private bool TryAnalyzeCsConversion(Microsoft.CodeAnalysis.VisualBasic.Syntax.ExpressionSyntax vbNode, ITypeSymbol csType,
ITypeSymbol csConvertedType, Conversion vbConversion, ITypeSymbol vbConvertedType, ITypeSymbol vbType,
VisualBasicCompilation vbCompilation, bool isConst, out TypeConversionKind typeConversionKind)
{
var csConversion = _csCompilation.ClassifyConversion(csType, csConvertedType);
bool isConvertToString =
(vbConversion.IsString || vbConversion.IsReference && vbConversion.IsNarrowing) && vbConvertedType.SpecialType == SpecialType.System_String;
bool isArithmetic = vbNode.IsKind(Microsoft.CodeAnalysis.VisualBasic.SyntaxKind.AddExpression,
Microsoft.CodeAnalysis.VisualBasic.SyntaxKind.SubtractExpression,
Microsoft.CodeAnalysis.VisualBasic.SyntaxKind.MultiplyExpression,
Microsoft.CodeAnalysis.VisualBasic.SyntaxKind.DivideExpression,
Microsoft.CodeAnalysis.VisualBasic.SyntaxKind.IntegerDivideExpression);
if (!csConversion.Exists || csConversion.IsUnboxing)
{
if (ConvertStringToCharLiteral(vbNode, vbConvertedType, out _))
{
typeConversionKind =
TypeConversionKind.Identity; // Already handled elsewhere by other usage of method
return(true);
}
if (vbType.SpecialType == SpecialType.System_String && vbConvertedType.IsArrayOf(SpecialType.System_Char))
{
typeConversionKind = TypeConversionKind.StringToCharArray;
return(true);
}
if (isConvertToString || vbConversion.IsNarrowing)
{
typeConversionKind = isConst ? TypeConversionKind.ConstConversion : TypeConversionKind.Conversion;
return(true);
}
}
else if (vbConversion.IsWidening && vbConversion.IsNumeric && csConversion.IsImplicit &&
csConversion.IsNumeric)
{
// Safe overapproximation: A cast is really only needed to help resolve the overload for the operator/method used.
// e.g. When VB "&" changes to C# "+", there are lots more overloads available that implicit casts could match.
// e.g. sbyte * ulong uses the decimal * operator in VB. In C# it's ambiguous - see ExpressionTests.vb "TestMul".
typeConversionKind = TypeConversionKind.NonDestructiveCast;
return(true);
}
else if (csConversion.IsExplicit && csConversion.IsEnumeration)
{
typeConversionKind = TypeConversionKind.NonDestructiveCast;
return(true);
}
else if (isArithmetic)
{
var arithmeticConversion =
vbCompilation.ClassifyConversion(vbConvertedType,
vbCompilation.GetTypeByMetadataName("System.Int32"));
if (arithmeticConversion.IsWidening && !arithmeticConversion.IsIdentity)
{
typeConversionKind = isConst ? TypeConversionKind.ConstConversion : TypeConversionKind.Conversion;
return(true);
}
}
else if (csConversion.IsExplicit && csConversion.IsNumeric && vbConversion.IsNarrowing && isConst)
{
typeConversionKind = IsImplicitConstantConversion(vbNode) ? TypeConversionKind.Identity : TypeConversionKind.NonDestructiveCast;
return(true);
}
else if (csConversion.IsExplicit && vbConversion.IsNumeric && vbType.TypeKind != TypeKind.Enum)
{
typeConversionKind = IsImplicitConstantConversion(vbNode) ? TypeConversionKind.Identity :
isConst ? TypeConversionKind.ConstConversion : TypeConversionKind.Conversion;
return(true);
}
else if (csConversion.IsExplicit && vbConversion.IsIdentity && csConversion.IsNumeric && vbType.TypeKind != TypeKind.Enum)
{
typeConversionKind = isConst ? TypeConversionKind.ConstConversion : TypeConversionKind.Conversion;
return(true);
}
else if (isConvertToString && vbType.SpecialType == SpecialType.System_Object)
{
typeConversionKind = isConst ? TypeConversionKind.ConstConversion : TypeConversionKind.Conversion;
return(true);
}
else if (csConversion.IsNullable && csConvertedType.SpecialType == SpecialType.System_Boolean)
{
typeConversionKind = TypeConversionKind.NullableBool;
return(true);
}
else if (csConversion.IsExplicit)
{
typeConversionKind = TypeConversionKind.DestructiveCast;
return(true);
}
typeConversionKind = csConversion.IsIdentity ? TypeConversionKind.Identity : TypeConversionKind.Unknown;
return(false);
}