[Clang][Sema] fix crash of attribute transform

Author: huqizhi

clang/docs/ReleaseNotes.rst

@@ -828,6 +828,8 @@ Bug Fixes in This Version
 - Fix an issue with missing symbol definitions when the first coroutine
   statement appears in a discarded ``if constexpr`` branch.
   Fixes (`#78290 <https://github.com/llvm/llvm-project/issues/78290>`_)
+- Fix crash when using lifetimebound attribute in function with trailing return.
+  Fixes (`#73619 <https://github.com/llvm/llvm-project/issues/73619>`_)
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

clang/include/clang/AST/TypeLoc.h

@@ -884,6 +884,10 @@ class AttributedTypeLoc : public ConcreteTypeLoc<UnqualTypeLoc,
     return getInnerTypeLoc();
   }
 
+  TypeLoc getEquivalentTypeLoc() const {
+    return TypeLoc(getTypePtr()->getEquivalentType(), getNonLocalData());
+  }
+
   /// The type attribute.
   const Attr *getAttr() const {
     return getLocalData()->TypeAttr;

clang/lib/Sema/TreeTransform.h

@@ -6124,7 +6124,9 @@ QualType TreeTransform<Derived>::TransformFunctionProtoType(
       //   "pointer to cv-qualifier-seq X" between the optional cv-qualifer-seq
       //   and the end of the function-definition, member-declarator, or
       //   declarator.
-      Sema::CXXThisScopeRAII ThisScope(SemaRef, ThisContext, ThisTypeQuals);
+      auto *RD = dyn_cast<CXXRecordDecl>(SemaRef.getCurLexicalContext());
+      Sema::CXXThisScopeRAII ThisScope(
+          SemaRef, !ThisContext && RD ? RD : ThisContext, ThisTypeQuals);
 
       ResultType = getDerived().TransformType(TLB, TL.getReturnLoc());
       if (ResultType.isNull())
@@ -7081,10 +7083,10 @@ QualType TreeTransform<Derived>::TransformAttributedType(
   // FIXME: dependent operand expressions?
   if (getDerived().AlwaysRebuild() ||
       modifiedType != oldType->getModifiedType()) {
-    // TODO: this is really lame; we should really be rebuilding the
-    // equivalent type from first principles.
-    QualType equivalentType
-      = getDerived().TransformType(oldType->getEquivalentType());
+    TypeLocBuilder AuxiliaryTLB;
+    AuxiliaryTLB.reserve(TL.getFullDataSize());
+    QualType equivalentType =
+        getDerived().TransformType(AuxiliaryTLB, TL.getEquivalentTypeLoc());
     if (equivalentType.isNull())
       return QualType();
 

clang/test/Sema/attr-lifetimebound-no-crash.cpp

@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 %s -verify -fsyntax-only
+
+// expected-no-diagnostics
+
+template<typename T>
+struct Bar {
+    int* data;
+
+    auto operator[](const int index) const [[clang::lifetimebound]] -> decltype(data[index]) {
+        return data[index];
+    }
+};
+
+int main() {
+    Bar<int> b;
+    (void)b[2];
+}