Fix RCS1009's handling of discard designations.

ChangeLog.md

@@ -34,6 +34,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Do not report `System.Windows.DependencyPropertyChangedEventArgs` as unused parameter ([RCS1163](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1163.md)) ([#1068](https://github.com/JosefPihrt/Roslynator/pull/1068)).
 - Fix ([RCS1032](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1032.md)) ([#1064](https://github.com/JosefPihrt/Roslynator/pull/1064)).
 - Update processing of .globalconfig file to prioritize file-specific diagnostic severities over global diagnostic severities. [#1066](https://github.com/JosefPihrt/Roslynator/pull/1066/files)
+- Fix RCS1009 to handles discard designations ([#1063](https://github.com/JosefPihrt/Roslynator/pull/1063/files)).
 
 ## [4.2.0] - 2022-11-27
 

src/Tests/Analyzers.Tests/RCS1009UseExplicitTypeInsteadOfVarInForEachTests.cs

@@ -169,4 +169,77 @@ public void M()
     }
 }");
     }
+
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.UseExplicitTypeInsteadOfVarWhenTypeIsObvious)]
+    public async Task Test_TupleExpression_WithDiscardPredefinedType()
+    {
+        await VerifyDiagnosticAndFixAsync(@"
+using System;
+using System.Collections.Generic;
+
+class C
+{
+    void M()
+    {
+        var items = new List<(object, System.DateTime)>();
+
+        foreach ([|var|] (_, y) in items)
+        {
+        }
+    }
+}
+", @"
+using System;
+using System.Collections.Generic;
+
+class C
+{
+    void M()
+    {
+        var items = new List<(object, System.DateTime)>();
+
+        foreach ((object _, DateTime y) in items)
+        {
+        }
+    }
+}
+");
+    }
+
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.UseExplicitTypeInsteadOfVarWhenTypeIsObvious)]
+        public async Task Test_TupleExpression_WithDiscardNonPredefinedType()
+        {
+            await VerifyDiagnosticAndFixAsync(@"
+using System;
+using System.Collections.Generic;
+
+class C
+{
+    void M()
+    {
+        var items = new List<(object, System.DateTime)>();
+
+        foreach ([|var|] (x, _) in items)
+        {
+        }
+    }
+}
+", @"
+using System;
+using System.Collections.Generic;
+
+class C
+{
+    void M()
+    {
+        var items = new List<(object, System.DateTime)>();
+
+        foreach ((object x, DateTime _) in items)
+        {
+        }
+    }
+}
+");
+    }
+
 }

src/Workspaces.Common/CSharp/DocumentRefactorings.cs

@@ -97,7 +97,11 @@ private static TupleExpressionSyntax CreateTupleExpression(ITypeSymbol typeSymbo
             {
                 if (f.Expression is DeclarationExpressionSyntax declarationExpression)
                     return f.WithExpression(declarationExpression.WithType(declarationExpression.Type.WithSimplifierAnnotation()));
-
+                if (f.Expression is PredefinedTypeSyntax or MemberAccessExpressionSyntax)
+                {
+                    return f.WithExpression(DeclarationExpression(ParseTypeName(f.Expression.ToString()).WithSimplifierAnnotation(), DiscardDesignation()));
+                }
+
                 SyntaxDebug.Fail(f.Expression);
 
                 return f;
@@ -106,7 +110,6 @@ private static TupleExpressionSyntax CreateTupleExpression(ITypeSymbol typeSymbo
 
         return tupleExpression.WithArguments(newArguments);
     }
-
     public static Task<Document> ChangeTypeToVarAsync(
         Document document,
         TypeSyntax type,