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When checking the constraint of a lambda, we need to respect the constness
of the call operator when establishing the type of capture variables.
In D124351 <https://reviews.llvm.org/D124351>, this was done by adding const to
the captured variable...
However, that would change the type of the variable outside of the scope
of the lambda, which is clearly not the desired outcome.
Instead, to ensure const-correctness, we need to populate
a LambdaScopeInfo with the capture variables before checking the
constraints of a generic lambda.
There is no changelog as I'd like to tentatively propose we backport
this change to RC3 as it is a regression introduced in the Clang 17
cycle.
Fixes #61267
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D158433
Files:
clang/include/clang/Sema/Sema.h
clang/lib/Sema/SemaConcept.cpp
clang/lib/Sema/SemaDecl.cpp
clang/lib/Sema/SemaExpr.cpp
clang/test/SemaCXX/lambda-capture-type-deduction.cpp
Index: clang/test/SemaCXX/lambda-capture-type-deduction.cpp
===================================================================
--- clang/test/SemaCXX/lambda-capture-type-deduction.cpp
+++ clang/test/SemaCXX/lambda-capture-type-deduction.cpp
@@ -246,3 +246,17 @@
static_assert(is_same<int&, decltype((ap))>);
};
}
+
+namespace GH61267 {
+template <typename> concept C = true;
+
+template<typename>
+void f(int) {
+ int i;
+ [i]<C P>(P) {}(0);
+ i = 4;
+}
+
+void test() { f<int>(0); }
+
+}
Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -19723,13 +19723,6 @@
FunctionScopesIndex == MaxFunctionScopesIndex && VarDC == DC)
return true;
- // When evaluating some attributes (like enable_if) we might refer to a
- // function parameter appertaining to the same declaration as that
- // attribute.
- if (const auto *Parm = dyn_cast<ParmVarDecl>(Var);
- Parm && Parm->getDeclContext() == DC)
- return true;
-
// Only block literals, captured statements, and lambda expressions can
// capture; other scopes don't work.
DeclContext *ParentDC =
@@ -19757,6 +19750,14 @@
CSI->getCapture(Var).markUsed(BuildAndDiagnose);
break;
}
+
+ // When evaluating some attributes (like enable_if) we might refer to a
+ // function parameter appertaining to the same declaration as that
+ // attribute.
+ if (const auto *Parm = dyn_cast<ParmVarDecl>(Var);
+ Parm && Parm->getDeclContext() == DC)
+ return true;
+
// If we are instantiating a generic lambda call operator body,
// we do not want to capture new variables. What was captured
// during either a lambdas transformation or initial parsing
Index: clang/lib/Sema/SemaDecl.cpp
===================================================================
--- clang/lib/Sema/SemaDecl.cpp
+++ clang/lib/Sema/SemaDecl.cpp
@@ -15289,11 +15289,10 @@
FD->setInvalidDecl();
}
-static void RebuildLambdaScopeInfo(CXXMethodDecl *CallOperator,
- Sema &S) {
- CXXRecordDecl *const LambdaClass = CallOperator->getParent();
+LambdaScopeInfo *Sema::RebuildLambdaScopeInfo(CXXMethodDecl *CallOperator) {
+ CXXRecordDecl *LambdaClass = CallOperator->getParent();
- LambdaScopeInfo *LSI = S.PushLambdaScope();
+ LambdaScopeInfo *LSI = PushLambdaScope();
LSI->CallOperator = CallOperator;
LSI->Lambda = LambdaClass;
LSI->ReturnType = CallOperator->getReturnType();
@@ -15317,7 +15316,7 @@
if (C.capturesVariable()) {
ValueDecl *VD = C.getCapturedVar();
if (VD->isInitCapture())
- S.CurrentInstantiationScope->InstantiatedLocal(VD, VD);
+ CurrentInstantiationScope->InstantiatedLocal(VD, VD);
const bool ByRef = C.getCaptureKind() == LCK_ByRef;
LSI->addCapture(VD, /*IsBlock*/false, ByRef,
/*RefersToEnclosingVariableOrCapture*/true, C.getLocation(),
@@ -15334,6 +15333,7 @@
}
++I;
}
+ return LSI;
}
Decl *Sema::ActOnStartOfFunctionDef(Scope *FnBodyScope, Decl *D,
@@ -15437,7 +15437,7 @@
assert(inTemplateInstantiation() &&
"There should be an active template instantiation on the stack "
"when instantiating a generic lambda!");
- RebuildLambdaScopeInfo(cast<CXXMethodDecl>(D), *this);
+ RebuildLambdaScopeInfo(cast<CXXMethodDecl>(D));
} else {
// Enter a new function scope
PushFunctionScope();
Index: clang/lib/Sema/SemaConcept.cpp
===================================================================
--- clang/lib/Sema/SemaConcept.cpp
+++ clang/lib/Sema/SemaConcept.cpp
@@ -13,12 +13,14 @@
#include "clang/Sema/SemaConcept.h"
#include "TreeTransform.h"
#include "clang/AST/ASTLambda.h"
+#include "clang/AST/DeclCXX.h"
#include "clang/AST/ExprConcepts.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/Basic/OperatorPrecedence.h"
#include "clang/Sema/EnterExpressionEvaluationContext.h"
#include "clang/Sema/Initialization.h"
#include "clang/Sema/Overload.h"
+#include "clang/Sema/ScopeInfo.h"
#include "clang/Sema/Sema.h"
#include "clang/Sema/SemaDiagnostic.h"
#include "clang/Sema/SemaInternal.h"
@@ -540,11 +542,6 @@
auto AddSingleCapture = [&](const ValueDecl *CapturedPattern,
unsigned Index) {
ValueDecl *CapturedVar = LambdaClass->getCapture(Index)->getCapturedVar();
- if (cast<CXXMethodDecl>(Function)->isConst()) {
- QualType T = CapturedVar->getType();
- T.addConst();
- CapturedVar->setType(T);
- }
if (CapturedVar->isInitCapture())
Scope.InstantiatedLocal(CapturedPattern, CapturedVar);
};
@@ -714,6 +711,19 @@
Record = const_cast<CXXRecordDecl *>(Method->getParent());
}
CXXThisScopeRAII ThisScope(*this, Record, ThisQuals, Record != nullptr);
+
+ // When checking the constraints of a lambda, we need to restore a
+ // LambdaScopeInfo populated with correct capture information so that the type
+ // of a variable referring to a capture is correctly const-adjusted.
+ FunctionScopeRAII FuncScope(*this);
+ if (isLambdaCallOperator(FD)) {
+ LambdaScopeInfo *LSI = RebuildLambdaScopeInfo(
+ const_cast<CXXMethodDecl *>(cast<CXXMethodDecl>(FD)));
+ // Captures are not checked from within the lambda.
+ LSI->AfterParameterList = false;
+ } else
+ FuncScope.disable();
+
return CheckConstraintSatisfaction(
FD, {FD->getTrailingRequiresClause()}, *MLTAL,
SourceRange(UsageLoc.isValid() ? UsageLoc : FD->getLocation()),
@@ -902,9 +912,11 @@
}
CXXThisScopeRAII ThisScope(*this, Record, ThisQuals, Record != nullptr);
FunctionScopeRAII FuncScope(*this);
- if (isLambdaCallOperator(Decl))
- PushLambdaScope();
- else
+
+ if (isLambdaCallOperator(Decl)) {
+ LambdaScopeInfo *LSI = RebuildLambdaScopeInfo(cast<CXXMethodDecl>(Decl));
+ LSI->AfterParameterList = false;
+ } else
FuncScope.disable();
llvm::SmallVector<Expr *, 1> Converted;
Index: clang/include/clang/Sema/Sema.h
===================================================================
--- clang/include/clang/Sema/Sema.h
+++ clang/include/clang/Sema/Sema.h
@@ -7344,6 +7344,8 @@
CXXConversionDecl *Conv,
Expr *Src);
+ sema::LambdaScopeInfo *RebuildLambdaScopeInfo(CXXMethodDecl *CallOperator);
+
/// Check whether the given expression is a valid constraint expression.
/// A diagnostic is emitted if it is not, false is returned, and
/// PossibleNonPrimary will be set to true if the failure might be due to a
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