Reapply "[Clang] Profile singly-resolved UnresolvedLookupExpr with the declaration" #140680
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
…e declaration" (llvm#140655) This reverts commit 383e5f3.
llvmbot
added
clang
|
@llvm/pr-subscribers-clang Author: Younan Zhang (zyn0217) ChangesFor a dependent variable template specialization, we don't build a dependent Decl node or a DeclRefExpr to represent it. Instead, we preserve the UnresolvedLookupExpr until instantiation. However, this approach isn't ideal for constraint normalization. We consider the qualifier during profiling, but since that's based on the written code, it can introduce confusing differences, even when the expressions resolve to the same declaration. This change profiles the underlying VarTemplateDecl if UnresolvedLookupExpr is used to model a dependent use of it. Fixes #139476 Full diff: https://github.com/llvm/llvm-project/pull/140680.diff 4 Files Affected:
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index f04cb7b91788c..4c839303f3621 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -741,6 +741,7 @@ Bug Fixes to C++ Support
- Fixed the handling of pack indexing types in the constraints of a member function redeclaration. (#GH138255)
- Clang now correctly parses arbitrary order of ``[[]]``, ``__attribute__`` and ``alignas`` attributes for declarations (#GH133107)
- Fixed a crash when forming an invalid function type in a dependent context. (#GH138657) (#GH115725) (#GH68852)
+- Fixed a function declaration mismatch that caused inconsistencies between concepts and variable template declarations. (#GH139476)
- Clang no longer segfaults when there is a configuration mismatch between modules and their users (http://crbug.com/400353616).
- Fix an incorrect deduction when calling an explicit object member function template through an overload set address.
- Fixed bug in constant evaluation that would allow using the value of a
diff --git a/clang/lib/AST/StmtProfile.cpp b/clang/lib/AST/StmtProfile.cpp
index f7d1655f67ed1..2f1dec434c30b 100644
--- a/clang/lib/AST/StmtProfile.cpp
+++ b/clang/lib/AST/StmtProfile.cpp
@@ -2189,8 +2189,14 @@ StmtProfiler::VisitCXXPseudoDestructorExpr(const CXXPseudoDestructorExpr *S) {
void StmtProfiler::VisitOverloadExpr(const OverloadExpr *S) {
VisitExpr(S);
- VisitNestedNameSpecifier(S->getQualifier());
- VisitName(S->getName(), /*TreatAsDecl*/ true);
+ bool DescribingDependentVarTemplate =
+ S->getNumDecls() == 1 && isa<VarTemplateDecl>(*S->decls_begin());
+ if (DescribingDependentVarTemplate) {
+ VisitDecl(*S->decls_begin());
+ } else {
+ VisitNestedNameSpecifier(S->getQualifier());
+ VisitName(S->getName(), /*TreatAsDecl*/ true);
+ }
ID.AddBoolean(S->hasExplicitTemplateArgs());
if (S->hasExplicitTemplateArgs())
VisitTemplateArguments(S->getTemplateArgs(), S->getNumTemplateArgs());
diff --git a/clang/test/SemaCXX/exception-spec.cpp b/clang/test/SemaCXX/exception-spec.cpp
index 6ad19aab397bd..31c691b28da4b 100644
--- a/clang/test/SemaCXX/exception-spec.cpp
+++ b/clang/test/SemaCXX/exception-spec.cpp
@@ -52,3 +52,24 @@ namespace AssignmentOp {
D2 &operator=(const D2&); // expected-error {{more lax}}
};
}
+
+namespace OverloadedFunctions {
+
+template <typename T>
+void f(T&) noexcept;
+
+template <typename T, int N>
+void f(T (&arr)[N]) noexcept(noexcept(f(*arr)));
+
+template <typename T>
+inline void f(T&) noexcept {}
+
+template <typename T, int N>
+inline void f(T (&arr)[N]) noexcept(noexcept(f(*arr))) {}
+
+void g() {
+ int x[1];
+ f(x);
+}
+
+}
diff --git a/clang/test/SemaTemplate/concepts-out-of-line-def.cpp b/clang/test/SemaTemplate/concepts-out-of-line-def.cpp
index e5d00491d3fb8..bf505dec0ca14 100644
--- a/clang/test/SemaTemplate/concepts-out-of-line-def.cpp
+++ b/clang/test/SemaTemplate/concepts-out-of-line-def.cpp
@@ -853,3 +853,18 @@ template <int... Ts>
requires C<Ts...[0]>
auto TplClass<int>::buggy() -> void {}
}
+
+namespace GH139476 {
+
+namespace moo {
+ template <typename T>
+ constexpr bool baa = true;
+
+ template <typename T> requires baa<T>
+ void caw();
+}
+
+template <typename T> requires moo::baa<T>
+void moo::caw() {}
+
+}
|
|
@llvm/pr-subscribers-clang-modules Author: Younan Zhang (zyn0217) ChangesFor a dependent variable template specialization, we don't build a dependent Decl node or a DeclRefExpr to represent it. Instead, we preserve the UnresolvedLookupExpr until instantiation. However, this approach isn't ideal for constraint normalization. We consider the qualifier during profiling, but since that's based on the written code, it can introduce confusing differences, even when the expressions resolve to the same declaration. This change profiles the underlying VarTemplateDecl if UnresolvedLookupExpr is used to model a dependent use of it. Fixes #139476 Full diff: https://github.com/llvm/llvm-project/pull/140680.diff 4 Files Affected:
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index f04cb7b91788c..4c839303f3621 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -741,6 +741,7 @@ Bug Fixes to C++ Support
- Fixed the handling of pack indexing types in the constraints of a member function redeclaration. (#GH138255)
- Clang now correctly parses arbitrary order of ``[[]]``, ``__attribute__`` and ``alignas`` attributes for declarations (#GH133107)
- Fixed a crash when forming an invalid function type in a dependent context. (#GH138657) (#GH115725) (#GH68852)
+- Fixed a function declaration mismatch that caused inconsistencies between concepts and variable template declarations. (#GH139476)
- Clang no longer segfaults when there is a configuration mismatch between modules and their users (http://crbug.com/400353616).
- Fix an incorrect deduction when calling an explicit object member function template through an overload set address.
- Fixed bug in constant evaluation that would allow using the value of a
diff --git a/clang/lib/AST/StmtProfile.cpp b/clang/lib/AST/StmtProfile.cpp
index f7d1655f67ed1..2f1dec434c30b 100644
--- a/clang/lib/AST/StmtProfile.cpp
+++ b/clang/lib/AST/StmtProfile.cpp
@@ -2189,8 +2189,14 @@ StmtProfiler::VisitCXXPseudoDestructorExpr(const CXXPseudoDestructorExpr *S) {
void StmtProfiler::VisitOverloadExpr(const OverloadExpr *S) {
VisitExpr(S);
- VisitNestedNameSpecifier(S->getQualifier());
- VisitName(S->getName(), /*TreatAsDecl*/ true);
+ bool DescribingDependentVarTemplate =
+ S->getNumDecls() == 1 && isa<VarTemplateDecl>(*S->decls_begin());
+ if (DescribingDependentVarTemplate) {
+ VisitDecl(*S->decls_begin());
+ } else {
+ VisitNestedNameSpecifier(S->getQualifier());
+ VisitName(S->getName(), /*TreatAsDecl*/ true);
+ }
ID.AddBoolean(S->hasExplicitTemplateArgs());
if (S->hasExplicitTemplateArgs())
VisitTemplateArguments(S->getTemplateArgs(), S->getNumTemplateArgs());
diff --git a/clang/test/SemaCXX/exception-spec.cpp b/clang/test/SemaCXX/exception-spec.cpp
index 6ad19aab397bd..31c691b28da4b 100644
--- a/clang/test/SemaCXX/exception-spec.cpp
+++ b/clang/test/SemaCXX/exception-spec.cpp
@@ -52,3 +52,24 @@ namespace AssignmentOp {
D2 &operator=(const D2&); // expected-error {{more lax}}
};
}
+
+namespace OverloadedFunctions {
+
+template <typename T>
+void f(T&) noexcept;
+
+template <typename T, int N>
+void f(T (&arr)[N]) noexcept(noexcept(f(*arr)));
+
+template <typename T>
+inline void f(T&) noexcept {}
+
+template <typename T, int N>
+inline void f(T (&arr)[N]) noexcept(noexcept(f(*arr))) {}
+
+void g() {
+ int x[1];
+ f(x);
+}
+
+}
diff --git a/clang/test/SemaTemplate/concepts-out-of-line-def.cpp b/clang/test/SemaTemplate/concepts-out-of-line-def.cpp
index e5d00491d3fb8..bf505dec0ca14 100644
--- a/clang/test/SemaTemplate/concepts-out-of-line-def.cpp
+++ b/clang/test/SemaTemplate/concepts-out-of-line-def.cpp
@@ -853,3 +853,18 @@ template <int... Ts>
requires C<Ts...[0]>
auto TplClass<int>::buggy() -> void {}
}
+
+namespace GH139476 {
+
+namespace moo {
+ template <typename T>
+ constexpr bool baa = true;
+
+ template <typename T> requires baa<T>
+ void caw();
+}
+
+template <typename T> requires moo::baa<T>
+void moo::caw() {}
+
+}
|
zyn0217
commented
May 20, 2025
Comment on lines
+2192
to
+2193
| bool DescribingDependentVarTemplate = | ||
| S->getNumDecls() == 1 && isa<VarTemplateDecl>(*S->decls_begin()); |
There was a problem hiding this comment.
Instead of OverloadExpr, I'm thinking if it would be better to invent a new Expr node to describe dependent cases (we use DeclRefExpr for non-dependent uses), just like ConceptSpecializationExpr.
There was a problem hiding this comment.
Except ConceptSpecializationExpr cannot be specialized, so there is that. Maybe a subclass?
I think this scenario can only happen for UnresolvedLookupExpr though, could you check?
We could add a getAsTemplatedDecl function in UnresolvedLookupExpr to help with that.
At the same time, I've used UnresolvedLookupExpr to model concept template template parameters too, and maybe having a dedicated class would be cleaner
cor3ntin
approved these changes
Jun 7, 2025
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
For a dependent variable template specialization, we don't build a dependent Decl node or a DeclRefExpr to represent it. Instead, we preserve the UnresolvedLookupExpr until instantiation.
However, this approach isn't ideal for constraint normalization. We consider the qualifier during profiling, but since that's based on the written code, it can introduce confusing differences, even when the expressions resolve to the same declaration.
This change profiles the underlying VarTemplateDecl if UnresolvedLookupExpr is used to model a dependent use of it.
Fixes #139476