[vm/ffi] Migrate dart:ffi to nnbd

Everything in FFI is nonnullable, because C does not accept null values or return null values (nullptr == 0, not null).
The only thing that needed migration in the FFI api is operator == (dynamic other) --> operator == (Object other).

This CL does not migrate any tests as the VM cannot run any tests yet.

Fixes: https://github.com/dart-lang/sdk/issues/39144

Change-Id: I5efc772b61228bd1bd4d95be1b7bcd969f0c9ac8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/131380
Commit-Queue: Daco Harkes <dacoharkes@google.com>
Reviewed-by: Leaf Petersen <leafp@google.com>

sdk_nnbd/lib/_internal/vm/lib/ffi_dynamic_library_patch.dart

@@ -44,9 +44,10 @@ class DynamicLibrary {
   int getHandle() native "Ffi_dl_getHandle";
 
   @patch
-  bool operator ==(other) {
-    if (other == null) return false;
-    return getHandle() == other.getHandle();
+  bool operator ==(Object other) {
+    if (other is! DynamicLibrary) return false;
+    DynamicLibrary otherLib = other;
+    return getHandle() == otherLib.getHandle();
   }
 
   @patch

sdk_nnbd/lib/ffi/annotations.dart

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// @dart = 2.5
-
 part of dart.ffi;
 
 class DartRepresentationOf {

sdk_nnbd/lib/ffi/dynamic_library.dart

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// @dart = 2.5
-
 part of dart.ffi;
 
 /// Represents a dynamically loaded C library.
@@ -35,7 +33,7 @@ class DynamicLibrary {
       String symbolName);
 
   /// Dynamic libraries are equal if they load the same library.
-  external bool operator ==(other);
+  external bool operator ==(Object other);
 
   /// The hash code for a DynamicLibrary only depends on the loaded library
   external int get hashCode;

sdk_nnbd/lib/ffi/ffi.dart

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file
 
-// @dart = 2.5
-
 /**
  * Foreign Function Interface for interoperability with the C programming language.
  *
@@ -15,6 +13,7 @@
  */
 library dart.ffi;
 
+import 'dart:isolate';
 import 'dart:typed_data';
 
 part "native_type.dart";
@@ -75,9 +74,10 @@ class Pointer<T extends NativeType> extends NativeType {
   external R asFunction<@DartRepresentationOf("T") R extends Function>();
 
   /// Equality for Pointers only depends on their address.
-  bool operator ==(other) {
-    if (other == null) return false;
-    return address == other.address;
+  bool operator ==(Object other) {
+    if (other is! Pointer) return false;
+    Pointer otherPointer = other;
+    return address == otherPointer.address;
   }
 
   /// The hash code for a Pointer only depends on its address.

sdk_nnbd/lib/ffi/native_type.dart

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// @dart = 2.5
-
 part of dart.ffi;
 
 /// [NativeType]'s subtypes represent a native type in C.

sdk_nnbd/lib/ffi/struct.dart

@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-// @dart = 2.5
-
 part of dart.ffi;
 
 /// This class is extended to define structs.

sdk_nnbd/lib/libraries.json

@@ -83,11 +83,11 @@
         ]
       },
       "ffi": {
-        "uri": "../../sdk/lib/ffi/ffi.dart",
+        "uri": "ffi/ffi.dart",
         "patches": [
-          "../../sdk/lib/_internal/vm/lib/ffi_patch.dart",
-          "../../sdk/lib/_internal/vm/lib/ffi_dynamic_library_patch.dart",
-          "../../sdk/lib/_internal/vm/lib/ffi_native_type_patch.dart"
+          "_internal/vm/lib/ffi_patch.dart",
+          "_internal/vm/lib/ffi_dynamic_library_patch.dart",
+          "_internal/vm/lib/ffi_native_type_patch.dart"
         ]
       },
       "wasm": {

sdk_nnbd/lib/libraries.yaml

@@ -88,11 +88,11 @@ vm:
         - "../../sdk/lib/_internal/vm/lib/timeline.dart"
 
     ffi:
-      uri: "../../sdk/lib/ffi/ffi.dart"
+      uri: "ffi/ffi.dart"
       patches:
-        - "../../sdk/lib/_internal/vm/lib/ffi_patch.dart"
-        - "../../sdk/lib/_internal/vm/lib/ffi_dynamic_library_patch.dart"
-        - "../../sdk/lib/_internal/vm/lib/ffi_native_type_patch.dart"
+        - "_internal/vm/lib/ffi_patch.dart"
+        - "_internal/vm/lib/ffi_dynamic_library_patch.dart"
+        - "_internal/vm/lib/ffi_native_type_patch.dart"
 
     wasm:
       uri: "wasm/wasm.dart"