[ddc] Use `.futureValueType` from CFE
The CFE FunctionNode has a new getter for the Future value type that
can be used in null safe libraries.
Legacy libraries will still rely on flatten to get the type of the
Future.
Change-Id: I54ad3bc096fdb981f7f499f2ba3ddfcb01fd97d6
Issue: https://github.com/dart-lang/sdk/issues/44745
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/185240
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Nicholas Shahan <nshahan@google.com>
diff --git a/pkg/dev_compiler/lib/src/kernel/compiler.dart b/pkg/dev_compiler/lib/src/kernel/compiler.dart
index 1bbce68..db471a1 100644
--- a/pkg/dev_compiler/lib/src/kernel/compiler.dart
+++ b/pkg/dev_compiler/lib/src/kernel/compiler.dart
@@ -3316,16 +3316,13 @@
//
// In the body of an `async`, `await` is generated simply as `yield`.
var gen = emitGeneratorFn((_) => []);
- // Return type of an async body is `Future<flatten(T)>`, where T is the
- // declared return type, unless T is Object. In that case the Object refers
- // to a return type of `Future<Object?>`.
- // TODO(nshahan) Use the Future type value when available on a FunctionNode.
- var declaredReturnType = function
- .computeThisFunctionType(_currentLibrary.nonNullable)
- .returnType;
- var returnType = _coreTypes.isObject(declaredReturnType)
- ? _coreTypes.objectNullableRawType
- : _types.flatten(declaredReturnType);
+ var returnType = _currentLibrary.isNonNullableByDefault
+ ? function.futureValueType
+ // Otherwise flatten the return type because futureValueType(T) is not
+ // defined for legacy libraries.
+ : _types.flatten(function
+ .computeThisFunctionType(_currentLibrary.nonNullable)
+ .returnType);
return js.call('#.async(#, #)',
[emitLibraryName(_coreTypes.asyncLibrary), _emitType(returnType), gen]);
}
