[clang][Index] Add a knob to index function parameters in declarations

Summary:
Parameters in declarations are useful for clangd, so that we can
provide symbol information for them as well. It also helps clangd to be
consistent whether a function's definition is accessible or not.

Reviewers: hokein, akyrtzi

Subscribers: ilya-biryukov, ioeric, arphaman, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D57949

llvm-svn: 353695
diff --git a/clang/unittests/Index/IndexTests.cpp b/clang/unittests/Index/IndexTests.cpp
index 147f7a7..2b574a5 100644
--- a/clang/unittests/Index/IndexTests.cpp
+++ b/clang/unittests/Index/IndexTests.cpp
@@ -119,6 +119,21 @@
   EXPECT_THAT(Index->Symbols, UnorderedElementsAre());
 }
 
+TEST(IndexTest, IndexParametersInDecls) {
+  std::string Code = "void foo(int bar);";
+  auto Index = std::make_shared<Indexer>();
+  IndexingOptions Opts;
+  Opts.IndexFunctionLocals = true;
+  Opts.IndexParametersInDeclarations = true;
+  tooling::runToolOnCode(new IndexAction(Index, Opts), Code);
+  EXPECT_THAT(Index->Symbols, Contains(QName("bar")));
+
+  Opts.IndexParametersInDeclarations = false;
+  Index->Symbols.clear();
+  tooling::runToolOnCode(new IndexAction(Index, Opts), Code);
+  EXPECT_THAT(Index->Symbols, Not(Contains(QName("bar"))));
+}
+
 } // namespace
 } // namespace index
 } // namespace clang