[ObjC] Diagnose implicit type coercion from ObjC 'Class' to object

pointer types.

For example, in Objective-C mode, the initialization of 'x' in:
```
  @implementation MyType
  + (void)someClassMethod {
    MyType *x = self;
  }
  @end
```
is correctly diagnosed with an incompatible-pointer-types warning, but
in Objective-C++ mode, it is not diagnosed at all -- even though
incompatible pointer conversions generally become an error in C++.

This patch fixes that oversight, allowing implicit conversions
involving Class only to/from unqualified-id, and between qualified and
unqualified Class, where the protocols are compatible.

Note that this does change some behaviors in Objective-C, as well, as
shown by the modified tests.

Of particular note is that assignment from from 'Class<MyProtocol>' to
'id<MyProtocol>' now warns. (Despite appearances, those are not
compatible types. 'Class<MyProtocol>' is not expected to have instance
methods defined by 'MyProtocol', while 'id<MyProtocol>' is.)

Differential Revision: https://reviews.llvm.org/D67983

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@375125 91177308-0d34-0410-b5e6-96231b3b80d8

7 files changed, 58 insertions, 50 deletions

diff --git a/lib/AST/ASTContext.cpp b/lib/AST/ASTContext.cpp
index 1a3bde00ee..cda51ec755 100644
--- a/lib/AST/ASTContext.cpp
+++ b/lib/AST/ASTContext.cpp
@@ -8025,14 +8025,15 @@ bool ASTContext::ObjCQualifiedClassTypesAreCompatible(
 bool ASTContext::ObjCQualifiedIdTypesAreCompatible(
     const ObjCObjectPointerType *lhs, const ObjCObjectPointerType *rhs,
     bool compare) {
-  // Allow id<P..> and an 'id' or void* type in all cases.
-  if (lhs->isVoidPointerType() ||
-      lhs->isObjCIdType() || lhs->isObjCClassType())
-    return true;
-  else if (rhs->isVoidPointerType() ||
-           rhs->isObjCIdType() || rhs->isObjCClassType())
+  // Allow id<P..> and an 'id' in all cases.
+  if (lhs->isObjCIdType() || rhs->isObjCIdType())
     return true;
 
+  // Don't allow id<P..> to convert to Class or Class<P..> in either direction.
+  if (lhs->isObjCClassType() || lhs->isObjCQualifiedClassType() ||
+      rhs->isObjCClassType() || rhs->isObjCQualifiedClassType())
+    return false;
+
   if (lhs->isObjCQualifiedIdType()) {
     if (rhs->qual_empty()) {
       // If the RHS is a unqualified interface pointer "NSString*",
@@ -8142,9 +8143,8 @@ bool ASTContext::canAssignObjCInterfaces(const ObjCObjectPointerType *LHSOPT,
   const ObjCObjectType* LHS = LHSOPT->getObjectType();
   const ObjCObjectType* RHS = RHSOPT->getObjectType();
 
-  // If either type represents the built-in 'id' or 'Class' types, return true.
-  if (LHS->isObjCUnqualifiedIdOrClass() ||
-      RHS->isObjCUnqualifiedIdOrClass())
+  // If either type represents the built-in 'id' type, return true.
+  if (LHS->isObjCUnqualifiedId() || RHS->isObjCUnqualifiedId())
     return true;
 
   // Function object that propagates a successful result or handles
@@ -8162,14 +8162,22 @@ bool ASTContext::canAssignObjCInterfaces(const ObjCObjectPointerType *LHSOPT,
                                    LHSOPT->stripObjCKindOfTypeAndQuals(*this));
   };
 
+  // Casts from or to id<P> are allowed when the other side has compatible
+  // protocols.
   if (LHS->isObjCQualifiedId() || RHS->isObjCQualifiedId()) {
     return finish(ObjCQualifiedIdTypesAreCompatible(LHSOPT, RHSOPT, false));
   }
 
+  // Verify protocol compatibility for casts from Class<P1> to Class<P2>.
   if (LHS->isObjCQualifiedClass() && RHS->isObjCQualifiedClass()) {
     return finish(ObjCQualifiedClassTypesAreCompatible(LHSOPT, RHSOPT));
   }
 
+  // Casts from Class to Class<Foo>, or vice-versa, are allowed.
+  if (LHS->isObjCClass() && RHS->isObjCClass()) {
+    return true;
+  }
+
   // If we have 2 user-defined types, fall into that path.
   if (LHS->getInterface() && RHS->getInterface()) {
     return finish(canAssignObjCInterfaces(LHS, RHS));
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 6e3980275a..333983a430 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -10068,8 +10068,8 @@ static bool convertPointersToCompositeType(Sema &S, SourceLocation Loc,
 
   QualType T = S.FindCompositePointerType(Loc, LHS, RHS);
   if (T.isNull()) {
-    if ((LHSType->isPointerType() || LHSType->isMemberPointerType()) &&
-        (RHSType->isPointerType() || RHSType->isMemberPointerType()))
+    if ((LHSType->isAnyPointerType() || LHSType->isMemberPointerType()) &&
+        (RHSType->isAnyPointerType() || RHSType->isMemberPointerType()))
       diagnoseDistinctPointerComparison(S, Loc, LHS, RHS, /*isError*/true);
     else
       S.InvalidOperands(Loc, LHS, RHS);
diff --git a/test/SemaObjC/comptypes-1.m b/test/SemaObjC/comptypes-1.m
index 9b62f97492..67b73ce0f8 100644
--- a/test/SemaObjC/comptypes-1.m
+++ b/test/SemaObjC/comptypes-1.m
@@ -49,7 +49,7 @@ int main()
   obj_p = obj_c;  // expected-warning {{assigning to 'id<MyProtocol>' from incompatible type 'MyClass *'}}
   obj_p = obj_cp; /* Ok  */
   obj_p = obj_C;  // expected-warning {{incompatible pointer types assigning to 'id<MyProtocol>' from 'Class'}}
-  obj_p = obj_CP; // FIXME -- should warn {{assigning to 'id<MyProtocol>' from incompatible type 'Class<MyProtocol>'}}
+  obj_p = obj_CP; // expected-warning {{assigning to 'id<MyProtocol>' from incompatible type 'Class<MyProtocol>'}}
 
   /* Assigning to a 'MyOtherClass *' variable should always generate
      a warning, unless done from an 'id' or an 'id<MyProtocol>' (since
@@ -92,8 +92,8 @@ int main()
   if (obj_c == obj_cp) foo(); // expected-warning {{comparison of distinct pointer types ('MyClass *' and 'MyOtherClass *')}}
   if (obj_cp == obj_c) foo(); // expected-warning {{comparison of distinct pointer types ('MyOtherClass *' and 'MyClass *')}}
 
-  if (obj_c == obj_C) foo();  // FIXME -- should warn {{comparison of distinct pointer types ('MyClass *' and 'Class')}}
-  if (obj_C == obj_c) foo();  // FIXME -- should warn {{comparison of distinct pointer types ('Class' and 'MyClass *')}}
+  if (obj_c == obj_C) foo();  // expected-warning {{comparison of distinct pointer types ('MyClass *' and 'Class')}}
+  if (obj_C == obj_c) foo();  // expected-warning {{comparison of distinct pointer types ('Class' and 'MyClass *')}}
 
   if (obj_c == obj_CP) foo(); // expected-warning {{comparison of distinct pointer types ('MyClass *' and 'Class<MyProtocol>')}}
   if (obj_CP == obj_c) foo(); // expected-warning {{comparison of distinct pointer types ('Class<MyProtocol>' and 'MyClass *')}}
@@ -103,15 +103,15 @@ int main()
   if (obj_p == obj_cp) foo();  /* Ok */
   if (obj_cp == obj_p) foo();  /* Ok */
 
-  if (obj_p == obj_C) foo();   // FIXME -- should warn {{comparison of distinct pointer types ('id<MyProtocol>' and 'Class')}}
-  if (obj_C == obj_p) foo();   // FIXME -- should warn {{comparison of distinct pointer types ('Class' and 'id<MyProtocol>')}}
+  if (obj_p == obj_C) foo();   // expected-warning {{comparison of distinct pointer types ('id<MyProtocol>' and 'Class')}}
+  if (obj_C == obj_p) foo();   // expected-warning {{comparison of distinct pointer types ('Class' and 'id<MyProtocol>')}}
 
-  if (obj_p == obj_CP) foo();  // FIXME -- should warn {{comparison of distinct pointer types ('id<MyProtocol>' and 'Class<MyProtocol>')}}
-  if (obj_CP == obj_p) foo();  // FIXME -- should warn {{comparison of distinct pointer types ('Class<MyProtocol>' and 'id<MyProtocol>')}}
+  if (obj_p == obj_CP) foo();  // expected-warning {{comparison of distinct pointer types ('id<MyProtocol>' and 'Class<MyProtocol>')}}
+  if (obj_CP == obj_p) foo();  // expected-warning {{comparison of distinct pointer types ('Class<MyProtocol>' and 'id<MyProtocol>')}}
 
   /* Comparisons between MyOtherClass * and Class types is a warning */
-  if (obj_cp == obj_C) foo();  // FIXME -- should warn {{comparison of distinct pointer types ('MyOtherClass *' and 'Class')}}
-  if (obj_C == obj_cp) foo();  // FIXME -- should warn {{comparison of distinct pointer types ('Class' and 'MyOtherClass *')}}
+  if (obj_cp == obj_C) foo();  // expected-warning {{comparison of distinct pointer types ('MyOtherClass *' and 'Class')}}
+  if (obj_C == obj_cp) foo();  // expected-warning {{comparison of distinct pointer types ('Class' and 'MyOtherClass *')}}
 
   if (obj_cp == obj_CP) foo(); // expected-warning {{comparison of distinct pointer types ('MyOtherClass *' and 'Class<MyProtocol>')}}
   if (obj_CP == obj_cp) foo(); // expected-warning {{comparison of distinct pointer types ('Class<MyProtocol>' and 'MyOtherClass *')}}
diff --git a/test/SemaObjCXX/class-method-self.mm b/test/SemaObjCXX/class-method-self.mm
index 560c1a14a5..bb0b60145a 100644
--- a/test/SemaObjCXX/class-method-self.mm
+++ b/test/SemaObjCXX/class-method-self.mm
@@ -1,8 +1,8 @@
 // RUN: %clang_cc1 -verify -Wno-objc-root-class %s
-// FIXME: expected-no-diagnostics
+
 @interface XX
 
-- (void)addObserver:(XX*)o; // FIXME -- should note 2{{passing argument to parameter 'o' here}}
+- (void)addObserver:(XX*)o; // expected-note 2{{passing argument to parameter 'o' here}}
 
 @end
 
@@ -17,9 +17,9 @@
 static XX *obj;
 
 + (void)classMethod {
-  [obj addObserver:self];     // FIXME -- should error {{cannot initialize a parameter of type 'XX *' with an lvalue of type 'Class'}}
+  [obj addObserver:self];     // expected-error {{cannot initialize a parameter of type 'XX *' with an lvalue of type 'Class'}}
   Class whatever;
-  [obj addObserver:whatever]; // FIXME -- should error {{cannot initialize a parameter of type 'XX *' with an lvalue of type 'Class'}}
+  [obj addObserver:whatever]; // expected-error {{cannot initialize a parameter of type 'XX *' with an lvalue of type 'Class'}}
 }
 @end
 
diff --git a/test/SemaObjCXX/comptypes-1.mm b/test/SemaObjCXX/comptypes-1.mm
index e1fbef5d9b..abb87775d1 100644
--- a/test/SemaObjCXX/comptypes-1.mm
+++ b/test/SemaObjCXX/comptypes-1.mm
@@ -38,7 +38,7 @@ int main()
   obj_c = obj;    /* Ok */
   obj_c = obj_p;  // expected-error {{assigning to 'MyClass *' from incompatible type 'id<MyProtocol>'}}
   obj_c = obj_cp; // expected-error {{assigning to 'MyClass *' from incompatible type 'MyOtherClass *'}}
-  obj_c = obj_C;  // FIXME -- should error {{assigning to 'MyClass *' from incompatible type 'Class'}}
+  obj_c = obj_C;  // expected-error {{assigning to 'MyClass *' from incompatible type 'Class'}}
   obj_c = obj_CP; // expected-error {{assigning to 'MyClass *' from incompatible type 'Class<MyProtocol>'}}
 
   /* Assigning to an 'id<MyProtocol>' variable should generate a
@@ -48,8 +48,8 @@ int main()
   obj_p = obj;    /* Ok */
   obj_p = obj_c;  // expected-error {{assigning to 'id<MyProtocol>' from incompatible type 'MyClass *'}}
   obj_p = obj_cp; /* Ok  */
-  obj_p = obj_C;  // FIXME -- should error {{assigning to 'id<MyProtocol>' from incompatible type 'Class'}}
-  obj_p = obj_CP; // FIXME -- should error {{assigning to 'id<MyProtocol>' from incompatible type 'Class<MyProtocol>'}}
+  obj_p = obj_C;  // expected-error {{assigning to 'id<MyProtocol>' from incompatible type 'Class'}}
+  obj_p = obj_CP; // expected-error {{assigning to 'id<MyProtocol>' from incompatible type 'Class<MyProtocol>'}}
 
   /* Assigning to a 'MyOtherClass *' variable should always generate
      a warning, unless done from an 'id' or an 'id<MyProtocol>' (since
@@ -57,17 +57,17 @@ int main()
   obj_cp = obj;    /* Ok */
   obj_cp = obj_c;  // expected-error {{assigning to 'MyOtherClass *' from incompatible type 'MyClass *'}}
   obj_cp = obj_p;  /* Ok */
-  obj_cp = obj_C;  // FIXME -- should error {{assigning to 'MyOtherClass *' from incompatible type 'Class'}}
+  obj_cp = obj_C;  // expected-error {{assigning to 'MyOtherClass *' from incompatible type 'Class'}}
   obj_cp = obj_CP; // expected-error {{assigning to 'MyOtherClass *' from incompatible type 'Class<MyProtocol>'}}
 
   obj_C = obj;     // Ok
-  obj_C = obj_p;   // FIXME -- should error {{assigning to 'Class' from incompatible type 'id<MyProtocol>'}}
-  obj_C = obj_c;   // FIXME -- should error {{assigning to 'Class' from incompatible type 'MyClass *'}}
-  obj_C = obj_cp;  // FIXME -- should error {{assigning to 'Class' from incompatible type 'MyOtherClass *'}}
+  obj_C = obj_p;   // expected-error {{assigning to 'Class' from incompatible type 'id<MyProtocol>'}}
+  obj_C = obj_c;   // expected-error {{assigning to 'Class' from incompatible type 'MyClass *'}}
+  obj_C = obj_cp;  // expected-error {{assigning to 'Class' from incompatible type 'MyOtherClass *'}}
   obj_C = obj_CP;  // Ok
 
   obj_CP = obj;     // Ok
-  obj_CP = obj_p;   // expected-warning {{incompatible pointer types assigning to 'Class<MyProtocol>' from 'id<MyProtocol>'}} FIXME -- should error {{assigning to 'Class<MyProtocol>' from incompatible type 'id<MyProtocol>'}}
+  obj_CP = obj_p;   // expected-error {{assigning to 'Class<MyProtocol>' from incompatible type 'id<MyProtocol>'}}
   obj_CP = obj_c;   // expected-error {{assigning to 'Class<MyProtocol>' from incompatible type 'MyClass *}}
   obj_CP = obj_cp;  // expected-error {{assigning to 'Class<MyProtocol>' from incompatible type 'MyOtherClass *'}}
   obj_CP = obj_C;   // Ok
@@ -92,8 +92,8 @@ int main()
   if (obj_c == obj_cp) foo(); // expected-warning {{comparison of distinct pointer types ('MyClass *' and 'MyOtherClass *')}}
   if (obj_cp == obj_c) foo(); // expected-warning {{comparison of distinct pointer types ('MyOtherClass *' and 'MyClass *')}}
 
-  if (obj_c == obj_C) foo();  // FIXME -- should warn {{comparison of distinct pointer types ('MyClass *' and 'Class')}}
-  if (obj_C == obj_c) foo();  // FIXME -- should warn {{comparison of distinct pointer types ('Class' and 'MyClass *')}}
+  if (obj_c == obj_C) foo();  // expected-warning {{comparison of distinct pointer types ('MyClass *' and 'Class')}}
+  if (obj_C == obj_c) foo();  // expected-warning {{comparison of distinct pointer types ('Class' and 'MyClass *')}}
 
   if (obj_c == obj_CP) foo(); // expected-warning {{comparison of distinct pointer types ('MyClass *' and 'Class<MyProtocol>')}}
   if (obj_CP == obj_c) foo(); // expected-warning {{comparison of distinct pointer types ('Class<MyProtocol>' and 'MyClass *')}}
@@ -103,15 +103,15 @@ int main()
   if (obj_p == obj_cp) foo();  /* Ok */
   if (obj_cp == obj_p) foo();  /* Ok */
 
-  if (obj_p == obj_C) foo();   // FIXME -- should warn {{comparison of distinct pointer types ('id<MyProtocol>' and 'Class')}}
-  if (obj_C == obj_p) foo();   // FIXME -- should warn {{comparison of distinct pointer types ('Class' and 'id<MyProtocol>')}}
+  if (obj_p == obj_C) foo();   // expected-warning {{comparison of distinct pointer types ('id<MyProtocol>' and 'Class')}}
+  if (obj_C == obj_p) foo();   // expected-warning {{comparison of distinct pointer types ('Class' and 'id<MyProtocol>')}}
 
-  if (obj_p == obj_CP) foo();  // FIXME -- should warn {{comparison of distinct pointer types ('id<MyProtocol>' and 'Class<MyProtocol>')}}
-  if (obj_CP == obj_p) foo();  // FIXME -- should warn {{comparison of distinct pointer types ('Class<MyProtocol>' and 'id<MyProtocol>')}}
+  if (obj_p == obj_CP) foo();  // expected-warning {{comparison of distinct pointer types ('id<MyProtocol>' and 'Class<MyProtocol>')}}
+  if (obj_CP == obj_p) foo();  // expected-warning {{comparison of distinct pointer types ('Class<MyProtocol>' and 'id<MyProtocol>')}}
 
   /* Comparisons between MyOtherClass * and Class types is a warning */
-  if (obj_cp == obj_C) foo();  // FIXME -- should warn {{comparison of distinct pointer types ('MyOtherClass *' and 'Class')}}
-  if (obj_C == obj_cp) foo();  // FIXME -- should warn {{comparison of distinct pointer types ('Class' and 'MyOtherClass *')}}
+  if (obj_cp == obj_C) foo();  // expected-warning {{comparison of distinct pointer types ('MyOtherClass *' and 'Class')}}
+  if (obj_C == obj_cp) foo();  // expected-warning {{comparison of distinct pointer types ('Class' and 'MyOtherClass *')}}
 
   if (obj_cp == obj_CP) foo(); // expected-warning {{comparison of distinct pointer types ('MyOtherClass *' and 'Class<MyProtocol>')}}
   if (obj_CP == obj_cp) foo(); // expected-warning {{comparison of distinct pointer types ('Class<MyProtocol>' and 'MyOtherClass *')}}
diff --git a/test/SemaObjCXX/comptypes-7.mm b/test/SemaObjCXX/comptypes-7.mm
index ca6c506aff..010c2cacc4 100644
--- a/test/SemaObjCXX/comptypes-7.mm
+++ b/test/SemaObjCXX/comptypes-7.mm
@@ -47,23 +47,23 @@ int main()
 
   if (obj == i) foo() ; // expected-error {{comparison between pointer and integer ('id' and 'int')}}
   if (i == obj) foo() ; // expected-error {{comparison between pointer and integer ('int' and 'id')}}
-  if (obj == j) foo() ; // expected-error {{invalid operands to binary expression ('id' and 'int *')}}
-  if (j == obj) foo() ; // expected-error {{invalid operands to binary expression ('int *' and 'id')}}
+  if (obj == j) foo() ; // expected-error {{comparison of distinct pointer types ('id' and 'int *')}}
+  if (j == obj) foo() ; // expected-error {{comparison of distinct pointer types ('int *' and 'id')}}
 
   if (obj_c == i) foo() ; // expected-error {{comparison between pointer and integer ('MyClass *' and 'int')}}
   if (i == obj_c) foo() ; // expected-error {{comparison between pointer and integer ('int' and 'MyClass *')}}
-  if (obj_c == j) foo() ; // expected-error {{invalid operands to binary expression ('MyClass *' and 'int *')}}
-  if (j == obj_c) foo() ; // expected-error {{invalid operands to binary expression ('int *' and 'MyClass *')}}
+  if (obj_c == j) foo() ; // expected-error {{comparison of distinct pointer types ('MyClass *' and 'int *')}}
+  if (j == obj_c) foo() ; // expected-error {{comparison of distinct pointer types ('int *' and 'MyClass *')}}
 
   if (obj_p == i) foo() ; // expected-error {{comparison between pointer and integer ('id<MyProtocol>' and 'int')}}
   if (i == obj_p) foo() ; // expected-error {{comparison between pointer and integer ('int' and 'id<MyProtocol>')}}
-  if (obj_p == j) foo() ; // expected-error {{invalid operands to binary expression ('id<MyProtocol>' and 'int *')}}
-  if (j == obj_p) foo() ; // expected-error {{invalid operands to binary expression ('int *' and 'id<MyProtocol>')}}
+  if (obj_p == j) foo() ; // expected-error {{comparison of distinct pointer types ('id<MyProtocol>' and 'int *')}}
+  if (j == obj_p) foo() ; // expected-error {{comparison of distinct pointer types ('int *' and 'id<MyProtocol>')}}
 
   if (obj_C == i) foo() ; // expected-error {{comparison between pointer and integer ('Class' and 'int')}}
   if (i == obj_C) foo() ; // expected-error {{comparison between pointer and integer ('int' and 'Class')}}
-  if (obj_C == j) foo() ; // expected-error {{invalid operands to binary expression ('Class' and 'int *')}}
-  if (j == obj_C) foo() ; // expected-error {{invalid operands to binary expression ('int *' and 'Class')}}
+  if (obj_C == j) foo() ; // expected-error {{comparison of distinct pointer types ('Class' and 'int *')}}
+  if (j == obj_C) foo() ; // expected-error {{comparison of distinct pointer types ('int *' and 'Class')}}
 
   Class bar1 = nil;
   Class <MyProtocol> bar = nil;
diff --git a/test/SemaObjCXX/instancetype.mm b/test/SemaObjCXX/instancetype.mm
index 95e65274fd..3030d043f4 100644
--- a/test/SemaObjCXX/instancetype.mm
+++ b/test/SemaObjCXX/instancetype.mm
@@ -5,7 +5,7 @@
 #endif
 
 @interface Root
-+ (instancetype)alloc; // FIXME -- should note {{explicitly declared 'instancetype'}}
++ (instancetype)alloc; // expected-note {{explicitly declared 'instancetype'}}
 - (instancetype)init; // expected-note{{overridden method is part of the 'init' method family}}
 - (instancetype)self; // expected-note {{explicitly declared 'instancetype'}}
 - (Class)class;
@@ -143,7 +143,7 @@ void test_instancetype_narrow_method_search() {
 
 @implementation Subclass4
 + (id)alloc {
-  return self; // FIXME -- should error{{cannot initialize return object of type 'Subclass4 *' with an lvalue of type 'Class'}}
+  return self; // expected-error{{cannot initialize return object of type 'Subclass4 *' with an lvalue of type 'Class'}}
 }
 
 - (Subclass3 *)init { return 0; } // don't complain: we lost the related return type