[ObjC] Warn on unguarded use of partial declaration

This commit adds a traversal of the AST after Sema of a function that diagnoses
unguarded references to declarations that are partially available (based on
availability attributes). This traversal is only done when we would otherwise
emit -Wpartial-availability.

This commit is part of a feature I proposed here:
http://lists.llvm.org/pipermail/cfe-dev/2016-July/049851.html

Differential revision: https://reviews.llvm.org/D23003

llvm-svn: 278826

clang/include/clang/AST/Stmt.h

@@ -933,6 +933,8 @@ class IfStmt : public Stmt {
   bool isConstexpr() const { return IfStmtBits.IsConstexpr; }
   void setConstexpr(bool C) { IfStmtBits.IsConstexpr = C; }
 
+  bool isObjCAvailabilityCheck() const;
+
   SourceLocation getLocStart() const LLVM_READONLY { return IfLoc; }
   SourceLocation getLocEnd() const LLVM_READONLY {
     if (SubExprs[ELSE])

clang/include/clang/Basic/DiagnosticGroups.td

@@ -95,8 +95,9 @@ def CXX11CompatDeprecatedWritableStr :
 def DeprecatedAttributes : DiagGroup<"deprecated-attributes">;
 def DeprecatedDeclarations : DiagGroup<"deprecated-declarations">;
 def UnavailableDeclarations : DiagGroup<"unavailable-declarations">;
-def PartialAvailability : DiagGroup<"partial-availability">;
 def UnguardedAvailability : DiagGroup<"unguarded-availability">;
+// partial-availability is an alias of unguarded-availability.
+def : DiagGroup<"partial-availability", [UnguardedAvailability]>;
 def DeprecatedImplementations :DiagGroup<"deprecated-implementations">;
 def DeprecatedIncrementBool : DiagGroup<"deprecated-increment-bool">;
 def DeprecatedRegister : DiagGroup<"deprecated-register">;

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -2656,8 +2656,20 @@ def note_overridden_method : Note<
 def note_protocol_method : Note<
   "protocol method is here">;
 
-def warn_available_using_star_case : Warning<
-  "using '*' case here, platform %0 is not accounted for">, InGroup<UnguardedAvailability>;
+def warn_unguarded_availability :
+  Warning<"%0 is only available on %1 %2 or newer">,
+  InGroup<UnguardedAvailability>, DefaultIgnore;
+def warn_partial_availability : Warning<"%0 is only available conditionally">,
+    InGroup<UnguardedAvailability>, DefaultIgnore;
+def note_partial_availability_silence : Note<
+  "explicitly redeclare %0 to silence this warning">;
+def note_unguarded_available_silence : Note<
+  "enclose %0 in an @available check to silence this warning">;
+def warn_partial_message : Warning<"%0 is partial: %1">,
+    InGroup<UnguardedAvailability>, DefaultIgnore;
+def warn_partial_fwdclass_message : Warning<
+    "%0 may be partial because the receiver type is unknown">,
+    InGroup<UnguardedAvailability>, DefaultIgnore;
 
 // Thread Safety Attributes
 def warn_invalid_capability_name : Warning<
@@ -4279,15 +4291,6 @@ def err_not_found_by_two_phase_lookup : Error<"call to function %0 that is neith
 def note_not_found_by_two_phase_lookup : Note<"%0 should be declared prior to the "
     "call site%select{| or in %2| or in an associated namespace of one of its arguments}1">;
 def err_undeclared_use : Error<"use of undeclared %0">;
-def warn_partial_availability : Warning<"%0 is only available conditionally">,
-    InGroup<PartialAvailability>, DefaultIgnore;
-def note_partial_availability_silence : Note<
-  "explicitly redeclare %0 to silence this warning">;
-def warn_partial_message : Warning<"%0 is partial: %1">,
-    InGroup<PartialAvailability>, DefaultIgnore;
-def warn_partial_fwdclass_message : Warning<
-    "%0 may be partial because the receiver type is unknown">,
-    InGroup<PartialAvailability>, DefaultIgnore;
 def warn_deprecated : Warning<"%0 is deprecated">,
     InGroup<DeprecatedDeclarations>;
 def warn_property_method_deprecated :
@@ -4738,6 +4741,8 @@ def note_protected_by_vla_type_alias : Note<
   "jump bypasses initialization of VLA type alias">;
 def note_protected_by_constexpr_if : Note<
   "jump enters controlled statement of constexpr if">;
+def note_protected_by_if_available : Note<
+  "jump enters controlled statement of if available">;
 def note_protected_by_vla : Note<
   "jump bypasses initialization of variable length array">;
 def note_protected_by_objc_try : Note<

clang/include/clang/Sema/ScopeInfo.h

@@ -106,11 +106,15 @@ class FunctionScopeInfo {
   bool HasDroppedStmt : 1;
 
   /// \brief True if current scope is for OpenMP declare reduction combiner.
-  bool HasOMPDeclareReductionCombiner;
+  bool HasOMPDeclareReductionCombiner : 1;
 
   /// \brief Whether there is a fallthrough statement in this function.
   bool HasFallthroughStmt : 1;
 
+  /// \brief Whether we make reference to a declaration that could be
+  /// unavailable.
+  bool HasPotentialAvailabilityViolations : 1;
+
   /// A flag that is set when parsing a method that must call super's
   /// implementation, such as \c -dealloc, \c -finalize, or any method marked
   /// with \c __attribute__((objc_requires_super)).
@@ -381,6 +385,7 @@ class FunctionScopeInfo {
       HasDroppedStmt(false),
       HasOMPDeclareReductionCombiner(false),
       HasFallthroughStmt(false),
+      HasPotentialAvailabilityViolations(false),
       ObjCShouldCallSuper(false),
       ObjCIsDesignatedInit(false),
       ObjCWarnForNoDesignatedInitChain(false),

clang/include/clang/Sema/Sema.h

@@ -3639,6 +3639,9 @@ class Sema {
   bool makeUnavailableInSystemHeader(SourceLocation loc,
                                      UnavailableAttr::ImplicitReason reason);
 
+  /// \brief Issue any -Wunguarded-availability warnings in \c FD
+  void DiagnoseUnguardedAvailabilityViolations(Decl *FD);
+
   //===--------------------------------------------------------------------===//
   // Expression Parsing Callbacks: SemaExpr.cpp.
 

clang/lib/AST/Stmt.cpp

@@ -794,6 +794,10 @@ void IfStmt::setConditionVariable(const ASTContext &C, VarDecl *V) {
                                    VarRange.getEnd());
 }
 
+bool IfStmt::isObjCAvailabilityCheck() const {
+  return isa<ObjCAvailabilityCheckExpr>(SubExprs[COND]);
+}
+
 ForStmt::ForStmt(const ASTContext &C, Stmt *Init, Expr *Cond, VarDecl *condVar,
                  Expr *Inc, Stmt *Body, SourceLocation FL, SourceLocation LP,
                  SourceLocation RP)

clang/lib/Sema/JumpDiagnostics.cpp

@@ -325,30 +325,27 @@ void JumpScopeChecker::BuildScopeInformation(Stmt *S,
 
   case Stmt::IfStmtClass: {
     IfStmt *IS = cast<IfStmt>(S);
-    if (!IS->isConstexpr())
+    if (!(IS->isConstexpr() || IS->isObjCAvailabilityCheck()))
       break;
 
+    unsigned Diag = IS->isConstexpr() ? diag::note_protected_by_constexpr_if
+                                      : diag::note_protected_by_if_available;
+
     if (VarDecl *Var = IS->getConditionVariable())
       BuildScopeInformation(Var, ParentScope);
 
     // Cannot jump into the middle of the condition.
     unsigned NewParentScope = Scopes.size();
-    Scopes.push_back(GotoScope(ParentScope,
-                               diag::note_protected_by_constexpr_if, 0,
-                               IS->getLocStart()));
+    Scopes.push_back(GotoScope(ParentScope, Diag, 0, IS->getLocStart()));
     BuildScopeInformation(IS->getCond(), NewParentScope);
 
     // Jumps into either arm of an 'if constexpr' are not allowed.
     NewParentScope = Scopes.size();
-    Scopes.push_back(GotoScope(ParentScope,
-                               diag::note_protected_by_constexpr_if, 0,
-                               IS->getLocStart()));
+    Scopes.push_back(GotoScope(ParentScope, Diag, 0, IS->getLocStart()));
     BuildScopeInformation(IS->getThen(), NewParentScope);
     if (Stmt *Else = IS->getElse()) {
       NewParentScope = Scopes.size();
-      Scopes.push_back(GotoScope(ParentScope,
-                                 diag::note_protected_by_constexpr_if, 0,
-                                 IS->getLocStart()));
+      Scopes.push_back(GotoScope(ParentScope, Diag, 0, IS->getLocStart()));
       BuildScopeInformation(Else, NewParentScope);
     }
     return;

clang/lib/Sema/ScopeInfo.cpp

@@ -29,6 +29,7 @@ void FunctionScopeInfo::Clear() {
   HasIndirectGoto = false;
   HasDroppedStmt = false;
   HasOMPDeclareReductionCombiner = false;
+  HasPotentialAvailabilityViolations = false;
   ObjCShouldCallSuper = false;
   ObjCIsDesignatedInit = false;
   ObjCWarnForNoDesignatedInitChain = false;

clang/lib/Sema/SemaDecl.cpp

@@ -11736,6 +11736,9 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
     return nullptr;
   }
 
+  if (Body && getCurFunction()->HasPotentialAvailabilityViolations)
+    DiagnoseUnguardedAvailabilityViolations(dcl);
+
   assert(!getCurFunction()->ObjCShouldCallSuper &&
          "This should only be set for ObjC methods, which should have been "
          "handled in the block above.");

clang/lib/Sema/SemaDeclAttr.cpp

@@ -21,6 +21,7 @@
 #include "clang/AST/Expr.h"
 #include "clang/AST/ExprCXX.h"
 #include "clang/AST/Mangle.h"
+#include "clang/AST/RecursiveASTVisitor.h"
 #include "clang/Basic/CharInfo.h"
 #include "clang/Basic/SourceManager.h"
 #include "clang/Basic/TargetInfo.h"
@@ -6330,6 +6331,9 @@ static void DoEmitAvailabilityWarning(Sema &S, AvailabilityResult K,
     break;
 
   case AR_NotYetIntroduced:
+    assert(!S.getCurFunctionOrMethodDecl() &&
+           "Function-level partial availablity should not be diagnosed here!");
+
     diag = diag::warn_partial_availability;
     diag_message = diag::warn_partial_message;
     diag_fwdclass_message = diag::warn_partial_fwdclass_message;
@@ -6511,3 +6515,146 @@ VersionTuple Sema::getVersionForDecl(const Decl *D) const {
 
   return std::max(DeclVersion, Context.getTargetInfo().getPlatformMinVersion());
 }
+
+namespace {
+
+/// \brief This class implements -Wunguarded-availability.
+///
+/// This is done with a traversal of the AST of a function that makes reference
+/// to a partially available declaration. Whenever we encounter an \c if of the
+/// form: \c if(@available(...)), we use the version from the condition to visit
+/// the then statement.
+class DiagnoseUnguardedAvailability
+    : public RecursiveASTVisitor<DiagnoseUnguardedAvailability> {
+  typedef RecursiveASTVisitor<DiagnoseUnguardedAvailability> Base;
+
+  Sema &SemaRef;
+
+  /// Stack of potentially nested 'if (@available(...))'s.
+  SmallVector<VersionTuple, 8> AvailabilityStack;
+
+  void DiagnoseDeclAvailability(NamedDecl *D, SourceRange Range);
+
+public:
+  DiagnoseUnguardedAvailability(Sema &SemaRef, VersionTuple BaseVersion)
+      : SemaRef(SemaRef) {
+    AvailabilityStack.push_back(BaseVersion);
+  }
+
+  void IssueDiagnostics(Stmt *S) { TraverseStmt(S); }
+
+  bool TraverseIfStmt(IfStmt *If);
+
+  bool VisitObjCMessageExpr(ObjCMessageExpr *Msg) {
+    if (ObjCMethodDecl *D = Msg->getMethodDecl())
+      DiagnoseDeclAvailability(
+          D, SourceRange(Msg->getSelectorStartLoc(), Msg->getLocEnd()));
+    return true;
+  }
+
+  bool VisitDeclRefExpr(DeclRefExpr *DRE) {
+    DiagnoseDeclAvailability(DRE->getDecl(),
+                             SourceRange(DRE->getLocStart(), DRE->getLocEnd()));
+    return true;
+  }
+
+  bool VisitMemberExpr(MemberExpr *ME) {
+    DiagnoseDeclAvailability(ME->getMemberDecl(),
+                             SourceRange(ME->getLocStart(), ME->getLocEnd()));
+    return true;
+  }
+
+  bool VisitTypeLoc(TypeLoc Ty);
+};
+
+void DiagnoseUnguardedAvailability::DiagnoseDeclAvailability(
+    NamedDecl *D, SourceRange Range) {
+
+  VersionTuple ContextVersion = AvailabilityStack.back();
+  if (AvailabilityResult Result = SemaRef.ShouldDiagnoseAvailabilityOfDecl(
+          D, ContextVersion, nullptr)) {
+    // All other diagnostic kinds have already been handled in
+    // DiagnoseAvailabilityOfDecl.
+    if (Result != AR_NotYetIntroduced)
+      return;
+
+    const AvailabilityAttr *AA = getAttrForPlatform(SemaRef.getASTContext(), D);
+    VersionTuple Introduced = AA->getIntroduced();
+
+    SemaRef.Diag(Range.getBegin(), diag::warn_unguarded_availability)
+        << Range << D
+        << AvailabilityAttr::getPrettyPlatformName(
+               SemaRef.getASTContext().getTargetInfo().getPlatformName())
+        << Introduced.getAsString();
+
+    SemaRef.Diag(D->getLocation(), diag::note_availability_specified_here)
+        << D << /* partial */ 3;
+
+    // FIXME: Replace this with a fixit diagnostic.
+    SemaRef.Diag(Range.getBegin(), diag::note_unguarded_available_silence)
+        << Range << D;
+  }
+}
+
+bool DiagnoseUnguardedAvailability::VisitTypeLoc(TypeLoc Ty) {
+  const Type *TyPtr = Ty.getTypePtr();
+  SourceRange Range{Ty.getBeginLoc(), Ty.getEndLoc()};
+
+  if (const TagType *TT = dyn_cast<TagType>(TyPtr)) {
+    TagDecl *TD = TT->getDecl();
+    DiagnoseDeclAvailability(TD, Range);
+
+  } else if (const TypedefType *TD = dyn_cast<TypedefType>(TyPtr)) {
+    TypedefNameDecl *D = TD->getDecl();
+    DiagnoseDeclAvailability(D, Range);
+
+  } else if (const auto *ObjCO = dyn_cast<ObjCObjectType>(TyPtr)) {
+    if (NamedDecl *D = ObjCO->getInterface())
+      DiagnoseDeclAvailability(D, Range);
+  }
+
+  return true;
+}
+
+bool DiagnoseUnguardedAvailability::TraverseIfStmt(IfStmt *If) {
+  VersionTuple CondVersion;
+  if (auto *E = dyn_cast<ObjCAvailabilityCheckExpr>(If->getCond())) {
+    CondVersion = E->getVersion();
+
+    // If we're using the '*' case here or if this check is redundant, then we
+    // use the enclosing version to check both branches.
+    if (CondVersion.empty() || CondVersion <= AvailabilityStack.back())
+      return Base::TraverseStmt(If->getThen()) &&
+             Base::TraverseStmt(If->getElse());
+  } else {
+    // This isn't an availability checking 'if', we can just continue.
+    return Base::TraverseIfStmt(If);
+  }
+
+  AvailabilityStack.push_back(CondVersion);
+  bool ShouldContinue = TraverseStmt(If->getThen());
+  AvailabilityStack.pop_back();
+
+  return ShouldContinue && TraverseStmt(If->getElse());
+}
+
+} // end anonymous namespace
+
+void Sema::DiagnoseUnguardedAvailabilityViolations(Decl *D) {
+  Stmt *Body = nullptr;
+
+  if (auto *FD = D->getAsFunction()) {
+    // FIXME: We only examine the pattern decl for availability violations now,
+    // but we should also examine instantiated templates.
+    if (FD->isTemplateInstantiation())
+      return;
+
+    Body = FD->getBody();
+  } else if (auto *MD = dyn_cast<ObjCMethodDecl>(D))
+    Body = MD->getBody();
+
+  assert(Body && "Need a body here!");
+
+  VersionTuple BaseVersion = getVersionForDecl(D);
+  DiagnoseUnguardedAvailability(*this, BaseVersion).IssueDiagnostics(Body);
+}

clang/lib/Sema/SemaExpr.cpp

@@ -184,6 +184,11 @@ DiagnoseAvailabilityOfDecl(Sema &S, NamedDecl *D, SourceLocation Loc,
   if (AvailabilityResult Result =
           S.ShouldDiagnoseAvailabilityOfDecl(D, ContextVersion, &Message)) {
 
+    if (Result == AR_NotYetIntroduced && S.getCurFunctionOrMethodDecl()) {
+      S.getEnclosingFunction()->HasPotentialAvailabilityViolations = true;
+      return;
+    }
+
     const ObjCPropertyDecl *ObjCPDecl = nullptr;
     if (const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(D)) {
       if (const ObjCPropertyDecl *PD = MD->findPropertyDecl()) {
@@ -15198,11 +15203,6 @@ ExprResult Sema::ActOnObjCAvailabilityCheckExpr(
   VersionTuple Version;
   if (Spec != AvailSpecs.end())
     Version = Spec->getVersion();
-  else
-    // This is the '*' case in @available. We should diagnose this; the
-    // programmer should explicitly account for this case if they target this
-    // platform.
-    Diag(AtLoc, diag::warn_available_using_star_case) << RParen << Platform;
 
   return new (Context)
       ObjCAvailabilityCheckExpr(Version, AtLoc, RParen, Context.BoolTy);

clang/lib/Sema/SemaStmt.cpp

@@ -536,7 +536,7 @@ StmtResult Sema::BuildIfStmt(SourceLocation IfLoc, bool IsConstexpr,
   if (Cond.isInvalid())
     return StmtError();
 
-  if (IsConstexpr)
+  if (IsConstexpr || isa<ObjCAvailabilityCheckExpr>(Cond.get().second))
     getCurFunction()->setHasBranchProtectedScope();
 
   DiagnoseUnusedExprResult(thenStmt);

clang/test/Parser/objc-available.m

@@ -15,8 +15,6 @@ void f() {
 
   (void)@available(erik_os 10.10, hat_os 1.0, *); // expected-error 2 {{unrecognized platform name}}
 
-  (void)@available(ios 8, *); // expected-warning{{using '*' case here, platform macos is not accounted for}}
-
   (void)@available(); // expected-error{{expected a platform name here}}
   (void)@available(macos 10.10,); // expected-error{{expected a platform name here}}
   (void)@available(macos); // expected-error{{expected a version}}

clang/test/Sema/attr-availability.c

@@ -30,7 +30,7 @@ void test_10095131() {
   ATSFontGetPostScriptName(100); // expected-error {{'ATSFontGetPostScriptName' is unavailable: obsoleted in macOS 9.0 - use ATSFontGetFullPostScriptName}}
 
 #if defined(WARN_PARTIAL)
-  // expected-warning@+2 {{is partial: introduced in macOS 10.8}} expected-note@+2 {{explicitly redeclare 'PartiallyAvailable' to silence this warning}}
+  // expected-warning@+2 {{is only available on macOS 10.8 or newer}} expected-note@+2 {{enclose 'PartiallyAvailable' in an @available check to silence this warning}}
 #endif
   PartiallyAvailable();
 }