[clang-tools-extra] [clangd] Support go-to-definition on type hints. The core part (PR #86629)

[Younan Zhang via cfe-commits]

================
@@ -1637,6 +1678,168 @@ TEST(TypeHints, SubstTemplateParameterAliases) {
                         ExpectedHint{": static_vector<int>", "vector_name"});
 }
 
+template <typename... Labels>
+void assertTypeLinkHints(StringRef Code, StringRef HintRange,
+                         Labels... ExpectedLabels) {
+  Annotations Source(Code);
+
+  TestTU TU = TestTU::withCode(Source.code());
+  TU.ExtraArgs.push_back("-std=c++2c");
+  auto AST = TU.build();
+
+  Config C;
+  C.InlayHints.TypeNameLimit = 0;
+  WithContextValue WithCfg(Config::Key, std::move(C));
+
+  auto Hints = hintsOfKind(AST, InlayHintKind::Type);
+  auto Hint = llvm::find_if(Hints, [&](const InlayHint &InlayHint) {
+    return InlayHint.range == Source.range(HintRange);
+  });
+  ASSERT_TRUE(Hint != Hints.end()) << "No hint was found at " << HintRange;
+  EXPECT_THAT(Hint->label,
+              ElementsAre(HintLabelPieceMatcher(ExpectedLabels, Source)...));
+}
+
+TEST(TypeHints, Links) {
+  StringRef Source(R"cpp(
+    template <class T, class U>
+    struct $Package[[Package]] {};
+
+    template <>
+    struct $SpecializationOfPackage[[Package]]<float, const int> {};
+
+    template <class... T>
+    struct $Container[[Container]] {};
+
+    template <auto... T>
+    struct $NttpContainer[[NttpContainer]] {};
+
+    enum struct $ScopedEnum[[ScopedEnum]] {
+      X = 1,
+    };
+
+    enum $Enum[[Enum]] {
+      E = 2,
+    };
+
+    namespace ns {
+      template <class T>
+      struct $Nested[[Nested]] {
+        template <class U>
+        struct $NestedClass[[Class]] {
+        };
+      };
+
+      using $NestedInt[[NestedInt]] = Nested<int>;
+    }
+
+    void basic() {
+      auto $1[[C]] = Container<Package<char, int>>();
+      auto $2[[D]] = Container<Package<float, const int>>();
+      auto $3[[E]] = Container<Container<int, int>, long>();
+      auto $4[[F]] = NttpContainer<D, E, ScopedEnum::X, Enum::E>();
+      auto $5[[G]] = ns::Nested<Container<int>>::Class<Package<char, int>>();
+    }
+
+    void compounds() {
+      auto $6[[A]] = Container<ns::Nested<int>::Class<float>&>();
+      auto $7[[B]] = Container<ns::Nested<int>::Class<float>&&>();
+      auto $8[[C]] = Container<ns::Nested<int>::Class<const Container<int>> *>();
+    }
+
+    namespace nns {
+      using ns::$UsingShadow[[NestedInt]];
+
+      void aliases() {
+        auto $9[[A]] = Container<NestedInt>();
+        auto $10[[B]] = Container<ns::NestedInt>();
+      }
+    }
+
+    auto $11[[A]] = Container<Enum, ScopedEnum>();
+
+  )cpp");
+  assertTypeLinkHints(Source, "1", ExpectedHintLabelPiece{": "},
+                      ExpectedHintLabelPiece{"Container", "Container"},
+                      ExpectedHintLabelPiece{"<"},
+                      ExpectedHintLabelPiece{"Package", "Package"},
+                      ExpectedHintLabelPiece{"<char, int>>"});
+
+  assertTypeLinkHints(
+      Source, "2", ExpectedHintLabelPiece{": "},
+      ExpectedHintLabelPiece{"Container", "Container"},
+      ExpectedHintLabelPiece{"<"},
+      ExpectedHintLabelPiece{"Package", "SpecializationOfPackage"},
+      ExpectedHintLabelPiece{"<float, const int>>"});
+
+  assertTypeLinkHints(Source, "3", ExpectedHintLabelPiece{": "},
+                      ExpectedHintLabelPiece{"Container", "Container"},
+                      ExpectedHintLabelPiece{"<"},
+                      ExpectedHintLabelPiece{"Container", "Container"},
+                      ExpectedHintLabelPiece{"<int, int>, long>"});
+
+  // TODO: Support links on NTTP arguments.
+  assertTypeLinkHints(Source, "4", ExpectedHintLabelPiece{": "},
+                      ExpectedHintLabelPiece{"NttpContainer", "NttpContainer"},
+                      ExpectedHintLabelPiece{"<D, E, ScopedEnum::X, Enum::E>"});
+
+  assertTypeLinkHints(Source, "5", ExpectedHintLabelPiece{": "},
+                      ExpectedHintLabelPiece{"ns::Nested", "Nested"},
----------------
zyn0217 wrote:

Fun that this is working on CI and my local build. Do you have any other modifications that happen to be overlooked locally?

https://github.com/llvm/llvm-project/pull/86629