private Expr GenerateUserDefinedConversion(Expr arg, CType CType, Expr target, MethWithInst method)
{
// The user-defined explicit conversion from enum? to decimal or decimal? requires
// that we convert the enum? to its nullable underlying CType.
if (isEnumToDecimalConversion(arg.Type, CType))
{
// Special case: If we have enum? to decimal? then we need to emit
// a conversion from enum? to its nullable underlying CType first.
// This is unfortunate; we ought to reorganize how conversions are
// represented in the Expr tree so that this is more transparent.
// converting an enum to its underlying CType never fails, so no need to check it.
CType underlyingType = arg.Type.StripNubs().underlyingEnumType();
CType nullableType = GetSymbolLoader().GetTypeManager().GetNullable(underlyingType);
Expr typeofNubEnum = CreateTypeOf(nullableType);
target = GenerateCall(PREDEFMETH.PM_EXPRESSION_CONVERT, target, typeofNubEnum);
}
// If the methodinfo does not return the target CType AND this is not a lifted conversion
// from one value CType to another, then we need to wrap the whole thing in another conversion,
// e.g. if we have a user-defined conversion from int to S? and we have (S)myint, then we need to generate
// Convert(Convert(myint, typeof(S?), op_implicit), typeof(S))
CType pMethodReturnType = GetSymbolLoader().GetTypeManager().SubstType(method.Meth().RetType,
method.GetType(), method.TypeArgs);
bool fDontLiftReturnType = (pMethodReturnType == CType || (IsNullableValueType(arg.Type) && IsNullableValueType(CType)));
Expr typeofInner = CreateTypeOf(fDontLiftReturnType ? CType : pMethodReturnType);
Expr methodInfo = GetExprFactory().CreateMethodInfo(method);
PREDEFMETH pdmInner = arg.isChecked() ? PREDEFMETH.PM_EXPRESSION_CONVERTCHECKED_USER_DEFINED : PREDEFMETH.PM_EXPRESSION_CONVERT_USER_DEFINED;
Expr callUserDefinedConversion = GenerateCall(pdmInner, target, typeofInner, methodInfo);
if (fDontLiftReturnType)
{
return(callUserDefinedConversion);
}
PREDEFMETH pdmOuter = arg.isChecked() ? PREDEFMETH.PM_EXPRESSION_CONVERTCHECKED : PREDEFMETH.PM_EXPRESSION_CONVERT;
Expr typeofOuter = CreateTypeOf(CType);
return(GenerateCall(pdmOuter, callUserDefinedConversion, typeofOuter));
}
private Expr GenerateConversion(Expr arg, CType CType, bool bChecked)
{
return(GenerateConversionWithSource(Visit(arg), CType, bChecked || arg.isChecked()));
}