/***************************************************************************************************
* Determine whether this expr has a constant value (EK_CONSTANT or EK_ZEROINIT), possibly with
* side effects (via EK_SEQUENCE or EK_SEQREV). Returns NULL if not, or the constant expr if so.
* The returned Expr will always be an EK_CONSTANT or EK_ZEROINIT.
***************************************************************************************************/
public static Expr GetConst(this Expr expr)
{
Expr exprVal = expr.GetSeqVal();
if (null == exprVal || !exprVal.isCONSTANT_OK() && exprVal.Kind != ExpressionKind.EK_ZEROINIT)
{
return(null);
}
return(exprVal);
}
/***************************************************************************************************
* Called by BindImplicitConversion when the destination type is Nullable<T>. The following
* conversions are handled by this method:
*
* For S in { object, ValueType, interfaces implemented by underlying type} there is an explicit
* unboxing conversion S => T?
* System.Enum => T? there is an unboxing conversion if T is an enum type
* null => T? implemented as default(T?)
*
* Implicit T?* => T?+ implemented by either wrapping or calling GetValueOrDefault the
* appropriate number of times.
* If imp/exp S => T then imp/exp S => T?+ implemented by converting to T then wrapping the
* appropriate number of times.
* If imp/exp S => T then imp/exp S?+ => T?+ implemented by calling GetValueOrDefault (m-1) times
* then calling HasValue, producing a null if it returns false, otherwise calling Value,
* converting to T then wrapping the appropriate number of times.
*
* The 3 rules above can be summarized with the following recursive rules:
*
* If imp/exp S => T? then imp/exp S? => T? implemented as
* qs.HasValue ? (T?)(qs.Value) : default(T?)
* If imp/exp S => T then imp/exp S => T? implemented as new T?((T)s)
*
* This method also handles calling bindUserDefinedConverion. This method does NOT handle
* the following conversions:
*
* Implicit boxing conversion from S? to { object, ValueType, Enum, ifaces implemented by S }. (Handled by BindImplicitConversion.)
* If imp/exp S => T then explicit S?+ => T implemented by calling Value the appropriate number
* of times. (Handled by BindExplicitConversion.)
*
* The recursive equivalent is:
*
* If imp/exp S => T and T is not nullable then explicit S? => T implemented as qs.Value
*
* Some nullable conversion are NOT standard conversions. In particular, if S => T is implicit
* then S? => T is not standard. Similarly if S => T is not implicit then S => T? is not standard.
***************************************************************************************************/
private bool BindNubConversion(NullableType nubDst)
{
// This code assumes that STANDARD and ISEXPLICIT are never both set.
// bindUserDefinedConversion should ensure this!
Debug.Assert(0 != (~_flags & (CONVERTTYPE.STANDARD | CONVERTTYPE.ISEXPLICIT)));
Debug.Assert(_exprSrc == null || _exprSrc.Type == _typeSrc);
Debug.Assert(!_needsExprDest || _exprSrc != null);
Debug.Assert(_typeSrc != nubDst); // BindImplicitConversion should have taken care of this already.
AggregateType atsDst = nubDst.GetAts();
// Check for the unboxing conversion. This takes precedence over the wrapping conversions.
if (GetSymbolLoader().HasBaseConversion(nubDst.GetUnderlyingType(), _typeSrc) && !CConversions.FWrappingConv(_typeSrc, nubDst))
{
// These should be different! Fix the caller if typeSrc is an AggregateType of Nullable.
Debug.Assert(atsDst != _typeSrc);
// typeSrc is a base type of the destination nullable type so there is an explicit
// unboxing conversion.
if (0 == (_flags & CONVERTTYPE.ISEXPLICIT))
{
return(false);
}
if (_needsExprDest)
{
_binder.bindSimpleCast(_exprSrc, _typeDest, out _exprDest, EXPRFLAG.EXF_UNBOX);
}
return(true);
}
bool dstWasNullable;
bool srcWasNullable;
CType typeDstBase = nubDst.StripNubs(out dstWasNullable);
CType typeSrcBase = _typeSrc.StripNubs(out srcWasNullable);
ConversionFunc pfn = (_flags & CONVERTTYPE.ISEXPLICIT) != 0 ?
(ConversionFunc)_binder.BindExplicitConversion :
(ConversionFunc)_binder.BindImplicitConversion;
if (!srcWasNullable)
{
Debug.Assert(_typeSrc == typeSrcBase);
// The null type can be implicitly converted to T? as the default value.
if (_typeSrc is NullType)
{
// If we have the constant null, generate it as a default value of T?. If we have
// some crazy expression which has been determined to be always null, like (null??null)
// keep it in its expression form and transform it in the nullable rewrite pass.
if (_needsExprDest)
{
if (_exprSrc.isCONSTANT_OK())
{
_exprDest = GetExprFactory().CreateZeroInit(nubDst);
}
else
{
_exprDest = GetExprFactory().CreateCast(_typeDest, _exprSrc);
}
}
return(true);
}
Expr exprTmp = _exprSrc;
// If there is an implicit/explicit S => T then there is an implicit/explicit S => T?
if (_typeSrc == typeDstBase || pfn(_exprSrc, _typeSrc, typeDstBase, _needsExprDest, out exprTmp, _flags | CONVERTTYPE.NOUDC))
{
if (_needsExprDest)
{
ExprUserDefinedConversion exprUDC = exprTmp as ExprUserDefinedConversion;
if (exprUDC != null)
{
exprTmp = exprUDC.UserDefinedCall;
}
if (dstWasNullable)
{
ExprCall call = _binder.BindNubNew(exprTmp);
exprTmp = call;
call.NullableCallLiftKind = NullableCallLiftKind.NullableConversionConstructor;
}
if (exprUDC != null)
{
exprUDC.UserDefinedCall = exprTmp;
exprTmp = exprUDC;
}
Debug.Assert(exprTmp.Type == nubDst);
_exprDest = exprTmp;
}
return(true);
}
// No builtin conversion. Maybe there is a user defined conversion....
return(0 == (_flags & CONVERTTYPE.NOUDC) && _binder.bindUserDefinedConversion(_exprSrc, _typeSrc, nubDst, _needsExprDest, out _exprDest, 0 == (_flags & CONVERTTYPE.ISEXPLICIT)));
}
// Both are Nullable so there is only a conversion if there is a conversion between the base types.
// That is, if there is an implicit/explicit S => T then there is an implicit/explicit S?+ => T?+.
if (typeSrcBase != typeDstBase && !pfn(null, typeSrcBase, typeDstBase, false, out _exprDest, _flags | CONVERTTYPE.NOUDC))
{
// No builtin conversion. Maybe there is a user defined conversion....
return(0 == (_flags & CONVERTTYPE.NOUDC) && _binder.bindUserDefinedConversion(_exprSrc, _typeSrc, nubDst, _needsExprDest, out _exprDest, 0 == (_flags & CONVERTTYPE.ISEXPLICIT)));
}
if (_needsExprDest)
{
MethWithInst mwi = new MethWithInst(null, null);
ExprMemberGroup pMemGroup = GetExprFactory().CreateMemGroup(null, mwi);
ExprCall exprDst = GetExprFactory().CreateCall(0, nubDst, _exprSrc, pMemGroup, null);
// Here we want to first check whether or not the conversions work on the base types.
Expr arg1 = _binder.mustCast(_exprSrc, typeSrcBase);
bool convertible = (_flags & CONVERTTYPE.ISEXPLICIT) != 0
? _binder.BindExplicitConversion(
arg1, arg1.Type, typeDstBase, out arg1, _flags | CONVERTTYPE.NOUDC)
: _binder.BindImplicitConversion(
arg1, arg1.Type, typeDstBase, out arg1, _flags | CONVERTTYPE.NOUDC);
if (!convertible)
{
Debug.Fail("bind(Im|Ex)plicitConversion failed unexpectedly");
return(false);
}
exprDst.CastOfNonLiftedResultToLiftedType = _binder.mustCast(arg1, nubDst, 0);
exprDst.NullableCallLiftKind = NullableCallLiftKind.NullableConversion;
exprDst.PConversions = exprDst.CastOfNonLiftedResultToLiftedType;
_exprDest = exprDst;
}
return(true);
}
public static bool isZero(this Expr expr)
{
return((expr.isCONSTANT_OK()) && (expr.asCONSTANT().IsZero));
}
public static bool isNull(this Expr expr)
{
return(expr.isCONSTANT_OK() && (expr.Type.fundType() == FUNDTYPE.FT_REF) && expr.asCONSTANT().Val.IsNullRef);
}