[clang] [Sema] Preserve ContainsUnexpandedParameterPack in TransformLambdaExpr (PR #86265)
Younan Zhang via cfe-commits
cfe-commits at lists.llvm.org
Thu Jul 18 00:27:12 PDT 2024
https://github.com/zyn0217 updated https://github.com/llvm/llvm-project/pull/86265
>From 6e7b38b3e3f781e11db2fa5d552fdfb6123609df Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Fri, 22 Mar 2024 17:34:08 +0800
Subject: [PATCH 01/10] [Sema] Preserve ContainsUnexpandedParameterPack in
TransformLambdaExpr
---
clang/docs/ReleaseNotes.rst | 2 +
clang/include/clang/Sema/Sema.h | 8 +++
clang/lib/Sema/SemaTemplateVariadic.cpp | 16 +++++-
clang/lib/Sema/TreeTransform.h | 18 ++++++
.../test/SemaTemplate/lambda-capture-pack.cpp | 57 +++++++++++++++++++
5 files changed, 98 insertions(+), 3 deletions(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 690fc7ed271a3..2d11a4b8c092a 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -344,6 +344,8 @@ Bug Fixes to C++ Support
when one of the function had more specialized templates.
Fixes (`#82509 <https://github.com/llvm/llvm-project/issues/82509>`_)
and (`#74494 <https://github.com/llvm/llvm-project/issues/74494>`_)
+- Fixed a crash where template parameter packs were not expanded correctly in a lambda being
+ used as a pattern of a folded expression. (#GH56852), (#GH85667)
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index cfc1c3b349478..0d1a2e54840e5 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -11201,6 +11201,14 @@ class Sema final {
void collectUnexpandedParameterPacks(
QualType T, SmallVectorImpl<UnexpandedParameterPack> &Unexpanded);
+ /// Collect the set of unexpanded parameter packs from a lambda call operator.
+ ///
+ /// \param LambdaCall The lambda call operator that will be traversed to find
+ /// unexpanded parameter packs.
+ void collectUnexpandedParameterPacksFromLambda(
+ CXXMethodDecl *LambdaCall,
+ SmallVectorImpl<UnexpandedParameterPack> &Unexpanded);
+
/// Collect the set of unexpanded parameter packs within the given
/// type.
///
diff --git a/clang/lib/Sema/SemaTemplateVariadic.cpp b/clang/lib/Sema/SemaTemplateVariadic.cpp
index 903fbfd18e779..638ceac4148ae 100644
--- a/clang/lib/Sema/SemaTemplateVariadic.cpp
+++ b/clang/lib/Sema/SemaTemplateVariadic.cpp
@@ -8,14 +8,15 @@
// This file implements semantic analysis for C++0x variadic templates.
//===----------------------------------------------------------------------===/
-#include "clang/Sema/Sema.h"
#include "TypeLocBuilder.h"
+#include "clang/AST/ASTLambda.h"
#include "clang/AST/Expr.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/AST/TypeLoc.h"
#include "clang/Sema/Lookup.h"
#include "clang/Sema/ParsedTemplate.h"
#include "clang/Sema/ScopeInfo.h"
+#include "clang/Sema/Sema.h"
#include "clang/Sema/SemaInternal.h"
#include "clang/Sema/Template.h"
#include <optional>
@@ -61,8 +62,9 @@ namespace {
public:
explicit CollectUnexpandedParameterPacksVisitor(
- SmallVectorImpl<UnexpandedParameterPack> &Unexpanded)
- : Unexpanded(Unexpanded) {}
+ SmallVectorImpl<UnexpandedParameterPack> &Unexpanded,
+ bool InLambda = false)
+ : Unexpanded(Unexpanded), InLambda(InLambda) {}
bool shouldWalkTypesOfTypeLocs() const { return false; }
@@ -544,6 +546,14 @@ void Sema::collectUnexpandedParameterPacks(QualType T,
CollectUnexpandedParameterPacksVisitor(Unexpanded).TraverseType(T);
}
+void Sema::collectUnexpandedParameterPacksFromLambda(
+ CXXMethodDecl *LambdaCall,
+ SmallVectorImpl<UnexpandedParameterPack> &Unexpanded) {
+ assert(isLambdaCallOperator(LambdaCall) && "Expected a lambda call operator");
+ CollectUnexpandedParameterPacksVisitor(Unexpanded, /*InLambda=*/true)
+ .TraverseDecl(LambdaCall);
+}
+
void Sema::collectUnexpandedParameterPacks(TypeLoc TL,
SmallVectorImpl<UnexpandedParameterPack> &Unexpanded) {
CollectUnexpandedParameterPacksVisitor(Unexpanded).TraverseTypeLoc(TL);
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 2d22692f3ab75..f5a859c57034a 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -13748,6 +13748,8 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
}
NewVDs.push_back(NewVD);
getSema().addInitCapture(LSI, NewVD, C->getCaptureKind() == LCK_ByRef);
+ LSI->ContainsUnexpandedParameterPack |=
+ Init.get()->containsUnexpandedParameterPack();
}
if (Invalid)
@@ -13936,6 +13938,22 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
/*IsInstantiation*/ true);
SavedContext.pop();
+ // The lambda may contain a pack that would be expanded by a fold expression
+ // outside. We should preserve the ContainsUnexpandedParameterPack flag here
+ // because CXXFoldExprs use it for the pattern.
+ // For example,
+ //
+ // []<class... Is>() { ([I = Is()]() {}, ...); }
+ //
+ // forgetting the flag will result in getPattern() of CXXFoldExpr returning
+ // null in terms of the inner lambda.
+ if (!LSICopy.ContainsUnexpandedParameterPack) {
+ llvm::SmallVector<UnexpandedParameterPack> UnexpandedPacks;
+ getSema().collectUnexpandedParameterPacksFromLambda(NewCallOperator,
+ UnexpandedPacks);
+ // Should we call DiagnoseUnexpandedParameterPacks() instead?
+ LSICopy.ContainsUnexpandedParameterPack = !UnexpandedPacks.empty();
+ }
return getSema().BuildLambdaExpr(E->getBeginLoc(), Body.get()->getEndLoc(),
&LSICopy);
}
diff --git a/clang/test/SemaTemplate/lambda-capture-pack.cpp b/clang/test/SemaTemplate/lambda-capture-pack.cpp
index 35b2ffcefea35..31d85e1689af1 100644
--- a/clang/test/SemaTemplate/lambda-capture-pack.cpp
+++ b/clang/test/SemaTemplate/lambda-capture-pack.cpp
@@ -23,3 +23,60 @@ namespace PR41576 {
}
static_assert(f(3, 4) == 6); // expected-note {{instantiation}}
}
+
+namespace PR85667 {
+
+template <class T>
+struct identity {
+ using type = T;
+};
+
+template <class = void> void f() {
+
+ static_assert([]<class... Is>(Is... x) {
+ return ([I(x)] {
+ return I;
+ }() + ...);
+ }(1, 2) == 3);
+
+ static_assert([]<class... Is>(Is... x) {
+ return ([](auto y = Is()) { return y + 1; } + ...);
+ }(0, 0, 0) == 3);
+
+ []<class... Is>() {
+ return ([]() noexcept(Is()) { return 0; }() + ...);
+ }.template operator()<int, int>();
+
+ static_assert(__is_same(decltype([]<class... Is>() {
+ return ([]() -> decltype(Is()) { return {}; }(),
+ ...);
+ }.template operator()<int, char>()),
+ char));
+
+ []<class... Is>() {
+ return ([]<class... Ts>() -> decltype(Is()) { return Ts(); }() + ...);
+ // expected-error at -1 {{unexpanded parameter pack 'Ts'}}
+ }.template operator()<int, int>();
+
+ // Note that GCC and EDG reject this case currently.
+ // GCC says the fold expression "has no unexpanded parameter packs", while
+ // EDG says the constraint is not allowed on a non-template function.
+ // MSVC is happy with it.
+ []<class... Is>() {
+ ([]()
+ requires(Is())
+ {},
+ ...);
+ }.template operator()<bool, bool>();
+
+ // https://github.com/llvm/llvm-project/issues/56852
+ []<class... Is>(Is...) {
+ ([] {
+ using T = identity<Is>::type;
+ }(), ...);
+ }(1, 2);
+}
+
+template void f();
+
+}
>From e76fedd9fbe557f5c9a9f980a141c2ed31c24424 Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Sat, 23 Mar 2024 19:39:37 +0800
Subject: [PATCH 02/10] Consider the captured pack variables - gh18873
---
clang/docs/ReleaseNotes.rst | 4 ++--
clang/lib/Sema/TreeTransform.h | 4 ++++
.../test/SemaTemplate/lambda-capture-pack.cpp | 21 +++++++++++++++++++
3 files changed, 27 insertions(+), 2 deletions(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 2d11a4b8c092a..41529cbc9bd9a 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -344,8 +344,8 @@ Bug Fixes to C++ Support
when one of the function had more specialized templates.
Fixes (`#82509 <https://github.com/llvm/llvm-project/issues/82509>`_)
and (`#74494 <https://github.com/llvm/llvm-project/issues/74494>`_)
-- Fixed a crash where template parameter packs were not expanded correctly in a lambda being
- used as a pattern of a folded expression. (#GH56852), (#GH85667)
+- Fixed a crash where template parameter packs were not expanded correctly in a lambda used
+ as the pattern of a folded expression. (#GH56852), (#GH85667), and partially fixes (#GH18873).
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index f5a859c57034a..fb29e5111fc54 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -13817,6 +13817,10 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
continue;
}
+ if (auto *PVD = dyn_cast<VarDecl>(CapturedVar);
+ PVD && !C->isPackExpansion())
+ LSI->ContainsUnexpandedParameterPack |= PVD->isParameterPack();
+
// Capture the transformed variable.
getSema().tryCaptureVariable(CapturedVar, C->getLocation(), Kind,
EllipsisLoc);
diff --git a/clang/test/SemaTemplate/lambda-capture-pack.cpp b/clang/test/SemaTemplate/lambda-capture-pack.cpp
index 31d85e1689af1..8a81417b6daee 100644
--- a/clang/test/SemaTemplate/lambda-capture-pack.cpp
+++ b/clang/test/SemaTemplate/lambda-capture-pack.cpp
@@ -75,6 +75,27 @@ template <class = void> void f() {
using T = identity<Is>::type;
}(), ...);
}(1, 2);
+
+ // https://github.com/llvm/llvm-project/issues/18873
+ [](auto ...y) {
+ ([y] { }, ...);
+ }();
+
+ [](auto ...x) {
+ ([&](auto ...y) {
+ // FIXME: This now hits the assertion with `PackIdx != -1 && "found declaration pack but not pack expanding"'
+ // in Sema::FindInstantiatedDecl.
+ // This is because the captured variable x has been expanded while transforming
+ // the outermost lambda call, but the expansion then gets holded off while transforming
+ // the folded expression. Then we would hit the assertion when instantiating the captured variable
+ // in TransformLambdaExpr.
+ // I think this is supposed to be ill-formed, but GCC and MSVC currently accept this.
+ // If x gets expanded with non-empty arguments, then GCC and MSVC will reject it - we probably
+ // miss a diagnostic for it.
+ // ([x, y] { }, ...);
+ ([x..., y] { }, ...);
+ })();
+ }();
}
template void f();
>From faf5d8710ba0177685cd65c6b81cf79b97223e4b Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Sat, 23 Mar 2024 23:00:51 +0800
Subject: [PATCH 03/10] comments
---
clang/lib/Sema/TreeTransform.h | 4 ++++
clang/test/SemaTemplate/lambda-capture-pack.cpp | 12 ++++++------
2 files changed, 10 insertions(+), 6 deletions(-)
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 0e2ea13d64d46..31592e6557f0d 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -13786,6 +13786,8 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
}
NewVDs.push_back(NewVD);
getSema().addInitCapture(LSI, NewVD, C->getCaptureKind() == LCK_ByRef);
+ // The initializer might be expanded later. This may happen
+ // if the lambda is within a folded expression.
LSI->ContainsUnexpandedParameterPack |=
Init.get()->containsUnexpandedParameterPack();
}
@@ -13855,6 +13857,8 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
continue;
}
+ // The captured variable might be expanded later. This may happen
+ // if the lambda is within a folded expression.
if (auto *PVD = dyn_cast<VarDecl>(CapturedVar);
PVD && !C->isPackExpansion())
LSI->ContainsUnexpandedParameterPack |= PVD->isParameterPack();
diff --git a/clang/test/SemaTemplate/lambda-capture-pack.cpp b/clang/test/SemaTemplate/lambda-capture-pack.cpp
index 8a81417b6daee..506902bc99dc6 100644
--- a/clang/test/SemaTemplate/lambda-capture-pack.cpp
+++ b/clang/test/SemaTemplate/lambda-capture-pack.cpp
@@ -83,15 +83,15 @@ template <class = void> void f() {
[](auto ...x) {
([&](auto ...y) {
- // FIXME: This now hits the assertion with `PackIdx != -1 && "found declaration pack but not pack expanding"'
+ // FIXME: This now hits assertion `PackIdx != -1 && "found declaration pack but not pack expanding"'
// in Sema::FindInstantiatedDecl.
// This is because the captured variable x has been expanded while transforming
- // the outermost lambda call, but the expansion then gets holded off while transforming
- // the folded expression. Then we would hit the assertion when instantiating the captured variable
- // in TransformLambdaExpr.
+ // the outermost lambda call, but the expansion is held off while transforming
+ // the folded expression. Then, we would hit the assertion when instantiating the
+ // captured variable in TransformLambdaExpr.
// I think this is supposed to be ill-formed, but GCC and MSVC currently accept this.
- // If x gets expanded with non-empty arguments, then GCC and MSVC will reject it - we probably
- // miss a diagnostic for it.
+ // However, if x gets expanded with non-empty arguments, then GCC and MSVC will reject it -
+ // we probably need a diagnostic for it.
// ([x, y] { }, ...);
([x..., y] { }, ...);
})();
>From c5765ec62f1d32b1cd817c8c78ef7b2d21bf296e Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Sun, 24 Mar 2024 00:15:14 +0800
Subject: [PATCH 04/10] format
---
clang/lib/Sema/TreeTransform.h | 34 ++++++++++++++++++++++++----------
1 file changed, 24 insertions(+), 10 deletions(-)
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index 31592e6557f0d..e2ec9b7085737 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -13786,8 +13786,9 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
}
NewVDs.push_back(NewVD);
getSema().addInitCapture(LSI, NewVD, C->getCaptureKind() == LCK_ByRef);
- // The initializer might be expanded later. This may happen
- // if the lambda is within a folded expression.
+ // If the lambda is written within a fold expression, the initializer
+ // may be expanded later. Preserve the ContainsUnexpandedParameterPack
+ // flag because CXXFoldExpr uses it for the pattern.
LSI->ContainsUnexpandedParameterPack |=
Init.get()->containsUnexpandedParameterPack();
}
@@ -13848,6 +13849,17 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
EllipsisLoc = C->getEllipsisLoc();
}
+#if 0
+ else if (auto *PVD = cast<VarDecl>(C->getCapturedVar()); PVD->isParameterPack()) {
+ // If the lambda is written within a fold expression, the captured
+ // variable may be expanded later. Preserve the
+ // ContainsUnexpandedParameterPack flag because CXXFoldExpr uses it for the
+ // pattern.
+ LSI->ContainsUnexpandedParameterPack |= true;
+ getSema().tryCaptureVariable(PVD, C->getLocation(), Kind, EllipsisLoc);
+ continue;
+ }
+#endif
// Transform the captured variable.
auto *CapturedVar = cast_or_null<ValueDecl>(
@@ -13857,11 +13869,15 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
continue;
}
- // The captured variable might be expanded later. This may happen
- // if the lambda is within a folded expression.
+ // If the lambda is written within a fold expression, the captured
+ // variable may be expanded later. Preserve the
+ // ContainsUnexpandedParameterPack flag because CXXFoldExpr uses it for the
+ // pattern.
+#if 1
if (auto *PVD = dyn_cast<VarDecl>(CapturedVar);
PVD && !C->isPackExpansion())
LSI->ContainsUnexpandedParameterPack |= PVD->isParameterPack();
+#endif
// Capture the transformed variable.
getSema().tryCaptureVariable(CapturedVar, C->getLocation(), Kind,
@@ -13984,12 +14000,10 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
/*IsInstantiation*/ true);
SavedContext.pop();
- // The lambda may contain a pack that would be expanded by a fold expression
- // outside. We should preserve the ContainsUnexpandedParameterPack flag here
- // because CXXFoldExprs use it for the pattern.
- // For example,
+ // The lambda function might contain a pack that would be expanded by a fold
+ // expression outside. For example,
//
- // []<class... Is>() { ([I = Is()]() {}, ...); }
+ // []<class... Is>() { ([](auto P = Is()) {}, ...); }
//
// forgetting the flag will result in getPattern() of CXXFoldExpr returning
// null in terms of the inner lambda.
@@ -13997,7 +14011,7 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
llvm::SmallVector<UnexpandedParameterPack> UnexpandedPacks;
getSema().collectUnexpandedParameterPacksFromLambda(NewCallOperator,
UnexpandedPacks);
- // Should we call DiagnoseUnexpandedParameterPacks() instead?
+ // FIXME: Should we call DiagnoseUnexpandedParameterPacks() instead?
LSICopy.ContainsUnexpandedParameterPack = !UnexpandedPacks.empty();
}
return getSema().BuildLambdaExpr(E->getBeginLoc(), Body.get()->getEndLoc(),
>From 6c2d311938839092f8fd1c5334673c6e35fe4651 Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Fri, 3 May 2024 21:50:42 +0800
Subject: [PATCH 05/10] Retain the 'unexpanded' Decls
---
.../lib/Sema/SemaTemplateInstantiateDecl.cpp | 8 ++++++
.../test/SemaTemplate/lambda-capture-pack.cpp | 26 +++++++++----------
2 files changed, 21 insertions(+), 13 deletions(-)
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 787a485e0b2f8..ac96449221384 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -6221,6 +6221,14 @@ NamedDecl *Sema::FindInstantiatedDecl(SourceLocation Loc, NamedDecl *D,
return cast<NamedDecl>(FD);
int PackIdx = ArgumentPackSubstitutionIndex;
+ // FIXME: Move it elsewhere e.g. TreeTransform::TransformDecl.
+ // This is for #18873.
+ if (PackIdx == -1) {
+ LocalInstantiationScope LIS(*this, /*CombineWithOuterScope=*/false);
+ MultiLevelTemplateArgumentList FakeArgs;
+ FakeArgs.addOuterRetainedLevels(D->getTemplateDepth() + 1);
+ return cast_if_present<NamedDecl>(SubstDecl(D, CurContext, FakeArgs));
+ }
assert(PackIdx != -1 &&
"found declaration pack but not pack expanding");
typedef LocalInstantiationScope::DeclArgumentPack DeclArgumentPack;
diff --git a/clang/test/SemaTemplate/lambda-capture-pack.cpp b/clang/test/SemaTemplate/lambda-capture-pack.cpp
index 506902bc99dc6..12cb2ba6cb86e 100644
--- a/clang/test/SemaTemplate/lambda-capture-pack.cpp
+++ b/clang/test/SemaTemplate/lambda-capture-pack.cpp
@@ -83,21 +83,21 @@ template <class = void> void f() {
[](auto ...x) {
([&](auto ...y) {
- // FIXME: This now hits assertion `PackIdx != -1 && "found declaration pack but not pack expanding"'
- // in Sema::FindInstantiatedDecl.
- // This is because the captured variable x has been expanded while transforming
- // the outermost lambda call, but the expansion is held off while transforming
- // the folded expression. Then, we would hit the assertion when instantiating the
- // captured variable in TransformLambdaExpr.
- // I think this is supposed to be ill-formed, but GCC and MSVC currently accept this.
- // However, if x gets expanded with non-empty arguments, then GCC and MSVC will reject it -
- // we probably need a diagnostic for it.
- // ([x, y] { }, ...);
([x..., y] { }, ...);
- })();
- }();
+ })(1);
+ }(2, 'b');
+
+ [](auto ...x) { // #outer
+ ([&](auto ...y) { // #inner
+ ([x, y] { }, ...);
+ // expected-error at -1 {{parameter pack 'y' that has a different length (4 vs. 3) from outer parameter packs}}
+ // expected-note-re@#inner {{function template specialization {{.*}} requested here}}
+ // expected-note-re@#outer {{function template specialization {{.*}} requested here}}
+ // expected-note-re@#instantiate-f {{function template specialization {{.*}} requested here}}
+ })('a', 'b', 'c');
+ }(0, 1, 2, 3);
}
-template void f();
+template void f(); // #instantiate-f
}
>From 1ac5ca73a1dd6084cae9ec54546f56fc18d7e0bc Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Fri, 3 May 2024 22:11:49 +0800
Subject: [PATCH 06/10] Update ReleaseNotes
---
clang/docs/ReleaseNotes.rst | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 81a6d67f42f7e..dd488f7ec17d1 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -561,7 +561,7 @@ Bug Fixes to C++ Support
- Fixed a crash when trying to evaluate a user-defined ``static_assert`` message whose ``size()``
function returns a large or negative value. Fixes (#GH89407).
- Fixed a crash where template parameter packs were not expanded correctly in a lambda used
- as the pattern of a folded expression. (#GH56852), (#GH85667), and partially fixed (#GH18873).
+ as the pattern of a folded expression. (#GH56852), (#GH85667) and (#GH18873).
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
>From db36bc87d2a5bb64a918a53636f3f97524f883ad Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Wed, 8 May 2024 09:50:01 +0800
Subject: [PATCH 07/10] Cleanup & silence the unused-expression warning
---
clang/lib/Sema/TreeTransform.h | 18 ++----------------
.../test/SemaTemplate/lambda-capture-pack.cpp | 12 +++++++++---
2 files changed, 11 insertions(+), 19 deletions(-)
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index ec14129259f83..e765d25ee606f 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -14092,17 +14092,6 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
EllipsisLoc = C->getEllipsisLoc();
}
-#if 0
- else if (auto *PVD = cast<VarDecl>(C->getCapturedVar()); PVD->isParameterPack()) {
- // If the lambda is written within a fold expression, the captured
- // variable may be expanded later. Preserve the
- // ContainsUnexpandedParameterPack flag because CXXFoldExpr uses it for the
- // pattern.
- LSI->ContainsUnexpandedParameterPack |= true;
- getSema().tryCaptureVariable(PVD, C->getLocation(), Kind, EllipsisLoc);
- continue;
- }
-#endif
// Transform the captured variable.
auto *CapturedVar = cast_or_null<ValueDecl>(
@@ -14116,11 +14105,8 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
// variable may be expanded later. Preserve the
// ContainsUnexpandedParameterPack flag because CXXFoldExpr uses it for the
// pattern.
-#if 1
- if (auto *PVD = dyn_cast<VarDecl>(CapturedVar);
- PVD && !C->isPackExpansion())
- LSI->ContainsUnexpandedParameterPack |= PVD->isParameterPack();
-#endif
+ LSI->ContainsUnexpandedParameterPack |=
+ cast<VarDecl>(CapturedVar)->isParameterPack();
// Capture the transformed variable.
getSema().tryCaptureVariable(CapturedVar, C->getLocation(), Kind,
diff --git a/clang/test/SemaTemplate/lambda-capture-pack.cpp b/clang/test/SemaTemplate/lambda-capture-pack.cpp
index 12cb2ba6cb86e..7b22c724eb20e 100644
--- a/clang/test/SemaTemplate/lambda-capture-pack.cpp
+++ b/clang/test/SemaTemplate/lambda-capture-pack.cpp
@@ -78,18 +78,24 @@ template <class = void> void f() {
// https://github.com/llvm/llvm-project/issues/18873
[](auto ...y) {
- ([y] { }, ...);
+ ([y] { }(), ...);
}();
[](auto ...x) {
([&](auto ...y) {
- ([x..., y] { }, ...);
+ ([x..., y] { }(), ...);
})(1);
}(2, 'b');
+ [](auto ...x) {
+ ([&](auto ...y) {
+ ([x, y] { }(), ...);
+ })(1, 'a');
+ }(2, 'b');
+
[](auto ...x) { // #outer
([&](auto ...y) { // #inner
- ([x, y] { }, ...);
+ ([x, y] { }(), ...);
// expected-error at -1 {{parameter pack 'y' that has a different length (4 vs. 3) from outer parameter packs}}
// expected-note-re@#inner {{function template specialization {{.*}} requested here}}
// expected-note-re@#outer {{function template specialization {{.*}} requested here}}
>From 66acffb605aa724f59a2667bc3e542a23163e1e3 Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Fri, 24 May 2024 13:33:20 +0800
Subject: [PATCH 08/10] Fix the CI
---
clang/lib/Sema/TreeTransform.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index e765d25ee606f..3be68d8d251f3 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -14105,8 +14105,8 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
// variable may be expanded later. Preserve the
// ContainsUnexpandedParameterPack flag because CXXFoldExpr uses it for the
// pattern.
- LSI->ContainsUnexpandedParameterPack |=
- cast<VarDecl>(CapturedVar)->isParameterPack();
+ if (auto *VD = dyn_cast<VarDecl>(CapturedVar); VD && !C->isPackExpansion())
+ LSI->ContainsUnexpandedParameterPack |= VD->isParameterPack();
// Capture the transformed variable.
getSema().tryCaptureVariable(CapturedVar, C->getLocation(), Kind,
>From 5285c104ed526311edc4a54842ca7844410d4780 Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Fri, 24 May 2024 13:34:00 +0800
Subject: [PATCH 09/10] Fix typos
---
clang/lib/Sema/SemaTemplateDeduction.cpp | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 0b6375001f532..2af3c44f49b3c 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -4296,7 +4296,7 @@ TemplateDeductionResult Sema::DeduceTemplateArguments(
// Deduce an argument of type ParamType from an expression with index ArgIdx.
auto DeduceCallArgument = [&](QualType ParamType, unsigned ArgIdx,
- bool ExplicitObjetArgument) {
+ bool ExplicitObjectArgument) {
// C++ [demp.deduct.call]p1: (DR1391)
// Template argument deduction is done by comparing each function template
// parameter that contains template-parameters that participate in
@@ -4304,7 +4304,7 @@ TemplateDeductionResult Sema::DeduceTemplateArguments(
if (!hasDeducibleTemplateParameters(*this, FunctionTemplate, ParamType))
return TemplateDeductionResult::Success;
- if (ExplicitObjetArgument) {
+ if (ExplicitObjectArgument) {
// ... with the type of the corresponding argument
return DeduceTemplateArgumentsFromCallArgument(
*this, TemplateParams, FirstInnerIndex, ParamType, ObjectType,
>From b2d28364d1729b3f90b37905b91554b9a5d75423 Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Thu, 18 Jul 2024 14:28:52 +0800
Subject: [PATCH 10/10] Fixup
---
.../lib/Sema/SemaTemplateInstantiateDecl.cpp | 8 -----
clang/lib/Sema/TreeTransform.h | 25 +++++++---------
.../test/SemaTemplate/lambda-capture-pack.cpp | 29 +++++++++++++++----
3 files changed, 34 insertions(+), 28 deletions(-)
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 896e38d45326e..01432301633ed 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -6113,14 +6113,6 @@ NamedDecl *Sema::FindInstantiatedDecl(SourceLocation Loc, NamedDecl *D,
return cast<NamedDecl>(FD);
int PackIdx = ArgumentPackSubstitutionIndex;
- // FIXME: Move it elsewhere e.g. TreeTransform::TransformDecl.
- // This is for #18873.
- if (PackIdx == -1) {
- LocalInstantiationScope LIS(*this, /*CombineWithOuterScope=*/false);
- MultiLevelTemplateArgumentList FakeArgs;
- FakeArgs.addOuterRetainedLevels(D->getTemplateDepth() + 1);
- return cast_if_present<NamedDecl>(SubstDecl(D, CurContext, FakeArgs));
- }
assert(PackIdx != -1 &&
"found declaration pack but not pack expanding");
typedef LocalInstantiationScope::DeclArgumentPack DeclArgumentPack;
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index ba074bc636361..1afe05d9ad524 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -14443,9 +14443,7 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
}
NewVDs.push_back(NewVD);
getSema().addInitCapture(LSI, NewVD, C->getCaptureKind() == LCK_ByRef);
- // If the lambda is written within a fold expression, the initializer
- // may be expanded later. Preserve the ContainsUnexpandedParameterPack
- // flag because CXXFoldExpr uses it for the pattern.
+ // The Init expression might be expanded by an outer fold expression.
LSI->ContainsUnexpandedParameterPack |=
Init.get()->containsUnexpandedParameterPack();
}
@@ -14515,10 +14513,7 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
continue;
}
- // If the lambda is written within a fold expression, the captured
- // variable may be expanded later. Preserve the
- // ContainsUnexpandedParameterPack flag because CXXFoldExpr uses it for the
- // pattern.
+ // The captured pack might be expanded by an outer fold expression.
if (auto *VD = dyn_cast<VarDecl>(CapturedVar); VD && !C->isPackExpansion())
LSI->ContainsUnexpandedParameterPack |= VD->isParameterPack();
@@ -14574,6 +14569,8 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
if (NewCallOpType.isNull())
return ExprError();
+ LSI->ContainsUnexpandedParameterPack |=
+ NewCallOpType->containsUnexpandedParameterPack();
NewCallOpTSI =
NewCallOpTLBuilder.getTypeSourceInfo(getSema().Context, NewCallOpType);
}
@@ -14648,18 +14645,18 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
/*IsInstantiation*/ true);
SavedContext.pop();
- // The lambda function might contain a pack that would be expanded by a fold
- // expression outside. For example,
+ // Parts other than the capture e.g. the lambda body might still contain a
+ // pattern that an outer fold expression would expand.
//
- // []<class... Is>() { ([](auto P = Is()) {}, ...); }
- //
- // forgetting the flag will result in getPattern() of CXXFoldExpr returning
- // null in terms of the inner lambda.
+ // We don't have a way to propagate up the ContainsUnexpandedParameterPack
+ // flag from a Stmt, so we have to revisit the lambda.
if (!LSICopy.ContainsUnexpandedParameterPack) {
llvm::SmallVector<UnexpandedParameterPack> UnexpandedPacks;
getSema().collectUnexpandedParameterPacksFromLambda(NewCallOperator,
UnexpandedPacks);
- // FIXME: Should we call DiagnoseUnexpandedParameterPacks() instead?
+ // FIXME: Should we call Sema::DiagnoseUnexpandedParameterPacks() instead?
+ // Unfortunately, that requires the LambdaScopeInfo to exist, which has been
+ // removed by ActOnFinishFunctionBody().
LSICopy.ContainsUnexpandedParameterPack = !UnexpandedPacks.empty();
}
// Recompute the dependency of the lambda so that we can defer the lambda call
diff --git a/clang/test/SemaTemplate/lambda-capture-pack.cpp b/clang/test/SemaTemplate/lambda-capture-pack.cpp
index 7b22c724eb20e..6d2ab50827759 100644
--- a/clang/test/SemaTemplate/lambda-capture-pack.cpp
+++ b/clang/test/SemaTemplate/lambda-capture-pack.cpp
@@ -76,7 +76,6 @@ template <class = void> void f() {
}(), ...);
}(1, 2);
- // https://github.com/llvm/llvm-project/issues/18873
[](auto ...y) {
([y] { }(), ...);
}();
@@ -87,11 +86,28 @@ template <class = void> void f() {
})(1);
}(2, 'b');
- [](auto ...x) {
- ([&](auto ...y) {
- ([x, y] { }(), ...);
- })(1, 'a');
- }(2, 'b');
+#if 0
+ // https://github.com/llvm/llvm-project/issues/18873
+ [](auto ...x) { // #1
+ ([&](auto ...y) { // #2
+ ([x, y] { }(), ...); // #3
+ })(1, 'a'); // #4
+ }(2, 'b'); // #5
+
+ // We run into another crash for the above lambda because of the absence of a
+ // mechanism that rebuilds an unexpanded pack from an expanded Decls.
+ //
+ // Basically, this happens after `x` at #1 being expanded when the template
+ // arguments at #5, deduced as <int, char>, are ready. When we want to
+ // instantiate the body of #1, we first instantiate the CallExpr at #4, which
+ // boils down to the lambda's instantiation at #2. To that end, we have to
+ // instantiate the body of it, which turns out to be #3. #3 is a CXXFoldExpr,
+ // and we immediately have to hold off on the expansion because we don't have
+ // corresponding template arguments for it. Therefore, we want to rebuild a
+ // CXXFoldExpr, which requires another pattern transformation of the lambda
+ // inside #3. Then we need to find an unexpanded form of such a Decl of x at
+ // the time of transforming the capture, which is impossible because the
+ // instantiated form has been expanded at #1!
[](auto ...x) { // #outer
([&](auto ...y) { // #inner
@@ -102,6 +118,7 @@ template <class = void> void f() {
// expected-note-re@#instantiate-f {{function template specialization {{.*}} requested here}}
})('a', 'b', 'c');
}(0, 1, 2, 3);
+#endif
}
template void f(); // #instantiate-f
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