r374202 - [ObjC generics] Fix not inheriting type bounds in categories/extensions.

[Hans Wennborg via cfe-commits]

Hi Volodymyr,

This broke the Chrome build in an interesting way. Here's a reduced repro:


$ cat /tmp/a.mm
#import <AVFoundation/AVFoundation.h>

void f(int width, int height) {
  FourCharCode best_fourcc = kCMPixelFormat_422YpCbCr8_yuvs;
  NSDictionary* videoSettingsDictionary = @{
    (id)kCVPixelBufferPixelFormatTypeKey : @(best_fourcc),
  };
}

$ build.release/bin/clang++ -isysroot
/work/chromium/src/build/mac_files/xcode_binaries/Contents/Developer/Platforms/MacOSX.platform/Developer/SDK
s/MacOSX10.14.sdk -c /tmp/a.mm

/tmp/a.mm:6:5: error: cannot initialize a parameter of type
'KeyType<NSCopying>  _Nonnull const' (aka 'const id') with an rvalue
of type 'id'
    (id)kCVPixelBufferPixelFormatTypeKey : @(best_fourcc),
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1 error generated.


To me, the "cannot initialize a parameter of type [nanana] (aka 'const
id') with an rvalue of type 'id'" message looks strange, but I'm not
an Obj-C expert. Is this expected behaviour, and if so how should we
change our code?

Thanks,
Hans

On Wed, Oct 9, 2019 at 12:26 PM Volodymyr Sapsai via cfe-commits
<cfe-commits at lists.llvm.org> wrote:
>
> Author: vsapsai
> Date: Wed Oct  9 12:29:13 2019
> New Revision: 374202
>
> URL: http://llvm.org/viewvc/llvm-project?rev=374202&view=rev
> Log:
> [ObjC generics] Fix not inheriting type bounds in categories/extensions.
>
> When a category/extension doesn't repeat a type bound, corresponding
> type parameter is substituted with `id` when used as a type argument. As
> a result, in the added test case it was causing errors like
>
> > type argument 'T' (aka 'id') does not satisfy the bound ('id<NSCopying>') of type parameter 'T'
>
> We are already checking that type parameters should be consistent
> everywhere (see `checkTypeParamListConsistency`) and update
> `ObjCTypeParamDecl` to have correct underlying type. And when we use the
> type parameter as a method return type or a method parameter type, it is
> substituted to the bounded type. But when we use the type parameter as a
> type argument, we check `ObjCTypeParamType` that ignores the updated
> underlying type and remains `id`.
>
> Fix by desugaring `ObjCTypeParamType` to the underlying type, the same
> way we are doing with `TypedefType`.
>
> rdar://problem/54329242
>
> Reviewers: erik.pilkington, ahatanak
>
> Reviewed By: erik.pilkington
>
> Subscribers: jkorous, dexonsmith, ributzka, cfe-commits
>
> Differential Revision: https://reviews.llvm.org/D66696
>
> Modified:
>     cfe/trunk/include/clang/AST/Type.h
>     cfe/trunk/lib/AST/Type.cpp
>     cfe/trunk/test/SemaObjC/parameterized_classes_subst.m
>
> Modified: cfe/trunk/include/clang/AST/Type.h
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/AST/Type.h?rev=374202&r1=374201&r2=374202&view=diff
> ==============================================================================
> --- cfe/trunk/include/clang/AST/Type.h (original)
> +++ cfe/trunk/include/clang/AST/Type.h Wed Oct  9 12:29:13 2019
> @@ -5569,7 +5569,7 @@ class ObjCTypeParamType : public Type,
>
>  public:
>    bool isSugared() const { return true; }
> -  QualType desugar() const { return getCanonicalTypeInternal(); }
> +  QualType desugar() const;
>
>    static bool classof(const Type *T) {
>      return T->getTypeClass() == ObjCTypeParam;
>
> Modified: cfe/trunk/lib/AST/Type.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/Type.cpp?rev=374202&r1=374201&r2=374202&view=diff
> ==============================================================================
> --- cfe/trunk/lib/AST/Type.cpp (original)
> +++ cfe/trunk/lib/AST/Type.cpp Wed Oct  9 12:29:13 2019
> @@ -663,6 +663,10 @@ ObjCTypeParamType::ObjCTypeParamType(con
>    initialize(protocols);
>  }
>
> +QualType ObjCTypeParamType::desugar() const {
> +  return getDecl()->getUnderlyingType();
> +}
> +
>  ObjCObjectType::ObjCObjectType(QualType Canonical, QualType Base,
>                                 ArrayRef<QualType> typeArgs,
>                                 ArrayRef<ObjCProtocolDecl *> protocols,
>
> Modified: cfe/trunk/test/SemaObjC/parameterized_classes_subst.m
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaObjC/parameterized_classes_subst.m?rev=374202&r1=374201&r2=374202&view=diff
> ==============================================================================
> --- cfe/trunk/test/SemaObjC/parameterized_classes_subst.m (original)
> +++ cfe/trunk/test/SemaObjC/parameterized_classes_subst.m Wed Oct  9 12:29:13 2019
> @@ -467,3 +467,17 @@ void bar(MyMutableDictionary<NSString *,
>  - (void)mapUsingBlock2:(id)block { // expected-warning{{conflicting parameter types in implementation}}
>  }
>  @end
> +
> +// --------------------------------------------------------------------------
> +// Use a type parameter as a type argument.
> +// --------------------------------------------------------------------------
> +// Type bounds in a category/extension are omitted. rdar://problem/54329242
> + at interface ParameterizedContainer<T : id<NSCopying>>
> +- (ParameterizedContainer<T> *)inInterface;
> + at end
> + at interface ParameterizedContainer<T> (Cat)
> +- (ParameterizedContainer<T> *)inCategory;
> + at end
> + at interface ParameterizedContainer<U> ()
> +- (ParameterizedContainer<U> *)inExtension;
> + at end
>
>
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