Implement Objective-C Related Result Type semantics.

Related result types apply Cocoa conventions to the type of message
sends and property accesses to Objective-C methods that are known to
always return objects whose type is the same as the type of the
receiving class (or a subclass thereof), such as +alloc and
-init. This tightens up static type safety for Objective-C, so that we
now diagnose mistakes like this:

t.m:4:10: warning: incompatible pointer types initializing 'NSSet *'
with an
      expression of type 'NSArray *' [-Wincompatible-pointer-types]
  NSSet *array = [[NSArray alloc] init];
         ^       ~~~~~~~~~~~~~~~~~~~~~~
/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:72:1:
note: 
      instance method 'init' is assumed to return an instance of its
      receiver
      type ('NSArray *')
- (id)init;
^

It also means that we get decent type inference when writing code in
Objective-C++0x:

  auto array = [[NSMutableArray alloc] initWithObjects:@"one",  @"two",nil];
  //    ^ now infers NSMutableArray* rather than id




git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@132868 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 6 insertions, 0 deletions

diff --git a/lib/Driver/Tools.cpp b/lib/Driver/Tools.cpp
index bc3ff6873b..8cd7adc42e 100644
--- a/lib/Driver/Tools.cpp
+++ b/lib/Driver/Tools.cpp
@@ -1542,6 +1542,12 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
                     options::OPT_fno_lax_vector_conversions))
     CmdArgs.push_back("-fno-lax-vector-conversions");
 
+  // -fobjc-infer-related-result-type is the default.
+  if (Args.hasFlag(options::OPT_fobjc_infer_related_result_type, 
+                   options::OPT_fno_objc_infer_related_result_type, 
+                   /*Default=*/true))
+    CmdArgs.push_back("-fobjc-infer-related-result-type");
+  
   // Handle -fobjc-gc and -fobjc-gc-only. They are exclusive, and -fobjc-gc-only
   // takes precedence.
   const Arg *GCArg = Args.getLastArg(options::OPT_fobjc_gc_only);