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Claude/fix issue 892 char empty comparison #1256

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e38a778
Fix VB -> C# char comparison with empty string
GrahamTheCoder Mar 25, 2026
947ab8c
Fix VB -> C# char comparison with empty string
GrahamTheCoder Apr 12, 2026
fd91263
Clean up stray files and expand test coverage for char/empty-string c…
claude Apr 13, 2026
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20 changes: 17 additions & 3 deletions CodeConverter/CSharp/BinaryExpressionConverter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -82,11 +82,25 @@ private async Task<CSharpSyntaxNode> ConvertBinaryExpressionAsync(VBasic.Syntax.
case VisualBasicEqualityComparison.RequiredType.StringOnly:
if (lhsTypeInfo.ConvertedType?.SpecialType == SpecialType.System_String &&
rhsTypeInfo.ConvertedType?.SpecialType == SpecialType.System_String &&
_visualBasicEqualityComparison.TryConvertToNullOrEmptyCheck(node, lhs, rhs, out CSharpSyntaxNode visitBinaryExpression)) {
_visualBasicEqualityComparison.TryConvertToNullOrEmptyCheck(node, lhs, rhs, lhsTypeInfo, rhsTypeInfo, out CSharpSyntaxNode visitBinaryExpression)) {
return visitBinaryExpression;
}
(lhs, rhs) = _visualBasicEqualityComparison.AdjustForVbStringComparison(node.Left, lhs, lhsTypeInfo, false, node.Right, rhs, rhsTypeInfo, false);
omitConversion = true; // Already handled within for the appropriate types (rhs can become int in comparison)
if (lhsTypeInfo.Type?.SpecialType == SpecialType.System_Char && rhsTypeInfo.Type?.SpecialType == SpecialType.System_Char) {
// Do nothing, char comparison
} else if (!_visualBasicEqualityComparison.OptionCompareTextCaseInsensitive &&
((lhsTypeInfo.Type?.SpecialType == SpecialType.System_Char && rhsTypeInfo.Type?.SpecialType == SpecialType.System_String && _visualBasicEqualityComparison.IsNothingOrEmpty(node.Right)) ||
(rhsTypeInfo.Type?.SpecialType == SpecialType.System_Char && lhsTypeInfo.Type?.SpecialType == SpecialType.System_String && _visualBasicEqualityComparison.IsNothingOrEmpty(node.Left)))) {
if (lhsTypeInfo.Type?.SpecialType == SpecialType.System_Char) {
rhs = CS.SyntaxFactory.MemberAccessExpression(CS.SyntaxKind.SimpleMemberAccessExpression, CS.SyntaxFactory.PredefinedType(CS.SyntaxFactory.Token(CS.SyntaxKind.CharKeyword)), CS.SyntaxFactory.IdentifierName("MinValue"));
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@GrahamTheCoder GrahamTheCoder Apr 13, 2026

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Look like a hack to make the specific test case work rather than the general fix to the root cause

omitConversion = true;
} else {
lhs = CS.SyntaxFactory.MemberAccessExpression(CS.SyntaxKind.SimpleMemberAccessExpression, CS.SyntaxFactory.PredefinedType(CS.SyntaxFactory.Token(CS.SyntaxKind.CharKeyword)), CS.SyntaxFactory.IdentifierName("MinValue"));
omitConversion = true;
}
} else {
(lhs, rhs) = _visualBasicEqualityComparison.AdjustForVbStringComparison(node.Left, lhs, lhsTypeInfo, false, node.Right, rhs, rhsTypeInfo, false);
omitConversion = true; // Already handled within for the appropriate types (rhs can become int in comparison)
}
break;
case VisualBasicEqualityComparison.RequiredType.Object:
return _visualBasicEqualityComparison.GetFullExpressionForVbObjectComparison(lhs, rhs, VisualBasicEqualityComparison.ComparisonKind.Equals, node.IsKind(VBasic.SyntaxKind.NotEqualsExpression));
Expand Down
11 changes: 9 additions & 2 deletions CodeConverter/CSharp/VisualBasicEqualityComparison.cs
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Expand Up @@ -79,6 +79,7 @@ public RequiredType GetObjectEqualityType(params TypeInfo[] typeInfos)

if (typeInfos.All(
t => t.Type == null || t.Type.SpecialType == SpecialType.System_String ||
t.Type.SpecialType == SpecialType.System_Char ||
t.Type.IsArrayOf(SpecialType.System_Char) ) ) {
return RequiredType.StringOnly;
}
Expand Down Expand Up @@ -177,7 +178,7 @@ private static ObjectCreationExpressionSyntax NewStringFromArg(ExpressionSyntax
}

public bool TryConvertToNullOrEmptyCheck(VBSyntax.BinaryExpressionSyntax node, ExpressionSyntax lhs,
ExpressionSyntax rhs, out CSharpSyntaxNode? visitBinaryExpression)
ExpressionSyntax rhs, TypeInfo lhsTypeInfo, TypeInfo rhsTypeInfo, out CSharpSyntaxNode? visitBinaryExpression)
{
if (OptionCompareTextCaseInsensitive)
{
Expand All @@ -191,6 +192,12 @@ public bool TryConvertToNullOrEmptyCheck(VBSyntax.BinaryExpressionSyntax node, E
if (lhsEmpty || rhsEmpty)
{
var arg = lhsEmpty ? rhs : lhs;
var argType = lhsEmpty ? rhsTypeInfo : lhsTypeInfo;
if (argType.Type?.SpecialType != SpecialType.System_String && argType.Type?.SpecialType != SpecialType.System_Object) {
visitBinaryExpression = null;
return false;
}

var nullOrEmpty = SyntaxFactory.InvocationExpression(
SyntaxFactory.MemberAccessExpression(SyntaxKind.SimpleMemberAccessExpression,
SyntaxFactory.PredefinedType(SyntaxFactory.Token(SyntaxKind.StringKeyword)),
Expand All @@ -207,7 +214,7 @@ public bool TryConvertToNullOrEmptyCheck(VBSyntax.BinaryExpressionSyntax node, E
return false;
}

private bool IsNothingOrEmpty(VBSyntax.ExpressionSyntax expressionSyntax)
public bool IsNothingOrEmpty(VBSyntax.ExpressionSyntax expressionSyntax)
{
expressionSyntax = expressionSyntax.SkipIntoParens();

Expand Down
23 changes: 23 additions & 0 deletions Tests/CSharp/ExpressionTests/StringExpressionTests.cs
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Expand Up @@ -541,6 +541,29 @@ public void Foo()
{
string x = Conversions.ToString(DateTime.Parse(""2022-01-01"")) + "" 15:00"";
}
}");
}

[Fact]
public async Task CharEqualityEmptyStringAsync()
{
await TestConversionVisualBasicToCSharpAsync(@"Class TestClass
Private Sub TestMethod()
Dim testChar As Char = Nothing
Dim testResult = testChar = """"
Dim testResult2 = """" = testChar
Dim testResult3 = testChar <> """"
End Sub
End Class", @"
internal partial class TestClass
{
private void TestMethod()
{
char testChar = default;
bool testResult = testChar == char.MinValue;
bool testResult2 = char.MinValue == testChar;
bool testResult3 = testChar != char.MinValue;
}
}");
}
}
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