diff --git a/include/clang/CodeGen/SwiftCallingConv.h b/include/clang/CodeGen/SwiftCallingConv.h
index 0f7d2a4..f9c2fd9 100644
--- a/include/clang/CodeGen/SwiftCallingConv.h
+++ b/include/clang/CodeGen/SwiftCallingConv.h
@@ -91,7 +91,7 @@
   bool shouldPassIndirectly(bool asReturnValue) const;
 
   using EnumerationCallback =
-    llvm::function_ref<void(CharUnits offset, CharUnits end, llvm::Type *type)>;
+    llvm::function_ref<void(CharUnits offset, llvm::Type *type)>;
 
   /// Enumerate the expanded components of this type.
   ///
diff --git a/lib/CodeGen/SwiftCallingConv.cpp b/lib/CodeGen/SwiftCallingConv.cpp
index 59c78bf..44b46f6 100644
--- a/lib/CodeGen/SwiftCallingConv.cpp
+++ b/lib/CodeGen/SwiftCallingConv.cpp
@@ -506,7 +506,7 @@
   assert(Finished && "haven't yet finished lowering");
 
   for (auto &entry : Entries) {
-    callback(entry.Begin, entry.End, entry.Type);
+    callback(entry.Begin, entry.Type);
   }
 }
 
diff --git a/lib/Sema/SemaType.cpp b/lib/Sema/SemaType.cpp
index 7561a10..6ff4adf 100644
--- a/lib/Sema/SemaType.cpp
+++ b/lib/Sema/SemaType.cpp
@@ -2340,16 +2340,28 @@
       }
       continue;
 
+    // swift_context parameters must be the last parameter except for
+    // a possible swift_error parameter.
     case ParameterABI::SwiftContext:
       checkForSwiftCC(paramIndex);
+      if (!(paramIndex == numParams - 1 ||
+            (paramIndex == numParams - 2 &&
+             EPI.ExtParameterInfos[numParams - 1].getABI()
+               == ParameterABI::SwiftErrorResult))) {
+        S.Diag(getParamLoc(paramIndex),
+               diag::err_swift_context_not_before_swift_error_result);
+      }
       continue;
 
-    // swift_error parameters must be preceded by a swift_context parameter.
+    // swift_error parameters must be the last parameter.
     case ParameterABI::SwiftErrorResult:
       checkForSwiftCC(paramIndex);
-      if (paramIndex == 0 ||
-          EPI.ExtParameterInfos[paramIndex - 1].getABI() !=
-              ParameterABI::SwiftContext) {
+      if (paramIndex != numParams - 1) {
+        S.Diag(getParamLoc(paramIndex),
+               diag::err_swift_error_result_not_last);
+      } else if (paramIndex == 0 ||
+                 EPI.ExtParameterInfos[paramIndex - 1].getABI()
+                   != ParameterABI::SwiftContext) {
         S.Diag(getParamLoc(paramIndex),
                diag::err_swift_error_result_not_after_swift_context);
       }
diff --git a/test/Sema/attr-swiftcall.c b/test/Sema/attr-swiftcall.c
index 1720612..3458167 100644
--- a/test/Sema/attr-swiftcall.c
+++ b/test/Sema/attr-swiftcall.c
@@ -18,13 +18,13 @@
 void indirect_result_multiple(INDIRECT_RESULT void *out1, INDIRECT_RESULT void *out2) SWIFTCALL;
 
 void error_result_nonswift(ERROR_RESULT void **error); // expected-error {{'swift_error_result' parameter can only be used with swiftcall calling convention}} expected-error{{'swift_error_result' parameter must follow 'swift_context' parameter}}
+void error_result_bad_position(ERROR_RESULT void **error, int last) SWIFTCALL; // expected-error {{'swift_error_result' parameter must be last parameter of function}}
 void error_result_bad_position2(int first, ERROR_RESULT void **error) SWIFTCALL; // expected-error {{'swift_error_result' parameter must follow 'swift_context' parameter}}
 void error_result_bad_type(CONTEXT void *context, ERROR_RESULT int error) SWIFTCALL; // expected-error {{'swift_error_result' parameter must have pointer to unqualified pointer type; type here is 'int'}}
 void error_result_bad_type2(CONTEXT void *context, ERROR_RESULT int *error) SWIFTCALL; // expected-error {{'swift_error_result' parameter must have pointer to unqualified pointer type; type here is 'int *'}}
 void error_result_okay(int a, int b, CONTEXT void *context, ERROR_RESULT void **error) SWIFTCALL;
-void error_result_okay2(CONTEXT void *context, ERROR_RESULT void **error, void *selfType, char **selfWitnessTable) SWIFTCALL;
 
 void context_nonswift(CONTEXT void *context); // expected-error {{'swift_context' parameter can only be used with swiftcall calling convention}}
+void context_bad_position(CONTEXT void *context, int x) SWIFTCALL; // expected-error {{'swift_context' parameter can only be followed by 'swift_error_result' parameter}}
 void context_bad_type(CONTEXT int context) SWIFTCALL; // expected-error {{'swift_context' parameter must have pointer type; type here is 'int'}}
 void context_okay(CONTEXT void *context) SWIFTCALL;
-void context_okay2(CONTEXT void *context, void *selfType, char **selfWitnessTable) SWIFTCALL;
diff --git a/test/SemaCXX/attr-swiftcall.cpp b/test/SemaCXX/attr-swiftcall.cpp
index eb9538e..fd17aae 100644
--- a/test/SemaCXX/attr-swiftcall.cpp
+++ b/test/SemaCXX/attr-swiftcall.cpp
@@ -17,16 +17,16 @@
 void indirect_result_multiple(INDIRECT_RESULT void *out1, INDIRECT_RESULT void *out2) SWIFTCALL;
 
 void error_result_nonswift(ERROR_RESULT void **error); // expected-error {{'swift_error_result' parameter can only be used with swiftcall calling convention}} expected-error{{'swift_error_result' parameter must follow 'swift_context' parameter}}
+void error_result_bad_position(ERROR_RESULT void **error, int last) SWIFTCALL; // expected-error {{'swift_error_result' parameter must be last parameter of function}}
 void error_result_bad_position2(int first, ERROR_RESULT void **error) SWIFTCALL; // expected-error {{'swift_error_result' parameter must follow 'swift_context' parameter}}
 void error_result_bad_type(CONTEXT void *context, ERROR_RESULT int error) SWIFTCALL; // expected-error {{'swift_error_result' parameter must have pointer to unqualified pointer type; type here is 'int'}}
 void error_result_bad_type2(CONTEXT void *context, ERROR_RESULT int *error) SWIFTCALL; // expected-error {{'swift_error_result' parameter must have pointer to unqualified pointer type; type here is 'int *'}}
 void error_result_okay(int a, int b, CONTEXT void *context, ERROR_RESULT void **error) SWIFTCALL;
-void error_result_okay(CONTEXT void *context, ERROR_RESULT void **error, void *selfType, char **selfWitnessTable) SWIFTCALL;
 
 void context_nonswift(CONTEXT void *context); // expected-error {{'swift_context' parameter can only be used with swiftcall calling convention}}
+void context_bad_position(CONTEXT void *context, int x) SWIFTCALL; // expected-error {{'swift_context' parameter can only be followed by 'swift_error_result' parameter}}
 void context_bad_type(CONTEXT int context) SWIFTCALL; // expected-error {{'swift_context' parameter must have pointer type; type here is 'int'}}
 void context_okay(CONTEXT void *context) SWIFTCALL;
-void context_okay(CONTEXT void *context, void *selfType, char **selfWitnessTable) SWIFTCALL;
 
 template <class T> void indirect_result_temp_okay1(INDIRECT_RESULT T *out) SWIFTCALL;
 template <class T> void indirect_result_temp_okay2(INDIRECT_RESULT T out) SWIFTCALL; // expected-note {{candidate template ignored: substitution failure [with T = int]: 'swift_indirect_result' parameter must have pointer type; type here is 'int'}}