pkg/front_end/lib/src/kernel/constant_collection_builders.dart

// Copyright (c) 2019, 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.

part of 'constant_evaluator.dart';

abstract class _ListOrSetConstantBuilder<L extends Expression> {
  final ConstantEvaluator evaluator;
  final Expression original;
  final DartType elementType;

  // Each element of [parts] is either a `List<Constant>` (containing fully
  // evaluated constants) or a `Constant` (potentially unevaluated).
  List<Object> parts = <Object>[<Constant>[]];

  new(this.original, this.elementType, this.evaluator);

  L makeLiteral(List<Expression> elements);

  /// Add an element to the constant list being built by this builder.
  ///
  /// Returns [null] on success and an error-"constant" on failure, as such the
  /// return value should be checked.
  AbortConstant? add(Expression element) {
    Constant constant = evaluator._evaluateSubexpression(element);
    if (constant is AbortConstant) return constant;
    if (evaluator.shouldBeUnevaluated) {
      parts.add(
        evaluator.unevaluated(
          element,
          makeLiteral([evaluator._wrap(constant)]),
        ),
      );
      return null;
    } else {
      return addConstant(constant, element);
    }
  }

  /// Returns [null] on success and an error-"constant" on failure, as such the
  /// return value should be checked.
  AbortConstant? addSpread(Expression spreadExpression) {
    Constant constant = evaluator._evaluateSubexpression(spreadExpression);
    if (constant is AbortConstant) return constant;
    Constant spread = evaluator.unlower(constant);
    if (evaluator.shouldBeUnevaluated) {
      // Coverage-ignore-block(suite): Not run.
      // Unevaluated spread
      parts.add(spread);
    } else if (spread == evaluator.nullConstant) {
      // Coverage-ignore-block(suite): Not run.
      // Null spread
      return evaluator.createEvaluationErrorConstant(
        spreadExpression,
        diag.constEvalNullValue,
      );
    } else {
      // Fully evaluated spread
      List<Constant> entries;
      if (spread is ListConstant) {
        entries = spread.entries;
      } else if (spread is SetConstant) {
        entries = spread.entries;
      } else if (evaluator.backend.isLoweredListConstant(spread)) {
        // Coverage-ignore-block(suite): Not run.
        entries = <Constant>[];
        evaluator.backend.forEachLoweredListConstantElement(spread, (
          Constant element,
        ) {
          entries.add(element);
        });
      } else if (evaluator.backend.isLoweredSetConstant(constant)) {
        // Coverage-ignore-block(suite): Not run.
        entries = <Constant>[];
        evaluator.backend.forEachLoweredSetConstantElement(spread, (
          Constant element,
        ) {
          entries.add(element);
        });
      } else {
        // Not list or set in spread
        return evaluator.createEvaluationErrorConstant(
          spreadExpression,
          diag.constEvalNotListOrSetInSpread,
        );
      }
      for (Constant entry in entries) {
        AbortConstant? error = addConstant(entry, spreadExpression);
        if (error != null) return error;
      }
    }
    return null;
  }

  /// Returns [null] on success and an error-"constant" on failure, as such the
  /// return value should be checked.
  AbortConstant? addConstant(Constant constant, TreeNode context);
}

class ListConstantBuilder extends _ListOrSetConstantBuilder<ListLiteral> {
  /// If [true], builds a [MutableListConstant].
  ///
  /// [MutableListConstant]s can be modified during constant evaluation, but
  /// still results in a normal constant list at runtime.
  final bool isMutable;

  new(
    Expression original,
    DartType elementType,
    ConstantEvaluator evaluator, {
    this.isMutable = false,
  }) : super(original, elementType, evaluator);

  @override
  ListLiteral makeLiteral(List<Expression> elements) =>
      new ListLiteral(new ExpressionList.from(elements), isConst: true);

  @override
  AbortConstant? addConstant(Constant constant, TreeNode context) {
    List<Constant> lastPart;
    if (parts.last is List<Constant>) {
      lastPart = parts.last as List<Constant>;
    } else {
      // Coverage-ignore: Probably unreachable.
      parts.add(lastPart = <Constant>[]);
    }
    Constant value = evaluator.ensureIsSubtype(constant, elementType, context);
    if (value is AbortConstant) return value;
    lastPart.add(value);
    return null;
  }

  Constant build() {
    if (parts.length == 1) {
      // Fully evaluated
      List<Constant> entries = parts.single as List<Constant>;
      if (isMutable) {
        return new MutableListConstant(elementType, entries);
      }
      return evaluator.lowerListConstant(
        new ListConstant(elementType, new ConstantList.from(entries)),
      );
    }
    // TODO(kallentu): Handle partially evaluated [isMutable] lists.
    List<Expression> lists = <Expression>[];
    for (Object part in parts) {
      if (part is List<Constant>) {
        if (part.isEmpty) continue;
        // Coverage-ignore-block(suite): Not run.
        lists.add(
          new ConstantExpression(
            new ListConstant(elementType, new ConstantList.from(part)),
          ),
        );
      } else if (part is Constant) {
        lists.add(evaluator._wrap(part));
      } else {
        throw 'Non-constant in constant list';
      }
    }
    return evaluator.unevaluated(
      original,
      new ListConcatenation(
        new ExpressionList.from(lists),
        typeArgument: elementType,
      ),
    );
  }
}

class SetConstantBuilder extends _ListOrSetConstantBuilder<SetLiteral> {
  final Set<Constant> seen = new Set<Constant>.identity();
  final Set<Constant> weakSeen = new Set<Constant>.identity();

  new(Expression original, DartType elementType, ConstantEvaluator evaluator)
    : super(original, elementType, evaluator);

  @override
  // Coverage-ignore(suite): Not run.
  SetLiteral makeLiteral(List<Expression> elements) =>
      new SetLiteral(new ExpressionList.from(elements), isConst: true);

  @override
  AbortConstant? addConstant(Constant constant, TreeNode context) {
    if (!evaluator.hasPrimitiveEqual(
      constant,
      staticTypeContext: evaluator.staticTypeContext,
    )) {
      if (evaluator.staticTypeContext.enablePrimitiveEquality) {
        return evaluator.createEvaluationErrorConstant(
          context,
          diag.constEvalElementNotPrimitiveEquality.withArguments(
            element: constant,
          ),
        );
      } else {
        return evaluator.createEvaluationErrorConstant(
          context,
          diag.constEvalElementImplementsEqual.withArguments(element: constant),
        );
      }
    }
    bool unseen = seen.add(constant);
    if (!unseen) {
      return evaluator.createEvaluationErrorConstant(
        context,
        diag.constEvalDuplicateElement.withArguments(element: constant),
      );
    }

    List<Constant> lastPart;
    if (parts.last is List<Constant>) {
      lastPart = parts.last as List<Constant>;
    } else {
      // Coverage-ignore: Probably unreachable.
      parts.add(lastPart = <Constant>[]);
    }
    Constant value = evaluator.ensureIsSubtype(constant, elementType, context);
    if (value is AbortConstant) return value;
    lastPart.add(value);
    return null;
  }

  Constant build() {
    if (parts.length == 1) {
      // Fully evaluated
      List<Constant> entries = parts.single as List<Constant>;
      SetConstant result = new SetConstant(
        elementType,
        new ConstantList.from(entries),
      );
      return evaluator.lowerSetConstant(result);
    }
    // Coverage-ignore-block(suite): Not run.
    List<Expression> sets = <Expression>[];
    for (Object part in parts) {
      if (part is List<Constant>) {
        if (part.isEmpty) continue;
        sets.add(
          new ConstantExpression(
            new SetConstant(elementType, new ConstantList.from(part)),
          ),
        );
      } else if (part is Constant) {
        sets.add(evaluator._wrap(part));
      } else {
        throw 'Non-constant in constant set';
      }
    }
    return evaluator.unevaluated(
      original,
      new SetConcatenation(
        new ExpressionList.from(sets),
        typeArgument: elementType,
      ),
    );
  }
}

class MapConstantBuilder {
  final ConstantEvaluator evaluator;
  final Expression original;
  final DartType keyType;
  final DartType valueType;

  /// Each element of [parts] is either a `List<ConstantMapEntry>` (containing
  /// fully evaluated map entries) or a `Constant` (potentially unevaluated).
  List<Object> parts = <Object>[<ConstantMapEntry>[]];

  final Set<Constant> seenKeys = new Set<Constant>.identity();
  final Set<Constant> weakSeenKeys = new Set<Constant>.identity();

  new(this.original, this.keyType, this.valueType, this.evaluator);

  /// Add a map entry to the constant map being built by this builder
  ///
  /// Returns [null] on success and an error-"constant" on failure, as such the
  /// return value should be checked.
  AbortConstant? add(MapLiteralEntry element) {
    Constant key = evaluator._evaluateSubexpression(element.key);
    if (key is AbortConstant) return key;
    Constant value = evaluator._evaluateSubexpression(element.value);
    if (value is AbortConstant) return value;
    if (evaluator.shouldBeUnevaluated) {
      // Coverage-ignore-block(suite): Not run.
      parts.add(
        evaluator.unevaluated(
          element.key,
          new MapLiteral([
            new MapLiteralEntry(evaluator._wrap(key), evaluator._wrap(value)),
          ], isConst: true),
        ),
      );
      return null;
    } else {
      return addConstant(key, value, element.key, element.value);
    }
  }

  /// Returns [null] on success and an error-"constant" on failure, as such the
  /// return value should be checked.
  AbortConstant? addSpread(Expression spreadExpression) {
    Constant constant = evaluator._evaluateSubexpression(spreadExpression);
    if (constant is AbortConstant) return constant;
    Constant spread = evaluator.unlower(constant);
    if (evaluator.shouldBeUnevaluated) {
      // Coverage-ignore-block(suite): Not run.
      // Unevaluated spread
      parts.add(spread);
    } else if (spread == evaluator.nullConstant) {
      // Coverage-ignore-block(suite): Not run.
      // Null spread
      return evaluator.createEvaluationErrorConstant(
        spreadExpression,
        diag.constEvalNullValue,
      );
    } else {
      // Fully evaluated spread
      if (spread is MapConstant) {
        for (ConstantMapEntry entry in spread.entries) {
          AbortConstant? error = addConstant(
            entry.key,
            entry.value,
            spreadExpression,
            spreadExpression,
          );
          if (error != null) return error;
        }
      } else if (evaluator.backend.isLoweredMapConstant(spread)) {
        // Coverage-ignore-block(suite): Not run.
        AbortConstant? error;
        evaluator.backend.forEachLoweredMapConstantEntry(spread, (
          Constant key,
          Constant value,
        ) {
          error ??= addConstant(key, value, spreadExpression, spreadExpression);
        });
        if (error != null) return error;
      } else {
        // Not map in spread
        return evaluator.createEvaluationErrorConstant(
          spreadExpression,
          diag.constEvalNotMapInSpread,
        );
      }
    }
    return null;
  }

  /// Returns [null] on success and an error-"constant" on failure, as such the
  /// return value should be checked.
  AbortConstant? addConstant(
    Constant key,
    Constant value,
    TreeNode keyContext,
    TreeNode valueContext,
  ) {
    List<ConstantMapEntry> lastPart;
    if (parts.last is List<ConstantMapEntry>) {
      lastPart = parts.last as List<ConstantMapEntry>;
    } else {
      // Coverage-ignore: Probably unreachable.
      parts.add(lastPart = <ConstantMapEntry>[]);
    }
    if (!evaluator.hasPrimitiveEqual(
      key,
      staticTypeContext: evaluator.staticTypeContext,
    )) {
      if (evaluator.staticTypeContext.enablePrimitiveEquality) {
        return evaluator.createEvaluationErrorConstant(
          keyContext,
          diag.constEvalKeyNotPrimitiveEquality.withArguments(key: key),
        );
      } else {
        // Coverage-ignore-block(suite): Not run.
        return evaluator.createEvaluationErrorConstant(
          keyContext,
          diag.constEvalKeyImplementsEqual.withArguments(key: key),
        );
      }
    }
    bool unseenKey = seenKeys.add(key);
    if (!unseenKey) {
      return evaluator.createEvaluationErrorConstant(
        keyContext,
        diag.constEvalDuplicateKey.withArguments(key: key),
      );
    }

    Constant key2 = evaluator.ensureIsSubtype(key, keyType, keyContext);
    if (key2 is AbortConstant) return key2;
    Constant value2 = evaluator.ensureIsSubtype(value, valueType, valueContext);
    if (value2 is AbortConstant) return value2;
    lastPart.add(new ConstantMapEntry(key2, value2));
    return null;
  }

  Constant build() {
    if (parts.length == 1) {
      // Fully evaluated
      List<ConstantMapEntry> entries = parts.single as List<ConstantMapEntry>;
      return evaluator.lowerMapConstant(
        new MapConstant(
          keyType,
          valueType,
          new ConstantMapEntryList.from(entries),
        ),
      );
    }
    // Coverage-ignore-block(suite): Not run.
    List<Expression> maps = <Expression>[];
    for (Object part in parts) {
      if (part is List<ConstantMapEntry>) {
        if (part.isEmpty) continue;
        maps.add(
          new ConstantExpression(
            new MapConstant(
              keyType,
              valueType,
              new ConstantMapEntryList.from(part),
            ),
          ),
        );
      } else if (part is Constant) {
        maps.add(evaluator._wrap(part));
      } else {
        throw 'Non-constant in constant map';
      }
    }
    return evaluator.unevaluated(
      original,
      new MapConcatenation(
        new ExpressionList.from(maps),
        keyType: keyType,
        valueType: valueType,
      ),
    );
  }
}