[clang] Revert [clang] Handle templated operators with reversed arguments and [STLExtras] Undo C++20 hack (PR #69937)
Utkarsh Saxena via cfe-commits
cfe-commits at lists.llvm.org
Mon Oct 23 09:06:36 PDT 2023
https://github.com/usx95 created https://github.com/llvm/llvm-project/pull/69937
None
>From b100ca6f219fda1fed5b92aba8471aa9a6ef8906 Mon Sep 17 00:00:00 2001
From: Utkarsh Saxena <usx at google.com>
Date: Mon, 23 Oct 2023 18:02:35 +0200
Subject: [PATCH 1/2] Revert "[STLExtras] Undo C++20 hack"
This reverts commit e558be51bab051d1471d92e967f8a2aecc13567a.
---
llvm/include/llvm/ADT/STLExtras.h | 14 +++++++++-----
1 file changed, 9 insertions(+), 5 deletions(-)
diff --git a/llvm/include/llvm/ADT/STLExtras.h b/llvm/include/llvm/ADT/STLExtras.h
index fade92d458675f2..d0b79fa91c03130 100644
--- a/llvm/include/llvm/ADT/STLExtras.h
+++ b/llvm/include/llvm/ADT/STLExtras.h
@@ -1291,11 +1291,15 @@ class indexed_accessor_range_base {
}
/// Compare this range with another.
- template <typename OtherT> bool operator==(const OtherT &rhs) const {
- return std::equal(begin(), end(), rhs.begin(), rhs.end());
- }
- template <typename OtherT> bool operator!=(const OtherT &rhs) const {
- return !(*this == rhs);
+ template <typename OtherT>
+ friend bool operator==(const indexed_accessor_range_base &lhs,
+ const OtherT &rhs) {
+ return std::equal(lhs.begin(), lhs.end(), rhs.begin(), rhs.end());
+ }
+ template <typename OtherT>
+ friend bool operator!=(const indexed_accessor_range_base &lhs,
+ const OtherT &rhs) {
+ return !(lhs == rhs);
}
/// Return the size of this range.
>From 69426793f377a7449a08cd2e8c9a6def5e63b583 Mon Sep 17 00:00:00 2001
From: Utkarsh Saxena <usx at google.com>
Date: Mon, 23 Oct 2023 18:05:03 +0200
Subject: [PATCH 2/2] Revert "[clang] Handle templated operators with reversed
arguments (#69595)"
This reverts commit 47747da6340b00e301d3656f95ecf9b04a6ec2bb.
---
clang/docs/ReleaseNotes.rst | 21 ---------------------
clang/lib/Sema/SemaOverload.cpp | 28 ++++++++++------------------
2 files changed, 10 insertions(+), 39 deletions(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index c292e012c4548d9..f71b458597e1833 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -37,27 +37,6 @@ These changes are ones which we think may surprise users when upgrading to
Clang |release| because of the opportunity they pose for disruption to existing
code bases.
-- Fix a bug in reversed argument for templated operators.
- This breaks code in C++20 which was previously accepted in C++17. Eg:
-
- .. code-block:: cpp
-
- struct P {};
- template<class S> bool operator==(const P&, const S&);
-
- struct A : public P {};
- struct B : public P {};
-
- // This equality is now ambiguous in C++20.
- bool ambiguous(A a, B b) { return a == b; }
-
- template<class S> bool operator!=(const P&, const S&);
- // Ok. Found a matching operator!=.
- bool fine(A a, B b) { return a == b; }
-
- To reduce such widespread breakages, as an extension, Clang accepts this code
- with an existing warning ``-Wambiguous-reversed-operator`` warning.
- Fixes `GH <https://github.com/llvm/llvm-project/issues/53954>`_.
C/C++ Language Potentially Breaking Changes
-------------------------------------------
diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index d2475459fa4f4f7..db386fef0661c05 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -7685,7 +7685,7 @@ bool Sema::CheckNonDependentConversions(
QualType ParamType = ParamTypes[I + Offset];
if (!ParamType->isDependentType()) {
unsigned ConvIdx = PO == OverloadCandidateParamOrder::Reversed
- ? Args.size() - 1 - (ThisConversions + I)
+ ? 0
: (ThisConversions + I);
Conversions[ConvIdx]
= TryCopyInitialization(*this, Args[I], ParamType,
@@ -10082,19 +10082,11 @@ getImplicitObjectParamType(ASTContext &Context, const FunctionDecl *F) {
return M->getFunctionObjectParameterReferenceType();
}
-// As a Clang extension, allow ambiguity among F1 and F2 if they represent
-// represent the same entity.
-static bool allowAmbiguity(ASTContext &Context, const FunctionDecl *F1,
- const FunctionDecl *F2) {
+static bool haveSameParameterTypes(ASTContext &Context, const FunctionDecl *F1,
+ const FunctionDecl *F2) {
if (declaresSameEntity(F1, F2))
return true;
- if (F1->isTemplateInstantiation() && F2->isTemplateInstantiation() &&
- declaresSameEntity(F1->getPrimaryTemplate(), F2->getPrimaryTemplate())) {
- return true;
- }
- // TODO: It is not clear whether comparing parameters is necessary (i.e.
- // different functions with same params). Consider removing this (as no test
- // fail w/o it).
+
auto NextParam = [&](const FunctionDecl *F, unsigned &I, bool First) {
if (First) {
if (std::optional<QualType> T = getImplicitObjectParamType(Context, F))
@@ -10279,14 +10271,14 @@ bool clang::isBetterOverloadCandidate(
case ImplicitConversionSequence::Worse:
if (Cand1.Function && Cand2.Function &&
Cand1.isReversed() != Cand2.isReversed() &&
- allowAmbiguity(S.Context, Cand1.Function, Cand2.Function)) {
+ haveSameParameterTypes(S.Context, Cand1.Function, Cand2.Function)) {
// Work around large-scale breakage caused by considering reversed
// forms of operator== in C++20:
//
- // When comparing a function against a reversed function, if we have a
- // better conversion for one argument and a worse conversion for the
- // other, the implicit conversion sequences are treated as being equally
- // good.
+ // When comparing a function against a reversed function with the same
+ // parameter types, if we have a better conversion for one argument and
+ // a worse conversion for the other, the implicit conversion sequences
+ // are treated as being equally good.
//
// This prevents a comparison function from being considered ambiguous
// with a reversed form that is written in the same way.
@@ -14457,7 +14449,7 @@ ExprResult Sema::CreateOverloadedBinOp(SourceLocation OpLoc,
llvm::SmallVector<FunctionDecl*, 4> AmbiguousWith;
for (OverloadCandidate &Cand : CandidateSet) {
if (Cand.Viable && Cand.Function && Cand.isReversed() &&
- allowAmbiguity(Context, Cand.Function, FnDecl)) {
+ haveSameParameterTypes(Context, Cand.Function, FnDecl)) {
for (unsigned ArgIdx = 0; ArgIdx < 2; ++ArgIdx) {
if (CompareImplicitConversionSequences(
*this, OpLoc, Cand.Conversions[ArgIdx],
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