llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-clang Author: Younan Zhang (zyn0217) <details> <summary>Changes</summary> 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 (I split up the commits to make the review easier. Also note that in #<!-- -->133719, Shafik and I discovered additional cases where clang behaves incorrectly. However, since those aren't regressions, their fixes aren't being considered at this time.) --- Full diff: https://github.com/llvm/llvm-project/pull/133863.diff 3 Files Affected: - (modified) clang/lib/Sema/SemaConcept.cpp (-69) - (modified) clang/lib/Sema/SemaLambda.cpp (+68) - (modified) clang/test/SemaTemplate/concepts-lambda.cpp (+15) ``````````diff diff --git a/clang/lib/Sema/SemaConcept.cpp b/clang/lib/Sema/SemaConcept.cpp index e7e0b4cfb72a7..2d29af4258cd7 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 292406f886362..6f114b71981fa 100644 --- a/clang/lib/Sema/SemaLambda.cpp +++ b/clang/lib/Sema/SemaLambda.cpp @@ -2412,6 +2412,74 @@ 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); +} + +} `````````` </details> https://github.com/llvm/llvm-project/pull/133863 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
