/* * BindImplicitConversion * * This is a complex routine with complex parameters. Generally, this should * be called through one of the helper methods that insulates you * from the complexity of the interface. This routine handles all the logic * associated with implicit conversions. * * exprSrc - the expression being converted. Can be null if only type conversion * info is being supplied. * typeSrc - type of the source * typeDest - type of the destination * exprDest - returns an expression of the src converted to the dest. If null, we * only care about whether the conversion can be attempted, not the * expression tree. * flags - flags possibly customizing the conversions allowed. E.g., can suppress * user-defined conversions. * * returns true if the conversion can be made, false if not. */ public bool Bind() { // 13.1 Implicit conversions // // The following conversions are classified as implicit conversions: // // * Identity conversions // * Implicit numeric conversions // * Implicit enumeration conversions // * Implicit reference conversions // * Boxing conversions // * Implicit type parameter conversions // * Implicit constant expression conversions // * User-defined implicit conversions // * Implicit conversions from an anonymous method expression to a compatible delegate type // * Implicit conversion from a method group to a compatible delegate type // * Conversions from the null type (11.2.7) to any nullable type // * Implicit nullable conversions // * Lifted user-defined implicit conversions // // Implicit conversions can occur in a variety of situations, including function member invocations // (14.4.3), cast expressions (14.6.6), and assignments (14.14). // Can't convert to or from the error type. if (typeSrc == null || typeDest == null || typeDest.IsNeverSameType()) { return(false); } Debug.Assert(typeSrc != null && typeDest != null); // types must be supplied. Debug.Assert(exprSrc == null || typeSrc == exprSrc.type); // type of source should be correct if source supplied Debug.Assert(!needsExprDest || exprSrc != null); // need source expr to create dest expr switch (typeDest.GetTypeKind()) { case TypeKind.TK_ErrorType: Debug.Assert(typeDest.AsErrorType().HasTypeParent() || typeDest.AsErrorType().HasNSParent()); if (typeSrc != typeDest) { return(false); } if (needsExprDest) { exprDest = exprSrc; } return(true); case TypeKind.TK_NullType: // Can only convert to the null type if src is null. if (!typeSrc.IsNullType()) { return(false); } if (needsExprDest) { exprDest = exprSrc; } return(true); case TypeKind.TK_MethodGroupType: VSFAIL("Something is wrong with Type.IsNeverSameType()"); return(false); case TypeKind.TK_NaturalIntegerType: case TypeKind.TK_ArgumentListType: return(typeSrc == typeDest); case TypeKind.TK_VoidType: return(false); default: break; } if (typeSrc.IsErrorType()) { Debug.Assert(!typeDest.IsErrorType()); return(false); } // 13.1.1 Identity conversion // // An identity conversion converts from any type to the same type. This conversion exists only // such that an entity that already has a required type can be said to be convertible to that type. if (typeSrc == typeDest && ((flags & CONVERTTYPE.ISEXPLICIT) == 0 || (!typeSrc.isPredefType(PredefinedType.PT_FLOAT) && !typeSrc.isPredefType(PredefinedType.PT_DOUBLE)))) { if (needsExprDest) { exprDest = exprSrc; } return(true); } if (typeDest.IsNullableType()) { return(BindNubConversion(typeDest.AsNullableType())); } if (typeSrc.IsNullableType()) { return(bindImplicitConversionFromNullable(typeSrc.AsNullableType())); } if ((flags & CONVERTTYPE.ISEXPLICIT) != 0) { flags |= CONVERTTYPE.NOUDC; } // Get the fundamental types of destination. FUNDTYPE ftDest = typeDest.fundType(); Debug.Assert(ftDest != FUNDTYPE.FT_NONE || typeDest.IsParameterModifierType()); switch (typeSrc.GetTypeKind()) { default: VSFAIL("Bad type symbol kind"); break; case TypeKind.TK_MethodGroupType: if (exprSrc.isMEMGRP()) { EXPRCALL outExpr; bool retVal = binder.BindGrpConversion(exprSrc.asMEMGRP(), typeDest, needsExprDest, out outExpr, false); exprDest = outExpr; return(retVal); } return(false); case TypeKind.TK_VoidType: case TypeKind.TK_ErrorType: case TypeKind.TK_ParameterModifierType: case TypeKind.TK_ArgumentListType: return(false); case TypeKind.TK_NullType: if (bindImplicitConversionFromNull()) { return(true); } // If not, try user defined implicit conversions. break; case TypeKind.TK_ArrayType: if (bindImplicitConversionFromArray()) { return(true); } // If not, try user defined implicit conversions. break; case TypeKind.TK_PointerType: if (bindImplicitConversionFromPointer()) { return(true); } // If not, try user defined implicit conversions. break; case TypeKind.TK_TypeParameterType: if (bindImplicitConversionFromTypeVar(typeSrc.AsTypeParameterType())) { return(true); } // If not, try user defined implicit conversions. break; case TypeKind.TK_AggregateType: // TypeReference and ArgIterator can't be boxed (or converted to anything else) if (typeSrc.isSpecialByRefType()) { return(false); } if (bindImplicitConversionFromAgg(typeSrc.AsAggregateType())) { return(true); } // If not, try user defined implicit conversions. break; } // !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! // RUNTIME BINDER ONLY CHANGE // !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! // // Every incoming dynamic operand should be implicitly convertible // to any type that it is an instance of. if (exprSrc != null && exprSrc.RuntimeObject != null && typeDest.AssociatedSystemType.IsInstanceOfType(exprSrc.RuntimeObject) && binder.GetSemanticChecker().CheckTypeAccess(typeDest, binder.Context.ContextForMemberLookup())) { if (needsExprDest) { binder.bindSimpleCast(exprSrc, exprTypeDest, out exprDest, exprSrc.flags & EXPRFLAG.EXF_CANTBENULL); } return(true); } // !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! // END RUNTIME BINDER ONLY CHANGE // !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! // 13.1.8 User-defined implicit conversions // // A user-defined implicit conversion consists of an optional standard implicit conversion, // followed by execution of a user-defined implicit conversion operator, followed by another // optional standard implicit conversion. The exact rules for evaluating user-defined // conversions are described in 13.4.3. if (0 == (flags & CONVERTTYPE.NOUDC)) { return(binder.bindUserDefinedConversion(exprSrc, typeSrc, typeDest, needsExprDest, out exprDest, true)); } // No conversion was found. return(false); }
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! // RUNTIME BINDER ONLY CHANGE // !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! internal bool GetBestAccessibleType(CSemanticChecker semanticChecker, BindingContext bindingContext, CType typeSrc, out CType typeDst) { // This method implements the "best accessible type" algorithm for determining the type // of untyped arguments in the runtime binder. It is also used in method type inference // to fix type arguments to types that are accessible. // The new type is returned in an out parameter. The result will be true (and the out param // non-null) only when the algorithm could find a suitable accessible type. Debug.Assert(semanticChecker != null); Debug.Assert(bindingContext != null); Debug.Assert(typeSrc != null); typeDst = null; if (semanticChecker.CheckTypeAccess(typeSrc, bindingContext.ContextForMemberLookup())) { // If we already have an accessible type, then use it. This is the terminal point of the recursion. typeDst = typeSrc; return true; } // These guys have no accessibility concerns. Debug.Assert(!typeSrc.IsVoidType() && !typeSrc.IsErrorType() && !typeSrc.IsTypeParameterType()); if (typeSrc.IsParameterModifierType() || typeSrc.IsPointerType()) { // We cannot vary these. return false; } CType intermediateType; if ((typeSrc.isInterfaceType() || typeSrc.isDelegateType()) && TryVarianceAdjustmentToGetAccessibleType(semanticChecker, bindingContext, typeSrc.AsAggregateType(), out intermediateType)) { // If we have an interface or delegate type, then it can potentially be varied by its type arguments // to produce an accessible type, and if that's the case, then return that. // Example: IEnumerable<PrivateConcreteFoo> --> IEnumerable<PublicAbstractFoo> typeDst = intermediateType; Debug.Assert(semanticChecker.CheckTypeAccess(typeDst, bindingContext.ContextForMemberLookup())); return true; } if (typeSrc.IsArrayType() && TryArrayVarianceAdjustmentToGetAccessibleType(semanticChecker, bindingContext, typeSrc.AsArrayType(), out intermediateType)) { // Similarly to the interface and delegate case, arrays are covariant in their element type and // so we can potentially produce an array type that is accessible. // Example: PrivateConcreteFoo[] --> PublicAbstractFoo[] typeDst = intermediateType; Debug.Assert(semanticChecker.CheckTypeAccess(typeDst, bindingContext.ContextForMemberLookup())); return true; } if (typeSrc.IsNullableType()) { // We have an inaccessible nullable type, which means that the best we can do is System.ValueType. typeDst = this.GetOptPredefAgg(PredefinedType.PT_VALUE).getThisType(); Debug.Assert(semanticChecker.CheckTypeAccess(typeDst, bindingContext.ContextForMemberLookup())); return true; } if (typeSrc.IsArrayType()) { // We have an inaccessible array type for which we could not earlier find a better array type // with a covariant conversion, so the best we can do is System.Array. typeDst = this.GetReqPredefAgg(PredefinedType.PT_ARRAY).getThisType(); Debug.Assert(semanticChecker.CheckTypeAccess(typeDst, bindingContext.ContextForMemberLookup())); return true; } Debug.Assert(typeSrc.IsAggregateType()); if (typeSrc.IsAggregateType()) { // We have an AggregateType, so recurse on its base class. AggregateType aggType = typeSrc.AsAggregateType(); AggregateType baseType = aggType.GetBaseClass(); if (baseType == null) { // This happens with interfaces, for instance. But in that case, the // conversion to object does exist, is an implicit reference conversion, // and so we will use it. baseType = this.GetReqPredefAgg(PredefinedType.PT_OBJECT).getThisType(); } return GetBestAccessibleType(semanticChecker, bindingContext, baseType, out typeDst); } return false; }