[clangd] Switch to Dex by default for the static index

[kbobyrev]

Summary

Dex is now mature enough to be used as the default static index. This patch performs the switch but introduces a hidden flag to allow users fallback to Mem in case something happens.

[kbobyrev]

Run clang-format.

[ioeric]

clang-tools-extra/clangd/tool/ClangdMain.cpp

32 ↗

(On Diff #162838)

I think we should stick to the same option and just flip the default. Introducing yet another option (that is going to be removed) could be confusing.

33 ↗

(On Diff #162838)

Also add FIXME indicating that the option will be removed soon.

[ioeric]

clang-tools-extra/clangd/tool/ClangdMain.cpp

32 ↗

(On Diff #162842)

Maybe: FIXME: remove this option when Dex is stable enough.

clang-tools-extra/trunk/clangd/tool/ClangdMain.cpp

 #include <iostream>
 #include <memory>
 #include <string>
 #include <thread>
 
 using namespace clang;
 using namespace clang::clangd;
 
+// FIXME: remove this option when Dex is stable enough.
 static llvm::cl::opt<bool>
     UseDex("use-dex-index",
            llvm::cl::desc("Use experimental Dex static index."),
-           llvm::cl::init(false), llvm::cl::Hidden);
+           llvm::cl::init(true), llvm::cl::Hidden);
 
 namespace {
 
 enum class PCHStorageFlag { Disk, Memory };
 
 // Build an in-memory static index for global symbols from a YAML-format file.
 // The size of global symbols should be relatively small, so that all symbols
 // can be managed in memory.