[analyzer] Refine the diagnostics in the nullability checker to differentiate between nil and null

This is a big deal for ObjC, where nullability annotations are extensively
used. I've also changed "Null" -> "null" and removed "is" as this is the
pattern that Sema is using.

Differential Revision: https://reviews.llvm.org/D27600

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@289885 91177308-0d34-0410-b5e6-96231b3b80d8

Author: AnnaZaks

lib/StaticAnalyzer/Checkers/NullabilityChecker.cpp

@@ -610,9 +610,9 @@ void NullabilityChecker::checkPreStmt(const ReturnStmt *S,
 
     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 @@ void NullabilityChecker::checkPreCall(const CallEvent &Call,
       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 @@ void NullabilityChecker::checkBind(SVal L, SVal V, const Stmt *S,
     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;

test/Analysis/nullability-no-arc.mm

@@ -17,20 +17,20 @@ - (void)release;
 @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 testObjCNonARCNoInitialization(TestObject * _Nonnull p) {
 }
 
 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

test/Analysis/nullability.mm

@@ -75,7 +75,7 @@ void testBasicRules() {
   }
   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 @@ void testArgumentTracking(Dummy *_Nonnull nonnull, Dummy *_Nullable nullable) {
 
 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() {
@@ -229,7 +229,7 @@ void testConditionalNilPassToNonnull(Dummy *p) {
 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() {

test/Analysis/nullability_nullonly.mm

@@ -24,7 +24,7 @@ void testBasicRules() {
 
 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() {
@@ -100,24 +100,24 @@ void testObjCARCImplicitZeroInitialization() {
 }
 
 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 @@ @interface SomeClass : NSObject
 @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 @@ void callFunctionInSystemHeader() {
 
   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 @@ void callMethodInSystemHeader() {
   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
 }