cmd/bind: add remaining Objc nullability specifiers

The `TestObjcSeqWrappers` test is failing because there are some missing nullability specifiers:

```
mobile master❯ go test -v ./bind/objc -run TestObjcSeqWrappers
=== RUN   TestObjcSeqWrappers
--- FAIL: TestObjcSeqWrappers (5.45s)
    seq_test.go:80: tmpdir = /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/bind-objc-seq-test-434219564
    seq_test.go:98: gomobile: darwin-arm: go build -tags aaa bbb ios -buildmode=c-archive -o /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/objcpkg-arm.a gobind failed: exit status 2
        # gobind
        In file included from /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/interfaces_darwin.go:5:
        In file included from /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/interfaces.h:8:
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:26:30: error: pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified) [-Werror,-Wnullability-completeness]
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:26:30: note: insert '_Nullable' if the pointer may be null
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:26:30: note: insert '_Nonnull' if the pointer should never be null
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:28:11: error: pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified) [-Werror,-Wnullability-completeness]
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:28:11: note: insert '_Nullable' if the pointer may be null
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:28:11: note: insert '_Nonnull' if the pointer should never be null
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:38:32: error: pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified) [-Werror,-Wnullability-completeness]
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:38:32: note: insert '_Nullable' if the pointer may be null
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:38:32: note: insert '_Nonnull' if the pointer should never be null
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:39:23: error: pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified) [-Werror,-Wnullability-completeness]
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:39:34: note: insert '_Nullable' if the pointer may be null
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:39:34: note: insert '_Nonnull' if the pointer should never be null
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:50:35: error: pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified) [-Werror,-Wnullability-completeness]
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:50:35: note: insert '_Nullable' if the pointer may be null
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:50:35: note: insert '_Nonnull' if the pointer should never be null
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:52:29: error: pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified) [-Werror,-Wnullability-completeness]
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:52:29: note: insert '_Nullable' if the pointer may be null
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:52:29: note: insert '_Nonnull' if the pointer should never be null
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:52:70: error: pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified) [-Werror,-Wnullability-completeness]
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:52:70: note: insert '_Nullable' if the pointer may be null
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:52:70: note: insert '_Nonnull' if the pointer should never be null
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:58:52: error: pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified) [-Werror,-Wnullability-completeness]
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:58:52: note: insert '_Nullable' if the pointer may be null
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:58:52: note: insert '_Nonnull' if the pointer should never be null
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:58:26: error: pointer is missing a nullability type specifier (_Nonnull, _Nullable, or _Null_unspecified) [-Werror,-Wnullability-completeness]
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:58:26: note: insert '_Nullable' if the pointer may be null
        /var/folders/cm/184j3xgn311dhh1tpm6cbmyr0000gn/T/gomobile-work-254743475/src/gobind/Objcpkg.objc.h:58:26: note: insert '_Nonnull' if the pointer should never be null

    seq_test.go:99: failed to run gomobile bind: exit status 1
FAIL
FAIL	golang.org/x/mobile/bind/objc	5.454s
```

I've decided to set them as `_Nullable`. Even if the implementation seems to raise an exception in case the object is `NULL` in all the cases I've checked, .e.g.:

```objc
- (NSDate * _Nullable)getSelf {
	int32_t refnum = go_seq_go_to_refnum(self._ref);
	int32_t _self = go_seq_to_refnum(self);
	int32_t r0 = proxyobjcpkg_GoNSDate_GetSelf(refnum, _self);
	NSDate* _ret0_ = nil;
	GoSeqRef* _ret0__ref = go_seq_from_refnum(r0);
	if (_ret0__ref != NULL) {
		_ret0_ = _ret0__ref.obj;
		if (_ret0_ == nil) {
			LOG_FATAL(@"unexpected NULL reference");
		}
	}
	return _ret0_;
}
```

Because there are cases where we are overriding a method in the superclass that might have different nullability specifiers, .e.g.: https://github.com/golang/mobile/blob/6621de06e1e9d52c38a8c542770bdbeac9ecfef6/bind/testdata/testpkg/objcpkg/classes.go#L65

And I haven't found an easy way to detect those.

Change-Id: I6386e48b1042a234f981fc7c351f54354ebb6cc9
GitHub-Last-Rev: 1cddbaaf785f9daeb1d210e1b6fe17b8ae860698
GitHub-Pull-Request: golang/mobile#32
Reviewed-on: https://go-review.googlesource.com/c/mobile/+/176137
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
1 file changed
tree: cdd9e6c4aaea85b88f6f75da6c47d4b1f046ea93
  1. .gitattributes
  2. .gitignore
  3. AUTHORS
  4. CONTRIBUTING.md
  5. CONTRIBUTORS
  6. LICENSE
  7. PATENTS
  8. README.md
  9. app/
  10. asset/
  11. bind/
  12. cmd/
  13. codereview.cfg
  14. doc/
  15. event/
  16. example/
  17. exp/
  18. geom/
  19. gl/
  20. go.mod
  21. go.sum
  22. internal/
  23. testdata/
README.md

Go support for Mobile devices

The Go mobile repository holds packages and build tools for using Go on mobile platforms.

Package documentation as a starting point:

Caution image

The Go Mobile project is experimental. Use this at your own risk. While we are working hard to improve it, neither Google nor the Go team can provide end-user support.

This is early work and installing the build system requires Go 1.5. Follow the instructions on golang.org/wiki/Mobile to install the gomobile command, build the basic and the bind example apps.


Contributions to Go are appreciated. See https://golang.org/doc/contribute.html.