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Fix #1462: Inconsistent enum flag check #1476

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merged 3 commits into from
May 1, 2019
Merged

Fix #1462: Inconsistent enum flag check #1476

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ff4812d
Fix #1462: Inconsistent enum flag check
mcpiroman Apr 4, 2019
5b41cc2
Fix TryUniteEqualityOperandType
mcpiroman Apr 4, 2019
983b7e5
Add test-case for #1462
siegfriedpammer May 1, 2019
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10 changes: 9 additions & 1 deletion ICSharpCode.Decompiler.Tests/TestCases/Pretty/ConstantsTests.cs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,6 @@
namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
using System.Threading.Tasks;

namespace ICSharpCode.Decompiler.Tests.TestCases.Pretty
{
internal class ConstantsTests
{
Expand All @@ -24,6 +26,12 @@ public void SByte_BitmaskingInCondition(sbyte v)
Test((v | 0x123) == 0);
}

public void Enum_Flag_Check(TaskCreationOptions v)
{
Test((v & TaskCreationOptions.AttachedToParent) != 0);
Test((v & TaskCreationOptions.AttachedToParent) == 0);
}

private void Test(bool expr)
{
}
Expand Down
22 changes: 19 additions & 3 deletions ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
// Copyright (c) 2014 Daniel Grunwald
// Copyright (c) 2014 Daniel Grunwald
//
// Permission is hereby granted, free of charge, to any person obtaining a copy of this
// software and associated documentation files (the "Software"), to deal in the Software
Expand Down Expand Up @@ -699,8 +699,8 @@ TranslatedExpression TranslateCeq(Comp inst, out bool negateOutput)
}

// Special case comparisons with enum and char literals
left = AdjustConstantExpressionToType(left, right.Type);
right = AdjustConstantExpressionToType(right, left.Type);
left = TryUniteEqualityOperandType(left, right);
right = TryUniteEqualityOperandType(right, left);

if (IsSpecialCasedReferenceComparisonWithNull(left, right)) {
// When comparing a string/delegate with null, the C# compiler generates a reference comparison.
Expand Down Expand Up @@ -763,6 +763,22 @@ TranslatedExpression TranslateCeq(Comp inst, out bool negateOutput)
.WithRR(rr);
}

TranslatedExpression TryUniteEqualityOperandType(TranslatedExpression left, TranslatedExpression right)
{
// Special case for enum flag check "(enum & EnumType.SomeValue) == 0"
// so that the const 0 value is printed as 0 integer and not as enum type, e.g. EnumType.None
if (left.ResolveResult.IsCompileTimeConstant &&
left.ResolveResult.Type.IsCSharpPrimitiveIntegerType() &&
(left.ResolveResult.ConstantValue as int?) == 0 &&
NullableType.GetUnderlyingType(right.Type).Kind == TypeKind.Enum &&
right.Expression is BinaryOperatorExpression binaryExpr &&
binaryExpr.Operator == BinaryOperatorType.BitwiseAnd)
{
return AdjustConstantExpressionToType(left, compilation.FindType(KnownTypeCode.Int32));
} else
return AdjustConstantExpressionToType(left, right.Type);
}

bool IsSpecialCasedReferenceComparisonWithNull(TranslatedExpression lhs, TranslatedExpression rhs)
{
if (lhs.Type.Kind == TypeKind.Null)
Expand Down