When checking availability attributes for consistency between an

overriding and overridden method, allow the overridden method to have
a narrower contract (introduced earlier, deprecated/obsoleted later)
than the overriding method. Fixes <rdar://problem/12992023>.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172567 91177308-0d34-0410-b5e6-96231b3b80d8

6 files changed, 129 insertions, 32 deletions

diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 3ea9df4d76..cd00919587 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1879,6 +1879,16 @@ def warn_availability_version_ordering : Warning<
   "attribute ignored">, InGroup<Availability>;
 def warn_mismatched_availability: Warning<
   "availability does not match previous declaration">, InGroup<Availability>;
+def warn_mismatched_availability_override : Warning<
+  "overriding method %select{introduced after|"
+  "deprecated before|obsoleted before}0 overridden method on %1 (%2 vs. %3)">, 
+  InGroup<Availability>;
+def warn_mismatched_availability_override_unavail : Warning<
+  "overriding method cannot be unavailable on %0 when its overridden method is "
+  "available">,
+  InGroup<Availability>;
+def note_overridden_method : Note<
+  "overridden method is here">;
 
 // Thread Safety Attributes
 def warn_thread_attribute_ignored : Warning<
diff --git a/include/clang/Sema/Sema.h b/include/clang/Sema/Sema.h
index 591ced11d5..5043fd75f8 100644
--- a/include/clang/Sema/Sema.h
+++ b/include/clang/Sema/Sema.h
@@ -1677,7 +1677,8 @@ public:
                                           VersionTuple Deprecated,
                                           VersionTuple Obsoleted,
                                           bool IsUnavailable,
-                                          StringRef Message);
+                                          StringRef Message,
+                                          bool Override);
   VisibilityAttr *mergeVisibilityAttr(Decl *D, SourceRange Range,
                                       VisibilityAttr::VisibilityType Vis);
   DLLImportAttr *mergeDLLImportAttr(Decl *D, SourceRange Range);
@@ -1685,10 +1686,24 @@ public:
   FormatAttr *mergeFormatAttr(Decl *D, SourceRange Range, StringRef Format,
                               int FormatIdx, int FirstArg);
   SectionAttr *mergeSectionAttr(Decl *D, SourceRange Range, StringRef Name);
-  bool mergeDeclAttribute(NamedDecl *New, InheritableAttr *Attr);
+  bool mergeDeclAttribute(NamedDecl *New, InheritableAttr *Attr,
+                          bool Override);
+
+  /// \brief Describes the kind of merge to perform for availability
+  /// attributes (including "deprecated", "unavailable", and "availability").
+  enum AvailabilityMergeKind {
+    /// \brief Don't merge availability attributes at all.
+    AMK_None,
+    /// \brief Merge availability attributes for a redeclaration, which requires
+    /// an exact match.
+    AMK_Redeclaration,
+    /// \brief Merge availability attributes for an override, which requires
+    /// an exact match or a weakening of constraints.
+    AMK_Override
+  };
 
   void mergeDeclAttributes(NamedDecl *New, Decl *Old,
-                           bool MergeDeprecation = true);
+                           AvailabilityMergeKind AMK = AMK_Redeclaration);
   void MergeTypedefNameDecl(TypedefNameDecl *New, LookupResult &OldDecls);
   bool MergeFunctionDecl(FunctionDecl *New, Decl *Old, Scope *S);
   bool MergeCompatibleFunctionDecls(FunctionDecl *New, FunctionDecl *Old,
@@ -6383,8 +6398,7 @@ public:
   /// \brief Check whether the given new method is a valid override of the
   /// given overridden method, and set any properties that should be inherited.
   void CheckObjCMethodOverride(ObjCMethodDecl *NewMethod,
-                               const ObjCMethodDecl *Overridden,
-                               bool IsImplementation);
+                               const ObjCMethodDecl *Overridden);
 
   /// \brief Describes the compatibility of a result type with its method.
   enum ResultTypeCompatibilityKind {
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 537e70bfbe..5d655e24c0 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -1822,13 +1822,14 @@ DeclHasAttr(const Decl *D, const Attr *A) {
   return false;
 }
 
-bool Sema::mergeDeclAttribute(NamedDecl *D, InheritableAttr *Attr) {
+bool Sema::mergeDeclAttribute(NamedDecl *D, InheritableAttr *Attr,
+                              bool Override) {
   InheritableAttr *NewAttr = NULL;
   if (AvailabilityAttr *AA = dyn_cast<AvailabilityAttr>(Attr))
     NewAttr = mergeAvailabilityAttr(D, AA->getRange(), AA->getPlatform(),
                                     AA->getIntroduced(), AA->getDeprecated(),
                                     AA->getObsoleted(), AA->getUnavailable(),
-                                    AA->getMessage());
+                                    AA->getMessage(), Override);
   else if (VisibilityAttr *VA = dyn_cast<VisibilityAttr>(Attr))
     NewAttr = mergeVisibilityAttr(D, VA->getRange(), VA->getVisibility());
   else if (DLLImportAttr *ImportA = dyn_cast<DLLImportAttr>(Attr))
@@ -1902,7 +1903,7 @@ static void checkNewAttributesAfterDef(Sema &S, Decl *New, const Decl *Old) {
 
 /// mergeDeclAttributes - Copy attributes from the Old decl to the New one.
 void Sema::mergeDeclAttributes(NamedDecl *New, Decl *Old,
-                               bool MergeDeprecation) {
+                               AvailabilityMergeKind AMK) {
   // attributes declared post-definition are currently ignored
   checkNewAttributesAfterDef(*this, New, Old);
 
@@ -1919,14 +1920,25 @@ void Sema::mergeDeclAttributes(NamedDecl *New, Decl *Old,
          i = Old->specific_attr_begin<InheritableAttr>(),
          e = Old->specific_attr_end<InheritableAttr>(); 
        i != e; ++i) {
+    bool Override = false;
     // Ignore deprecated/unavailable/availability attributes if requested.
-    if (!MergeDeprecation &&
-        (isa<DeprecatedAttr>(*i) || 
-         isa<UnavailableAttr>(*i) ||
-         isa<AvailabilityAttr>(*i)))
-      continue;
+    if (isa<DeprecatedAttr>(*i) ||
+        isa<UnavailableAttr>(*i) ||
+        isa<AvailabilityAttr>(*i)) {
+      switch (AMK) {
+      case AMK_None:
+        continue;
+
+      case AMK_Redeclaration:
+        break;
+
+      case AMK_Override:
+        Override = true;
+        break;
+      }
+    }
 
-    if (mergeDeclAttribute(New, *i))
+    if (mergeDeclAttribute(New, *i, Override))
       foundAny = true;
   }
 
@@ -2475,7 +2487,7 @@ void Sema::mergeObjCMethodDecls(ObjCMethodDecl *newMethod,
                                 ObjCMethodDecl *oldMethod) {
 
   // Merge the attributes, including deprecated/unavailable
-  mergeDeclAttributes(newMethod, oldMethod, /* mergeDeprecation */true);
+  mergeDeclAttributes(newMethod, oldMethod, AMK_Override);
 
   // Merge attributes from the parameters.
   ObjCMethodDecl::param_const_iterator oi = oldMethod->param_begin(),
@@ -2485,7 +2497,7 @@ void Sema::mergeObjCMethodDecls(ObjCMethodDecl *newMethod,
        ni != ne && oi != oe; ++ni, ++oi)
     mergeParamDeclAttributes(*ni, *oi, Context);
 
-  CheckObjCMethodOverride(newMethod, oldMethod, true);
+  CheckObjCMethodOverride(newMethod, oldMethod);
 }
 
 /// MergeVarDeclTypes - We parsed a variable 'New' which has the same name and
diff --git a/lib/Sema/SemaDeclAttr.cpp b/lib/Sema/SemaDeclAttr.cpp
index bd81c27ad1..74a6bc5546 100644
--- a/lib/Sema/SemaDeclAttr.cpp
+++ b/lib/Sema/SemaDeclAttr.cpp
@@ -2001,13 +2001,32 @@ static bool checkAvailabilityAttr(Sema &S, SourceRange Range,
   return false;
 }
 
+/// \brief Check whether the two versions match.
+///
+/// If either version tuple is empty, then they are assumed to match. If
+/// \p BeforeIsOkay is true, then \p X can be less than or equal to \p Y.
+static bool versionsMatch(const VersionTuple &X, const VersionTuple &Y,
+                          bool BeforeIsOkay) {
+  if (X.empty() || Y.empty())
+    return true;
+
+  if (X == Y)
+    return true;
+
+  if (BeforeIsOkay && X < Y)
+    return true;
+
+  return false;
+}
+
 AvailabilityAttr *Sema::mergeAvailabilityAttr(NamedDecl *D, SourceRange Range,
                                               IdentifierInfo *Platform,
                                               VersionTuple Introduced,
                                               VersionTuple Deprecated,
                                               VersionTuple Obsoleted,
                                               bool IsUnavailable,
-                                              StringRef Message) {
+                                              StringRef Message,
+                                              bool Override) {
   VersionTuple MergedIntroduced = Introduced;
   VersionTuple MergedDeprecated = Deprecated;
   VersionTuple MergedObsoleted = Obsoleted;
@@ -2033,18 +2052,47 @@ AvailabilityAttr *Sema::mergeAvailabilityAttr(NamedDecl *D, SourceRange Range,
       VersionTuple OldDeprecated = OldAA->getDeprecated();
       VersionTuple OldObsoleted = OldAA->getObsoleted();
       bool OldIsUnavailable = OldAA->getUnavailable();
-      StringRef OldMessage = OldAA->getMessage();
-
-      if ((!OldIntroduced.empty() && !Introduced.empty() &&
-           OldIntroduced != Introduced) ||
-          (!OldDeprecated.empty() && !Deprecated.empty() &&
-           OldDeprecated != Deprecated) ||
-          (!OldObsoleted.empty() && !Obsoleted.empty() &&
-           OldObsoleted != Obsoleted) ||
-          (OldIsUnavailable != IsUnavailable) ||
-          (OldMessage != Message)) {
-        Diag(OldAA->getLocation(), diag::warn_mismatched_availability);
-        Diag(Range.getBegin(), diag::note_previous_attribute);
+
+      if (!versionsMatch(OldIntroduced, Introduced, Override) ||
+          !versionsMatch(Deprecated, OldDeprecated, Override) ||
+          !versionsMatch(Obsoleted, OldObsoleted, Override) ||
+          !(OldIsUnavailable == IsUnavailable ||
+            (Override && OldIsUnavailable && !IsUnavailable))) {
+        if (Override) {
+          int Which = -1;
+          VersionTuple FirstVersion;
+          VersionTuple SecondVersion;
+          if (!versionsMatch(OldIntroduced, Introduced, Override)) {
+            Which = 0;
+            FirstVersion = OldIntroduced;
+            SecondVersion = Introduced;
+          } else if (!versionsMatch(Deprecated, OldDeprecated, Override)) {
+            Which = 1;
+            FirstVersion = Deprecated;
+            SecondVersion = OldDeprecated;
+          } else if (!versionsMatch(Obsoleted, OldObsoleted, Override)) {
+            Which = 2;
+            FirstVersion = Obsoleted;
+            SecondVersion = OldObsoleted;
+          }
+
+          if (Which == -1) {
+            Diag(OldAA->getLocation(),
+                 diag::warn_mismatched_availability_override_unavail)
+              << AvailabilityAttr::getPrettyPlatformName(Platform->getName());
+          } else {
+            Diag(OldAA->getLocation(),
+                 diag::warn_mismatched_availability_override)
+              << Which
+              << AvailabilityAttr::getPrettyPlatformName(Platform->getName())
+              << FirstVersion.getAsString() << SecondVersion.getAsString();
+          }
+          Diag(Range.getBegin(), diag::note_overridden_method);
+        } else {
+          Diag(OldAA->getLocation(), diag::warn_mismatched_availability);
+          Diag(Range.getBegin(), diag::note_previous_attribute);
+        }
+
         Attrs.erase(Attrs.begin() + i);
         --e;
         continue;
@@ -2121,7 +2169,8 @@ static void handleAvailabilityAttr(Sema &S, Decl *D,
                                                       Introduced.Version,
                                                       Deprecated.Version,
                                                       Obsoleted.Version,
-                                                      IsUnavailable, Str);
+                                                      IsUnavailable, Str,
+                                                      /*Override=*/false);
   if (NewAttr)
     D->addAttr(NewAttr);
 }
diff --git a/lib/Sema/SemaDeclObjC.cpp b/lib/Sema/SemaDeclObjC.cpp
index d22d7a14f6..870c52b6e6 100644
--- a/lib/Sema/SemaDeclObjC.cpp
+++ b/lib/Sema/SemaDeclObjC.cpp
@@ -109,8 +109,7 @@ bool Sema::checkInitMethod(ObjCMethodDecl *method,
 }
 
 void Sema::CheckObjCMethodOverride(ObjCMethodDecl *NewMethod, 
-                                   const ObjCMethodDecl *Overridden,
-                                   bool IsImplementation) {
+                                   const ObjCMethodDecl *Overridden) {
   if (Overridden->hasRelatedResultType() && 
       !NewMethod->hasRelatedResultType()) {
     // This can only happen when the method follows a naming convention that
diff --git a/test/SemaObjC/attr-availability.m b/test/SemaObjC/attr-availability.m
index ed6b7608b9..0905733906 100644
--- a/test/SemaObjC/attr-availability.m
+++ b/test/SemaObjC/attr-availability.m
@@ -6,11 +6,24 @@
 
 @interface A <P>
 - (void)method __attribute__((availability(macosx,introduced=10.1,deprecated=10.2))); // expected-note {{method 'method' declared here}}
+
+- (void)overridden __attribute__((availability(macosx,introduced=10.3))); // expected-note{{overridden method is here}}
+- (void)overridden2 __attribute__((availability(macosx,introduced=10.3)));
+- (void)overridden3 __attribute__((availability(macosx,deprecated=10.3)));
+- (void)overridden4 __attribute__((availability(macosx,deprecated=10.3))); // expected-note{{overridden method is here}}
+- (void)overridden5 __attribute__((availability(macosx,unavailable))); // expected-note{{overridden method is here}}
+- (void)overridden6 __attribute__((availability(macosx,introduced=10.3)));
 @end
 
 // rdar://11475360
 @interface B : A
 - (void)method; // expected-note {{method 'method' declared here}}
+- (void)overridden __attribute__((availability(macosx,introduced=10.4))); // expected-warning{{overriding method introduced after overridden method on OS X (10.4 vs. 10.3)}}
+- (void)overridden2 __attribute__((availability(macosx,introduced=10.2)));
+- (void)overridden3 __attribute__((availability(macosx,deprecated=10.4)));
+- (void)overridden4 __attribute__((availability(macosx,deprecated=10.2))); // expected-warning{{overriding method deprecated before overridden method on OS X (10.3 vs. 10.2)}}
+- (void)overridden5 __attribute__((availability(macosx,introduced=10.3))); // expected-warning{{overriding method cannot be unavailable on OS X when its overridden method is available}}
+- (void)overridden6 __attribute__((availability(macosx,unavailable)));
 @end
 
 void f(A *a, B *b) {