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

[Younan Zhang via cfe-commits]

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@@ -1637,6 +1678,144 @@ TEST(TypeHints, SubstTemplateParameterAliases) {
                         ExpectedHint{": static_vector<int>", "vector_name"});
 }
 
+template <typename... Labels>
+void assertTypeLinkHints(StringRef Code, StringRef HintRange,
+                         Labels... ExpectedLabels) {
+  Annotations Source(Code);
+  auto HintAt = [&](llvm::ArrayRef<InlayHint> InlayHints,
+                    llvm::StringRef Range) {
+    auto *Hint = llvm::find_if(InlayHints, [&](const InlayHint &InlayHint) {
+      return InlayHint.range == Source.range(Range);
+    });
+    assert(Hint && "No range was found");
+    return llvm::ArrayRef(Hint->label);
+  };
+
+  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);
+  EXPECT_THAT(HintAt(Hints, HintRange),
+              ElementsAre(HintLabelPieceMatcher(ExpectedLabels, Source)...));
+}
+
+TEST(TypeHints, Links) {
+  StringRef Source(R"cpp(
+    $Package[[template <class T, class U>
----------------
zyn0217 wrote:

Oh, thanks - indeed we have an identifier location with `getLocation()`.
(I promise I have seen `getLocation()` while looking at the definition of `Decl::getBeginLoc()`, but I thought it was the same as `getLocation()` because that's how the base `getSourceRange()` implements, although it is overridden by the subclasses. I should have looked into the subclasses' constructors, my fault!)

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