dotnet / roslyn

The Roslyn .NET compiler provides C# and Visual Basic languages with rich code analysis APIs.
https://docs.microsoft.com/dotnet/csharp/roslyn-sdk/
MIT License
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FixALl issue with 'remove redundant assignment' (IDE0059) #53960

Open CyrusNajmabadi opened 3 years ago

CyrusNajmabadi commented 3 years ago

Happened while fixing up code in roslyn. original code is:

            ResultProperties resultProperties;
            string error;
            var testData = Evaluate(
                source,
                OutputKind.DynamicallyLinkedLibrary,
                methodName: "C.M",
                expr: "global::$exception",
                resultProperties: out resultProperties,
                error: out error);

both resultProperties and testData are unused. FixAll crashes with:

System.InvalidOperationException : GetCurrentNode returned null with the following node: resultProperties
   at Roslyn.Utilities.Contract.Fail(String message)
   at Microsoft.CodeAnalysis.Editing.SyntaxEditor.ReplaceChange.Apply(SyntaxNode root,SyntaxGenerator generator)
   at Microsoft.CodeAnalysis.Editing.SyntaxEditor.GetChangedRoot()
   at async Microsoft.CodeAnalysis.RemoveUnusedParametersAndValues.AbstractRemoveUnusedValuesCodeFixProvider`11.FixAllAsync[TExpressionSyntax,TStatementSyntax,TBlockSyntax,TExpressionStatementSyntax,TLocalDeclarationStatementSyntax,TVariableDeclaratorSyntax,TForEachStatementSyntax,TSwitchCaseBlockSyntax,TSwitchCaseLabelOrClauseSyntax,TCatchStatementSyntax,TCatchBlockSyntax](<Unknown Parameters>)
   at async Microsoft.CodeAnalysis.CodeFixes.SyntaxEditorBasedCodeFixProvider.FixAllWithEditorAsync(<Unknown Parameters>)
   at async Microsoft.CodeAnalysis.CodeFixes.SyntaxEditorBasedCodeFixProvider.<GetFixAllProvider>b__2_0(<Unknown Parameters>)
   at async Microsoft.CodeAnalysis.CodeFixes.DocumentBasedFixAllProvider.<>c__DisplayClass8_1.<GetFixedDocumentsAsync>b__2(<Unknown Parameters>)
   at async Microsoft.CodeAnalysis.CodeFixes.DocumentBasedFixAllProvider.GetFixedDocumentsAsync(<Unknown Parameters>)
   at async Microsoft.CodeAnalysis.CodeFixes.DocumentBasedFixAllProvider.FixSingleContextAsync(<Unknown Parameters>)
   at async Microsoft.CodeAnalysis.CodeFixes.DocumentBasedFixAllProvider.FixAllContextsAsync(<Unknown Parameters>)
   at async Microsoft.CodeAnalysis.CodeFixes.DefaultFixAllProviderHelpers.GetFixAsync(<Unknown Parameters>)
   at async Microsoft.CodeAnalysis.Editor.Implementation.Suggestions.FixAllGetFixesService.GetFixAllCodeActionAsync(<Unknown Parameters>)
   at async Microsoft.CodeAnalysis.Editor.Implementation.Suggestions.FixAllGetFixesService.GetFixAllOperationsAsync(<Unknown Parameters>)
   at async Microsoft.CodeAnalysis.CodeActions.CodeAction.GetOperationsCoreAsync(<Unknown Parameters>)

My psychic guess is that our fix all fails here when you have both an out parameter that is becoming a discard and the assignment is transformed to a discard as well. When trying to do both, we die.

CyrusNajmabadi commented 3 years ago

@allisonchou I think this could be good to take a look at. If you have trouble finding a repro, lmk and we can work through what's going on in roslyn itself that is causing this fix-all to crash.