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P0962R1: only use the member form of 'begin' and 'end' in a range-based 

for loop if both members exist.

This resolves a DR whereby an errant 'begin' or 'end' member in a base
class could result in a derived class not being usable as a range with
non-member 'begin' and 'end'.

llvm-svn: 342925
This commit is contained in:
Richard Smith 2018-09-24 23:17:44 +00:00
parent 44ecb0e3c2
commit 236ffdeeb2
4 changed files with 156 additions and 57 deletions
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4
clang/include/clang/Basic/DiagnosticSemaKinds.td
View File

@ -2254,8 +2254,6 @@ def err_for_range_incomplete_type : Error<
"cannot use incomplete type %0 as a range">;
def err_for_range_iter_deduction_failure : Error<
"cannot use type %0 as an iterator">;
def err_for_range_member_begin_end_mismatch : Error<
"range type %0 has '%select{begin|end}1' member but no '%select{end|begin}1' member">;
def ext_for_range_begin_end_types_differ : ExtWarn<
"'begin' and 'end' returning different types (%0 and %1) is a C++17 extension">,
InGroup<CXX17>;
@ -2268,6 +2266,8 @@ def note_in_for_range: Note<
def err_for_range_invalid: Error<
"invalid range expression of type %0; no viable '%select{begin|end}1' "
"function available">;
def note_for_range_member_begin_end_ignored : Note<
"member is not a candidate because range type %0 has no '%select{end|begin}1' member">;
def err_range_on_array_parameter : Error<
"cannot build range expression with array function parameter %0 since "
"parameter with array type %1 is treated as pointer type %2">;

144
clang/lib/Sema/SemaStmt.cpp
View File

@ -2149,6 +2149,56 @@ BuildNonArrayForRange(Sema &SemaRef, Expr *BeginRange, Expr *EndRange,
Sema::LookupMemberName);
LookupResult EndMemberLookup(SemaRef, EndNameInfo, Sema::LookupMemberName);
auto BuildBegin = [&] {
*BEF = BEF_begin;
Sema::ForRangeStatus RangeStatus =
SemaRef.BuildForRangeBeginEndCall(ColonLoc, ColonLoc, BeginNameInfo,
BeginMemberLookup, CandidateSet,
BeginRange, BeginExpr);
if (RangeStatus != Sema::FRS_Success) {
if (RangeStatus == Sema::FRS_DiagnosticIssued)
SemaRef.Diag(BeginRange->getBeginLoc(), diag::note_in_for_range)
<< ColonLoc << BEF_begin << BeginRange->getType();
return RangeStatus;
}
if (!CoawaitLoc.isInvalid()) {
// FIXME: getCurScope() should not be used during template instantiation.
// We should pick up the set of unqualified lookup results for operator
// co_await during the initial parse.
*BeginExpr = SemaRef.ActOnCoawaitExpr(SemaRef.getCurScope(), ColonLoc,
BeginExpr->get());
if (BeginExpr->isInvalid())
return Sema::FRS_DiagnosticIssued;
}
if (FinishForRangeVarDecl(SemaRef, BeginVar, BeginExpr->get(), ColonLoc,
diag::err_for_range_iter_deduction_failure)) {
NoteForRangeBeginEndFunction(SemaRef, BeginExpr->get(), *BEF);
return Sema::FRS_DiagnosticIssued;
}
return Sema::FRS_Success;
};
auto BuildEnd = [&] {
*BEF = BEF_end;
Sema::ForRangeStatus RangeStatus =
SemaRef.BuildForRangeBeginEndCall(ColonLoc, ColonLoc, EndNameInfo,
EndMemberLookup, CandidateSet,
EndRange, EndExpr);
if (RangeStatus != Sema::FRS_Success) {
if (RangeStatus == Sema::FRS_DiagnosticIssued)
SemaRef.Diag(EndRange->getBeginLoc(), diag::note_in_for_range)
<< ColonLoc << BEF_end << EndRange->getType();
return RangeStatus;
}
if (FinishForRangeVarDecl(SemaRef, EndVar, EndExpr->get(), ColonLoc,
diag::err_for_range_iter_deduction_failure)) {
NoteForRangeBeginEndFunction(SemaRef, EndExpr->get(), *BEF);
return Sema::FRS_DiagnosticIssued;
}
return Sema::FRS_Success;
};
if (CXXRecordDecl *D = RangeType->getAsCXXRecordDecl()) {
// - if _RangeT is a class type, the unqualified-ids begin and end are
// looked up in the scope of class _RangeT as if by class member access
@ -2156,68 +2206,62 @@ BuildNonArrayForRange(Sema &SemaRef, Expr *BeginRange, Expr *EndRange,
// declaration, begin-expr and end-expr are __range.begin() and
// __range.end(), respectively;
SemaRef.LookupQualifiedName(BeginMemberLookup, D);
if (BeginMemberLookup.isAmbiguous())
return Sema::FRS_DiagnosticIssued;
SemaRef.LookupQualifiedName(EndMemberLookup, D);
if (EndMemberLookup.isAmbiguous())
return Sema::FRS_DiagnosticIssued;
if (BeginMemberLookup.empty() != EndMemberLookup.empty()) {
SourceLocation RangeLoc = BeginVar->getLocation();
*BEF = BeginMemberLookup.empty() ? BEF_end : BEF_begin;
// Look up the non-member form of the member we didn't find, first.
// This way we prefer a "no viable 'end'" diagnostic over a "i found
// a 'begin' but ignored it because there was no member 'end'"
// diagnostic.
auto BuildNonmember = [&](
BeginEndFunction BEFFound, LookupResult &Found,
llvm::function_ref<Sema::ForRangeStatus()> BuildFound,
llvm::function_ref<Sema::ForRangeStatus()> BuildNotFound) {
LookupResult OldFound = std::move(Found);
Found.clear();
SemaRef.Diag(RangeLoc, diag::err_for_range_member_begin_end_mismatch)
<< RangeLoc << BeginRange->getType() << *BEF;
return Sema::FRS_DiagnosticIssued;
if (Sema::ForRangeStatus Result = BuildNotFound())
return Result;
switch (BuildFound()) {
case Sema::FRS_Success:
return Sema::FRS_Success;
case Sema::FRS_NoViableFunction:
SemaRef.Diag(BeginRange->getBeginLoc(), diag::err_for_range_invalid)
<< BeginRange->getType() << BEFFound;
CandidateSet->NoteCandidates(SemaRef, OCD_AllCandidates, BeginRange);
LLVM_FALLTHROUGH;
case Sema::FRS_DiagnosticIssued:
for (NamedDecl *D : OldFound) {
SemaRef.Diag(D->getLocation(),
diag::note_for_range_member_begin_end_ignored)
<< BeginRange->getType() << BEFFound;
}
return Sema::FRS_DiagnosticIssued;
}
llvm_unreachable("unexpected ForRangeStatus");
};
if (BeginMemberLookup.empty())
return BuildNonmember(BEF_end, EndMemberLookup, BuildEnd, BuildBegin);
return BuildNonmember(BEF_begin, BeginMemberLookup, BuildBegin, BuildEnd);
}
} else {
// - otherwise, begin-expr and end-expr are begin(__range) and
// end(__range), respectively, where begin and end are looked up with
// argument-dependent lookup (3.4.2). For the purposes of this name
// lookup, namespace std is an associated namespace.
}
*BEF = BEF_begin;
Sema::ForRangeStatus RangeStatus =
SemaRef.BuildForRangeBeginEndCall(ColonLoc, ColonLoc, BeginNameInfo,
BeginMemberLookup, CandidateSet,
BeginRange, BeginExpr);
if (RangeStatus != Sema::FRS_Success) {
if (RangeStatus == Sema::FRS_DiagnosticIssued)
SemaRef.Diag(BeginRange->getBeginLoc(), diag::note_in_for_range)
<< ColonLoc << BEF_begin << BeginRange->getType();
return RangeStatus;
}
if (!CoawaitLoc.isInvalid()) {
// FIXME: getCurScope() should not be used during template instantiation.
// We should pick up the set of unqualified lookup results for operator
// co_await during the initial parse.
*BeginExpr = SemaRef.ActOnCoawaitExpr(SemaRef.getCurScope(), ColonLoc,
BeginExpr->get());
if (BeginExpr->isInvalid())
return Sema::FRS_DiagnosticIssued;
}
if (FinishForRangeVarDecl(SemaRef, BeginVar, BeginExpr->get(), ColonLoc,
diag::err_for_range_iter_deduction_failure)) {
NoteForRangeBeginEndFunction(SemaRef, BeginExpr->get(), *BEF);
return Sema::FRS_DiagnosticIssued;
}
*BEF = BEF_end;
RangeStatus =
SemaRef.BuildForRangeBeginEndCall(ColonLoc, ColonLoc, EndNameInfo,
EndMemberLookup, CandidateSet,
EndRange, EndExpr);
if (RangeStatus != Sema::FRS_Success) {
if (RangeStatus == Sema::FRS_DiagnosticIssued)
SemaRef.Diag(EndRange->getBeginLoc(), diag::note_in_for_range)
<< ColonLoc << BEF_end << EndRange->getType();
return RangeStatus;
}
if (FinishForRangeVarDecl(SemaRef, EndVar, EndExpr->get(), ColonLoc,
diag::err_for_range_iter_deduction_failure)) {
NoteForRangeBeginEndFunction(SemaRef, EndExpr->get(), *BEF);
return Sema::FRS_DiagnosticIssued;
}
return Sema::FRS_Success;
if (Sema::ForRangeStatus Result = BuildBegin())
return Result;
return BuildEnd();
}
/// Speculatively attempt to dereference an invalid range expression.

59
clang/test/CXX/stmt.stmt/stmt.iter/stmt.ranged/p1.cpp
View File

@ -150,9 +150,9 @@ void g() {
struct NoEnd {
null_t begin();
};
for (auto u : NoBegin()) { // expected-error {{range type 'NoBegin' has 'end' member but no 'begin' member}}
for (auto u : NoBegin()) { // expected-error {{no viable 'begin' function available}}
}
for (auto u : NoEnd()) { // expected-error {{range type 'NoEnd' has 'begin' member but no 'end' member}}
for (auto u : NoEnd()) { // expected-error {{no viable 'end' function available}}
}
struct NoIncr {
@ -271,3 +271,58 @@ namespace rdar13712739 {
template void foo(const int&); // expected-note{{in instantiation of function template specialization}}
}
namespace p0962r1 {
namespace NA {
struct A {
void begin();
};
int *begin(A);
int *end(A);
}
namespace NB {
struct B {
void end();
};
int *begin(B);
int *end(B);
}
namespace NC {
struct C {
void begin();
};
int *begin(C);
}
namespace ND {
struct D {
void end();
};
int *end(D);
}
namespace NE {
struct E {
void begin(); // expected-note {{member is not a candidate because range type 'p0962r1::NE::E' has no 'end' member}}
};
int *end(E);
}
namespace NF {
struct F {
void end(); // expected-note {{member is not a candidate because range type 'p0962r1::NF::F' has no 'begin' member}}
};
int *begin(F);
}
void use(NA::A a, NB::B b, NC::C c, ND::D d, NE::E e, NF::F f) {
for (auto x : a) {}
for (auto x : b) {}
for (auto x : c) {} // expected-error {{no viable 'end' function}}
for (auto x : d) {} // expected-error {{no viable 'begin' function}}
for (auto x : e) {} // expected-error {{no viable 'begin' function}}
for (auto x : f) {} // expected-error {{no viable 'end' function}}
}
}

6
clang/test/SemaCXX/for-range-dereference.cpp
View File

@ -17,7 +17,7 @@ struct DeletedEnd : public T {
struct DeletedADLBegin { };
int* begin(DeletedADLBegin) = delete; //expected-note {{candidate function has been explicitly deleted}} \
expected-note 5 {{candidate function not viable: no known conversion}}
expected-note 6 {{candidate function not viable: no known conversion}}
struct PrivateEnd {
Data *begin();
@ -27,7 +27,7 @@ struct PrivateEnd {
};
struct ADLNoEnd { };
Data * begin(ADLNoEnd); // expected-note 6 {{candidate function not viable: no known conversion}}
Data * begin(ADLNoEnd); // expected-note 7 {{candidate function not viable: no known conversion}}
struct OverloadedStar {
T operator*();
@ -45,7 +45,7 @@ void f() {
for (auto i : parr) { }// expected-error{{invalid range expression of type 'int (*)[10]'; did you mean to dereference it with '*'?}}
NoBegin NB;
for (auto i : NB) { }// expected-error{{range type 'NoBegin' has 'end' member but no 'begin' member}}
for (auto i : NB) { }// expected-error{{invalid range expression of type 'NoBegin'; no viable 'begin' function available}}
NoBegin *pNB;
for (auto i : pNB) { }// expected-error{{invalid range expression of type 'NoBegin *'; no viable 'begin' function available}}
NoBegin **ppNB;