[clang] [Clang][Sema] Fix lookup of dependent operator= outside of complete-class contexts (PR #91498)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Krystian Stasiowski (sdkrystian)

<details>
<summary>Changes</summary>

Fixes [this crash](https://github.com/llvm/llvm-project/pull/90152#issuecomment-2100688849) caused by #<!-- -->90152.

Will add tests shortly.

---
Full diff: https://github.com/llvm/llvm-project/pull/91498.diff


2 Files Affected:

- (modified) clang/lib/Sema/SemaLookup.cpp (+13-15) 
- (modified) clang/lib/Sema/SemaTemplate.cpp (+2-5) 


``````````diff
diff --git a/clang/lib/Sema/SemaLookup.cpp b/clang/lib/Sema/SemaLookup.cpp
index e63da5875d2c9..6bd5932212b92 100644
--- a/clang/lib/Sema/SemaLookup.cpp
+++ b/clang/lib/Sema/SemaLookup.cpp
@@ -1269,19 +1269,19 @@ struct FindLocalExternScope {
 };
 } // end anonymous namespace
 
+static bool isDependentAssignmentOperator(DeclarationName Name,
+                                          DeclContext *LookupContext) {
+  auto *LookupRecord = dyn_cast_if_present<CXXRecordDecl>(LookupContext);
+  return Name.getCXXOverloadedOperator() == OO_Equal && LookupRecord &&
+         !LookupRecord->isBeingDefined() && LookupRecord->isDependentContext();
+}
+
 bool Sema::CppLookupName(LookupResult &R, Scope *S) {
   assert(getLangOpts().CPlusPlus && "Can perform only C++ lookup");
 
   DeclarationName Name = R.getLookupName();
   Sema::LookupNameKind NameKind = R.getLookupKind();
 
-  // If this is the name of an implicitly-declared special member function,
-  // go through the scope stack to implicitly declare
-  if (isImplicitlyDeclaredMemberFunctionName(Name)) {
-    for (Scope *PreS = S; PreS; PreS = PreS->getParent())
-      if (DeclContext *DC = PreS->getEntity())
-        DeclareImplicitMemberFunctionsWithName(*this, Name, R.getNameLoc(), DC);
-  }
   // C++23 [temp.dep.general]p2:
   //   The component name of an unqualified-id is dependent if
   //   - it is a conversion-function-id whose conversion-type-id
@@ -1299,9 +1299,8 @@ bool Sema::CppLookupName(LookupResult &R, Scope *S) {
   if (isImplicitlyDeclaredMemberFunctionName(Name)) {
     for (Scope *PreS = S; PreS; PreS = PreS->getParent())
       if (DeclContext *DC = PreS->getEntity()) {
-        if (DC->isDependentContext() && isa<CXXRecordDecl>(DC) &&
-            Name.getCXXOverloadedOperator() == OO_Equal &&
-            !R.isTemplateNameLookup()) {
+        if (!R.isTemplateNameLookup() &&
+            isDependentAssignmentOperator(Name, DC)) {
           R.setNotFoundInCurrentInstantiation();
           return false;
         }
@@ -2472,8 +2471,6 @@ bool Sema::LookupQualifiedName(LookupResult &R, DeclContext *LookupCtx,
     }
   } QL(LookupCtx);
 
-  bool TemplateNameLookup = R.isTemplateNameLookup();
-  CXXRecordDecl *LookupRec = dyn_cast<CXXRecordDecl>(LookupCtx);
   if (!InUnqualifiedLookup && !R.isForRedeclaration()) {
     // C++23 [temp.dep.type]p5:
     //   A qualified name is dependent if
@@ -2486,13 +2483,14 @@ bool Sema::LookupQualifiedName(LookupResult &R, DeclContext *LookupCtx,
     if (DeclarationName Name = R.getLookupName();
         (Name.getNameKind() == DeclarationName::CXXConversionFunctionName &&
          Name.getCXXNameType()->isDependentType()) ||
-        (Name.getCXXOverloadedOperator() == OO_Equal && LookupRec &&
-         LookupRec->isDependentContext() && !TemplateNameLookup)) {
+        (!R.isTemplateNameLookup() &&
+         isDependentAssignmentOperator(Name, LookupCtx))) {
       R.setNotFoundInCurrentInstantiation();
       return false;
     }
   }
 
+  CXXRecordDecl *LookupRec = dyn_cast<CXXRecordDecl>(LookupCtx);
   if (LookupDirect(*this, R, LookupCtx)) {
     R.resolveKind();
     if (LookupRec)
@@ -2604,7 +2602,7 @@ bool Sema::LookupQualifiedName(LookupResult &R, DeclContext *LookupCtx,
         //   template, and if the name is used as a template-name, the
         //   reference refers to the class template itself and not a
         //   specialization thereof, and is not ambiguous.
-        if (TemplateNameLookup)
+        if (R.isTemplateNameLookup())
           if (auto *TD = getAsTemplateNameDecl(ND))
             ND = TD;
 
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 7e57fa0696725..480bc74c2001a 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -726,7 +726,7 @@ Sema::ActOnDependentIdExpression(const CXXScopeSpec &SS,
                                  const DeclarationNameInfo &NameInfo,
                                  bool isAddressOfOperand,
                            const TemplateArgumentListInfo *TemplateArgs) {
-  DeclContext *DC = getFunctionLevelDeclContext();
+  QualType ThisType = getCurrentThisType();
 
   // C++11 [expr.prim.general]p12:
   //   An id-expression that denotes a non-static data member or non-static
@@ -748,10 +748,7 @@ Sema::ActOnDependentIdExpression(const CXXScopeSpec &SS,
     IsEnum = isa_and_nonnull<EnumType>(NNS->getAsType());
 
   if (!MightBeCxx11UnevalField && !isAddressOfOperand && !IsEnum &&
-      isa<CXXMethodDecl>(DC) &&
-      cast<CXXMethodDecl>(DC)->isImplicitObjectMemberFunction()) {
-    QualType ThisType = cast<CXXMethodDecl>(DC)->getThisType().getNonReferenceType();
-
+      !ThisType.isNull()) {
     // Since the 'this' expression is synthesized, we don't need to
     // perform the double-lookup check.
     NamedDecl *FirstQualifierInScope = nullptr;

``````````

</details>


https://github.com/llvm/llvm-project/pull/91498