Remove the fixit for the diagnostics regarding capturing autoreleasing variables in a block

[george.karpenkov]

Summary

The fixit is actively harmful, as it encourages developers to ignore the warning and to write unsafe code.
It is almost impossible to write safe code while capturing autoreleasing variables in the block, as in order to check that the block is never called in the autoreleasing pool the developer has to check the transitive closure of all potential callers of the block.

[arphaman]

LGTM.

[george.karpenkov]

@ahatanak Any feedback?

[ahatanak]

Sorry for the delay, LGTM.

include/clang/Basic/DiagnosticSemaKinds.td

   "declared %select{|__unsafe_unretained|__strong|__weak|__autoreleasing}2">;
 
 } // end "ARC and @properties" category
 
 def warn_block_capture_autoreleasing : Warning<
   "block captures an autoreleasing out-parameter, which may result in "
   "use-after-free bugs">,
   InGroup<BlockCaptureAutoReleasing>;
-def note_declare_parameter_autoreleasing : Note<
-  "declare the parameter __autoreleasing explicitly to suppress this warning">;
 def note_declare_parameter_strong : Note<
   "declare the parameter __strong or capture a __block __strong variable to "
   "keep values alive across autorelease pools">;
 
 def err_arc_atomic_ownership : Error<
   "cannot perform atomic operation on a pointer to type %0: type has "
   "non-trivial ownership">;
 

lib/Sema/SemaExpr.cpp

     QualType PointeeTy = PT->getPointeeType();
 
     if (PointeeTy->getAs<ObjCObjectPointerType>() &&
         PointeeTy.getObjCLifetime() == Qualifiers::OCL_Autoreleasing &&
         !IsObjCOwnershipAttributedType(PointeeTy)) {
       if (BuildAndDiagnose) {
         SourceLocation VarLoc = Var->getLocation();
         S.Diag(Loc, diag::warn_block_capture_autoreleasing);
-        {
-          auto AddAutoreleaseNote =
-              S.Diag(VarLoc, diag::note_declare_parameter_autoreleasing);
-          // Provide a fix-it for the '__autoreleasing' keyword at the
-          // appropriate location in the variable's type.
-          if (const auto *TSI = Var->getTypeSourceInfo()) {
-            PointerTypeLoc PTL =
-                TSI->getTypeLoc().getAsAdjusted<PointerTypeLoc>();
-            if (PTL) {
-              SourceLocation Loc = PTL.getPointeeLoc().getEndLoc();
-              Loc = Lexer::getLocForEndOfToken(Loc, 0, S.getSourceManager(),
-                                               S.getLangOpts());
-              if (Loc.isValid()) {
-                StringRef CharAtLoc = Lexer::getSourceText(
-                    CharSourceRange::getCharRange(Loc, Loc.getLocWithOffset(1)),
-                    S.getSourceManager(), S.getLangOpts());
-                AddAutoreleaseNote << FixItHint::CreateInsertion(
-                    Loc, CharAtLoc.empty() || !isWhitespace(CharAtLoc[0])
-                             ? " __autoreleasing "
-                             : " __autoreleasing");
-              }
-            }
-          }
-        }
         S.Diag(VarLoc, diag::note_declare_parameter_strong);
       }
     }
   }
 
   const bool HasBlocksAttr = Var->hasAttr<BlocksAttr>();
   if (HasBlocksAttr || CaptureType->isReferenceType() ||
       (S.getLangOpts().OpenMP && S.isOpenMPCapturedDecl(Var))) {

test/SemaObjC/arc.m

 // RUN: %clang_cc1 -triple x86_64-apple-darwin11 -fobjc-runtime-has-weak -fsyntax-only -fobjc-arc -fblocks -verify -Wno-objc-root-class %s
-// RUN: not %clang_cc1 -triple x86_64-apple-darwin11 -fobjc-runtime-has-weak -fsyntax-only -fobjc-arc -fblocks -Wno-objc-root-class -fdiagnostics-parseable-fixits %s 2>&1 | FileCheck %s
+// RUN: not %clang_cc1 -triple x86_64-apple-darwin11 -fobjc-runtime-has-weak -fsyntax-only -fobjc-arc -fblocks -Wno-objc-root-class -fdiagnostics-parseable-fixits %s 2>&1
 
 typedef unsigned long NSUInteger;
 typedef const void * CFTypeRef;
 CFTypeRef CFBridgingRetain(id X);
 id CFBridgingRelease(CFTypeRef);
 @protocol NSCopying @end
 @interface NSDictionary
 + (id)dictionaryWithObjects:(const id [])objects forKeys:(const id <NSCopying> [])keys count:(NSUInteger)cnt;

 
 int garf() {
   id object;
   TKAssertEqual(object, nil);
   TKAssertEqual(object, (id)nil);
 }
 
 void block_capture_autoreleasing(A * __autoreleasing *a,
-                                 A **b, // expected-note {{declare the parameter __autoreleasing explicitly to suppress this warning}} expected-note {{declare the parameter __strong or capture a __block __strong variable to keep values alive across autorelease pools}}
-                                 A * _Nullable *c, // expected-note {{declare the parameter __autoreleasing explicitly to suppress this warning}} expected-note {{declare the parameter __strong or capture a __block __strong variable to keep values alive across autorelease pools}}
+                                 A **b, //  expected-note {{declare the parameter __strong or capture a __block __strong variable to keep values alive across autorelease pools}}
+                                 A * _Nullable *c, // expected-note {{declare the parameter __strong or capture a __block __strong variable to keep values alive across autorelease pools}}
                                  A * _Nullable __autoreleasing *d,
-                                 A ** _Nullable e, // expected-note {{declare the parameter __autoreleasing explicitly to suppress this warning}} expected-note {{declare the parameter __strong or capture a __block __strong variable to keep values alive across autorelease pools}}
+                                 A ** _Nullable e, // expected-note {{declare the parameter __strong or capture a __block __strong variable to keep values alive across autorelease pools}}
                                  A * __autoreleasing * _Nullable f,
                                  id __autoreleasing *g,
-                                 id *h, // expected-note {{declare the parameter __autoreleasing explicitly to suppress this warning}} expected-note {{declare the parameter __strong or capture a __block __strong variable to keep values alive across autorelease pools}}
-                                 id _Nullable *i, // expected-note {{declare the parameter __autoreleasing explicitly to suppress this warning}} expected-note {{declare the parameter __strong or capture a __block __strong variable to keep values alive across autorelease pools}}
+                                 id *h, // expected-note {{declare the parameter __strong or capture a __block __strong variable to keep values alive across autorelease pools}}
+                                 id _Nullable *i, // expected-note {{declare the parameter __strong or capture a __block __strong variable to keep values alive across autorelease pools}}
                                  id _Nullable __autoreleasing *j,
-                                 id * _Nullable k, // expected-note {{declare the parameter __autoreleasing explicitly to suppress this warning}} expected-note {{declare the parameter __strong or capture a __block __strong variable to keep values alive across autorelease pools}}
+                                 id * _Nullable k, // expected-note {{declare the parameter __strong or capture a __block __strong variable to keep values alive across autorelease pools}}
                                  id __autoreleasing * _Nullable l) {
-  // CHECK: fix-it:"{{.*}}":{[[@LINE-11]]:37-[[@LINE-11]]:37}:" __autoreleasing "
-  // CHECK: fix-it:"{{.*}}":{[[@LINE-11]]:47-[[@LINE-11]]:47}:" __autoreleasing"
-  // CHECK: fix-it:"{{.*}}":{[[@LINE-10]]:37-[[@LINE-10]]:37}:" __autoreleasing "
-  // CHECK: fix-it:"{{.*}}":{[[@LINE-8]]:36-[[@LINE-8]]:36}:" __autoreleasing"
-  // CHECK: fix-it:"{{.*}}":{[[@LINE-8]]:46-[[@LINE-8]]:46}:" __autoreleasing"
-  // CHECK: fix-it:"{{.*}}":{[[@LINE-7]]:36-[[@LINE-7]]:36}:" __autoreleasing"
   ^{
     (void)*a;
     (void)*b; // expected-warning {{block captures an autoreleasing out-parameter, which may result in use-after-free bugs}}
     (void)*c; // expected-warning {{block captures an autoreleasing out-parameter, which may result in use-after-free bugs}}
     (void)*d;
     (void)*e; // expected-warning {{block captures an autoreleasing out-parameter, which may result in use-after-free bugs}}
     (void)*f;
     (void)*g;
     (void)*h; // expected-warning {{block captures an autoreleasing out-parameter, which may result in use-after-free bugs}}
     (void)*i; // expected-warning {{block captures an autoreleasing out-parameter, which may result in use-after-free bugs}}
     (void)*j;
     (void)*k; // expected-warning {{block captures an autoreleasing out-parameter, which may result in use-after-free bugs}}
     (void)*l;
   }();
 }