src/main/java/com/android/tools/r8/shaking/KeepFieldInfo.java

// Copyright (c) 2020, the R8 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.
package com.android.tools.r8.shaking;

/** Immutable keep requirements for a field. */
public final class KeepFieldInfo extends KeepMemberInfo<KeepFieldInfo.Builder, KeepFieldInfo> {

  // Requires all aspects of a field to be kept.
  private static final KeepFieldInfo TOP = new Builder().makeTop().build();

  // Requires no aspects of a field to be kept.
  private static final KeepFieldInfo BOTTOM = new Builder().makeBottom().build();

  public static KeepFieldInfo top() {
    return TOP;
  }

  public static KeepFieldInfo bottom() {
    return BOTTOM;
  }

  public static Joiner newEmptyJoiner() {
    return bottom().joiner();
  }

  private final boolean allowFieldTypeStrengthening;

  private KeepFieldInfo(Builder builder) {
    super(builder);
    this.allowFieldTypeStrengthening = builder.isFieldTypeStrengtheningAllowed();
  }

  // This builder is not private as there are known instances where it is safe to modify keep info
  // in a non-upwards direction.
  @Override
  Builder builder() {
    return new Builder(this);
  }

  public boolean isFieldTypeStrengtheningAllowed(GlobalKeepInfoConfiguration configuration) {
    return internalIsFieldTypeStrengtheningAllowed();
  }

  boolean internalIsFieldTypeStrengtheningAllowed() {
    return allowFieldTypeStrengthening;
  }

  public Joiner joiner() {
    assert !isTop();
    return new Joiner(this);
  }

  @Override
  public boolean isTop() {
    return this.equals(top());
  }

  @Override
  public boolean isBottom() {
    return this.equals(bottom());
  }

  public static class Builder extends KeepInfo.Builder<Builder, KeepFieldInfo> {

    private boolean allowFieldTypeStrengthening;

    private Builder() {
      super();
    }

    private Builder(KeepFieldInfo original) {
      super(original);
      allowFieldTypeStrengthening = original.internalIsFieldTypeStrengtheningAllowed();
    }

    @Override
    public Builder makeTop() {
      return super.makeTop().disallowFieldTypeStrengthening();
    }

    @Override
    public Builder makeBottom() {
      return super.makeBottom().allowFieldTypeStrengthening();
    }

    public boolean isFieldTypeStrengtheningAllowed() {
      return allowFieldTypeStrengthening;
    }

    public Builder setAllowFieldTypeStrengthening(boolean allowFieldTypeStrengthening) {
      this.allowFieldTypeStrengthening = allowFieldTypeStrengthening;
      return self();
    }

    public Builder allowFieldTypeStrengthening() {
      return setAllowFieldTypeStrengthening(true);
    }

    public Builder disallowFieldTypeStrengthening() {
      return setAllowFieldTypeStrengthening(false);
    }

    @Override
    public KeepFieldInfo getTopInfo() {
      return TOP;
    }

    @Override
    public KeepFieldInfo getBottomInfo() {
      return BOTTOM;
    }

    @Override
    public Builder self() {
      return this;
    }

    @Override
    public boolean isEqualTo(KeepFieldInfo other) {
      return internalIsEqualTo(other);
    }

    @Override
    boolean internalIsEqualTo(KeepFieldInfo other) {
      return super.internalIsEqualTo(other)
          && isFieldTypeStrengtheningAllowed() == other.internalIsFieldTypeStrengtheningAllowed();
    }

    @Override
    public KeepFieldInfo doBuild() {
      return new KeepFieldInfo(this);
    }
  }

  public static class Joiner extends KeepInfo.Joiner<Joiner, Builder, KeepFieldInfo> {

    public Joiner(KeepFieldInfo info) {
      super(info.builder());
    }

    public Joiner disallowFieldTypeStrengthening() {
      builder.disallowFieldTypeStrengthening();
      return self();
    }

    @Override
    public Joiner asFieldJoiner() {
      return this;
    }

    @Override
    public Joiner merge(Joiner joiner) {
      // Should be extended to merge the fields of this class in case any are added.
      return super.merge(joiner)
          .applyIf(
              !joiner.builder.isFieldTypeStrengtheningAllowed(),
              KeepFieldInfo.Joiner::disallowFieldTypeStrengthening);
    }

    @Override
    Joiner self() {
      return this;
    }
  }
}