portable\Binder\InContainerBinder.cs, around line 151).

It looks like there is no inherent circularity there, but it arises because of the particular order of method calls in our implementation. We unconditionally call GetImports first to completely bind all using directives, but this is not actually necessary if we find the declaration of the required symbol directly in the corresponding namespace declaration, we only need to check the names of aliases introduced in using alias directives for potential conflicts (we do not even need to bind the symbols they refer to), and we should not care at all about using namespace or using static directives in this case.

[Migrated from TFS DevDiv 1108103]

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Tech stack
csharp
Domain
tooling
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
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stale
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clear
Prerequisites
C# programmingRoslyn compiler architecture
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
Investigate the method LookupSymbolsInSingleBinder in InContainerBinder.cs (around line 151). The issue suggests that calling GetImports for all using directives is unnecessary when the desired symbol is found directly. Focus on optimizing the order of method calls to avoid triggering the circular base class error. No linked PRs or recent comments provide additional guidance.