[llvm-branch-commits] [clang] release/20.x: [Clang] Fix a lambda pattern comparison mismatch after ecc7e6ce4 (#133863) (PR #134194)
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Wed Apr 2 20:47:37 PDT 2025
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 <zyn7109 at gmail.com>
Date: Thu, 3 Apr 2025 11:15:42 +0800
Subject: [PATCH] [Clang] Fix a lambda pattern comparison mismatch after
ecc7e6ce4 (#133863)
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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);
+}
+
+}
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