From e31cb0c83680944e8c50c7c9fb0dfab424fbe801 Mon Sep 17 00:00:00 2001
From: Josef Pihrt <josef.pihrt@outlook.com>
Date: Thu, 15 Sep 2022 22:45:02 +0200
Subject: [PATCH] Do not remove async/await

---
 ChangeLog.md                                  |  1 +
 .../Analysis/RemoveAsyncAwaitAnalysis.cs      | 16 ++++++++++++-
 .../RCS1174RemoveRedundantAsyncAwaitTests.cs  | 24 +++++++++++++++++++
 3 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/ChangeLog.md b/ChangeLog.md
index 90790c6828..ac26e49dc2 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -32,6 +32,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Prefix identifier with `@` if necessary ([RCS1220](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1220.md)) ([#943](https://github.com/josefpihrt/roslynator/pull/943).
 - Do not suggest to make local variable a const when it is used in ref extension method ([RCS1118](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1118.md)) ([#948](https://github.com/josefpihrt/roslynator/pull/948).
 - Fix formatting of argument list ([#952](https://github.com/josefpihrt/roslynator/pull/952).
+- Do not remove async/await when 'using declaration' is used ([#953](https://github.com/josefpihrt/roslynator/pull/953).
 
 -----
 <!-- Content below does not adhere to 'Keep a Changelog' format -->
diff --git a/src/Common/CSharp/Analysis/RemoveAsyncAwaitAnalysis.cs b/src/Common/CSharp/Analysis/RemoveAsyncAwaitAnalysis.cs
index 2ff7677190..587f34f427 100644
--- a/src/Common/CSharp/Analysis/RemoveAsyncAwaitAnalysis.cs
+++ b/src/Common/CSharp/Analysis/RemoveAsyncAwaitAnalysis.cs
@@ -154,7 +154,21 @@ private static RemoveAsyncAwaitAnalysis AnalyzeMethodBody(
         {
             SyntaxList<StatementSyntax> statements = body.Statements;
 
-            StatementSyntax statement = statements.LastOrDefault(f => !f.IsKind(SyntaxKind.LocalFunctionStatement));
+            StatementSyntax statement = null;
+
+            foreach (StatementSyntax s in statements)
+            {
+                if (s is LocalDeclarationStatementSyntax localDeclarationStatement
+                    && localDeclarationStatement.UsingKeyword.IsKind(SyntaxKind.UsingKeyword))
+                {
+                    return default;
+                }
+
+                if (!s.IsKind(SyntaxKind.LocalFunctionStatement))
+                {
+                    statement = s;
+                }
+            }
 
             if (statement == null)
                 return default;
diff --git a/src/Tests/Analyzers.Tests/RCS1174RemoveRedundantAsyncAwaitTests.cs b/src/Tests/Analyzers.Tests/RCS1174RemoveRedundantAsyncAwaitTests.cs
index 9ea76e4d4a..5e45401cb7 100644
--- a/src/Tests/Analyzers.Tests/RCS1174RemoveRedundantAsyncAwaitTests.cs
+++ b/src/Tests/Analyzers.Tests/RCS1174RemoveRedundantAsyncAwaitTests.cs
@@ -970,6 +970,30 @@ async Task<object> SwitchWithDefaultAsync()
         }
     }
 }
+");
+        }
+
+        [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.RemoveRedundantAsyncAwait)]
+        public async Task TestNoDiagnostic_UsingDeclaration()
+        {
+            await VerifyNoDiagnosticAsync(@"
+using System;
+using System.IO;
+using System.Threading.Tasks;
+
+class C
+{
+    private async Task<string> M()
+    {
+        using var stream = File.OpenRead("""");
+        return await this.M2(stream);
+    }
+
+    private Task<string> M2(FileStream stream)
+    {
+        throw new NotImplementedException();
+    }
+}
 ");
         }
     }