Index: lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp
===================================================================
--- lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp
+++ lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp
@@ -610,9 +610,9 @@
 
     SmallString<256> SBuf;
     llvm::raw_svector_ostream OS(SBuf);
-    OS << "Null is returned from a " << C.getDeclDescription(D) <<
+    OS << (RetExpr->getType()->isObjCObjectPointerType() ? "nil" : "null");
+    OS << " returned from a " << C.getDeclDescription(D) <<
           " that is expected to return a non-null value";
-
     reportBugIfInvariantHolds(OS.str(),
                               ErrorKind::NilReturnedToNonnull, N, nullptr, C,
                               RetExpr);
@@ -707,9 +707,11 @@
       ExplodedNode *N = C.generateErrorNode(State);
       if (!N)
         return;
+
       SmallString<256> SBuf;
       llvm::raw_svector_ostream OS(SBuf);
-      OS << "Null passed to a callee that requires a non-null " << ParamIdx
+      OS << (Param->getType()->isObjCObjectPointerType() ? "nil" : "null");
+      OS << " passed to a callee that requires a non-null " << ParamIdx
          << llvm::getOrdinalSuffix(ParamIdx) << " parameter";
       reportBugIfInvariantHolds(OS.str(), ErrorKind::NilPassedToNonnull, N,
                                 nullptr, C,
@@ -1128,8 +1130,11 @@
     if (ValueExpr)
       ValueStmt = ValueExpr;
 
-    reportBugIfInvariantHolds("Null is assigned to a pointer which is "
-                              "expected to have non-null value",
+    SmallString<256> SBuf;
+    llvm::raw_svector_ostream OS(SBuf);
+    OS << (LocType->isObjCObjectPointerType() ? "nil" : "null");
+    OS << " assigned to a pointer which is expected to have non-null value";
+    reportBugIfInvariantHolds(OS.str(),
                               ErrorKind::NilAssignedToNonnull, N, nullptr, C,
                               ValueStmt);
     return;
Index: test/Analysis/nullability-no-arc.mm
===================================================================
--- test/Analysis/nullability-no-arc.mm
+++ test/Analysis/nullability-no-arc.mm
@@ -17,20 +17,20 @@
 @interface TestObject : NSObject
 @end
 
-TestObject * _Nonnull returnsNilObjCInstanceIndirectly() {
-  TestObject *local = 0;
-  return local; // expected-warning {{Null is returned from a function that is expected to return a non-null value}}
+TestObject *_Nonnull returnsNilObjCInstanceIndirectly() {
+  TestObject *local = nil;
+  return local; // expected-warning {{nil returned from a function that is expected to return a non-null value}}
 }
 
 TestObject * _Nonnull returnsNilObjCInstanceIndirectlyWithSupressingCast() {
-  TestObject *local = 0;
+  TestObject *local = nil;
   return (TestObject * _Nonnull)local; // no-warning
 }
 
 TestObject * _Nonnull returnsNilObjCInstanceDirectly() {
   // The first warning is from Sema. The second is from the static analyzer.
   return nil; // expected-warning {{null returned from function that requires a non-null return value}}
-              // expected-warning@-1 {{Null is returned from a function that is expected to return a non-null value}}
+              // expected-warning@-1 {{nil returned from a function that is expected to return a non-null value}}
 }
 
 TestObject * _Nonnull returnsNilObjCInstanceDirectlyWithSuppressingCast() {
@@ -43,7 +43,7 @@
 }
 
 void testObjCNonARCExplicitZeroInitialization() {
-  TestObject * _Nonnull explicitlyZeroInitialized = nil; // expected-warning {{Null is assigned to a pointer which is expected to have non-null value}}
+  TestObject * _Nonnull explicitlyZeroInitialized = nil; // expected-warning {{nil assigned to a pointer which is expected to have non-null value}}
 }
 
 @interface ClassWithInitializers : NSObject
Index: test/Analysis/nullability.mm
===================================================================
--- test/Analysis/nullability.mm
+++ test/Analysis/nullability.mm
@@ -71,11 +71,11 @@
   Dummy *q = 0;
   if (getRandom()) {
     takesNullable(q);
-    takesNonnull(q); // expected-warning {{Null passed to a callee that requires a non-null 1st parameter}}
+    takesNonnull(q); // expected-warning {{null passed to a callee that requires a non-null 1st parameter}}
   }
   Dummy a;
   Dummy *_Nonnull nonnull = &a;
-  nonnull = q; // expected-warning {{Null is assigned to a pointer which is expected to have non-null value}}
+  nonnull = q; // expected-warning {{null assigned to a pointer which is expected to have non-null value}}
   q = &a;
   takesNullable(q);
   takesNonnull(q);
@@ -107,7 +107,7 @@
 
 Dummy *_Nonnull testNullReturn() {
   Dummy *p = 0;
-  return p; // expected-warning {{Null is returned from a function that is expected to return a non-null value}}
+  return p; // expected-warning {{null returned from a function that is expected to return a non-null value}}
 }
 
 void testObjCMessageResultNullability() {
@@ -171,7 +171,7 @@
 void testIndirectCastNilToNonnullAndPass() {
   Dummy *p = (Dummy * _Nonnull)0;
   // FIXME: Ideally the cast above would suppress this warning.
-  takesNonnull(p);  // expected-warning {{Null passed to a callee that requires a non-null 1st parameter}}
+  takesNonnull(p);  // expected-warning {{null passed to a callee that requires a non-null 1st parameter}}
 }
 
 void testDirectCastNilToNonnullAndAssignToLocalInInitializer() {
@@ -217,19 +217,19 @@
 
 void testIndirectNilPassToNonnull() {
   Dummy *p = 0;
-  takesNonnull(p);  // expected-warning {{Null passed to a callee that requires a non-null 1st parameter}}
+  takesNonnull(p);  // expected-warning {{null passed to a callee that requires a non-null 1st parameter}}
 }
 
 void testConditionalNilPassToNonnull(Dummy *p) {
   if (!p) {
-    takesNonnull(p);  // expected-warning {{Null passed to a callee that requires a non-null 1st parameter}}
+    takesNonnull(p);  // expected-warning {{null passed to a callee that requires a non-null 1st parameter}}
   }
 }
 
 Dummy * _Nonnull testIndirectCastNilToNonnullAndReturn() {
   Dummy *p = (Dummy * _Nonnull)0;
   // FIXME: Ideally the cast above would suppress this warning.
-  return p; // expected-warning {{Null is returned from a function that is expected to return a non-null value}}
+  return p; // expected-warning {{null returned from a function that is expected to return a non-null value}}
 }
 
 void testInvalidPropagation() {
Index: test/Analysis/nullability_nullonly.mm
===================================================================
--- test/Analysis/nullability_nullonly.mm
+++ test/Analysis/nullability_nullonly.mm
@@ -18,18 +18,18 @@
   Dummy *q = 0;
   if (getRandom()) {
     takesNullable(q);
-    takesNonnull(q); // expected-warning {{Null passed to a callee that requires a non-null 1st parameter}}
+    takesNonnull(q); // expected-warning {{null passed to a callee that requires a non-null 1st parameter}}
   }
 }
 
 Dummy *_Nonnull testNullReturn() {
   Dummy *p = 0;
-  return p; // expected-warning {{Null is returned from a function that is expected to return a non-null value}}
+  return p; // expected-warning {{null returned from a function that is expected to return a non-null value}}
 }
 
 void onlyReportFirstPreconditionViolationOnPath() {
   Dummy *p = 0;
-  takesNonnull(p); // expected-warning {{Null passed to a callee that requires a non-null 1st parameter}}
+  takesNonnull(p); // expected-warning {{null passed to a callee that requires a non-null 1st parameter}}
   takesNonnull(p); // No warning.
   // Passing null to nonnull is a sink. Stop the analysis.
   int i = 0;
@@ -100,24 +100,24 @@
 }
 
 void testObjCARCExplicitZeroInitialization() {
-  TestObject * _Nonnull explicitlyZeroInitialized = nil; // expected-warning {{Null is assigned to a pointer which is expected to have non-null value}}
+  TestObject * _Nonnull explicitlyZeroInitialized = nil; // expected-warning {{nil assigned to a pointer which is expected to have non-null value}}
 }
 
 // Under ARC, returned expressions of ObjC objects types are are implicitly
 // cast to _Nonnull when the functions return type is _Nonnull, so make
 // sure this doesn't implicit cast doesn't suppress a legitimate warning.
 TestObject * _Nonnull returnsNilObjCInstanceIndirectly() {
-  TestObject *local = 0;
-  return local; // expected-warning {{Null is returned from a function that is expected to return a non-null value}}
+  TestObject *local = nil;
+  return local; // expected-warning {{nil returned from a function that is expected to return a non-null value}}
 }
 
 TestObject * _Nonnull returnsNilObjCInstanceIndirectlyWithSupressingCast() {
-  TestObject *local = 0;
+  TestObject *local = nil;
   return (TestObject * _Nonnull)local; // no-warning
 }
 
 TestObject * _Nonnull returnsNilObjCInstanceDirectly() {
-  return nil; // expected-warning {{Null is returned from a function that is expected to return a non-null value}}
+  return nil; // expected-warning {{nil returned from a function that is expected to return a non-null value}}
 }
 
 TestObject * _Nonnull returnsNilObjCInstanceDirectlyWithSuppressingCast() {
@@ -130,7 +130,7 @@
 @implementation SomeClass (MethodReturn)
 - (SomeClass * _Nonnull)testReturnsNilInNonnull {
   SomeClass *local = nil;
-  return local; // expected-warning {{Null is returned from a method that is expected to return a non-null value}}
+  return local; // expected-warning {{nil returned from a method that is expected to return a non-null value}}
 }
 
 - (SomeClass * _Nonnull)testReturnsCastSuppressedNilInNonnull {
@@ -154,7 +154,7 @@
 
   NSSystemFunctionTakingNonnull(s);
   #if !NOSYSTEMHEADERS
-  // expected-warning@-2{{Null passed to a callee that requires a non-null 1st parameter}}
+  // expected-warning@-2{{nil passed to a callee that requires a non-null 1st parameter}}
   #endif
 }
 
@@ -165,6 +165,6 @@
   NSSystemClass *sc = [[NSSystemClass alloc] init];
   [sc takesNonnull:s];
   #if !NOSYSTEMHEADERS
-  // expected-warning@-2{{Null passed to a callee that requires a non-null 1st parameter}}
+  // expected-warning@-2{{nil passed to a callee that requires a non-null 1st parameter}}
   #endif
 }