diff --git a/llvm/lib/Demangle/RustDemangle.cpp b/llvm/lib/Demangle/RustDemangle.cpp
--- a/llvm/lib/Demangle/RustDemangle.cpp
+++ b/llvm/lib/Demangle/RustDemangle.cpp
@@ -203,7 +203,9 @@
   }
   size_t Dot = Mangled.find('.');
   Input = Mangled.substr(0, Dot);
-  StringView Suffix = Mangled.dropFront(Dot);
+  StringView Suffix;
+  if (Dot != StringView::npos)
+    Suffix = Mangled.substr(Dot);
 
   demanglePath(IsInType::No);