[PATCH] D94382: [clangd] Avoid recusion in TargetFinder::add()

[Nathan Ridge via Phabricator via cfe-commits]

nridge created this revision.
Herald added subscribers: usaxena95, kadircet, arphaman.
nridge requested review of this revision.
Herald added subscribers: cfe-commits, MaskRay, ilya-biryukov.
Herald added a project: clang.

Fixes https://github.com/clangd/clangd/issues/633


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D94382

Files:
  clang-tools-extra/clangd/FindTarget.cpp
  clang-tools-extra/clangd/unittests/FindTargetTests.cpp


Index: clang-tools-extra/clangd/unittests/FindTargetTests.cpp
===================================================================
--- clang-tools-extra/clangd/unittests/FindTargetTests.cpp
+++ clang-tools-extra/clangd/unittests/FindTargetTests.cpp
@@ -787,6 +787,47 @@
                "template <typename> struct B");
 }
 
+TEST_F(TargetDeclTest, TypedefCascade) {
+  Code = R"cpp(
+        struct C {
+          using type = int;
+        };
+        struct B {
+          using type = C::type;
+        };
+        struct A {
+          using type = B::type;
+        };
+        A::[[type]] waldo;
+  )cpp";
+  EXPECT_DECLS("TypedefTypeLoc",
+               {"using type = int", Rel::Alias | Rel::Underlying},
+               {"using type = C::type", Rel::Alias | Rel::Underlying},
+               {"using type = B::type", Rel::Alias});
+}
+
+TEST_F(TargetDeclTest, RecursiveTemplate) {
+  Flags.push_back("-std=c++20"); // the test case uses concepts
+
+  Code = R"cpp(
+        template <typename T>
+        concept Leaf = false;
+
+        template <typename Tree>
+        struct descend_left {
+          using type = typename descend_left<typename Tree::left>::[[type]];
+        };
+
+        template <Leaf Tree>
+        struct descend_left<Tree> {
+          using type = typename Tree::value;
+        };
+  )cpp";
+  EXPECT_DECLS("DependentNameTypeLoc",
+               {"using type = typename descend_left<typename Tree::left>::type",
+                Rel::Alias});
+}
+
 TEST_F(TargetDeclTest, ObjC) {
   Flags = {"-xobjective-c"};
   Code = R"cpp(
Index: clang-tools-extra/clangd/FindTarget.cpp
===================================================================
--- clang-tools-extra/clangd/FindTarget.cpp
+++ clang-tools-extra/clangd/FindTarget.cpp
@@ -330,6 +330,7 @@
   llvm::SmallDenseMap<const NamedDecl *,
                       std::pair<RelSet, /*InsertionOrder*/ size_t>>
       Decls;
+  const Decl *CurrentlyProcessing = nullptr;
   RelSet Flags;
 
   template <typename T> void debug(T &Node, RelSet Flags) {
@@ -354,11 +355,28 @@
     return Result;
   }
 
+  bool seenDecl(const Decl *Dcl) const {
+    if (CurrentlyProcessing == Dcl)
+      return true;
+    for (const auto &D : Decls)
+      if (D.first == Dcl)
+        return true;
+    return false;
+  }
+
   void add(const Decl *Dcl, RelSet Flags) {
     const NamedDecl *D = llvm::dyn_cast_or_null<NamedDecl>(Dcl);
     if (!D)
       return;
     debug(*D, Flags);
+
+    // Avoid recursion (which can arise in the presence of heuristic
+    // resolution of dependent names) by exiting early if we have
+    // already seen this decl.
+    if (seenDecl(D))
+      return;
+    CurrentlyProcessing = D;
+
     if (const UsingDirectiveDecl *UDD = llvm::dyn_cast<UsingDirectiveDecl>(D))
       D = UDD->getNominatedNamespaceAsWritten();
 


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