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Fix #1462: Inconsistent enum flag check #1476

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merged 3 commits into from
May 1, 2019
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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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21 changes: 18 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 +763,21 @@ TranslatedExpression TranslateCeq(Comp inst, out bool negateOutput)
.WithRR(rr);
}

TranslatedExpression TryUniteEqualityOperandType(TranslatedExpression operand, TranslatedExpression otherOperand)
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Using names like left and right instead of operand and otherOperand will improve readability of the code.

{
// 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 (operand.ResolveResult.IsCompileTimeConstant &&
operand.ResolveResult.Type.IsCSharpPrimitiveIntegerType() &&
(int)operand.ResolveResult.ConstantValue == 0 &&
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operand.ResolveResult.ConstantValue might be something else than a boxed int, so this can go wrong. This makes the unit tests fail. See https://ci.appveyor.com/project/icsharpcode/ilspy/build/job/wnhtrte5t1i7g5u9/tests

NullableType.GetUnderlyingType(otherOperand.Type).Kind == TypeKind.Enum &&
otherOperand.Expression is BinaryOperatorExpression binaryExpr &&
binaryExpr.Operator == BinaryOperatorType.BitwiseAnd)
return AdjustConstantExpressionToType(operand, compilation.FindType(KnownTypeCode.Int32));
else
return AdjustConstantExpressionToType(operand, otherOperand.Type);
}

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