Serialize constant initializers.

pkg/analyzer/lib/src/summary/summarize_elements.dart

Index: pkg/analyzer/lib/src/summary/summarize_elements.dart
diff --git a/pkg/analyzer/lib/src/summary/summarize_elements.dart b/pkg/analyzer/lib/src/summary/summarize_elements.dart
index 13d568870817c9f97de5ac933963014ac6dd8554..d18f856829781a0b327ba261d743162f3e104444 100644
--- a/pkg/analyzer/lib/src/summary/summarize_elements.dart
+++ b/pkg/analyzer/lib/src/summary/summarize_elements.dart
@@ -6,8 +6,11 @@ library serialization.elements;
 
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
+import 'package:analyzer/src/dart/element/element.dart';
 import 'package:analyzer/src/dart/element/type.dart';
+import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/resolver.dart';
+import 'package:analyzer/src/generated/scanner.dart';
 import 'package:analyzer/src/generated/utilities_dart.dart';
 import 'package:analyzer/src/summary/format.dart';
 import 'package:analyzer/src/summary/name_filter.dart';
@@ -50,8 +53,278 @@ class LibrarySerializationResult {
 }
 
 /**
+ * Error that described a problem during a constant expression serialization.

[Paul Berry, 2016/01/19 20:02:10]

s/described/describes/

[scheglov, 2016/01/19 20:59:28]

Done.

+ */
+class _ConstExprSerializationError {
+  final String message;
+
+  _ConstExprSerializationError(this.message);
+
+  @override
+  String toString() => message;
+}
+
+/**
  * Instances of this class keep track of intermediate state during
- * serialization of a single library.`
+ * serialization of a single constant [Expression].
+ */
+class _ConstExprSerializer {
+  final _LibrarySerializer serializer;
+
+  /**
+   * See [UnlinkedConstBuilder.operations].
+   */
+  final List<UnlinkedConstOperation> operations = <UnlinkedConstOperation>[];
+
+  /**
+   * See [UnlinkedConstBuilder.ints].
+   */
+  final List<int> ints = <int>[];
+
+  /**
+   * See [UnlinkedConstBuilder.doubles].
+   */
+  final List<double> doubles = <double>[];
+
+  /**
+   * See [UnlinkedConstBuilder.strings].
+   */
+  final List<String> strings = <String>[];
+
+  /**
+   * See [UnlinkedConstBuilder.references].
+   */
+  final List<UnlinkedTypeRefBuilder> references = <UnlinkedTypeRefBuilder>[];
+
+  _ConstExprSerializer(this.serializer);
+
+  /**
+   * Serialize the given [expr] expression into this serializer state.
+   */
+  void serialize(Expression expr) {
+    if (expr is IntegerLiteral) {
+      _pushInt(expr.value);
+    } else if (expr is DoubleLiteral) {
+      operations.add(UnlinkedConstOperation.pushDouble);
+      doubles.add(expr.value);
+    } else if (expr is BooleanLiteral) {
+      if (expr.value) {
+        operations.add(UnlinkedConstOperation.pushTrue);
+      } else {
+        operations.add(UnlinkedConstOperation.pushFalse);
+      }
+    } else if (expr is StringLiteral) {
+      _serializeString(expr);
+    } else if (expr is SymbolLiteral) {
+      for (Token component in expr.components) {

[Paul Berry, 2016/01/19 20:02:10]

Nit: why not just concatenate all the components together using '.' and then
change the meaning of "makeSymbol" to convert a single string into a symbol? 
AFAICT, there's no real benefit to storing the components of the string
separately since we're just going to concatenate them using '.' at evaluation
time anyhow.

[scheglov, 2016/01/19 20:59:28]

Done.

+        operations.add(UnlinkedConstOperation.pushString);
+        strings.add(component.lexeme);
+      }
+      operations.add(UnlinkedConstOperation.makeSymbol);
+      ints.add(expr.components.length);
+    } else if (expr is NullLiteral) {
+      operations.add(UnlinkedConstOperation.pushNull);
+    } else if (expr is Identifier) {
+      Element element = expr.staticElement;
+      assert(element != null);
+      // TODO(scheglov) how to serialize element references?

[Paul Berry, 2016/01/19 20:02:10]

Is this TODO still applicable?  At first glance it looks like you're doing the
right thing.

[scheglov, 2016/01/19 20:59:28]

Yes, I don't like how we do this.
We discussed this offline.

+      operations.add(UnlinkedConstOperation.pushReference);
+      references.add(_serializeIdentifier(element));
+    } else if (expr is InstanceCreationExpression) {
+      _serializeInstanceCreation(expr);
+    } else if (expr is ListLiteral) {
+      _serializeListLiteral(expr);
+    } else if (expr is MapLiteral) {
+      _serializeMapLiteral(expr);
+    } else if (expr is MethodInvocation) {
+      String name = expr.methodName.name;
+      assert(name == 'identical');

[Paul Berry, 2016/01/19 20:02:10]

Add a TODO noting that these assertions will fail if presented with erroneous
code.  That's not a problem for now because at the moment we're just summarizing
the SDK, but it will be in the future when we want to summarize code under
development.

[scheglov, 2016/01/19 20:59:28]

I've added checks that throw _ConstExprSerializationError.

+      assert(expr.argumentList != null);
+      assert(expr.argumentList.arguments.length == 2);
+      expr.argumentList.arguments.forEach(serialize);
+      operations.add(UnlinkedConstOperation.identical);
+    } else if (expr is BinaryExpression) {
+      _serializeBinaryExpression(expr);
+    } else if (expr is ConditionalExpression) {
+      serialize(expr.condition);
+      serialize(expr.thenExpression);
+      serialize(expr.elseExpression);
+      operations.add(UnlinkedConstOperation.conditional);
+    } else if (expr is PrefixExpression) {
+      _serializePrefixExpression(expr);
+    } else if (expr is PropertyAccess && expr.propertyName.name == 'length') {
+      serialize(expr.target);
+      operations.add(UnlinkedConstOperation.length);
+    } else if (expr is ParenthesizedExpression) {
+      serialize(expr.expression);
+    } else {
+      throw new _ConstExprSerializationError('Unknown expression type: $expr');
+    }
+  }
+
+  /**
+   * Return the [UnlinkedConstBuilder] that corresponds to the state of this
+   * serializer.
+   */
+  UnlinkedConstBuilder toBuilder() {
+    return new UnlinkedConstBuilder(
+        operations: operations,
+        ints: ints,
+        doubles: doubles,
+        strings: strings,
+        references: references);
+  }
+
+  void _pushInt(int value) {
+    if (value >= (2 << 32)) {

[Paul Berry, 2016/01/19 20:02:10]

I don't think this code handles all possible ints correctly.  AFAICT it
mishandles:

- Values from 2^31 through 2^32-1 (e.g. 2^31 gets encoded as
pushInt(0x80000000), which is -2^31.  We want pushInt(0) shiftOr(0x80000000).)
- Values smaller than -2^31 (e.g. -2^31-1 gets encoded as pushInt(0x7fffffff),
which is 2^31-1.  We want pushInt(-1) shiftOr(0x7fffffff).)
- Values from 2^63 through 2^64-1 (e.g. 2^63 gets encoded as 
pushInt(0x80000000) shiftOr(0), which is -2^63.  We want pushInt(0)
shiftOr(0x80000000) shiftOr(0).)
- Values from 2^64 onward (e.g. 2^64 gets encoded as pushInt(0) shiftOr(0),
which is 0.  We want pushInt(1) shiftOr(0) shiftOr(0).  We need a while loop to
produce the shiftOrs because Dart supports arbitrary precision ints).

Note: since I suspect these values don't occur in the SDK, I would also be ok,
for now, with asserting that abs(value) < (2 << 31) and adding a TODO comment.

[scheglov, 2016/01/19 20:59:28]

Done.

+      _pushInt(value >> 32);
+      operations.add(UnlinkedConstOperation.shiftOr);
+      ints.add(value & 0xFFFFFFFF);
+    } else {
+      operations.add(UnlinkedConstOperation.pushInt);
+      ints.add(value & 0xFFFFFFFF);
+    }
+  }
+
+  void _serializeBinaryExpression(BinaryExpression expr) {
+    serialize(expr.leftOperand);
+    serialize(expr.rightOperand);
+    TokenType operator = expr.operator.type;
+    if (operator == TokenType.EQ_EQ) {
+      operations.add(UnlinkedConstOperation.equal);
+    } else if (operator == TokenType.BANG_EQ) {
+      operations.add(UnlinkedConstOperation.equal);
+      operations.add(UnlinkedConstOperation.not);
+    } else if (operator == TokenType.AMPERSAND_AMPERSAND) {
+      operations.add(UnlinkedConstOperation.and);
+    } else if (operator == TokenType.BAR_BAR) {
+      operations.add(UnlinkedConstOperation.or);
+    } else if (operator == TokenType.CARET) {
+      operations.add(UnlinkedConstOperation.bitXor);
+    } else if (operator == TokenType.AMPERSAND) {
+      operations.add(UnlinkedConstOperation.bitAnd);
+    } else if (operator == TokenType.BAR) {
+      operations.add(UnlinkedConstOperation.bitOr);
+    } else if (operator == TokenType.GT_GT) {
+      operations.add(UnlinkedConstOperation.bitShiftRight);
+    } else if (operator == TokenType.LT_LT) {
+      operations.add(UnlinkedConstOperation.bitShiftLeft);
+    } else if (operator == TokenType.PLUS) {
+      operations.add(UnlinkedConstOperation.add);
+    } else if (operator == TokenType.MINUS) {
+      operations.add(UnlinkedConstOperation.subtract);
+    } else if (operator == TokenType.STAR) {
+      operations.add(UnlinkedConstOperation.multiply);
+    } else if (operator == TokenType.SLASH) {
+      operations.add(UnlinkedConstOperation.divide);
+    } else if (operator == TokenType.TILDE_SLASH) {
+      operations.add(UnlinkedConstOperation.floorDivide);
+    } else if (operator == TokenType.GT) {
+      operations.add(UnlinkedConstOperation.greater);
+    } else if (operator == TokenType.LT) {
+      operations.add(UnlinkedConstOperation.less);
+    } else if (operator == TokenType.GT_EQ) {
+      operations.add(UnlinkedConstOperation.greaterEqual);
+    } else if (operator == TokenType.LT_EQ) {
+      operations.add(UnlinkedConstOperation.lessEqual);
+    } else if (operator == TokenType.PERCENT) {
+      operations.add(UnlinkedConstOperation.modulo);
+    } else {
+      throw new _ConstExprSerializationError('Unknown operator: $operator');
+    }
+  }
+
+  UnlinkedTypeRefBuilder _serializeIdentifier(Element element) {
+    return new UnlinkedTypeRefBuilder(
+        reference: serializer._getElementReferenceId(element));
+  }
+
+  void _serializeInstanceCreation(InstanceCreationExpression expr) {
+    List<Expression> arguments = expr.argumentList.arguments;
+    arguments.forEach(serialize);
+    ConstructorElement element = expr.staticElement;
+    assert(element != null);
+    operations.add(UnlinkedConstOperation.invokeConstructor);
+    references.add(serializer.serializeTypeRef(element.returnType, null));
+    strings.add(element.name);
+    // TODO(scheglov) named arguments?

[Paul Berry, 2016/01/19 20:02:10]

Oh yeah, good catch.  Let me know if you want to brainstorm about how to deal
with this.

+    ints.add(arguments.length);
+  }
+
+  void _serializeListLiteral(ListLiteral expr) {
+    List<Expression> elements = expr.elements;
+    elements.forEach(serialize);
+    DartType typeArgument;
+    if (expr.typeArguments != null &&
+        expr.typeArguments.arguments.length == 1) {
+      typeArgument = expr.typeArguments.arguments[0].type;
+    } else {
+      typeArgument = serializer.typeProvider.dynamicType;
+    }
+    references.add(serializer.serializeTypeRef(typeArgument, null));
+    ints.add(elements.length);
+    operations.add(UnlinkedConstOperation.makeList);
+  }
+
+  void _serializeMapLiteral(MapLiteral expr) {
+    for (MapLiteralEntry entry in expr.entries) {
+      serialize(entry.key);
+      serialize(entry.value);
+    }
+    DartType keyTypeArgument;
+    DartType valueTypeArgument;
+    if (expr.typeArguments != null &&
+        expr.typeArguments.arguments.length == 2) {
+      keyTypeArgument = expr.typeArguments.arguments[0].type;
+      valueTypeArgument = expr.typeArguments.arguments[1].type;
+    } else {
+      keyTypeArgument = serializer.typeProvider.dynamicType;
+      valueTypeArgument = serializer.typeProvider.dynamicType;
+    }
+    references.add(serializer.serializeTypeRef(keyTypeArgument, null));
+    references.add(serializer.serializeTypeRef(valueTypeArgument, null));
+    ints.add(expr.entries.length);
+    operations.add(UnlinkedConstOperation.makeMap);
+  }
+
+  void _serializePrefixExpression(PrefixExpression expr) {
+    serialize(expr.operand);
+    TokenType operator = expr.operator.type;
+    if (operator == TokenType.BANG) {
+      operations.add(UnlinkedConstOperation.not);
+    } else if (operator == TokenType.TILDE) {
+      operations.add(UnlinkedConstOperation.complement);
+    } else {
+      throw new _ConstExprSerializationError('Unknown operator: $operator');
+    }
+  }
+
+  void _serializeString(StringLiteral expr) {
+    if (expr is AdjacentStrings) {
+      operations.add(UnlinkedConstOperation.pushString);

[Paul Berry, 2016/01/19 20:02:10]

I think this does the wrong thing if one or more of the component strings uses
interpolation.

[scheglov, 2016/01/19 20:59:28]

Done.

+      strings.add(expr.stringValue);
+    } else if (expr is SimpleStringLiteral) {
+      operations.add(UnlinkedConstOperation.pushString);
+      strings.add(expr.value);
+    } else {
+      StringInterpolation interpolation = expr as StringInterpolation;
+      for (InterpolationElement element in interpolation.elements) {
+        if (element is InterpolationString) {
+          operations.add(UnlinkedConstOperation.pushString);
+          strings.add(element.value);
+        } else {
+          serialize((element as InterpolationExpression).expression);
+        }
+      }
+      operations.add(UnlinkedConstOperation.concatenate);
+      ints.add(interpolation.elements.length);
+    }
+  }
+}
+
+/**
+ * Instances of this class keep track of intermediate state during
+ * serialization of a single library.
  */
 class _LibrarySerializer {
   /**
@@ -385,6 +658,15 @@ class _LibrarySerializer {
   }
 
   /**
+   * Serialize the given [expression], creating an [UnlinkedConstBuilder].
+   */
+  UnlinkedConstBuilder serializeConstExpr(Expression expression) {
+    _ConstExprSerializer serializer = new _ConstExprSerializer(this);
+    serializer.serialize(expression);
+    return serializer.toBuilder();
+  }
+
+  /**
    * Return the index of the entry in the dependency table
    * ([LinkedLibrary.dependencies]) for the given [dependentLibrary].  A new
    * entry is added to the table if necessary to satisfy the request.
@@ -564,18 +846,7 @@ class _LibrarySerializer {
           element.getAncestor((Element e) => e is CompilationUnitElement);
       int unit = dependentLibrary.units.indexOf(unitElement);
       assert(unit != -1);
-      ReferenceKind kind;
-      if (element is PropertyAccessorElement) {
-        kind = ReferenceKind.topLevelPropertyAccessor;
-      } else if (element is FunctionTypeAliasElement) {
-        kind = ReferenceKind.typedef;
-      } else if (element is ClassElement) {
-        kind = ReferenceKind.classOrEnum;
-      } else if (element is FunctionElement) {
-        kind = ReferenceKind.topLevelFunction;
-      } else {
-        throw new Exception('Unexpected element kind: ${element.runtimeType}');
-      }
+      ReferenceKind kind = _getReferenceKind(element);
       exportNames.add(new LinkedExportNameBuilder(
           name: name,
           dependency: serializeDependency(dependentLibrary),
@@ -694,38 +965,7 @@ class _LibrarySerializer {
           b.reference = serializeDynamicReference();
         }
       } else {
-        b.reference = referenceMap.putIfAbsent(element, () {
-          assert(unlinkedReferences.length == linkedReferences.length);
-          CompilationUnitElement unitElement =
-              element.getAncestor((Element e) => e is CompilationUnitElement);
-          int unit = dependentLibrary.units.indexOf(unitElement);
-          assert(unit != -1);
-          int numTypeParameters = 0;
-          if (element is TypeParameterizedElement) {
-            numTypeParameters = element.typeParameters.length;
-          }
-          // Figure out a prefix that may be used to refer to the given type.
-          // TODO(paulberry): to avoid subtle relinking inconsistencies we
-          // should use the actual prefix from the AST (a given type may be
-          // reachable via multiple prefixes), but sadly, this information is
-          // not recorded in the element model.
-          int prefixReference = 0;
-          PrefixElement prefix = prefixMap[element];
-          if (prefix != null) {
-            prefixReference = serializePrefix(prefix);
-          }
-          int index = unlinkedReferences.length;
-          unlinkedReferences.add(new UnlinkedReferenceBuilder(
-              name: element.name, prefixReference: prefixReference));
-          linkedReferences.add(new LinkedReferenceBuilder(
-              dependency: serializeDependency(dependentLibrary),
-              kind: element is FunctionTypeAliasElement
-                  ? ReferenceKind.typedef
-                  : ReferenceKind.classOrEnum,
-              unit: unit,
-              numTypeParameters: numTypeParameters));
-          return index;
-        });
+        b.reference = _getElementReferenceId(element);
       }
       List<DartType> typeArguments;
       if (type is InterfaceType) {
@@ -778,6 +1018,63 @@ class _LibrarySerializer {
     b.isConst = variable.isConst;
     b.hasImplicitType = variable.hasImplicitType;
     b.documentationComment = serializeDocumentation(variable);
+    if (variable.isConst && variable is ConstVariableElement) {
+      ConstVariableElement constVariable = variable as ConstVariableElement;
+      Expression initializer = constVariable.constantInitializer;
+      if (initializer != null) {
+        b.constExpr = serializeConstExpr(initializer);
+      }
+    }
     return b;
   }
+
+  int _getElementReferenceId(Element element) {
+    LibraryElement dependentLibrary = element.library;
+    return referenceMap.putIfAbsent(element, () {
+      assert(unlinkedReferences.length == linkedReferences.length);
+      CompilationUnitElement unitElement =
+          element.getAncestor((Element e) => e is CompilationUnitElement);
+      int unit = dependentLibrary.units.indexOf(unitElement);
+      assert(unit != -1);
+      int numTypeParameters = 0;
+      if (element is TypeParameterizedElement) {
+        numTypeParameters = element.typeParameters.length;
+      }
+      // Figure out a prefix that may be used to refer to the given type.
+      // TODO(paulberry): to avoid subtle relinking inconsistencies we
+      // should use the actual prefix from the AST (a given type may be
+      // reachable via multiple prefixes), but sadly, this information is
+      // not recorded in the element model.
+      int prefixReference = 0;
+      PrefixElement prefix = prefixMap[element];
+      if (prefix != null) {
+        prefixReference = serializePrefix(prefix);
+      }
+      int index = unlinkedReferences.length;
+      unlinkedReferences.add(new UnlinkedReferenceBuilder(
+          name: element.name, prefixReference: prefixReference));
+      linkedReferences.add(new LinkedReferenceBuilder(
+          dependency: serializeDependency(dependentLibrary),
+          kind: _getReferenceKind(element),
+          unit: unit,
+          numTypeParameters: numTypeParameters));
+      return index;
+    });
+  }
+
+  ReferenceKind _getReferenceKind(Element element) {
+    ReferenceKind kind;
+    if (element is PropertyAccessorElement) {
+      kind = ReferenceKind.topLevelPropertyAccessor;
+    } else if (element is FunctionTypeAliasElement) {
+      kind = ReferenceKind.typedef;
+    } else if (element is ClassElement) {
+      kind = ReferenceKind.classOrEnum;
+    } else if (element is FunctionElement) {
+      kind = ReferenceKind.topLevelFunction;
+    } else {
+      throw new Exception('Unexpected element kind: ${element.runtimeType}');
+    }
+    return kind;
+  }
 }