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[ddc] Move FutureOr normalization to its own visitor

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Will make it easier to reuse the normalization when compiling
with the new runtime type representation.

Change-Id: Ie767a2b676950205b0b50eadac305c29914433f2
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/247420
Reviewed-by: Srujan Gaddam <srujzs@google.com>
Commit-Queue: Nicholas Shahan <nshahan@google.com>
This commit is contained in:
Nicholas Shahan 2022-07-01 18:55:50 +00:00 committed by Commit Bot
parent f3daca2ef6
commit 624dd76b6f
2 changed files with 94 additions and 60 deletions
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63
pkg/dev_compiler/lib/src/kernel/compiler.dart
View file

@ -32,6 +32,7 @@ import '../js_ast/js_ast.dart' show ModuleItem, js;
import '../js_ast/source_map_printer.dart'
show NodeEnd, NodeSpan, HoverComment, continueSourceMap;
import 'constants.dart';
import 'future_or_normalizer.dart';
import 'js_interop.dart';
import 'js_typerep.dart';
import 'kernel_helpers.dart';
@ -939,7 +940,7 @@ class ProgramCompiler extends ComputeOnceConstantVisitor<js_ast.Expression>
}
return _emitInterfaceType(t, emitNullability: emitNullability);
} else if (t is FutureOrType) {
var normalizedType = _normalizeFutureOr(t);
var normalizedType = normalizeFutureOr(t, _coreTypes);
if (normalizedType is FutureOrType) {
_declareBeforeUse(_coreTypes.deprecatedFutureOrClass);
var typeRep = _emitFutureOrTypeWithArgument(
@ -2911,64 +2912,6 @@ class ProgramCompiler extends ComputeOnceConstantVisitor<js_ast.Expression>
? visitNullType(const NullType())
: _emitNullabilityWrapper(runtimeCall('Never'), type.nullability);
/// Normalizes `FutureOr` types.
///
/// Any changes to the normalization logic here should be mirrored in the
/// classes.dart runtime library method named `normalizeFutureOr`.
DartType _normalizeFutureOr(FutureOrType futureOr) {
var typeArgument = futureOr.typeArgument;
if (typeArgument is DynamicType) {
// FutureOr<dynamic> --> dynamic
return typeArgument;
}
if (typeArgument is VoidType) {
// FutureOr<void> --> void
return typeArgument;
}
if (typeArgument is InterfaceType &&
typeArgument.classNode == _coreTypes.objectClass) {
// Normalize FutureOr of Object, Object?, Object*.
var nullable = futureOr.nullability == Nullability.nullable ||
typeArgument.nullability == Nullability.nullable;
var legacy = futureOr.nullability == Nullability.legacy ||
typeArgument.nullability == Nullability.legacy;
var nullability = nullable
? Nullability.nullable
: legacy
? Nullability.legacy
: Nullability.nonNullable;
return typeArgument.withDeclaredNullability(nullability);
} else if (typeArgument is NeverType) {
// FutureOr<Never> --> Future<Never>
return InterfaceType(
_coreTypes.futureClass, futureOr.nullability, [typeArgument]);
} else if (typeArgument is NullType) {
// FutureOr<Null> --> Future<Null>?
return InterfaceType(
_coreTypes.futureClass, Nullability.nullable, [typeArgument]);
} else if (futureOr.declaredNullability == Nullability.nullable &&
typeArgument.nullability == Nullability.nullable) {
// FutureOr<T?>? --> FutureOr<T?>
return futureOr.withDeclaredNullability(Nullability.nonNullable);
}
// The following is not part of the normalization spec but this is a
// convenient place to perform this change of nullability consistently. This
// only applies at compile-time and is not needed in the runtime version of
// the FutureOr normalization.
// FutureOr<T%>% --> FutureOr<T%>
//
// If the type argument has undetermined nullability the CFE propagates
// it to the FutureOr type as well. In this case we can represent the
// FutureOr type without any nullability wrappers and rely on the runtime to
// handle the nullability of the instantiated type appropriately.
if (futureOr.nullability == Nullability.undetermined &&
typeArgument.nullability == Nullability.undetermined) {
return futureOr.withDeclaredNullability(Nullability.nonNullable);
}
return futureOr;
}
@override
js_ast.Expression visitInterfaceType(InterfaceType type) =>
_emitInterfaceType(type);
@ -2979,7 +2922,7 @@ class ProgramCompiler extends ComputeOnceConstantVisitor<js_ast.Expression>
@override
js_ast.Expression visitFutureOrType(FutureOrType type) {
var normalizedType = _normalizeFutureOr(type);
var normalizedType = normalizeFutureOr(type, _coreTypes);
return normalizedType is FutureOrType
? _emitFutureOrType(normalizedType)
: normalizedType.accept(this);

91
pkg/dev_compiler/lib/src/kernel/future_or_normalizer.dart Normal file
View file

@ -0,0 +1,91 @@
// Copyright (c) 2022, the Dart project authors. Please see the AUTHORS file
// 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.
import 'package:kernel/ast.dart';
import 'package:kernel/core_types.dart';
import 'package:kernel/kernel.dart';
import 'package:kernel/src/replacement_visitor.dart';
/// Normalizes all `FutureOr` types found in [type].
DartType normalizeFutureOr(DartType type, CoreTypes coreTypes) =>
type.accept1(_FutureOrNormalizer.instance(coreTypes), Variance.unrelated) ??
type;
/// Visit methods returns a normalized version of `FutureOr` types or `null` if
/// no normalization was applied.
///
/// The `variance` parameters in the visit methods are unused in this type
/// replacement.
///
/// `FutureOr` types are normalized per the spec:
/// https://github.com/dart-lang/language/blob/master/resources/type-system/normalization.md
///
/// Any changes to the normalization logic here should be mirrored in the
/// classes.dart runtime library method named `normalizeFutureOr`.
class _FutureOrNormalizer extends ReplacementVisitor {
final CoreTypes _coreTypes;
static _FutureOrNormalizer? _instance;
_FutureOrNormalizer._(this._coreTypes);
factory _FutureOrNormalizer.instance(CoreTypes coreTypes) =>
_instance ?? (_instance = _FutureOrNormalizer._(coreTypes));
@override
DartType? visitFutureOrType(FutureOrType futureOr, int variance) {
var normalizedTypeArg = futureOr.typeArgument.accept1(this, variance);
var typeArgument = normalizedTypeArg ?? futureOr.typeArgument;
if (typeArgument is DynamicType) {
// FutureOr<dynamic> --> dynamic
return typeArgument;
}
if (typeArgument is VoidType) {
// FutureOr<void> --> void
return typeArgument;
}
if (typeArgument is InterfaceType &&
typeArgument.classNode == _coreTypes.objectClass) {
// Normalize FutureOr of Object, Object?, Object*.
var nullable = futureOr.nullability == Nullability.nullable ||
typeArgument.nullability == Nullability.nullable;
var legacy = futureOr.nullability == Nullability.legacy ||
typeArgument.nullability == Nullability.legacy;
var nullability = nullable
? Nullability.nullable
: legacy
? Nullability.legacy
: Nullability.nonNullable;
return typeArgument.withDeclaredNullability(nullability);
} else if (typeArgument is NeverType) {
// FutureOr<Never> --> Future<Never>
return InterfaceType(
_coreTypes.futureClass, futureOr.nullability, [typeArgument]);
} else if (typeArgument is NullType) {
// FutureOr<Null> --> Future<Null>?
return InterfaceType(
_coreTypes.futureClass, Nullability.nullable, [typeArgument]);
} else if (futureOr.declaredNullability == Nullability.nullable &&
typeArgument.nullability == Nullability.nullable) {
// FutureOr<T?>? --> FutureOr<T?>
return futureOr.withDeclaredNullability(Nullability.nonNullable);
}
// The following is not part of the normalization spec but this is a
// convenient place to perform this change of nullability consistently. This
// only applies at compile-time and is not needed in the runtime version of
// the FutureOr normalization.
// FutureOr<T%>% --> FutureOr<T%>
//
// If the type argument has undetermined nullability the CFE propagates
// it to the FutureOr type as well. In this case we can represent the
// FutureOr type without any nullability wrappers and rely on the runtime to
// handle the nullability of the instantiated type appropriately.
if (futureOr.declaredNullability == Nullability.undetermined &&
typeArgument.declaredNullability == Nullability.undetermined) {
return futureOr.withDeclaredNullability(Nullability.nonNullable);
}
return null;
}
}