Index: include/llvm/ADT/StringSwitch.h
===================================================================
--- include/llvm/ADT/StringSwitch.h
+++ include/llvm/ADT/StringSwitch.h
@@ -15,6 +15,7 @@
 
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Compiler.h"
+#include "llvm/Support/Error.h"
 #include <cassert>
 #include <cstring>
 
@@ -68,6 +69,7 @@
 
   ~StringSwitch() = default;
 
+  // Case-sensitive case matchers
   template<unsigned N>
   LLVM_ATTRIBUTE_ALWAYS_INLINE
   StringSwitch& Case(const char (&S)[N], const T& Value) {
@@ -182,14 +184,76 @@
     return Case(S0, Value).Cases(S1, S2, S3, S4, S5, S6, S7, S8, S9, Value);
   }
 
+  // Case-insensitive case matchers.
+  template <unsigned N>
+  LLVM_ATTRIBUTE_ALWAYS_INLINE StringSwitch &CaseLower(const char (&S)[N],
+                                                       const T &Value) {
+    if (!Result && Str.equals_lower(StringRef(S, N - 1)))
+      Result = &Value;
+
+    return *this;
+  }
+
+  template <unsigned N>
+  LLVM_ATTRIBUTE_ALWAYS_INLINE StringSwitch &EndsWithLower(const char (&S)[N],
+                                                           const T &Value) {
+    if (!Result && Str.endswith_lower(StringRef(S, N - 1)))
+      Result = &Value;
+
+    return *this;
+  }
+
+  template <unsigned N>
+  LLVM_ATTRIBUTE_ALWAYS_INLINE StringSwitch &StartsWithLower(const char (&S)[N],
+                                                             const T &Value) {
+    if (!Result && Str.startswith_lower(StringRef(S, N - 1)))
+      Result = &Value;
+
+    return *this;
+  }
+  template <unsigned N0, unsigned N1>
+  LLVM_ATTRIBUTE_ALWAYS_INLINE StringSwitch &
+  CasesLower(const char (&S0)[N0], const char (&S1)[N1], const T &Value) {
+    return CaseLower(S0, Value).CaseLower(S1, Value);
+  }
+
+  template <unsigned N0, unsigned N1, unsigned N2>
+  LLVM_ATTRIBUTE_ALWAYS_INLINE StringSwitch &
+  CasesLower(const char (&S0)[N0], const char (&S1)[N1], const char (&S2)[N2],
+             const T &Value) {
+    return CaseLower(S0, Value).CasesLower(S1, S2, Value);
+  }
+
+  template <unsigned N0, unsigned N1, unsigned N2, unsigned N3>
+  LLVM_ATTRIBUTE_ALWAYS_INLINE StringSwitch &
+  CasesLower(const char (&S0)[N0], const char (&S1)[N1], const char (&S2)[N2],
+             const char (&S3)[N3], const T &Value) {
+    return CaseLower(S0, Value).CasesLower(S1, S2, S3, Value);
+  }
+
+  template <unsigned N0, unsigned N1, unsigned N2, unsigned N3, unsigned N4>
+  LLVM_ATTRIBUTE_ALWAYS_INLINE StringSwitch &
+  CasesLower(const char (&S0)[N0], const char (&S1)[N1], const char (&S2)[N2],
+             const char (&S3)[N3], const char (&S4)[N4], const T &Value) {
+    return CaseLower(S0, Value).CasesLower(S1, S2, S3, S4, Value);
+  }
+
   LLVM_ATTRIBUTE_ALWAYS_INLINE
-  R Default(const T& Value) const {
+  R Default(const T &Value) const {
     if (Result)
       return *Result;
     return Value;
   }
 
   LLVM_ATTRIBUTE_ALWAYS_INLINE
+  Expected<R> Expect() const {
+    if (Result)
+      return *Result;
+    return make_error<StringError>("Value did not occur in StringSwitch",
+                                   inconvertibleErrorCode());
+  }
+
+  LLVM_ATTRIBUTE_ALWAYS_INLINE
   operator R() const {
     assert(Result && "Fell off the end of a string-switch");
     return *Result;
Index: unittests/ADT/CMakeLists.txt
===================================================================
--- unittests/ADT/CMakeLists.txt
+++ unittests/ADT/CMakeLists.txt
@@ -56,6 +56,7 @@
   StringExtrasTest.cpp
   StringMapTest.cpp
   StringRefTest.cpp
+  StringSwitchTest.cpp
   TinyPtrVectorTest.cpp
   TripleTest.cpp
   TwineTest.cpp