[clangd] Fix subtle use after return.

I didn't find this because my main development machine still happens to
use libstdc++ with the broken C++11 ABI, which has a global empty
string.

llvm-svn: 294309

1 files changed, 4 insertions, 1 deletions

diff --git a/clang-tools-extra/clangd/DocumentStore.h b/clang-tools-extra/clangd/DocumentStore.h
index dd4555c0131..dbe5687f85c 100644
--- a/clang-tools-extra/clangd/DocumentStore.h
+++ b/clang-tools-extra/clangd/DocumentStore.h
@@ -26,7 +26,10 @@ public:
   /// Delete a document from the store.
   void removeDocument(StringRef Uri) { Docs.erase(Uri); }
   /// Retrieve a document from the store. Empty string if it's unknown.
-  StringRef getDocument(StringRef Uri) const { return Docs.lookup(Uri); }
+  StringRef getDocument(StringRef Uri) const {
+    auto I = Docs.find(Uri);
+    return I == Docs.end() ? StringRef("") : StringRef(I->second);
+  }
 
 private:
   llvm::StringMap<std::string> Docs;