[clang] edf14ed - [Clang] Don't form a type constraint if the concept is invalid (#122065)

[via cfe-commits]

Author: Younan Zhang
Date: 2025-01-08T19:40:16+08:00
New Revision: edf14ed6b182b9ae9efa0c854f3d4744bb67bf08

URL: https://github.com/llvm/llvm-project/commit/edf14ed6b182b9ae9efa0c854f3d4744bb67bf08
DIFF: https://github.com/llvm/llvm-project/commit/edf14ed6b182b9ae9efa0c854f3d4744bb67bf08.diff

LOG: [Clang] Don't form a type constraint if the concept is invalid (#122065)

After 0dedd6fe1 and 03229e7c0, invalid concept declarations might lack
expressions for evaluation and normalization. This could make it crash
in certain scenarios, apart from the one of evaluation concepts showed
in 03229e7c0, there's also an issue when checking specializations where
the normalization also relies on a non-null expression.

This patch prevents that by avoiding building up a type constraint in
such situations, thereafter the template parameter wouldn't have a
concept specialization of a null expression.

With this patch, the assumption in ASTWriterDecl is no longer valid.
Namely, HasConstraint and TypeConstraintInitialized must now represent
different meanings for both source fidelity and semantic requirements.

Fixes https://github.com/llvm/llvm-project/issues/115004
Fixes https://github.com/llvm/llvm-project/issues/121980

Added: 
    

Modified: 
    clang/lib/Sema/SemaTemplate.cpp
    clang/lib/Serialization/ASTReaderDecl.cpp
    clang/lib/Serialization/ASTWriterDecl.cpp
    clang/test/SemaTemplate/concepts.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 20ec2fbeaa6a8b..ce672b00893b0d 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -4557,6 +4557,9 @@ Sema::CheckConceptTemplateId(const CXXScopeSpec &SS,
                              const TemplateArgumentListInfo *TemplateArgs) {
   assert(NamedConcept && "A concept template id without a template?");
 
+  if (NamedConcept->isInvalidDecl())
+    return ExprError();
+
   llvm::SmallVector<TemplateArgument, 4> SugaredConverted, CanonicalConverted;
   if (CheckTemplateArgumentList(
           NamedConcept, ConceptNameInfo.getLoc(),

diff  --git a/clang/lib/Serialization/ASTReaderDecl.cpp b/clang/lib/Serialization/ASTReaderDecl.cpp
index 719bc0d06f5b11..8c60e85c93d70e 100644
--- a/clang/lib/Serialization/ASTReaderDecl.cpp
+++ b/clang/lib/Serialization/ASTReaderDecl.cpp
@@ -2663,7 +2663,8 @@ void ASTDeclReader::VisitTemplateTypeParmDecl(TemplateTypeParmDecl *D) {
 
   D->setDeclaredWithTypename(Record.readInt());
 
-  if (D->hasTypeConstraint()) {
+  bool TypeConstraintInitialized = D->hasTypeConstraint() && Record.readBool();
+  if (TypeConstraintInitialized) {
     ConceptReference *CR = nullptr;
     if (Record.readBool())
       CR = Record.readConceptReference();

diff  --git a/clang/lib/Serialization/ASTWriterDecl.cpp b/clang/lib/Serialization/ASTWriterDecl.cpp
index 75c1d9a6d438ce..f8ed155ca389d7 100644
--- a/clang/lib/Serialization/ASTWriterDecl.cpp
+++ b/clang/lib/Serialization/ASTWriterDecl.cpp
@@ -1951,7 +1951,8 @@ void ASTDeclWriter::VisitTemplateTypeParmDecl(TemplateTypeParmDecl *D) {
   Record.push_back(D->wasDeclaredWithTypename());
 
   const TypeConstraint *TC = D->getTypeConstraint();
-  assert((bool)TC == D->hasTypeConstraint());
+  if (D->hasTypeConstraint())
+    Record.push_back(/*TypeConstraintInitialized=*/TC != nullptr);
   if (TC) {
     auto *CR = TC->getConceptReference();
     Record.push_back(CR != nullptr);
@@ -1969,7 +1970,7 @@ void ASTDeclWriter::VisitTemplateTypeParmDecl(TemplateTypeParmDecl *D) {
   if (OwnsDefaultArg)
     Record.AddTemplateArgumentLoc(D->getDefaultArgument());
 
-  if (!TC && !OwnsDefaultArg &&
+  if (!D->hasTypeConstraint() && !OwnsDefaultArg &&
       D->getDeclContext() == D->getLexicalDeclContext() &&
       !D->isInvalidDecl() && !D->hasAttrs() &&
       !D->isTopLevelDeclInObjCContainer() && !D->isImplicit() &&

diff  --git a/clang/test/SemaTemplate/concepts.cpp b/clang/test/SemaTemplate/concepts.cpp
index 312469313fc535..f335ca3bd22bc3 100644
--- a/clang/test/SemaTemplate/concepts.cpp
+++ b/clang/test/SemaTemplate/concepts.cpp
@@ -1165,3 +1165,15 @@ concept C = invalid; // expected-error {{use of undeclared identifier 'invalid'}
 bool val2 = C<int>;
 
 } // namespace GH109780
+
+namespace GH121980 {
+
+template <class>
+concept has_member_
diff erence_type; // expected-error {{expected '='}}
+
+template <has_member_
diff erence_type> struct incrementable_traits; // expected-note {{declared here}}
+
+template <has_member_
diff erence_type Tp>
+struct incrementable_traits<Tp>; // expected-error {{not more specialized than the primary}}
+
+}