This revision was landed with ongoing or failed builds.
This revision was automatically updated to reflect the committed changes.
Closed by commit rGb1193c13a5f9: [clangd] Avoid unexpected desugaring in 
isSugaredTemplateParameter (authored by zyounan).

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D156300/new/

https://reviews.llvm.org/D156300

Files:
  clang-tools-extra/clangd/InlayHints.cpp
  clang-tools-extra/clangd/unittests/InlayHintTests.cpp

Index: clang-tools-extra/clangd/unittests/InlayHintTests.cpp
===================================================================
--- clang-tools-extra/clangd/unittests/InlayHintTests.cpp
+++ clang-tools-extra/clangd/unittests/InlayHintTests.cpp
@@ -84,11 +84,13 @@
 }
 
 template <typename... ExpectedHints>
-void assertHints(InlayHintKind Kind, llvm::StringRef AnnotatedSource,
-                 ExpectedHints... Expected) {
+void assertHintsWithHeader(InlayHintKind Kind, llvm::StringRef AnnotatedSource,
+                           llvm::StringRef HeaderContent,
+                           ExpectedHints... Expected) {
   Annotations Source(AnnotatedSource);
   TestTU TU = TestTU::withCode(Source.code());
   TU.ExtraArgs.push_back("-std=c++20");
+  TU.HeaderCode = HeaderContent;
   auto AST = TU.build();
 
   EXPECT_THAT(hintsOfKind(AST, Kind),
@@ -99,6 +101,13 @@
   EXPECT_THAT(inlayHints(AST, std::nullopt), IsEmpty());
 }
 
+template <typename... ExpectedHints>
+void assertHints(InlayHintKind Kind, llvm::StringRef AnnotatedSource,
+                 ExpectedHints... Expected) {
+  return assertHintsWithHeader(Kind, AnnotatedSource, "",
+                               std::move(Expected)...);
+}
+
 // Hack to allow expression-statements operating on parameter packs in C++14.
 template <typename... T> void ignore(T &&...) {}
 
@@ -1433,8 +1442,7 @@
 }
 
 TEST(TypeHints, SubstTemplateParameterAliases) {
-  assertTypeHints(
-      R"cpp(
+  llvm::StringRef Header = R"cpp(
   template <class T> struct allocator {};
 
   template <class T, class A>
@@ -1467,9 +1475,34 @@
 
     T elements[10];
   };
+  )cpp";
 
-  vector<int> array;
+  llvm::StringRef VectorIntPtr = R"cpp(
+    vector<int *> array;
+    auto $no_modifier[[x]] = array[3];
+    auto* $ptr_modifier[[ptr]] = &array[3];
+    auto& $ref_modifier[[ref]] = array[3];
+    auto& $at[[immutable]] = array.at(3);
+
+    auto $data[[data]] = array.data();
+    auto $allocator[[alloc]] = array.get_allocator();
+    auto $size[[size]] = array.size();
+    auto $begin[[begin]] = array.begin();
+    auto $end[[end]] = array.end();
+  )cpp";
+
+  assertHintsWithHeader(
+      InlayHintKind::Type, VectorIntPtr, Header,
+      ExpectedHint{": int *", "no_modifier"},
+      ExpectedHint{": int **", "ptr_modifier"},
+      ExpectedHint{": int *&", "ref_modifier"},
+      ExpectedHint{": int *const &", "at"}, ExpectedHint{": int **", "data"},
+      ExpectedHint{": allocator<int *>", "allocator"},
+      ExpectedHint{": size_type", "size"}, ExpectedHint{": iterator", "begin"},
+      ExpectedHint{": non_template_iterator", "end"});
 
+  llvm::StringRef VectorInt = R"cpp(
+  vector<int> array;
   auto $no_modifier[[by_value]] = array[3];
   auto* $ptr_modifier[[ptr]] = &array[3];
   auto& $ref_modifier[[ref]] = array[3];
@@ -1480,8 +1513,19 @@
   auto $size[[size]] = array.size();
   auto $begin[[begin]] = array.begin();
   auto $end[[end]] = array.end();
+  )cpp";
 
+  assertHintsWithHeader(
+      InlayHintKind::Type, VectorInt, Header,
+      ExpectedHint{": int", "no_modifier"},
+      ExpectedHint{": int *", "ptr_modifier"},
+      ExpectedHint{": int &", "ref_modifier"},
+      ExpectedHint{": const int &", "at"}, ExpectedHint{": int *", "data"},
+      ExpectedHint{": allocator<int>", "allocator"},
+      ExpectedHint{": size_type", "size"}, ExpectedHint{": iterator", "begin"},
+      ExpectedHint{": non_template_iterator", "end"});
 
+  llvm::StringRef TypeAlias = R"cpp(
   // If the type alias is not of substituted template parameter type,
   // do not show desugared type.
   using VeryLongLongTypeName = my_iterator;
@@ -1496,16 +1540,11 @@
   using static_vector = basic_static_vector<T, allocator<T>>;
 
   auto $vector_name[[vec]] = static_vector<int>();
-  )cpp",
-      ExpectedHint{": int", "no_modifier"},
-      ExpectedHint{": int *", "ptr_modifier"},
-      ExpectedHint{": int &", "ref_modifier"},
-      ExpectedHint{": const int &", "at"}, ExpectedHint{": int *", "data"},
-      ExpectedHint{": allocator<int>", "allocator"},
-      ExpectedHint{": size_type", "size"}, ExpectedHint{": iterator", "begin"},
-      ExpectedHint{": non_template_iterator", "end"},
-      ExpectedHint{": Short", "short_name"},
-      ExpectedHint{": static_vector<int>", "vector_name"});
+  )cpp";
+
+  assertHintsWithHeader(InlayHintKind::Type, TypeAlias, Header,
+                        ExpectedHint{": Short", "short_name"},
+                        ExpectedHint{": static_vector<int>", "vector_name"});
 }
 
 TEST(DesignatorHints, Basic) {
Index: clang-tools-extra/clangd/InlayHints.cpp
===================================================================
--- clang-tools-extra/clangd/InlayHints.cpp
+++ clang-tools-extra/clangd/InlayHints.cpp
@@ -405,22 +405,47 @@
 // Determines if any intermediate type in desugaring QualType QT is of
 // substituted template parameter type. Ignore pointer or reference wrappers.
 bool isSugaredTemplateParameter(QualType QT) {
-  static auto PeelWrappers = [](QualType QT) {
+  static auto PeelWrapper = [](QualType QT) {
     // Neither `PointerType` nor `ReferenceType` is considered as sugared
     // type. Peel it.
-    QualType Next;
-    while (!(Next = QT->getPointeeType()).isNull())
-      QT = Next;
-    return QT;
+    QualType Peeled = QT->getPointeeType();
+    return Peeled.isNull() ? QT : Peeled;
   };
+
+  // This is a bit tricky: we traverse the type structure and find whether or
+  // not a type in the desugaring process is of SubstTemplateTypeParmType.
+  // During the process, we may encounter pointer or reference types that are
+  // not marked as sugared; therefore, the desugar function won't apply. To
+  // move forward the traversal, we retrieve the pointees using
+  // QualType::getPointeeType().
+  //
+  // However, getPointeeType could leap over our interests: The QT::getAs<T>()
+  // invoked would implicitly desugar the type. Consequently, if the
+  // SubstTemplateTypeParmType is encompassed within a TypedefType, we may lose
+  // the chance to visit it.
+  // For example, given a QT that represents `std::vector<int *>::value_type`:
+  //  `-ElaboratedType 'value_type' sugar
+  //    `-TypedefType 'vector<int *>::value_type' sugar
+  //      |-Typedef 'value_type'
+  //      `-SubstTemplateTypeParmType 'int *' sugar class depth 0 index 0 T
+  //        |-ClassTemplateSpecialization 'vector'
+  //        `-PointerType 'int *'
+  //          `-BuiltinType 'int'
+  // Applying `getPointeeType` to QT results in 'int', a child of our target
+  // node SubstTemplateTypeParmType.
+  //
+  // As such, we always prefer the desugared over the pointee for next type
+  // in the iteration. It could avoid the getPointeeType's implicit desugaring.
   while (true) {
-    QualType Desugared =
-        PeelWrappers(QT->getLocallyUnqualifiedSingleStepDesugaredType());
-    if (Desugared == QT)
-      break;
-    if (Desugared->getAs<SubstTemplateTypeParmType>())
+    if (QT->getAs<SubstTemplateTypeParmType>())
       return true;
-    QT = Desugared;
+    QualType Desugared = QT->getLocallyUnqualifiedSingleStepDesugaredType();
+    if (Desugared != QT)
+      QT = Desugared;
+    else if (auto Peeled = PeelWrapper(Desugared); Peeled != QT)
+      QT = Peeled;
+    else
+      break;
   }
   return false;
 }
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