https://github.com/llvmbot created https://github.com/llvm/llvm-project/pull/134194
Backport dcc2182bc Requested by: @zyn0217 >From 235cb3d75d0fc80860c493520a584242c609393d Mon Sep 17 00:00:00 2001 From: Younan Zhang <zyn7...@gmail.com> Date: Thu, 3 Apr 2025 11:15:42 +0800 Subject: [PATCH] [Clang] Fix a lambda pattern comparison mismatch after ecc7e6ce4 (#133863) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit In ecc7e6ce4, we tried to inspect the `LambdaScopeInfo` on stack to recover the instantiating lambda captures. However, there was a mismatch in how we compared the pattern declarations of lambdas: the constraint instantiation used a tailored `getPatternFunctionDecl()` which is localized in SemaLambda that finds the very primal template declaration of a lambda, while `FunctionDecl::getTemplateInstantiationPattern` finds the latest template pattern of a lambda. This difference causes issues when lambdas are nested, as we always want the primary template declaration. This corrects that by moving `Sema::addInstantiatedCapturesToScope` from SemaConcept to SemaLambda, allowing it to use the localized version of `getPatternFunctionDecl`. It is also worth exploring to coalesce the implementation of `getPatternFunctionDecl` with `FunctionDecl::getTemplateInstantiationPattern`. But I’m leaving that for the future, as I’d like to backport this fix (ecc7e6ce4 made the issue more visible in clang 20, sorry!), and changing Sema’s ABI would not be suitable in that regards. Hence, no release note. Fixes https://github.com/llvm/llvm-project/issues/133719 (cherry picked from commit dcc2182bce3d2ef0e0a991664c51b4b3bfcf7197) --- clang/lib/Sema/SemaConcept.cpp | 69 --------------------- clang/lib/Sema/SemaLambda.cpp | 68 ++++++++++++++++++++ clang/test/SemaTemplate/concepts-lambda.cpp | 15 +++++ 3 files changed, 83 insertions(+), 69 deletions(-) diff --git a/clang/lib/Sema/SemaConcept.cpp b/clang/lib/Sema/SemaConcept.cpp index a7b609f7f3ce4..8adebccde042c 100644 --- a/clang/lib/Sema/SemaConcept.cpp +++ b/clang/lib/Sema/SemaConcept.cpp @@ -702,75 +702,6 @@ bool Sema::CheckConstraintSatisfaction(const Expr *ConstraintExpr, .isInvalid(); } -bool Sema::addInstantiatedCapturesToScope( - FunctionDecl *Function, const FunctionDecl *PatternDecl, - LocalInstantiationScope &Scope, - const MultiLevelTemplateArgumentList &TemplateArgs) { - const auto *LambdaClass = cast<CXXMethodDecl>(Function)->getParent(); - const auto *LambdaPattern = cast<CXXMethodDecl>(PatternDecl)->getParent(); - - unsigned Instantiated = 0; - - // FIXME: This is a workaround for not having deferred lambda body - // instantiation. - // When transforming a lambda's body, if we encounter another call to a - // nested lambda that contains a constraint expression, we add all of the - // outer lambda's instantiated captures to the current instantiation scope to - // facilitate constraint evaluation. However, these captures don't appear in - // the CXXRecordDecl until after the lambda expression is rebuilt, so we - // pull them out from the corresponding LSI. - LambdaScopeInfo *InstantiatingScope = nullptr; - if (LambdaPattern->capture_size() && !LambdaClass->capture_size()) { - for (FunctionScopeInfo *Scope : llvm::reverse(FunctionScopes)) { - auto *LSI = dyn_cast<LambdaScopeInfo>(Scope); - if (!LSI || - LSI->CallOperator->getTemplateInstantiationPattern() != PatternDecl) - continue; - InstantiatingScope = LSI; - break; - } - assert(InstantiatingScope); - } - - auto AddSingleCapture = [&](const ValueDecl *CapturedPattern, - unsigned Index) { - ValueDecl *CapturedVar = - InstantiatingScope ? InstantiatingScope->Captures[Index].getVariable() - : LambdaClass->getCapture(Index)->getCapturedVar(); - assert(CapturedVar->isInitCapture()); - Scope.InstantiatedLocal(CapturedPattern, CapturedVar); - }; - - for (const LambdaCapture &CapturePattern : LambdaPattern->captures()) { - if (!CapturePattern.capturesVariable()) { - Instantiated++; - continue; - } - ValueDecl *CapturedPattern = CapturePattern.getCapturedVar(); - - if (!CapturedPattern->isInitCapture()) { - Instantiated++; - continue; - } - - if (!CapturedPattern->isParameterPack()) { - AddSingleCapture(CapturedPattern, Instantiated++); - } else { - Scope.MakeInstantiatedLocalArgPack(CapturedPattern); - SmallVector<UnexpandedParameterPack, 2> Unexpanded; - SemaRef.collectUnexpandedParameterPacks( - dyn_cast<VarDecl>(CapturedPattern)->getInit(), Unexpanded); - auto NumArgumentsInExpansion = - getNumArgumentsInExpansionFromUnexpanded(Unexpanded, TemplateArgs); - if (!NumArgumentsInExpansion) - continue; - for (unsigned Arg = 0; Arg < *NumArgumentsInExpansion; ++Arg) - AddSingleCapture(CapturedPattern, Instantiated++); - } - } - return false; -} - bool Sema::SetupConstraintScope( FunctionDecl *FD, std::optional<ArrayRef<TemplateArgument>> TemplateArgs, const MultiLevelTemplateArgumentList &MLTAL, diff --git a/clang/lib/Sema/SemaLambda.cpp b/clang/lib/Sema/SemaLambda.cpp index ceb32ee15dfa3..981856fbf25a7 100644 --- a/clang/lib/Sema/SemaLambda.cpp +++ b/clang/lib/Sema/SemaLambda.cpp @@ -2389,6 +2389,74 @@ static FunctionDecl *getPatternFunctionDecl(FunctionDecl *FD) { return FTD->getTemplatedDecl(); } +bool Sema::addInstantiatedCapturesToScope( + FunctionDecl *Function, const FunctionDecl *PatternDecl, + LocalInstantiationScope &Scope, + const MultiLevelTemplateArgumentList &TemplateArgs) { + const auto *LambdaClass = cast<CXXMethodDecl>(Function)->getParent(); + const auto *LambdaPattern = cast<CXXMethodDecl>(PatternDecl)->getParent(); + + unsigned Instantiated = 0; + + // FIXME: This is a workaround for not having deferred lambda body + // instantiation. + // When transforming a lambda's body, if we encounter another call to a + // nested lambda that contains a constraint expression, we add all of the + // outer lambda's instantiated captures to the current instantiation scope to + // facilitate constraint evaluation. However, these captures don't appear in + // the CXXRecordDecl until after the lambda expression is rebuilt, so we + // pull them out from the corresponding LSI. + LambdaScopeInfo *InstantiatingScope = nullptr; + if (LambdaPattern->capture_size() && !LambdaClass->capture_size()) { + for (FunctionScopeInfo *Scope : llvm::reverse(FunctionScopes)) { + auto *LSI = dyn_cast<LambdaScopeInfo>(Scope); + if (!LSI || getPatternFunctionDecl(LSI->CallOperator) != PatternDecl) + continue; + InstantiatingScope = LSI; + break; + } + assert(InstantiatingScope); + } + + auto AddSingleCapture = [&](const ValueDecl *CapturedPattern, + unsigned Index) { + ValueDecl *CapturedVar = + InstantiatingScope ? InstantiatingScope->Captures[Index].getVariable() + : LambdaClass->getCapture(Index)->getCapturedVar(); + assert(CapturedVar->isInitCapture()); + Scope.InstantiatedLocal(CapturedPattern, CapturedVar); + }; + + for (const LambdaCapture &CapturePattern : LambdaPattern->captures()) { + if (!CapturePattern.capturesVariable()) { + Instantiated++; + continue; + } + ValueDecl *CapturedPattern = CapturePattern.getCapturedVar(); + + if (!CapturedPattern->isInitCapture()) { + Instantiated++; + continue; + } + + if (!CapturedPattern->isParameterPack()) { + AddSingleCapture(CapturedPattern, Instantiated++); + } else { + Scope.MakeInstantiatedLocalArgPack(CapturedPattern); + SmallVector<UnexpandedParameterPack, 2> Unexpanded; + SemaRef.collectUnexpandedParameterPacks( + dyn_cast<VarDecl>(CapturedPattern)->getInit(), Unexpanded); + auto NumArgumentsInExpansion = + getNumArgumentsInExpansionFromUnexpanded(Unexpanded, TemplateArgs); + if (!NumArgumentsInExpansion) + continue; + for (unsigned Arg = 0; Arg < *NumArgumentsInExpansion; ++Arg) + AddSingleCapture(CapturedPattern, Instantiated++); + } + } + return false; +} + Sema::LambdaScopeForCallOperatorInstantiationRAII:: LambdaScopeForCallOperatorInstantiationRAII( Sema &SemaRef, FunctionDecl *FD, MultiLevelTemplateArgumentList MLTAL, diff --git a/clang/test/SemaTemplate/concepts-lambda.cpp b/clang/test/SemaTemplate/concepts-lambda.cpp index dcb09c76d26b6..1f67c2511e096 100644 --- a/clang/test/SemaTemplate/concepts-lambda.cpp +++ b/clang/test/SemaTemplate/concepts-lambda.cpp @@ -325,3 +325,18 @@ template <class> void f() { template void f<int>(); } + +namespace GH133719 { + +template <class T> +constexpr auto f{[] (auto arg) { + return [a{arg}] { + [] () requires true {}(); + }; +}}; + +void foo() { + f<int>(0); +} + +} _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
