Use ConstExp for storing constants.

sdk/lib/_internal/compiler/implementation/cps_ir/const_expression.dart

 // Copyright (c) 2014, 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.
 
 library const_expression;
 
 import '../dart2jslib.dart' show Constant, ListConstant, MapConstant,
     PrimitiveConstant, ConstructedConstant, TypeConstant, FunctionConstant,
     StringConstant;
 import '../dart_types.dart';
 import '../elements/elements.dart';
 import '../universe/universe.dart';
 
 /// An expression that is a compile-time constant.
 ///
 /// Whereas [Constant] represent a compile-time value, a [ConstExp]
 /// represents an expression for creating a constant.
 ///
 /// There is no one-to-one mapping between [ConstExp] and [Constant], because
 /// different expressions can denote the same constant. For instance,
 /// multiple `const` constructors may be used to create the same object, and
 /// different `const` variables may hold the same value.
 abstract class ConstExp {
+  /// Returns the value of this constant expression.
+  Constant get value;
+
+  // TODO(johnniwinther): Unify precedence handled between constants, front-end
+  // and back-end.
+  int get precedence => 16;
+
   accept(ConstExpVisitor visitor);
+
+  String toString() {
+    ConstExpPrinter printer = new ConstExpPrinter();
+    accept(printer);
+    return printer.toString();
+  }
 }
 
 /// Boolean, int, double, string, or null constant.
 class PrimitiveConstExp extends ConstExp {
-  final PrimitiveConstant constant;
+  final PrimitiveConstant value;
 
-  PrimitiveConstExp(this.constant) {
-    assert(constant != null);
+  PrimitiveConstExp(this.value) {
+    assert(value != null);
   }
 
   accept(ConstExpVisitor visitor) => visitor.visitPrimitive(this);
 }
 
 /// Literal list constant.
 class ListConstExp extends ConstExp {
+  final ListConstant value;
   final GenericType type;
   final List<ConstExp> values;
 
-  ListConstExp(this.type, this.values);
+  ListConstExp(this.value, this.type, this.values);
 
   accept(ConstExpVisitor visitor) => visitor.visitList(this);
 }
 
 /// Literal map constant.
 class MapConstExp extends ConstExp {
+  final MapConstant value;
   final GenericType type;
   final List<ConstExp> keys;
   final List<ConstExp> values;
 
-  MapConstExp(this.type, this.keys, this.values);
+  MapConstExp(this.value, this.type, this.keys, this.values);
 
   accept(ConstExpVisitor visitor) => visitor.visitMap(this);
 }
 
 /// Invocation of a const constructor.
 class ConstructorConstExp extends ConstExp {
+  final Constant value;
   final GenericType type;
   final FunctionElement target;
   final Selector selector;
   final List<ConstExp> arguments;
 
-  ConstructorConstExp(this.type, this.target, this.selector, this.arguments) {
+  ConstructorConstExp(this.value,
+                      this.type,
+                      this.target,
+                      this.selector,
+                      this.arguments) {
     assert(type.element == target.enclosingClass);
   }
 
   accept(ConstExpVisitor visitor) => visitor.visitConstructor(this);
 }
 
 /// String literal with juxtaposition and/or interpolations.
+// TODO(johnniwinther): Do we need this?
 class ConcatenateConstExp extends ConstExp {
+  final StringConstant value;
   final List<ConstExp> arguments;
 
-  ConcatenateConstExp(this.arguments);
+  ConcatenateConstExp(this.value, this.arguments);
 
   accept(ConstExpVisitor visitor) => visitor.visitConcatenate(this);
 }
 
 /// Symbol literal.
 class SymbolConstExp extends ConstExp {
+  final ConstructedConstant value;
   final String name;
 
-  SymbolConstExp(this.name);
+  SymbolConstExp(this.value, this.name);
 
   accept(ConstExpVisitor visitor) => visitor.visitSymbol(this);
 }
 
 /// Type literal.
 class TypeConstExp extends ConstExp {
+  final TypeConstant value;
   /// Either [DynamicType] or a raw [GenericType].
   final DartType type;
 
-  TypeConstExp(this.type) {
+  TypeConstExp(this.value, this.type) {
     assert(type is GenericType || type is DynamicType);
   }
 
   accept(ConstExpVisitor visitor) => visitor.visitType(this);
 }
 
 /// A constant local, top-level, or static variable.
 class VariableConstExp extends ConstExp {
+  final Constant value;
   final VariableElement element;
 
-  VariableConstExp(this.element);
+  VariableConstExp(this.value, this.element);
 
   accept(ConstExpVisitor visitor) => visitor.visitVariable(this);
 }
 
 /// Reference to a top-level or static function.
 class FunctionConstExp extends ConstExp {
+  final FunctionConstant value;
   final FunctionElement element;
 
-  FunctionConstExp(this.element);
+  FunctionConstExp(this.value, this.element);
 
   accept(ConstExpVisitor visitor) => visitor.visitFunction(this);
 }
 
+/// A constant binary expression like `a * b` or `identical(a, b)`.
+class BinaryConstExp extends ConstExp {
+  final Constant value;
+  final ConstExp left;
+  final String operator;
+  final ConstExp right;
+
+  BinaryConstExp(this.value, this.left, this.operator, this.right) {
+    assert(PRECEDENCE_MAP[operator] != null);
+  }
+
+  accept(ConstExpVisitor visitor) => visitor.visitBinary(this);
+
+  int get precedence => PRECEDENCE_MAP[operator];
+
+  static const Map<String, int> PRECEDENCE_MAP = const {
+    'identical': 15,
+    '==': 6,
+    '!=': 6,
+    '&&': 5,
+    '||': 4,
+    '^': 9,
+    '&': 10,
+    '|': 8,
+    '>>': 11,
+    '<<': 11,
+    '+': 12,
+    '-': 12,
+    '*': 13,
+    '/': 13,
+    '~/': 13,
+    '>': 7,
+    '<': 7,
+    '>=': 7,
+    '<=': 7,
+    '%': 13,
+  };
+}
+
+/// A unary constant expression like `-a`.
+class UnaryConstExp extends ConstExp {
+  final Constant value;
+  final String operator;
+  final ConstExp expression;
+
+  UnaryConstExp(this.value, this.operator, this.expression) {
+    assert(PRECEDENCE_MAP[operator] != null);
+  }
+
+  accept(ConstExpVisitor visitor) => visitor.visitUnary(this);
+
+  int get precedence => PRECEDENCE_MAP[operator];
+
+  static const Map<String, int> PRECEDENCE_MAP = const {
+    '!': 14,
+    '~': 14,
+    '-': 14,
+  };
+}
+
+/// A constant conditional expression like `a ? b : c`.
+class ConditionalConstExp extends ConstExp {
+  final Constant value;
+  final ConstExp condition;
+  final ConstExp trueExp;
+  final ConstExp falseExp;
+
+  ConditionalConstExp(this.value, this.condition, this.trueExp, this.falseExp);
+
+  accept(ConstExpVisitor visitor) => visitor.visitConditional(this);
+
+  int get precedence => 3;
+}
+
 abstract class ConstExpVisitor<T> {
   T visit(ConstExp constant) => constant.accept(this);
 
   T visitPrimitive(PrimitiveConstExp exp);
   T visitList(ListConstExp exp);
   T visitMap(MapConstExp exp);
   T visitConstructor(ConstructorConstExp exp);
   T visitConcatenate(ConcatenateConstExp exp);
   T visitSymbol(SymbolConstExp exp);
   T visitType(TypeConstExp exp);
   T visitVariable(VariableConstExp exp);
   T visitFunction(FunctionConstExp exp);
+  T visitBinary(BinaryConstExp exp);
+  T visitUnary(UnaryConstExp exp);
+  T visitConditional(ConditionalConstExp exp);
 }
 
 /// Represents the declaration of a constant [element] with value [expression].
 class ConstDeclaration {
   final VariableElement element;
   final ConstExp expression;
 
   ConstDeclaration(this.element, this.expression);
 }
+
+class ConstExpPrinter extends ConstExpVisitor {
+  final StringBuffer sb = new StringBuffer();
+
+  write(ConstExp parent, ConstExp child, {bool leftAssociative: true}) {
+    if (child.precedence < parent.precedence ||
+        !leftAssociative && child.precedence == parent.precedence) {
+      sb.write('(');
+      child.accept(this);
+      sb.write(')');
+    } else {
+      child.accept(this);
+    }
+  }
+
+  writeTypeArguments(InterfaceType type) {
+    if (type.treatAsRaw) return;
+    sb.write('<');
+    bool needsComma = false;
+    for (DartType value in type.typeArguments) {
+      if (needsComma) {
+        sb.write(', ');
+      }
+      sb.write(value);
+      needsComma = true;
+    }
+    sb.write('>');
+  }
+
+  visitPrimitive(PrimitiveConstExp exp) {
+    sb.write(exp.value.toSyntax());
+  }
+
+  visitList(ListConstExp exp) {
+    sb.write('const ');
+    writeTypeArguments(exp.type);
+    sb.write('[');
+    bool needsComma = false;
+    for (ConstExp value in exp.values) {
+      if (needsComma) {
+        sb.write(', ');
+      }
+      visit(value);
+      needsComma = true;
+    }
+    sb.write(']');
+  }
+
+  visitMap(MapConstExp exp) {
+    sb.write('const ');
+    writeTypeArguments(exp.type);
+    sb.write('{');
+    for (int index = 0; index < exp.keys.length; index++) {
+      if (index > 0) {
+        sb.write(', ');
+      }
+      visit(exp.keys[index]);
+      sb.write(': ');
+      visit(exp.values[index]);
+    }
+    sb.write('}');
+  }
+
+  visitConstructor(ConstructorConstExp exp) {
+    sb.write('const ');
+    sb.write(exp.target.enclosingClass.name);
+    if (exp.target.name != '') {
+      sb.write('.');
+      sb.write(exp.target.name);
+    }
+    writeTypeArguments(exp.type);
+    sb.write('(');
+    bool needsComma = false;
+
+    int namedOffset = exp.selector.positionalArgumentCount;
+    for (int index = 0; index < namedOffset; index++) {
+      if (needsComma) {
+        sb.write(', ');
+      }
+      visit(exp.arguments[index]);
+      needsComma = true;
+    }
+    for (int index = 0; index < exp.selector.namedArgumentCount; index++) {
+      if (needsComma) {
+        sb.write(', ');
+      }
+      sb.write(exp.selector.namedArguments[index]);
+      sb.write(': ');
+      visit(exp.arguments[namedOffset + index]);
+      needsComma = true;
+    }
+    sb.write(')');
+  }
+
+  visitConcatenate(ConcatenateConstExp exp) {
+    sb.write(exp.value.toSyntax());
+  }
+
+  visitSymbol(SymbolConstExp exp) {
+    sb.write('#');
+    sb.write(exp.name);
+  }
+
+  visitType(TypeConstExp exp) {
+    sb.write(exp.type.name);
+  }
+
+  visitVariable(VariableConstExp exp) {
+    if (exp.element.isStatic) {
+      sb.write(exp.element.enclosingClass.name);
+      sb.write('.');
+    }
+    sb.write(exp.element.name);
+  }
+
+  visitFunction(FunctionConstExp exp) {
+    if (exp.element.isStatic) {
+      sb.write(exp.element.enclosingClass.name);
+      sb.write('.');
+    }
+    sb.write(exp.element.name);
+  }
+
+  visitBinary(BinaryConstExp exp) {
+    if (exp.operator == 'identical') {
+      sb.write('identical(');
+      visit(exp.left);
+      sb.write(', ');
+      visit(exp.right);
+      sb.write(')');
+    } else {
+      write(exp, exp.left);
+      sb.write(' ');
+      sb.write(exp.operator);
+      sb.write(' ');
+      write(exp, exp.right);
+    }
+  }
+
+  visitUnary(UnaryConstExp exp) {
+    sb.write(exp.operator);
+    write(exp, exp.expression);
+  }
+
+  visitConditional(ConditionalConstExp exp) {
+    write(exp, exp.condition, leftAssociative: false);
+    sb.write(' ? ');
+    write(exp, exp.trueExp);
+    sb.write(' : ');
+    write(exp, exp.falseExp);
+  }
+
+  String toString() => sb.toString();
+}