[clang][AST] Fix end location of DeclarationNameInfo on instantiated methods (#92654)

Fixes #71161

[D64087](https://reviews.llvm.org/D64087) updated some locations of the
instantiated method but forgot `DNLoc`.

`FunctionDecl::getNameInfo()` constructs a `DeclarationNameInfo` using
`Decl::Loc` as the beginning of the declaration name, and
`FunctionDecl::DNLoc` to compute the end of the declaration name. The
former was updated, but the latter was not, so
`DeclarationName::getSourceRange()` would return a range where the end
of the declaration name could come before its beginning.

Patch by Alejandro Alvarez Ayllon
Co-authored-by: steakhal

CPP-5166

Co-authored-by: Alejandro Alvarez Ayllon <[email protected]>

Author: steakhal

clang/docs/ReleaseNotes.rst

@@ -766,6 +766,7 @@ Miscellaneous Bug Fixes
 
 - Fixed an infinite recursion in ASTImporter, on return type declared inside
   body of C++11 lambda without trailing return (#GH68775).
+- Fixed declaration name source location of instantiated function definitions (GH71161).
 
 Miscellaneous Clang Crashes Fixed
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

clang/include/clang/AST/Decl.h

@@ -2188,6 +2188,8 @@ class FunctionDecl : public DeclaratorDecl,
 
   void setRangeEnd(SourceLocation E) { EndRangeLoc = E; }
 
+  void setDeclarationNameLoc(DeclarationNameLoc L) { DNLoc = L; }
+
   /// Returns the location of the ellipsis of a variadic function.
   SourceLocation getEllipsisLoc() const {
     const auto *FPT = getType()->getAs<FunctionProtoType>();

clang/lib/Sema/SemaTemplateInstantiateDecl.cpp

@@ -5055,6 +5055,7 @@ void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
   Function->setLocation(PatternDecl->getLocation());
   Function->setInnerLocStart(PatternDecl->getInnerLocStart());
   Function->setRangeEnd(PatternDecl->getEndLoc());
+  Function->setDeclarationNameLoc(PatternDecl->getNameInfo().getInfo());
 
   EnterExpressionEvaluationContext EvalContext(
       *this, Sema::ExpressionEvaluationContext::PotentiallyEvaluated);

clang/unittests/AST/DeclTest.cpp

@@ -545,3 +545,34 @@ TEST(Decl, TemplateArgumentDefaulted) {
   EXPECT_TRUE(ArgList.get(2).getIsDefaulted());
   EXPECT_TRUE(ArgList.get(3).getIsDefaulted());
 }
+
+TEST(Decl, CXXDestructorDeclsShouldHaveWellFormedNameInfoRanges) {
+  // GH71161
+  llvm::Annotations Code(R"cpp(
+template <typename T> struct Resource {
+  ~Resource(); // 1
+};
+template <typename T>
+Resource<T>::~Resource() {} // 2,3
+
+void instantiate_template() {
+  Resource<int> x;
+}
+)cpp");
+
+  auto AST = tooling::buildASTFromCode(Code.code());
+  ASTContext &Ctx = AST->getASTContext();
+
+  const auto &SM = Ctx.getSourceManager();
+  auto GetNameInfoRange = [&SM](const BoundNodes &Match) {
+    const auto *D = Match.getNodeAs<CXXDestructorDecl>("dtor");
+    return D->getNameInfo().getSourceRange().printToString(SM);
+  };
+
+  auto Matches = match(findAll(cxxDestructorDecl().bind("dtor")),
+                       *Ctx.getTranslationUnitDecl(), Ctx);
+  ASSERT_EQ(Matches.size(), 3U);
+  EXPECT_EQ(GetNameInfoRange(Matches[0]), "<input.cc:3:3, col:4>");
+  EXPECT_EQ(GetNameInfoRange(Matches[1]), "<input.cc:6:14, col:15>");
+  EXPECT_EQ(GetNameInfoRange(Matches[2]), "<input.cc:6:14, col:15>");
+}