Improve our handling of the second step in a user-defined conversion
sequence. Previously, we weren't permitting the second step to call
copy constructors, which left user-defined conversion sequences
surprisingly broken.
Now, we perform overload resolution among all of the constructors, but
only accept the result if it makes the conversion a standard
conversion. Note that this behavior is different from both GCC and EDG
(which don't agree with each other, either); I've submitted a core
issue on the matter.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@63450 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index 17ad387..1fa703c 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -366,13 +366,13 @@
ImplicitConversionSequence
Sema::TryImplicitConversion(Expr* From, QualType ToType,
bool SuppressUserConversions,
- bool AllowExplict)
+ bool AllowExplicit)
{
ImplicitConversionSequence ICS;
if (IsStandardConversion(From, ToType, ICS.Standard))
ICS.ConversionKind = ImplicitConversionSequence::StandardConversion;
- else if (!SuppressUserConversions &&
- IsUserDefinedConversion(From, ToType, ICS.UserDefined, AllowExplict)) {
+ else if (IsUserDefinedConversion(From, ToType, ICS.UserDefined,
+ !SuppressUserConversions, AllowExplicit)) {
ICS.ConversionKind = ImplicitConversionSequence::UserDefinedConversion;
// C++ [over.ics.user]p4:
// A conversion of an expression of class type to the same class
@@ -396,6 +396,17 @@
ICS.Standard.Second = ICK_Derived_To_Base;
}
}
+
+ // C++ [over.best.ics]p4:
+ // However, when considering the argument of a user-defined
+ // conversion function that is a candidate by 13.3.1.3 when
+ // invoked for the copying of the temporary in the second step
+ // of a class copy-initialization, or by 13.3.1.4, 13.3.1.5, or
+ // 13.3.1.6 in all cases, only standard conversion sequences and
+ // ellipsis conversion sequences are allowed.
+ if (SuppressUserConversions &&
+ ICS.ConversionKind == ImplicitConversionSequence::UserDefinedConversion)
+ ICS.ConversionKind = ImplicitConversionSequence::BadConversion;
} else
ICS.ConversionKind = ImplicitConversionSequence::BadConversion;
@@ -1188,17 +1199,23 @@
FromType.getUnqualifiedType() == ToType.getUnqualifiedType();
}
-/// IsUserDefinedConversion - Determines whether there is a
-/// user-defined conversion sequence (C++ [over.ics.user]) that
-/// converts expression From to the type ToType. If such a conversion
-/// exists, User will contain the user-defined conversion sequence
-/// that performs such a conversion and this routine will return
-/// true. Otherwise, this routine returns false and User is
-/// unspecified. AllowExplicit is true if the conversion should
-/// consider C++0x "explicit" conversion functions as well as
-/// non-explicit conversion functions (C++0x [class.conv.fct]p2).
+/// Determines whether there is a user-defined conversion sequence
+/// (C++ [over.ics.user]) that converts expression From to the type
+/// ToType. If such a conversion exists, User will contain the
+/// user-defined conversion sequence that performs such a conversion
+/// and this routine will return true. Otherwise, this routine returns
+/// false and User is unspecified.
+///
+/// \param AllowConversionFunctions true if the conversion should
+/// consider conversion functions at all. If false, only constructors
+/// will be considered.
+///
+/// \param AllowExplicit true if the conversion should consider C++0x
+/// "explicit" conversion functions as well as non-explicit conversion
+/// functions (C++0x [class.conv.fct]p2).
bool Sema::IsUserDefinedConversion(Expr *From, QualType ToType,
UserDefinedConversionSequence& User,
+ bool AllowConversionFunctions,
bool AllowExplicit)
{
OverloadCandidateSet CandidateSet;
@@ -1226,8 +1243,11 @@
}
}
- if (const CXXRecordType *FromRecordType
- = dyn_cast_or_null<CXXRecordType>(From->getType()->getAsRecordType())) {
+ if (!AllowConversionFunctions) {
+ // Don't allow any conversion functions to enter the overload set.
+ } else if (const CXXRecordType *FromRecordType
+ = dyn_cast_or_null<CXXRecordType>(
+ From->getType()->getAsRecordType())) {
// Add all of the conversion functions as candidates.
// FIXME: Look for conversions in base classes!
CXXRecordDecl *FromRecordDecl = FromRecordType->getDecl();