[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
joker-eph wrote: You're right, it's visible on the link I posted, the build was already broken! Somehow I fat-fingered and didn't hit the first red build but the third one! https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
mizvekov wrote: I just double checked, the issue is present on main before this PR was merged, it's completely unrelated. https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
joker-eph wrote: Great, thanks for the quick fix! https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
mizvekov wrote: I just pushed a fix. https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
mizvekov wrote: Yep, I confirm the behavior happens if I add `-triple x86_64-windows-msvc` to RUN line. https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
mizvekov wrote: Weirdly enough the test passes on my machine, latest MacOS. Maybe the test is not constrained on target, and this is causing differences between machines? https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
mizvekov wrote: The quick fix would be to change the expectations of the test, I can do it for you. https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
joker-eph wrote: So are we reverting here or do you have quick fix available? https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
mizvekov wrote: That test was merged after the last time pre-commit CI was run on this MR. The change looks like a consequence of my refactoring, we now preserve the type sugar from the injected arguments. https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
joker-eph wrote: Seems like a bot is broken: https://lab.llvm.org/buildbot/#/builders/271/builds/7701 ; can you check? https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
https://github.com/mizvekov closed https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
https://github.com/zygoloid commented: I think we should go ahead with this. The behavior here is subtle but I think it does make sense, and we're in the process of proposing this change to WG21. https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
https://github.com/erichkeane approved this pull request. https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
https://github.com/cor3ntin approved this pull request. LGTM but gives @zygoloid @erichkeane a few days to review https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
Endilll wrote: > Despite CWG2398 not being voted in yet, the status in > > https://github.com/llvm/llvm-project/blob/e3f42b02a4129947ca2dd820bfb63ffed83027b7/clang/www/cxx_dr_status.html#L14195-L14200 > > should be updated. The only way to update it is to add a test to `clang/test/CXX/drs`. Me and the author had a discussion couple of weeks ago, and the conclusion was that what he implements is not (yet) documented in the CWG2398 filing, so we don't have anything to write a DR test and claim conformance against. If something has changes since then, we should revisit that conclusion. https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
https://github.com/mizvekov edited https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
https://github.com/mizvekov edited https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
https://github.com/mizvekov edited https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
https://github.com/mizvekov updated
https://github.com/llvm/llvm-project/pull/90820
>From 39e0af93163068f8de190649eccf91fda84178b6 Mon Sep 17 00:00:00 2001
From: Matheus Izvekov
Date: Wed, 1 May 2024 22:29:45 -0300
Subject: [PATCH] [clang] Implement provisional wording for CWG2398 regarding
packs
This solves some ambuguity introduced in P0522 regarding how
template template parameters are partially ordered, and should reduce
the negative impact of enabling `-frelaxed-template-template-args`
by default.
When performing template argument deduction, a template template parameter
containing no packs should be more specialized than one that does.
Given the following example:
```C++
template struct A;
template class TT1, class T4> struct A>; // #1
template class TT2, class T6> struct A>; // #2
template struct B;
template struct A>;
```
Prior to P0522, candidate #2 would be more specialized.
After P0522, neither is more specialized, so this becomes ambiguous.
With this change, #2 becomes more specialized again,
maintaining compatibility with pre-P0522 implementations.
The problem is that in P0522, candidates are at least as specialized
when matching packs to fixed-size lists both ways, whereas before,
a fixed-size list is more specialized.
This patch keeps the original behavior when checking template arguments
outside deduction, but restores this aspect of pre-P0522 matching
during deduction.
---
Since this changes provisional implementation of CWG2398 which has
not been released yet, and already contains a changelog entry,
we don't provide a changelog entry here.
---
clang/include/clang/Sema/Sema.h | 5 +-
clang/lib/Sema/SemaTemplate.cpp | 10 ++--
clang/lib/Sema/SemaTemplateDeduction.cpp | 67 +++-
clang/test/SemaTemplate/cwg2398.cpp | 15 ++
4 files changed, 65 insertions(+), 32 deletions(-)
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 6a414aa57f32b..7d7eb6c559110 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -9133,7 +9133,7 @@ class Sema final : public SemaBase {
CheckTemplateArgumentKind CTAK);
bool CheckTemplateTemplateArgument(TemplateTemplateParmDecl *Param,
TemplateParameterList *Params,
- TemplateArgumentLoc );
+ TemplateArgumentLoc , bool IsDeduced);
void NoteTemplateLocation(const NamedDecl ,
std::optional ParamRange = {});
@@ -9603,7 +9603,8 @@ class Sema final : public SemaBase {
sema::TemplateDeductionInfo );
bool isTemplateTemplateParameterAtLeastAsSpecializedAs(
- TemplateParameterList *PParam, TemplateDecl *AArg, SourceLocation Loc);
+ TemplateParameterList *PParam, TemplateDecl *AArg, SourceLocation Loc,
+ bool IsDeduced);
void MarkUsedTemplateParameters(const Expr *E, bool OnlyDeduced,
unsigned Depth, llvm::SmallBitVector );
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index c7aac068e264b..116d1ac077b29 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -6484,7 +6484,8 @@ bool Sema::CheckTemplateArgument(
case TemplateArgument::Template:
case TemplateArgument::TemplateExpansion:
-if (CheckTemplateTemplateArgument(TempParm, Params, Arg))
+if (CheckTemplateTemplateArgument(TempParm, Params, Arg,
+ /*IsDeduced=*/CTAK != CTAK_Specified))
return true;
SugaredConverted.push_back(Arg.getArgument());
@@ -8402,7 +8403,8 @@ static void DiagnoseTemplateParameterListArityMismatch(
/// It returns true if an error occurred, and false otherwise.
bool Sema::CheckTemplateTemplateArgument(TemplateTemplateParmDecl *Param,
TemplateParameterList *Params,
- TemplateArgumentLoc ) {
+ TemplateArgumentLoc ,
+ bool IsDeduced) {
TemplateName Name = Arg.getArgument().getAsTemplateOrTemplatePattern();
TemplateDecl *Template = Name.getAsTemplateDecl();
if (!Template) {
@@ -8454,8 +8456,8 @@ bool
Sema::CheckTemplateTemplateArgument(TemplateTemplateParmDecl *Param,
!Template->hasAssociatedConstraints())
return false;
-if (isTemplateTemplateParameterAtLeastAsSpecializedAs(Params, Template,
- Arg.getLocation())) {
+if (isTemplateTemplateParameterAtLeastAsSpecializedAs(
+Params, Template, Arg.getLocation(), IsDeduced)) {
// P2113
// C++20[temp.func.order]p2
// [...] If both deductions succeed, the partial ordering selects the
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
https://github.com/mizvekov edited https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
https://github.com/mizvekov updated
https://github.com/llvm/llvm-project/pull/90820
>From c4b72afa655c0e35005dca8aea18e651189f8938 Mon Sep 17 00:00:00 2001
From: Matheus Izvekov
Date: Wed, 1 May 2024 22:29:45 -0300
Subject: [PATCH] [clang] Implement provisional wording for CWG2398 regarding
packs
This solves some ambuguity introduced in P0522 regarding how
template template parameters are partially ordered, and should reduce
the negative impact of enabling `-frelaxed-template-template-args`
by default.
When performing template argument deduction, a template template parameter
containing no packs should be more specialized than one that does.
Given the following example:
```C++
template struct A;
template class TT1, class T4> struct A>; // #1
template class TT2, class T6> struct A>; // #2
template struct B;
template struct A>;
```
Prior to P0522, candidate #2 would be more specialized.
After P0522, neither is more specialized, so this becomes ambiguous.
With this change, #2 becomes more specialized again,
maintaining compatibility with pre-P0522 implementations.
The problem is that in P0522, candidates are at least as specialized
when matching packs to fixed-size lists both ways, whereas before,
a fixed-size list is more specialized.
This patch keeps the original behavior when checking template arguments
outside deduction, but restores this aspect of pre-P0522 matching
during deduction.
---
Since this changes provisional implementation of CWG2398 which has
not been released yet, and already contains a changelog entry,
we don't provide a changelog entry here.
---
clang/include/clang/Sema/Sema.h | 5 +-
clang/lib/Sema/SemaTemplate.cpp | 10 ++--
clang/lib/Sema/SemaTemplateDeduction.cpp | 67 +++-
clang/test/SemaTemplate/cwg2398.cpp | 24 ++---
4 files changed, 80 insertions(+), 26 deletions(-)
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 6a414aa57f32b..7d7eb6c559110 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -9133,7 +9133,7 @@ class Sema final : public SemaBase {
CheckTemplateArgumentKind CTAK);
bool CheckTemplateTemplateArgument(TemplateTemplateParmDecl *Param,
TemplateParameterList *Params,
- TemplateArgumentLoc );
+ TemplateArgumentLoc , bool IsDeduced);
void NoteTemplateLocation(const NamedDecl ,
std::optional ParamRange = {});
@@ -9603,7 +9603,8 @@ class Sema final : public SemaBase {
sema::TemplateDeductionInfo );
bool isTemplateTemplateParameterAtLeastAsSpecializedAs(
- TemplateParameterList *PParam, TemplateDecl *AArg, SourceLocation Loc);
+ TemplateParameterList *PParam, TemplateDecl *AArg, SourceLocation Loc,
+ bool IsDeduced);
void MarkUsedTemplateParameters(const Expr *E, bool OnlyDeduced,
unsigned Depth, llvm::SmallBitVector );
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index c7aac068e264b..116d1ac077b29 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -6484,7 +6484,8 @@ bool Sema::CheckTemplateArgument(
case TemplateArgument::Template:
case TemplateArgument::TemplateExpansion:
-if (CheckTemplateTemplateArgument(TempParm, Params, Arg))
+if (CheckTemplateTemplateArgument(TempParm, Params, Arg,
+ /*IsDeduced=*/CTAK != CTAK_Specified))
return true;
SugaredConverted.push_back(Arg.getArgument());
@@ -8402,7 +8403,8 @@ static void DiagnoseTemplateParameterListArityMismatch(
/// It returns true if an error occurred, and false otherwise.
bool Sema::CheckTemplateTemplateArgument(TemplateTemplateParmDecl *Param,
TemplateParameterList *Params,
- TemplateArgumentLoc ) {
+ TemplateArgumentLoc ,
+ bool IsDeduced) {
TemplateName Name = Arg.getArgument().getAsTemplateOrTemplatePattern();
TemplateDecl *Template = Name.getAsTemplateDecl();
if (!Template) {
@@ -8454,8 +8456,8 @@ bool
Sema::CheckTemplateTemplateArgument(TemplateTemplateParmDecl *Param,
!Template->hasAssociatedConstraints())
return false;
-if (isTemplateTemplateParameterAtLeastAsSpecializedAs(Params, Template,
- Arg.getLocation())) {
+if (isTemplateTemplateParameterAtLeastAsSpecializedAs(
+Params, Template, Arg.getLocation(), IsDeduced)) {
// P2113
// C++20[temp.func.order]p2
// [...] If both deductions succeed, the partial ordering selects the
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
@@ -2583,8 +2584,11 @@ DeduceTemplateArguments(Sema , TemplateParameterList *TemplateParams, return TemplateDeductionResult::MiscellaneousDeductionFailure; // Perform deduction for this Pi/Ai pair. - if (auto Result = DeduceTemplateArguments(S, TemplateParams, P, -As[ArgIdx], Info, Deduced); + TemplateArgument Pi = P, Ai = As[ArgIdx]; + if (Swapped) +std::swap(Pi, Ai); cor3ntin wrote: We might want a comment here too https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
@@ -2552,7 +2553,7 @@ DeduceTemplateArguments(Sema , TemplateParameterList
*TemplateParams,
ArrayRef As,
TemplateDeductionInfo ,
SmallVectorImpl ,
-bool NumberOfArgumentsMustMatch) {
+bool NumberOfArgumentsMustMatch, bool Swapped) {
cor3ntin wrote:
I think this needs a comment.
`Swapped` should be defaulted and have a better name.
Maybe `ForPartialOrderingOfDeducedTemplateTemplateArgument`
https://github.com/llvm/llvm-project/pull/90820
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[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
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[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
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[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
Endilll wrote: > Sounds like should perhaps note that we are implementing our own resolution, > until there's an update to the cwg issue that can be referred to? Our tooling is not ready for describing own own resolutions, unfortunately. Ideally if we have a resolution, it should be submitted to CWG and documented in the issue, making it easy to reference. https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
mizvekov wrote: > Sounds like should perhaps note that we are implementing our own resolution, > until there's an update to the cwg issue that can be referred to? That could be. Is there another similar issue we could use as a reference on the format for this? https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
mizvekov wrote: It would not be splitting though, it would be wholesale duplication in that case. This file is the only part of the suite still testing the old non-conformant mode, and I fail to see a test case we wouldn't be wanting to test on both. https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
h-vetinari wrote: > Note we are not implementing the solution Jason posted on the core mailing > list, neither on the previous patch, as we have a better solution than > current GCC on this, nor on this MR, as GCC implements no such workaround and > still fails this test. Sounds like should perhaps note that we are implementing our own resolution, until there's an update to the cwg issue that can be referred to? https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
Endilll wrote: > Also, this needs to test a non-conforming mode until we finally remove the > corresponding flag, and that is against the rules for the DR suite. You should be able to split conforming part of the test into DR test, though. https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
mizvekov wrote: Note we are not implementing the solution Jason posted on the core mailing list, neither on the previous patch, as we have a better solution than current GCC on this, nor on this MR, as GCC implements no such workaround and still fails this test. https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
Endilll wrote: This file is not going to be picked up by the `make_cxx_dr_status`, because it's not in `clang/test/CXX/drs`. If we're implementing what Jason Merill speaks of (_In deduction we can determine that P is more specialized than B, then substitute B into P, and then compare B to B_), then I agree with `// cwg2398: 19 drafting 2016-12-03` marking. In the previous PR on this topic I asked for this test to be moved out of DR test suite, because it was testing with `-fno-relaxed-template-template-args`, which is not a conformance mode. This still holds, so this file can't be simply moved to DR test suite as is. I also don't see why CWG2398 test can't be placed in `dr23xx.cpp`. We place DR tests in separate files only if they require special handling. Typical case is codegen tests. Note that special handling doesn't mean testing non-conformance modes, or reduced number of conformance modes. https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
https://github.com/mizvekov edited https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
mizvekov wrote: I had some discussion about that with @Endilll on the previous MR regarding this core issue: https://github.com/llvm/llvm-project/pull/89807 Since there is no posting at all in core about any possible solutions, I wanted to get feedback from them before claiming to be implementing a solution in the public documentation. Also, this needs to test a non-confirming mode until we finally remove the corresponding flag, and that is against the rules for the DR suite. https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
h-vetinari wrote: AFAIU, for this to be picked up by [make_cxx_dr_status](https://github.com/llvm/llvm-project/blob/main/clang/www/make_cxx_dr_status) correctly, this file should have a comment near the top like: ``` // cwg2398: 19 drafting 2016-12-03 ``` and for consistency should be mentioned in `dr23xx.cpp` like so: https://github.com/llvm/llvm-project/blob/b86e0992bfa6c58be077d82d824016f590ac5d90/clang/test/CXX/drs/dr23xx.cpp#L276 https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
https://github.com/h-vetinari commented: Despite CWG2398 not being voted in yet, the status in https://github.com/llvm/llvm-project/blob/e3f42b02a4129947ca2dd820bfb63ffed83027b7/clang/www/cxx_dr_status.html#L14195-L14200 should be updated. https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
https://github.com/h-vetinari edited https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
https://github.com/Endilll commented: `Sema.h` changes look good to me. https://github.com/llvm/llvm-project/pull/90820 ___ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
llvmbot wrote:
@llvm/pr-subscribers-clang
Author: Matheus Izvekov (mizvekov)
Changes
This solves some ambuguity introduced in P0522 regarding how template template
parameters are partially ordered, and should reduce the negative impact of
enabling `-frelaxed-template-template-args` by default.
A template template parameter containing no packs should be more specialized
than one that does.
Given the following example:
```C++
templateclass T2 struct A;
templatetemplateclass ...T3s class TT1, class T4 struct
ATT1T4; #1
templatetemplateclassT5 class TT2, class T6 struct
ATT2T6; #2
templateclass T1 struct B;
template struct ABchar;
```
Prior to P0522, #2 would be the only viable candidate. After P0522,
#1 is also viable, and neither is considered more specialized, so this
becomes ambiguous.
With this change, #2 is considered more specialized, so that is what is
picked and we remain compatible with pre-P0522 implementations.
The problem we solve here is that the specialization rules in
`[temp.arg.template]/4` are defined in terms of a rewrite to function
templates, but in the case of partial ordering, the rules on how P and A lists
are matched to each other is swapped regarding how specialization makes sense
conceptually.
---
Since this changes provisional implementation of CWG2398 which has not been
released yet, and already contains a changelog entry, we don't provide a
changelog entry here.
---
Full diff: https://github.com/llvm/llvm-project/pull/90820.diff
4 Files Affected:
- (modified) clang/include/clang/Sema/Sema.h (+3-2)
- (modified) clang/lib/Sema/SemaTemplate.cpp (+6-4)
- (modified) clang/lib/Sema/SemaTemplateDeduction.cpp (+59-20)
- (modified) clang/test/SemaTemplate/cwg2398.cpp (-6)
``diff
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index a80ac6dbc76137..2bea8732f61fcd 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -9238,7 +9238,7 @@ class Sema final : public SemaBase {
CheckTemplateArgumentKind CTAK);
bool CheckTemplateTemplateArgument(TemplateTemplateParmDecl *Param,
TemplateParameterList *Params,
- TemplateArgumentLoc );
+ TemplateArgumentLoc , bool IsDeduced);
void NoteTemplateLocation(const NamedDecl ,
std::optional ParamRange = {});
@@ -9708,7 +9708,8 @@ class Sema final : public SemaBase {
sema::TemplateDeductionInfo );
bool isTemplateTemplateParameterAtLeastAsSpecializedAs(
- TemplateParameterList *PParam, TemplateDecl *AArg, SourceLocation Loc);
+ TemplateParameterList *PParam, TemplateDecl *AArg, SourceLocation Loc,
+ bool IsDeduced);
void MarkUsedTemplateParameters(const Expr *E, bool OnlyDeduced,
unsigned Depth, llvm::SmallBitVector );
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 989f3995ca5991..2c921d4365db0a 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -6384,7 +6384,8 @@ bool Sema::CheckTemplateArgument(
case TemplateArgument::Template:
case TemplateArgument::TemplateExpansion:
-if (CheckTemplateTemplateArgument(TempParm, Params, Arg))
+if (CheckTemplateTemplateArgument(TempParm, Params, Arg,
+ /*IsDeduced=*/CTAK != CTAK_Specified))
return true;
SugaredConverted.push_back(Arg.getArgument());
@@ -8296,7 +8297,8 @@ static void DiagnoseTemplateParameterListArityMismatch(
/// It returns true if an error occurred, and false otherwise.
bool Sema::CheckTemplateTemplateArgument(TemplateTemplateParmDecl *Param,
TemplateParameterList *Params,
- TemplateArgumentLoc ) {
+ TemplateArgumentLoc ,
+ bool IsDeduced) {
TemplateName Name = Arg.getArgument().getAsTemplateOrTemplatePattern();
TemplateDecl *Template = Name.getAsTemplateDecl();
if (!Template) {
@@ -8348,8 +8350,8 @@ bool
Sema::CheckTemplateTemplateArgument(TemplateTemplateParmDecl *Param,
!Template->hasAssociatedConstraints())
return false;
-if (isTemplateTemplateParameterAtLeastAsSpecializedAs(Params, Template,
- Arg.getLocation())) {
+if (isTemplateTemplateParameterAtLeastAsSpecializedAs(
+Params, Template, Arg.getLocation(), IsDeduced)) {
// P2113
// C++20[temp.func.order]p2
// [...] If both deductions succeed, the partial ordering selects the
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp
b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 9f9e4422827173..4fbaecd7dba960 100644
---
[clang] [clang] Implement provisional wording for CWG2398 regarding packs (PR #90820)
https://github.com/mizvekov created
https://github.com/llvm/llvm-project/pull/90820
This solves some ambuguity introduced in P0522 regarding how template template
parameters are partially ordered, and should reduce the negative impact of
enabling `-frelaxed-template-template-args` by default.
A template template parameter containing no packs should be more specialized
than one that does.
Given the following example:
```C++
template struct A;
template class TT1, class T4> struct A>; #1
template class TT2, class T6> struct A>; #2
template struct B;
template struct A>;
```
Prior to P0522, #2 would be the only viable candidate. After P0522, #1 is also
viable, and neither is considered more specialized, so this becomes ambiguous.
With this change, #2 is considered more specialized, so that is what is picked
and we remain compatible with pre-P0522 implementations.
The problem we solve here is that the specialization rules in
`[temp.arg.template]/4` are defined in terms of a rewrite to function
templates, but in the case of partial ordering, the rules on how P and A lists
are matched to each other is swapped regarding how specialization makes sense
conceptually.
---
Since this changes provisional implementation of CWG2398 which has not been
released yet, and already contains a changelog entry, we don't provide a
changelog entry here.
>From b7df9a342724479e129af252f2ff37229f30d41b Mon Sep 17 00:00:00 2001
From: Matheus Izvekov
Date: Wed, 1 May 2024 22:29:45 -0300
Subject: [PATCH] [clang] Implement provisional wording for CWG2398 regarding
packs
This solves some ambuguity introduced in P0522 regarding how
template template parameters are partially ordered, and should reduce
the negative impact of enabling `-frelaxed-template-template-args`
by default.
A template template parameter containing no packs should be more
specialized than one that does.
Given the following example:
```C++
template struct A;
template class TT1, class T4> struct A>; #1
template class TT2, class T6> struct A>; #2
template struct B;
template struct A>;
```
Prior to P0522, #2 would be the only viable candidate.
After P0522, #1 is also viable, and neither is considered more specialized,
so this becomes ambiguous.
With this change, #2 is considered more specialized, so that is what is picked
and we remain compatible with pre-P0522 implementations.
The problem we solve here is that the specialization rules in
`[temp.arg.template]/4` are defined in terms of a rewrite to
function templates, but in the case of partial ordering, the
rules on how P and A lists are matched to each other
is swapped regarding how specialization makes sense conceptually.
---
Since this changes provisional implementation of CWG2398 which has
not been released yet, and already contains a changelog entry,
we don't provide a changelog entry here.
---
clang/include/clang/Sema/Sema.h | 5 +-
clang/lib/Sema/SemaTemplate.cpp | 10 +--
clang/lib/Sema/SemaTemplateDeduction.cpp | 79 ++--
clang/test/SemaTemplate/cwg2398.cpp | 6 --
4 files changed, 68 insertions(+), 32 deletions(-)
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index a80ac6dbc76137..2bea8732f61fcd 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -9238,7 +9238,7 @@ class Sema final : public SemaBase {
CheckTemplateArgumentKind CTAK);
bool CheckTemplateTemplateArgument(TemplateTemplateParmDecl *Param,
TemplateParameterList *Params,
- TemplateArgumentLoc );
+ TemplateArgumentLoc , bool IsDeduced);
void NoteTemplateLocation(const NamedDecl ,
std::optional ParamRange = {});
@@ -9708,7 +9708,8 @@ class Sema final : public SemaBase {
sema::TemplateDeductionInfo );
bool isTemplateTemplateParameterAtLeastAsSpecializedAs(
- TemplateParameterList *PParam, TemplateDecl *AArg, SourceLocation Loc);
+ TemplateParameterList *PParam, TemplateDecl *AArg, SourceLocation Loc,
+ bool IsDeduced);
void MarkUsedTemplateParameters(const Expr *E, bool OnlyDeduced,
unsigned Depth, llvm::SmallBitVector );
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 989f3995ca5991..2c921d4365db0a 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -6384,7 +6384,8 @@ bool Sema::CheckTemplateArgument(
case TemplateArgument::Template:
case TemplateArgument::TemplateExpansion:
-if (CheckTemplateTemplateArgument(TempParm, Params, Arg))
+if (CheckTemplateTemplateArgument(TempParm, Params, Arg,
+ /*IsDeduced=*/CTAK != CTAK_Specified))
return true;
SugaredConverted.push_back(Arg.getArgument());
@@ -8296,7
