Re-duplicate frontend_accessors.dart.

pkg/front_end/lib/src/fasta/kernel/frontend_accessors.dart

+// Copyright (c) 2016, 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.
+
+/// A library to help transform compounds and null-aware accessors into
+/// let expressions.
+
+import 'package:kernel/ast.dart';
+
+final Name indexGetName = new Name("[]");

[ahe, 2017/04/04 09:18:50]

We could export these from the kernel version.

[Paul Berry, 2017/04/04 16:21:10]

Done.

[Paul Berry, 2017/04/04 17:45:20]

But for some reason this caused test failures which I wasn't able to
understand--at this point I'm suspecting that it exposes a VM bug.  So I'm going
to do it as a follow-up CL and I'll reach out to one of the VM folks to get help
debugging it.

+
+final Name indexSetName = new Name("[]=");
+
+/// An [Accessor] represents a subexpression for which we can't yet build a
+/// kernel [Expression] because we don't yet know the context in which it is
+/// used.
+///
+/// Once the context is known, an [Accessor] can be converted into an
+/// [Expression] by calling a "build" method.
+///
+/// For example, when building a kernel representation for `a[x] = b`, after
+/// parsing `a[x]` but before parsing `= b`, we don't yet know whether to
+/// generate an invocation of `operator[]` or `operator[]=`, so we generate an
+/// [Accessor] object.  Later, after `= b` is parsed, [buildAssignment] will be
+/// called.
+abstract class Accessor {
+  final int offset;
+
+  // [builtBinary] and [builtGetter] capture the inner nodes. Used by
+  // dart2js+rasta for determining how subexpressions map to legacy dart2js Ast
+  // nodes. This will be removed once dart2js type analysis (aka inference) is
+  // reimplemented on kernel.
+  Expression builtBinary;
+  Expression builtGetter;
+
+  Accessor(this.offset);
+
+  /// Builds an [Expression] representing a read from the accessor.
+  Expression buildSimpleRead() {
+    return _finish(_makeSimpleRead());
+  }
+
+  /// Builds an [Expression] representing an assignment with the accessor on
+  /// the LHS and [value] on the RHS.
+  ///
+  /// The returned expression evaluates to the assigned value, unless
+  /// [voidContext] is true, in which case it may evaluate to anything.
+  Expression buildAssignment(Expression value, {bool voidContext: false}) {
+    return _finish(_makeSimpleWrite(value, voidContext));
+  }
+
+  /// Returns an [Expression] representing a null-aware assignment (`??=`) with
+  /// the accessor on the LHS and [value] on the RHS.
+  ///
+  /// The returned expression evaluates to the assigned value, unless
+  /// [voidContext] is true, in which case it may evaluate to anything.
+  ///
+  /// [type] is the static type of the RHS.
+  Expression buildNullAwareAssignment(Expression value, DartType type,
+      {bool voidContext: false}) {
+    if (voidContext) {
+      return _finish(new ConditionalExpression(buildIsNull(_makeRead()),
+          _makeWrite(value, false), new NullLiteral(), type));
+    }
+    var tmp = new VariableDeclaration.forValue(_makeRead());
+    return _finish(makeLet(
+        tmp,
+        new ConditionalExpression(buildIsNull(new VariableGet(tmp)),
+            _makeWrite(value, false), new VariableGet(tmp), type)));
+  }
+
+  /// Returns an [Expression] representing a compound assignment (e.g. `+=`)
+  /// with the accessor on the LHS and [value] on the RHS.
+  Expression buildCompoundAssignment(Name binaryOperator, Expression value,
+      {int offset: TreeNode.noOffset,
+      bool voidContext: false,
+      Procedure interfaceTarget}) {
+    return _finish(_makeWrite(
+        builtBinary = makeBinary(
+            _makeRead(), binaryOperator, interfaceTarget, value,
+            offset: offset),
+        voidContext));
+  }
+
+  /// Returns an [Expression] representing a pre-increment or pre-decrement
+  /// of the accessor.
+  Expression buildPrefixIncrement(Name binaryOperator,
+      {int offset: TreeNode.noOffset,
+      bool voidContext: false,
+      Procedure interfaceTarget}) {
+    return buildCompoundAssignment(binaryOperator, new IntLiteral(1),
+        offset: offset,
+        voidContext: voidContext,
+        interfaceTarget: interfaceTarget);
+  }
+
+  /// Returns an [Expression] representing a post-increment or post-decrement
+  /// of the accessor.
+  Expression buildPostfixIncrement(Name binaryOperator,
+      {int offset: TreeNode.noOffset,
+      bool voidContext: false,
+      Procedure interfaceTarget}) {
+    if (voidContext) {
+      return buildPrefixIncrement(binaryOperator,
+          offset: offset, voidContext: true, interfaceTarget: interfaceTarget);
+    }
+    var value = new VariableDeclaration.forValue(_makeRead());
+    valueAccess() => new VariableGet(value);
+    var dummy = new VariableDeclaration.forValue(_makeWrite(
+        builtBinary = makeBinary(
+            valueAccess(), binaryOperator, interfaceTarget, new IntLiteral(1),
+            offset: offset),
+        true));
+    return _finish(makeLet(value, makeLet(dummy, valueAccess())));
+  }
+
+  Expression _makeSimpleRead() => _makeRead();
+
+  Expression _makeSimpleWrite(Expression value, bool voidContext) {
+    return _makeWrite(value, voidContext);
+  }
+
+  Expression _makeRead();
+
+  Expression _makeWrite(Expression value, bool voidContext);
+
+  Expression _finish(Expression body) => body;
+
+  /// Returns an [Expression] representing a compile-time error.
+  ///
+  /// At runtime, an exception will be thrown.
+  makeInvalidRead() => new InvalidExpression();
+
+  /// Returns an [Expression] representing a compile-time error wrapping
+  /// [value].
+  ///
+  /// At runtime, [value] will be evaluated before throwing an exception.
+  makeInvalidWrite(Expression value) => wrapInvalid(value);
+}
+
+class VariableAccessor extends Accessor {
+  VariableDeclaration variable;
+  DartType promotedType;
+
+  VariableAccessor(this.variable, this.promotedType, int offset)
+      : super(offset);
+
+  _makeRead() => new VariableGet(variable, promotedType)..fileOffset = offset;
+
+  _makeWrite(Expression value, bool voidContext) {
+    return variable.isFinal || variable.isConst
+        ? makeInvalidWrite(value)
+        : new VariableSet(variable, value)..fileOffset = offset;
+  }
+}
+
+class PropertyAccessor extends Accessor {
+  VariableDeclaration _receiverVariable;
+  Expression receiver;
+  Name name;
+  Member getter, setter;
+
+  static Accessor make(
+      Expression receiver, Name name, Member getter, Member setter,
+      {int offset: TreeNode.noOffset}) {
+    if (receiver is ThisExpression) {
+      return new ThisPropertyAccessor(name, getter, setter, offset);
+    } else {
+      return new PropertyAccessor.internal(
+          receiver, name, getter, setter, offset);
+    }
+  }
+
+  PropertyAccessor.internal(
+      this.receiver, this.name, this.getter, this.setter, int offset)
+      : super(offset);
+
+  _makeSimpleRead() =>
+      new PropertyGet(receiver, name, getter)..fileOffset = offset;
+
+  _makeSimpleWrite(Expression value, bool voidContext) {
+    return new PropertySet(receiver, name, value, setter)..fileOffset = offset;
+  }
+
+  receiverAccess() {
+    _receiverVariable ??= new VariableDeclaration.forValue(receiver);
+    return new VariableGet(_receiverVariable)..fileOffset = offset;
+  }
+
+  _makeRead() => builtGetter = new PropertyGet(receiverAccess(), name, getter)
+    ..fileOffset = offset;
+
+  _makeWrite(Expression value, bool voidContext) {
+    return new PropertySet(receiverAccess(), name, value, setter)
+      ..fileOffset = offset;
+  }
+
+  _finish(Expression body) => makeLet(_receiverVariable, body);
+}
+
+/// Special case of [PropertyAccessor] to avoid creating an indirect access to
+/// 'this'.
+class ThisPropertyAccessor extends Accessor {
+  Name name;
+  Member getter, setter;
+
+  ThisPropertyAccessor(this.name, this.getter, this.setter, int offset)
+      : super(offset);
+
+  _makeRead() => builtGetter =
+      new PropertyGet(new ThisExpression(), name, getter)..fileOffset = offset;
+
+  _makeWrite(Expression value, bool voidContext) {
+    return new PropertySet(new ThisExpression(), name, value, setter)
+      ..fileOffset = offset;
+  }
+}
+
+class NullAwarePropertyAccessor extends Accessor {
+  VariableDeclaration receiver;
+  Name name;
+  Member getter, setter;
+  DartType type;
+
+  NullAwarePropertyAccessor(Expression receiver, this.name, this.getter,
+      this.setter, this.type, int offset)
+      : this.receiver = makeOrReuseVariable(receiver),
+        super(offset);
+
+  receiverAccess() => new VariableGet(receiver);
+
+  _makeRead() => builtGetter = new PropertyGet(receiverAccess(), name, getter);
+
+  _makeWrite(Expression value, bool voidContext) {
+    return new PropertySet(receiverAccess(), name, value, setter);
+  }
+
+  _finish(Expression body) => makeLet(
+      receiver,
+      new ConditionalExpression(
+          buildIsNull(receiverAccess()), new NullLiteral(), body, type));
+}
+
+class SuperPropertyAccessor extends Accessor {
+  Name name;
+  Member getter, setter;
+
+  SuperPropertyAccessor(this.name, this.getter, this.setter, int offset)
+      : super(offset);
+
+  _makeRead() {
+    if (getter == null) return makeInvalidRead();
+    // TODO(ahe): Use [DirectPropertyGet] when possible.
+    return builtGetter = new SuperPropertyGet(name, getter)
+      ..fileOffset = offset;
+  }
+
+  _makeWrite(Expression value, bool voidContext) {
+    if (setter == null) return makeInvalidWrite(value);
+    // TODO(ahe): Use [DirectPropertySet] when possible.
+    return new SuperPropertySet(name, value, setter)..fileOffset = offset;
+  }
+}
+
+class IndexAccessor extends Accessor {
+  Expression receiver;
+  Expression index;
+  VariableDeclaration receiverVariable;
+  VariableDeclaration indexVariable;
+  Procedure getter, setter;
+
+  static Accessor make(
+      Expression receiver, Expression index, Procedure getter, Procedure setter,
+      {int offset: TreeNode.noOffset}) {
+    if (receiver is ThisExpression) {
+      return new ThisIndexAccessor(index, getter, setter, offset);
+    } else {
+      return new IndexAccessor.internal(
+          receiver, index, getter, setter, offset);
+    }
+  }
+
+  IndexAccessor.internal(
+      this.receiver, this.index, this.getter, this.setter, int offset)
+      : super(offset);
+
+  _makeSimpleRead() => new MethodInvocation(
+      receiver, indexGetName, new Arguments(<Expression>[index]), getter)
+    ..fileOffset = offset;
+
+  _makeSimpleWrite(Expression value, bool voidContext) {
+    if (!voidContext) return _makeWriteAndReturn(value);
+    return new MethodInvocation(receiver, indexSetName,
+        new Arguments(<Expression>[index, value]), setter)..fileOffset = offset;
+  }
+
+  receiverAccess() {
+    // We cannot reuse the receiver if it is a variable since it might be
+    // reassigned in the index expression.
+    receiverVariable ??= new VariableDeclaration.forValue(receiver);
+    return new VariableGet(receiverVariable)..fileOffset = offset;
+  }
+
+  indexAccess() {
+    indexVariable ??= new VariableDeclaration.forValue(index);
+    return new VariableGet(indexVariable)..fileOffset = offset;
+  }
+
+  _makeRead() {
+    return builtGetter = new MethodInvocation(
+        receiverAccess(),
+        indexGetName,
+        new Arguments(<Expression>[indexAccess()]),
+        getter)..fileOffset = offset;
+  }
+
+  _makeWrite(Expression value, bool voidContext) {
+    if (!voidContext) return _makeWriteAndReturn(value);
+    return new MethodInvocation(
+        receiverAccess(),
+        indexSetName,
+        new Arguments(<Expression>[indexAccess(), value]),
+        setter)..fileOffset = offset;
+  }
+
+  // TODO(dmitryas): remove this method after the "[]=" operator of the Context
+  // class is made to return a value.
+  _makeWriteAndReturn(Expression value) {
+    // The call to []= does not return the value like direct-style assignments
+    // do.  We need to bind the value in a let.
+    var valueVariable = new VariableDeclaration.forValue(value);
+    var dummy = new VariableDeclaration.forValue(new MethodInvocation(
+        receiverAccess(),
+        indexSetName,
+        new Arguments(
+            <Expression>[indexAccess(), new VariableGet(valueVariable)]),
+        setter)..fileOffset = offset);
+    return makeLet(
+        valueVariable, makeLet(dummy, new VariableGet(valueVariable)));
+  }
+
+  Expression _finish(Expression body) {
+    return makeLet(receiverVariable, makeLet(indexVariable, body));
+  }
+}
+
+/// Special case of [IndexAccessor] to avoid creating an indirect access to
+/// 'this'.
+class ThisIndexAccessor extends Accessor {
+  Expression index;
+  VariableDeclaration indexVariable;
+  Procedure getter, setter;
+
+  ThisIndexAccessor(this.index, this.getter, this.setter, int offset)
+      : super(offset);
+
+  _makeSimpleRead() {
+    return new MethodInvocation(new ThisExpression(), indexGetName,
+        new Arguments(<Expression>[index]), getter);
+  }
+
+  _makeSimpleWrite(Expression value, bool voidContext) {
+    if (!voidContext) return _makeWriteAndReturn(value);
+    return new MethodInvocation(new ThisExpression(), indexSetName,
+        new Arguments(<Expression>[index, value]), setter);
+  }
+
+  indexAccess() {
+    indexVariable ??= new VariableDeclaration.forValue(index);
+    return new VariableGet(indexVariable);
+  }
+
+  _makeRead() => builtGetter = new MethodInvocation(new ThisExpression(),
+      indexGetName, new Arguments(<Expression>[indexAccess()]), getter);
+
+  _makeWrite(Expression value, bool voidContext) {
+    if (!voidContext) return _makeWriteAndReturn(value);
+    return new MethodInvocation(new ThisExpression(), indexSetName,
+        new Arguments(<Expression>[indexAccess(), value]), setter);
+  }
+
+  _makeWriteAndReturn(Expression value) {
+    var valueVariable = new VariableDeclaration.forValue(value);
+    var dummy = new VariableDeclaration.forValue(new MethodInvocation(
+        new ThisExpression(),
+        indexSetName,
+        new Arguments(
+            <Expression>[indexAccess(), new VariableGet(valueVariable)]),
+        setter));
+    return makeLet(
+        valueVariable, makeLet(dummy, new VariableGet(valueVariable)));
+  }
+
+  Expression _finish(Expression body) => makeLet(indexVariable, body);
+}
+
+class SuperIndexAccessor extends Accessor {
+  Expression index;
+  VariableDeclaration indexVariable;
+  Member getter, setter;
+
+  SuperIndexAccessor(this.index, this.getter, this.setter, int offset)
+      : super(offset);
+
+  indexAccess() {
+    indexVariable ??= new VariableDeclaration.forValue(index);
+    return new VariableGet(indexVariable);
+  }
+
+  _makeSimpleRead() => new SuperMethodInvocation(
+      indexGetName, new Arguments(<Expression>[index]), getter);
+
+  _makeSimpleWrite(Expression value, bool voidContext) {
+    if (!voidContext) return _makeWriteAndReturn(value);
+    return new SuperMethodInvocation(
+        indexSetName, new Arguments(<Expression>[index, value]), setter);
+  }
+
+  _makeRead() {
+    return builtGetter = new SuperMethodInvocation(
+        indexGetName, new Arguments(<Expression>[indexAccess()]), getter);
+  }
+
+  _makeWrite(Expression value, bool voidContext) {
+    if (!voidContext) return _makeWriteAndReturn(value);
+    return new SuperMethodInvocation(indexSetName,
+        new Arguments(<Expression>[indexAccess(), value]), setter);
+  }
+
+  _makeWriteAndReturn(Expression value) {
+    var valueVariable = new VariableDeclaration.forValue(value);
+    var dummy = new VariableDeclaration.forValue(new SuperMethodInvocation(
+        indexSetName,
+        new Arguments(
+            <Expression>[indexAccess(), new VariableGet(valueVariable)]),
+        setter));
+    return makeLet(
+        valueVariable, makeLet(dummy, new VariableGet(valueVariable)));
+  }
+
+  Expression _finish(Expression body) {
+    return makeLet(indexVariable, body);
+  }
+}
+
+class StaticAccessor extends Accessor {
+  Member readTarget;
+  Member writeTarget;
+
+  StaticAccessor(this.readTarget, this.writeTarget, int offset) : super(offset);
+
+  _makeRead() => builtGetter = readTarget == null
+      ? makeInvalidRead()
+      : new StaticGet(readTarget)..fileOffset = offset;
+
+  _makeWrite(Expression value, bool voidContext) {
+    return writeTarget == null
+        ? makeInvalidWrite(value)
+        : new StaticSet(writeTarget, value)..fileOffset = offset;
+  }
+}
+
+class ReadOnlyAccessor extends Accessor {
+  Expression expression;
+  VariableDeclaration value;
+
+  ReadOnlyAccessor(this.expression, int offset) : super(offset);
+
+  _makeSimpleRead() => expression;
+
+  _makeRead() {
+    value ??= new VariableDeclaration.forValue(expression);
+    return new VariableGet(value);
+  }
+
+  _makeWrite(Expression value, bool voidContext) => makeInvalidWrite(value);
+
+  Expression _finish(Expression body) => makeLet(value, body);
+}
+
+Expression makeLet(VariableDeclaration variable, Expression body) {

[ahe, 2017/04/04 09:18:50]

These helper methods could probably also be exported from the kernel version.

[Paul Berry, 2017/04/04 16:21:10]

I'm going to leave these as is for now because I believe that they're going to
need to be rewritten in terms of the AstFactory.

+  if (variable == null) return body;
+  return new Let(variable, body);
+}
+
+Expression makeBinary(
+    Expression left, Name operator, Procedure interfaceTarget, Expression right,
+    {int offset: TreeNode.noOffset}) {
+  return new MethodInvocation(
+      left, operator, new Arguments(<Expression>[right]), interfaceTarget)
+    ..fileOffset = offset;
+}
+
+final Name _equalOperator = new Name('==');
+
+Expression buildIsNull(Expression value, {int offset: TreeNode.noOffset}) {
+  return makeBinary(value, _equalOperator, null, new NullLiteral(),
+      offset: offset);
+}
+
+VariableDeclaration makeOrReuseVariable(Expression value) {
+  // TODO: Devise a way to remember if a variable declaration was reused
+  // or is fresh (hence needs a let binding).
+  return new VariableDeclaration.forValue(value);
+}
+
+Expression wrapInvalid(Expression e) {
+  return new Let(new VariableDeclaration.forValue(e), new InvalidExpression());
+}