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

[Nathan Ridge 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>
----------------
HighCommander4 wrote:

>    1. Using `RecordDecl::getBeginLoc()` does work in terms of the protocol, but this SourceLocation points to the first keyword token of the definition, i.e., the location of `struct/class`, which doesn't seem acceptable to us.

I was thinking of `Decl::getLocation()`, which should point to the location of the declaration's name.

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