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
@@ -202,8 +202,7 @@
     return false;
   }
   size_t Dot = Mangled.find('.');
-  Input = Mangled.substr(0, Dot);
-  StringView Suffix = Mangled.dropFront(Dot);
+  Input = Dot == StringView::npos ? Mangled : Mangled.substr(0, Dot);
 
   demanglePath(IsInType::No);
 
@@ -215,9 +214,9 @@
   if (Position != Input.size())
     Error = true;
 
-  if (!Suffix.empty()) {
+  if (Dot != StringView::npos) {
     print(" (");
-    print(Suffix);
+    print(Mangled.substr(Dot));
     print(")");
   }