dotnet/roslyn

Implementing interface (or abstract class) whose members reference a type included via a global import adds empty line to the beginning of file

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#79,363 opened on Jul 14, 2025

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 (5 comments) (0 reactions) (0 assignees)C# (4,257 forks)batch import
Area-IDEhelp wanted

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Description

Full issue information + repro project:
https://github.com/just-ero/roslyn-issues-repros/tree/main/5.0.0/003_ImplementInterface_ReturnTypeInGlobalUsings

Version

[!NOTE]
Roslyn: 5.0.0-1.25319.11
.NET SDK: 10.0.100-preview.5.25277.114

Visual Studio Code: 1.102.0
C# Extension: 2.84.19
C# Dev Kit Extension: 1.30.44

Steps to Reproduce

  1. Add the following code in separate files: 
    namespace N;

class C;

    interface II
{
    C M();
}

    class Repro : II;
    Note: C must be in a different namespace than II, and Repro and Repro must not know of C before implemetation.
  2. Add N to the global usings anywhere.
  3. Apply the Implement interface quick fix to Repro.

Expected Behavior

No new line is added to the beginning of the file.

Actual Behavior

It is.

Speculation: this is possibly due to Roslyn making an attempt to add missing namespaces, but stopping after finding the global import.

Contributor guide

Research direction
Investigate the 'Implement Interface' code action in Roslyn, focusing on how it handles return types that are resolved via global usings. Trace the code that generates the method implementation and check for any logic that inserts an empty line when adding missing usings for the return type.
Tech stack
csharp
Domain
backend
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
C#.NETRoslyn
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50