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Don't remove null-casts in switch expressions #43701

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Apr 27, 2020
Merged

Don't remove null-casts in switch expressions #43701

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212 changes: 212 additions & 0 deletions src/Analyzers/CSharp/Tests/RemoveUnnecessaryCast/RemoveUnnecessaryCastTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -6957,5 +6957,217 @@ public static void Main()

await VerifyCS.VerifyCodeFixAsync(source, source);
}

[WorkItem(20211, "https://github.com/dotnet/roslyn/issues/20211")]
[Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryCast)]
public async Task DoNotRemoveNullCastInSwitch1()
{
var source =
@"class Program
{
static void Main()
{
switch ((object)null)
{
case bool _:
break;
}
}
}";

await VerifyCS.VerifyCodeFixAsync(source, source);
}

[WorkItem(20211, "https://github.com/dotnet/roslyn/issues/20211")]
[Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryCast)]
public async Task DoNotRemoveNullCastInSwitch2()
{
var source =
@"class Program
{
static void Main()
{
switch ((object)(null))
{
case bool _:
break;
}
}
}";

await VerifyCS.VerifyCodeFixAsync(source, source);
}

[WorkItem(20211, "https://github.com/dotnet/roslyn/issues/20211")]
[Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryCast)]
public async Task DoNotRemoveNullCastInSwitch3()
{
var source =
@"class Program
{
static void Main()
{
switch ((bool?)null)
{
case bool _:
break;
}
}
}";

await VerifyCS.VerifyCodeFixAsync(source, source);
}

[WorkItem(20211, "https://github.com/dotnet/roslyn/issues/20211")]
[Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryCast)]
public async Task DoNotRemoveNullCastInSwitch4()
{
var source =
@"class Program
{
static void Main()
{
switch ((bool?)(null))
{
case bool _:
break;
}
}
}";

await VerifyCS.VerifyCodeFixAsync(source, source);
}

[WorkItem(20211, "https://github.com/dotnet/roslyn/issues/20211")]
[Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryCast)]
public async Task DoNotRemoveNullCastInSwitch5()
{
var source =
@"class Program
{
static void Main()
{
switch (((object)null))
{
case bool _:
break;
}
}
}";

await VerifyCS.VerifyCodeFixAsync(source, source);
}

[WorkItem(20211, "https://github.com/dotnet/roslyn/issues/20211")]
[Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryCast)]
public async Task DoNotRemoveDefaultCastInSwitch1()
{
var source =
@"class Program
{
static void Main()
{
switch ((object)default)
{
case bool _:
break;
}
}
}";

await VerifyCS.VerifyCodeFixAsync(source, source);
}

[WorkItem(20211, "https://github.com/dotnet/roslyn/issues/20211")]
[Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryCast)]
public async Task DoNotRemoveDefaultCastInSwitch2()
{
var source =
@"class Program
{
static void Main()
{
switch ((object)(default))
{
case bool _:
break;
}
}
}";

await VerifyCS.VerifyCodeFixAsync(source, source);
}

[WorkItem(20211, "https://github.com/dotnet/roslyn/issues/20211")]
[Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryCast)]
public async Task DoNotRemoveDefaultCastInSwitch3()
{
var source =
@"class Program
{
static void Main()
{
switch ((bool?)default)
{
case bool _:
break;
}
}
}";

await VerifyCS.VerifyCodeFixAsync(source, source);
}

[WorkItem(20211, "https://github.com/dotnet/roslyn/issues/20211")]
[Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryCast)]
public async Task DoNotRemoveDefaultCastInSwitch4()
{
var source =
@"class Program
{
static void Main()
{
switch ((bool?)(default))
{
case bool _:
break;
}
}
}";

await VerifyCS.VerifyCodeFixAsync(source, source);
}

[WorkItem(20211, "https://github.com/dotnet/roslyn/issues/20211")]
[Fact, Trait(Traits.Feature, Traits.Features.CodeActionsRemoveUnnecessaryCast)]
public async Task RemoveDoubleNullCastInSwitch1()
{
var source =
@"class Program
{
static void Main()
{
switch ([|(object)|][|(string)|]null)
{
case var _:
break;
}
}
}";
var fixedCode =
@"class Program
{
static void Main()
{
switch ((string)null)
{
case var _:
break;
}
}
}";

await VerifyCS.VerifyCodeFixAsync(source, fixedCode);
}
}
}
5 changes: 5 additions & 0 deletions src/Workspaces/SharedUtilitiesAndExtensions/Compiler/CSharp/Utilities/SpeculationAnalyzer.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -426,6 +426,11 @@ protected override bool ReplacementChangesSemanticsForNodeLanguageSpecific(Synta
// expression type are not broken.

var newSwitchStatement = (SwitchStatementSyntax)currentReplacedNode;
var previousReplacedExpression = (ExpressionSyntax)previousReplacedNode;

// it is never legal to use `default/null` in a switch statement's expression.
if (previousReplacedExpression.WalkDownParentheses().IsKind(SyntaxKind.NullLiteralExpression, SyntaxKind.DefaultLiteralExpression))
return true;

var originalSwitchLabels = originalSwitchStatement.Sections.SelectMany(section => section.Labels).ToArray();
var newSwitchLabels = newSwitchStatement.Sections.SelectMany(section => section.Labels).ToArray();
Expand Down