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Switch on enum type nested in generic type produces LangVersion error #34911

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merged 1 commit into from
Apr 10, 2019
Merged

Switch on enum type nested in generic type produces LangVersion error #34911

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3 changes: 1 addition & 2 deletions src/Compilers/CSharp/Portable/Binder/Binder_Patterns.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -210,8 +210,7 @@ internal BoundExpression ConvertPatternExpression(
{
var requiredVersion = MessageID.IDS_FeatureRecursivePatterns.RequiredVersion();
if (Compilation.LanguageVersion < requiredVersion &&
// A null pattern can be tested against a type that can be assigned null, even in C# 7.3
!(expression.ConstantValue == ConstantValue.Null && inputType.CanBeAssignedNull()))
!this.Conversions.ClassifyConversionFromExpression(expression, inputType, ref useSiteDiagnostics).IsImplicit)
{
diagnostics.Add(ErrorCode.ERR_ConstantPatternVsOpenType,
expression.Syntax.Location, inputType, expression.Display, new CSharpRequiredLanguageVersion(requiredVersion));
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26 changes: 26 additions & 0 deletions src/Compilers/CSharp/Test/Semantic/Semantics/PatternMatchingTests2.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2317,5 +2317,31 @@ static bool Test4(T t)
// return t is "frog"; // 3
Diagnostic(ErrorCode.ERR_ConstantPatternVsOpenType, @"""frog""").WithArguments("T", "string", "preview").WithLocation(17, 21));
}

[Fact]
[WorkItem(34905, "https://github.com/dotnet/roslyn/issues/34905")]
public void ConstantPatternVsUnconstrainedTypeParameter06()
{
var source =
@"public class C<T>
{
public enum E
{
V1, V2
}

public void M()
{
switch (default(E))
{
case E.V1:
break;
}
}
}
";
CreateCompilation(source, options: TestOptions.ReleaseDll).VerifyDiagnostics();
CreateCompilation(source, options: TestOptions.ReleaseDll, parseOptions: TestOptions.Regular7_3).VerifyDiagnostics();
}
}
}