Fasta type inference prototype #2

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

Index: pkg/front_end/lib/src/fasta/kernel/body_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
index 99d52df96e4e934f17d9a0273722e96a9d053a75..fbdeef31713749ce212dc0ac77d6d562adc1db29 100644
--- a/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/body_builder.dart
@@ -10,6 +10,11 @@ import '../parser/error_kind.dart' show ErrorKind;
 
 import '../parser/identifier_context.dart' show IdentifierContext;
 
+import 'package:front_end/src/fasta/builder/ast_factory.dart';
+import 'package:front_end/src/fasta/kernel/kernel_ast_factory.dart';
+import 'package:front_end/src/fasta/kernel/kernel_shadow_ast.dart';
+import 'package:front_end/src/fasta/type_inference/local_type_inferrer.dart';
+import '../builder/shadow_ast.dart';
 import 'package:kernel/ast.dart';
 
 import 'package:kernel/clone.dart' show CloneVisitor;
@@ -102,19 +107,26 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   // from VM engineers. TODO(ahe): Does this still apply?
   int currentLocalVariableModifiers = -1;
 
+  final AstFactory _ast = new KernelAstFactory();
+
+  final LocalTypeInferrer _typeInferrer;
+
   BodyBuilder(
       KernelLibraryBuilder library,
       this.member,
       Scope scope,
       this.formalParameterScope,
       this.hierarchy,
-      this.coreTypes,
+      CoreTypes coreTypes,
       this.classBuilder,
       this.isInstanceMember,
       this.uri)
-      : enclosingScope = scope,
+      : coreTypes = coreTypes,
+        enclosingScope = scope,
         library = library,
         isDartLibrary = library.uri.scheme == "dart",
+        // TODO(paulberry): put this behind a flag.
+        _typeInferrer = new LocalTypeInferrer(coreTypes),
         super(scope);
 
   bool get hasParserError => recoverableErrors.isNotEmpty;
@@ -133,23 +145,23 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
     super.push(node);
   }
 
-  Expression popForValue() => toValue(pop());
+  ShadowExpression popForValue() => toValue(pop());
 
-  Expression popForEffect() => toEffect(pop());
+  ShadowExpression popForEffect() => toEffect(pop());
 
-  Expression popForValueIfNotNull(Object value) {
+  ShadowExpression popForValueIfNotNull(Object value) {
     return value == null ? null : popForValue();
   }
 
   @override
-  Expression toValue(Object node) {
+  ShadowExpression toValue(Object node) {
     if (node is UnresolvedIdentifier) {
       if (isDartLibrary &&
           node.name.name == "main" &&
           library.uri.path == "_builtin" &&
           member?.name == "_getMainClosure") {
         // TODO(ahe): https://github.com/dart-lang/sdk/issues/28989
-        return new NullLiteral()..fileOffset = node.fileOffset;
+        return _ast.nullLiteral(node.fileOffset);
       }
       return throwNoSuchMethodError(
           node.name.name, new Arguments.empty(), node.fileOffset,
@@ -166,13 +178,14 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
           addCompileTimeError(-1,
               "Type variable can't be used as a constant expression $type.");
         }
-        return new TypeLiteral(type);
+        return new TypeLiteral(type) as ShadowExpression;
       }
     } else if (node is TypeDeclarationBuilder) {
-      return new TypeLiteral(node.buildTypesWithBuiltArguments(library, null));
+      return new TypeLiteral(node.buildTypesWithBuiltArguments(library, null))
+          as ShadowExpression;
     } else if (node is KernelTypeBuilder) {
-      return new TypeLiteral(node.build(library));
-    } else if (node is Expression) {
+      return new TypeLiteral(node.build(library)) as ShadowExpression;
+    } else if (node is ShadowExpression) {
       return node;
     } else if (node is PrefixBuilder) {
       return buildCompileTimeError("A library can't be used as an expression.");
@@ -183,30 +196,28 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
     }
   }
 
-  Expression toEffect(Object node) {
+  ShadowExpression toEffect(Object node) {
     if (node is BuilderAccessor) return node.buildForEffect();
     return toValue(node);
   }
 
-  List<Expression> popListForValue(int n) {
-    List<Expression> list =
-        new List<Expression>.filled(n, null, growable: true);
+  List<ShadowExpression> popListForValue(int n) {
+    List<ShadowExpression> list = _ast.expressionList(n);
     for (int i = n - 1; i >= 0; i--) {
       list[i] = popForValue();
     }
     return list;
   }
 
-  List<Expression> popListForEffect(int n) {
-    List<Expression> list =
-        new List<Expression>.filled(n, null, growable: true);
+  List<ShadowExpression> popListForEffect(int n) {
+    List<ShadowExpression> list = _ast.expressionList(n);
     for (int i = n - 1; i >= 0; i--) {
       list[i] = popForEffect();
     }
     return list;
   }
 
-  Block popBlock(int count, int charOffset) {
+  ShadowBlock popBlock(int count, int charOffset) {
     List<dynamic /*Statement | List<Statement>*/ > statements =
         popList(count) ?? <Statement>[];
     List<Statement> copy;
@@ -221,7 +232,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
         copy.add(statement);
       }
     }
-    return new Block(copy ?? statements)..fileOffset = charOffset;
+    return _ast.block(copy ?? statements, charOffset);
   }
 
   Statement popStatementIfNotNull(Object value) {
@@ -337,7 +348,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
       assert(count == 0);
       push(NullValue.Block);
     } else {
-      Block block = popBlock(count, beginToken.charOffset);
+      ShadowBlock block = popBlock(count, beginToken.charOffset);
       exitLocalScope();
       push(block);
     }
@@ -418,14 +429,14 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   }
 
   @override
-  void finishFunction(
-      FormalParameters formals, AsyncMarker asyncModifier, Statement body) {
+  void finishFunction(FormalParameters formals, AsyncMarker asyncModifier,
+      ShadowStatement body) {
     debugEvent("finishFunction");
     KernelFunctionBuilder builder = member;
     if (builder is KernelConstructorBuilder) {
       if (asyncModifier != AsyncMarker.Sync) {
         // TODO(ahe): Change this to a null check.
-        addCompileTimeError(body?.fileOffset,
+        addCompileTimeError((body as Statement)?.fileOffset,
             "Can't be marked as ${asyncModifier}: ${builder.name}");
       }
     } else if (builder is KernelProcedureBuilder) {
@@ -433,7 +444,8 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
     } else {
       internalError("Unhandled: ${builder.runtimeType}");
     }
-    builder.body = body;
+    _typeInferrer.inferBody(body);
+    builder.body = body as Statement;
     if (formals?.optional != null) {
       Iterator<FormalParameterBuilder> formalBuilders =
           builder.formals.skip(formals.required.length).iterator;
@@ -450,7 +462,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   @override
   void endExpressionStatement(Token token) {
     debugEvent("ExpressionStatement");
-    push(new ExpressionStatement(popForEffect()));
+    push(new ExpressionStatement(popForEffect() as Expression));
   }
 
   @override
@@ -469,7 +481,8 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
           arguments[i] = new NamedExpression(
               "#$i",
               buildCompileTimeError(
-                  "Expected named argument.", arguments[i].fileOffset));
+                      "Expected named argument.", arguments[i].fileOffset)
+                  as Expression);
         }
       }
     }
@@ -533,14 +546,14 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
           receiver.name.name, arguments, receiver.fileOffset);
     } else {
       return buildMethodInvocation(
-          toValue(receiver), callName, arguments, charOffset);
+          toValue(receiver) as Expression, callName, arguments, charOffset);
     }
   }
 
   @override
   void beginCascade(Token token) {
     debugEvent("beginCascade");
-    Expression expression = popForValue();
+    Expression expression = popForValue() as Expression;
     if (expression is CascadeReceiver) {
       push(expression);
       push(new VariableAccessor(
@@ -557,7 +570,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   @override
   void endCascade() {
     debugEvent("endCascade");
-    Expression expression = popForEffect();
+    Expression expression = popForEffect() as Expression;
     CascadeReceiver cascadeReceiver = pop();
     cascadeReceiver.finalize(expression);
     push(cascadeReceiver);
@@ -574,14 +587,15 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
     }
     if (optional("??", token)) return doIfNull(token);
     if (optional("?.", token)) return doIfNotNull(token);
-    Expression argument = popForValue();
+    Expression argument = popForValue() as Expression;
     var receiver = pop();
     bool isSuper = false;
     if (receiver is ThisAccessor && receiver.isSuper) {
       isSuper = true;
       receiver = new ThisExpression();
     }
-    push(buildBinaryOperator(toValue(receiver), token, argument, isSuper));
+    push(buildBinaryOperator(
+        toValue(receiver) as Expression, token, argument, isSuper));
   }
 
   Expression buildBinaryOperator(
@@ -594,7 +608,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
     }
     if (!isBinaryOperator(operator) && !isMinusOperator(operator)) {
       return buildCompileTimeError(
-          "Not an operator: '$operator'.", token.charOffset);
+          "Not an operator: '$operator'.", token.charOffset) as Expression;
     } else {
       Expression result =
           makeBinary(a, new Name(operator), null, b, token.charOffset);
@@ -606,15 +620,15 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   }
 
   void doLogicalExpression(Token token) {
-    Expression argument = popForValue();
-    Expression receiver = popForValue();
+    Expression argument = popForValue() as Expression;
+    Expression receiver = popForValue() as Expression;
     push(new LogicalExpression(receiver, token.stringValue, argument));
   }
 
   /// Handle `a ?? b`.
   void doIfNull(Token token) {
-    Expression b = popForValue();
-    Expression a = popForValue();
+    Expression b = popForValue() as Expression;
+    Expression a = popForValue() as Expression;
     VariableDeclaration variable = new VariableDeclaration.forValue(a);
     push(makeLet(
         variable,
@@ -654,8 +668,8 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
     }
     if (isNoSuchMethod) {
       return throwNoSuchMethodError(
-          node.name.name, node.arguments, node.fileOffset,
-          isSuper: true);
+              node.name.name, node.arguments, node.fileOffset, isSuper: true)
+          as Expression;
     }
     // TODO(ahe): Use [DirectPropertyGet] when possible.
     Expression receiver = new DirectPropertyGet(new ThisExpression(), target);
@@ -670,7 +684,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   }
 
   @override
-  Expression throwNoSuchMethodError(
+  ShadowExpression throwNoSuchMethodError(
       String name, Arguments arguments, int charOffset,
       {bool isSuper: false, isGetter: false, isSetter: false}) {
     String errorName = isSuper ? "super.$name" : name;
@@ -693,7 +707,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
             return new MapEntry(new SymbolLiteral(arg.name), arg.value);
           }).toList()),
           new NullLiteral()
-        ])));
+        ]))) as ShadowExpression;
   }
 
   @override
@@ -860,7 +874,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
             expressions.add(new StringLiteral(unescape(part.lexeme, quote)));
           }
         } else {
-          expressions.add(toValue(part));
+          expressions.add(toValue(part) as Expression);
         }
       }
       // Contains more than just \' or \".
@@ -881,7 +895,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   @override
   void handleStringJuxtaposition(int literalCount) {
     debugEvent("StringJuxtaposition");
-    List<Expression> parts = popListForValue(literalCount);
+    List<Expression> parts = popListForValue(literalCount) as List<Expression>;
     List<Expression> expressions;
     // Flatten string juxtapositions of string interpolation.
     for (int i = 0; i < parts.length; i++) {
@@ -903,8 +917,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   @override
   void handleLiteralInt(Token token) {
     debugEvent("LiteralInt");
-    push(
-        new IntLiteral(int.parse(token.lexeme))..fileOffset = token.charOffset);
+    push(_ast.intLiteral(int.parse(token.lexeme), token.charOffset));
   }
 
   @override
@@ -923,12 +936,12 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   void endReturnStatement(
       bool hasExpression, Token beginToken, Token endToken) {
     debugEvent("ReturnStatement");
-    Expression expression = hasExpression ? popForValue() : null;
+    ShadowExpression expression = hasExpression ? popForValue() : null;
     if (expression != null && inConstructor) {
       push(buildCompileTimeErrorStatement(
           "Can't return from a constructor.", beginToken.charOffset));
     } else {
-      push(new ReturnStatement(expression)..fileOffset = beginToken.charOffset);
+      push(_ast.returnStatement(expression, beginToken.charOffset));
     }
   }
 
@@ -936,7 +949,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   void endIfStatement(Token ifToken, Token elseToken) {
     Statement elsePart = popStatementIfNotNull(elseToken);
     Statement thenPart = popStatement();
-    Expression condition = popForValue();
+    Expression condition = popForValue() as Expression;
     push(new IfStatement(condition, thenPart, elsePart));
   }
 
@@ -954,18 +967,22 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
     pushNewLocalVariable(null);
   }
 
-  void pushNewLocalVariable(Expression initializer,
+  void pushNewLocalVariable(ShadowExpression initializer,
       {int equalsCharOffset: TreeNode.noOffset}) {
     Identifier identifier = pop();
     assert(currentLocalVariableModifiers != -1);
     bool isConst = (currentLocalVariableModifiers & constMask) != 0;
     bool isFinal = (currentLocalVariableModifiers & finalMask) != 0;
     assert(isConst == constantExpressionRequired);
-    push(new VariableDeclaration(identifier.name,
+    var variable = _ast.variableDeclaration(identifier.name,
         initializer: initializer,
-        type: currentLocalVariableType ?? const DynamicType(),
+        type: currentLocalVariableType,
         isFinal: isFinal,
-        isConst: isConst)..fileEqualsOffset = equalsCharOffset);
+        isConst: isConst,
+        charOffset: equalsCharOffset);
+    _typeInferrer.finishVariableDeclaration(
+        currentLocalVariableType, initializer, variable);
+    push(variable);
   }
 
   @override
@@ -1022,7 +1039,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   @override
   void endBlock(int count, Token beginToken, Token endToken) {
     debugEvent("Block");
-    Block block = popBlock(count, beginToken.charOffset);
+    ShadowBlock block = popBlock(count, beginToken.charOffset);
     exitLocalScope();
     push(block);
   }
@@ -1030,7 +1047,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   @override
   void handleAssignmentExpression(Token token) {
     debugEvent("AssignmentExpression");
-    Expression value = popForValue();
+    Expression value = popForValue() as Expression;
     var accessor = pop();
     if (accessor is TypeDeclarationBuilder) {
       push(wrapInvalid(new TypeLiteral(
@@ -1069,7 +1086,8 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
       int updateExpressionCount, Token endToken) {
     debugEvent("ForStatement");
     Statement body = popStatement();
-    List<Expression> updates = popListForEffect(updateExpressionCount);
+    List<Expression> updates =
+        popListForEffect(updateExpressionCount) as List<Expression>;
     Statement conditionStatement = popStatement();
     Expression condition = null;
     if (conditionStatement is ExpressionStatement) {
@@ -1117,8 +1135,8 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   @override
   void endAwaitExpression(Token beginToken, Token endToken) {
     debugEvent("AwaitExpression");
-    push(
-        new AwaitExpression(popForValue())..fileOffset = beginToken.charOffset);
+    push(new AwaitExpression(popForValue() as Expression)
+      ..fileOffset = beginToken.charOffset);
   }
 
   @override
@@ -1131,20 +1149,19 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   void handleLiteralList(
       int count, Token beginToken, Token constKeyword, Token endToken) {
     debugEvent("LiteralList");
-    List<Expression> expressions = popListForValue(count);
+    List<ShadowExpression> expressions = popListForValue(count);
     List<DartType> typeArguments = pop();
-    DartType typeArgument = const DynamicType();
+    DartType typeArgument;
     if (typeArguments != null) {
       typeArgument = typeArguments.first;
       if (typeArguments.length > 1) {
-        typeArgument = const DynamicType();
+        typeArgument = null;
         warning(
             "Too many type arguments on List literal.", beginToken.charOffset);
       }
     }
-    push(new ListLiteral(expressions,
-        typeArgument: typeArgument, isConst: constKeyword != null)
-      ..fileOffset = constKeyword?.charOffset ?? beginToken.charOffset);
+    push(_ast.listLiteral(expressions, typeArgument, constKeyword != null,
+        constKeyword?.charOffset ?? beginToken.charOffset));
   }
 
   @override
@@ -1165,7 +1182,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   @override
   void handleLiteralNull(Token token) {
     debugEvent("LiteralNull");
-    push(new NullLiteral()..fileOffset = token.charOffset);
+    push(_ast.nullLiteral(token.charOffset));
   }
 
   @override
@@ -1195,8 +1212,8 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   @override
   void endLiteralMapEntry(Token colon, Token endToken) {
     debugEvent("LiteralMapEntry");
-    Expression value = popForValue();
-    Expression key = popForValue();
+    Expression value = popForValue() as Expression;
+    Expression key = popForValue() as Expression;
     push(new MapEntry(key, value));
   }
 
@@ -1336,7 +1353,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   void handleAsOperator(Token operator, Token endToken) {
     debugEvent("AsOperator");
     DartType type = pop();
-    Expression expression = popForValue();
+    Expression expression = popForValue() as Expression;
     push(new AsExpression(expression, type)..fileOffset = operator.charOffset);
   }
 
@@ -1344,7 +1361,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   void handleIsOperator(Token operator, Token not, Token endToken) {
     debugEvent("IsOperator");
     DartType type = pop();
-    Expression expression = popForValue();
+    Expression expression = popForValue() as Expression;
     expression = new IsExpression(expression, type)
       ..fileOffset = operator.charOffset;
     if (not != null) {
@@ -1356,9 +1373,9 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   @override
   void handleConditionalExpression(Token question, Token colon) {
     debugEvent("ConditionalExpression");
-    Expression elseExpression = popForValue();
-    Expression thenExpression = popForValue();
-    Expression condition = popForValue();
+    Expression elseExpression = popForValue() as Expression;
+    Expression thenExpression = popForValue() as Expression;
+    Expression condition = popForValue() as Expression;
     push(new ConditionalExpression(
         condition, thenExpression, elseExpression, const DynamicType()));
   }
@@ -1366,7 +1383,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   @override
   void endThrowExpression(Token throwToken, Token endToken) {
     debugEvent("ThrowExpression");
-    Expression expression = popForValue();
+    Expression expression = popForValue() as Expression;
     push(new Throw(expression)..fileOffset = throwToken.charOffset);
   }
 
@@ -1387,7 +1404,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
     DartType type = pop();
     pop(); // Modifiers.
     ignore(Unhandled.Metadata);
-    VariableDeclaration variable;
+    ShadowVariableDeclaration variable;
     if (!inCatchClause && functionNestingLevel == 0) {
       dynamic builder = formalParameterScope.lookup(name.name, charOffset, uri);
       if (builder == null) {
@@ -1400,7 +1417,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
         }
       } else if (thisKeyword == null) {
         variable = builder.build(library);
-        variable.initializer = name.initializer;
+        (variable as VariableDeclaration).initializer = name.initializer;
       } else if (builder.isField && builder.parent == classBuilder) {
         FieldBuilder field = builder;
         if (type != null) {
@@ -1408,16 +1425,19 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
               thisKeyword.charOffset);
         }
         type = field.target.type ?? const DynamicType();
-        variable = new VariableDeclaration(name.name,
-            type: type, initializer: name.initializer);
+        variable = _ast.variableDeclaration(name.name,
+            type: type,
+            initializer: name.initializer as ShadowExpression,
+            charOffset: name.fileOffset);
       } else {
         addCompileTimeError(
             name.fileOffset, "'${name.name}' isn't a field in this class.");
       }
     }
-    variable ??= new VariableDeclaration(name.name,
-        type: type ?? const DynamicType(),
-        initializer: name.initializer)..fileOffset = name.fileOffset;
+    variable ??= _ast.variableDeclaration(name.name,
+        type: type,
+        initializer: name.initializer as ShadowExpression,
+        charOffset: name.fileOffset);
     push(variable);
   }
 
@@ -1456,7 +1476,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   @override
   void handleValuedFormalParameter(Token equals, Token token) {
     debugEvent("ValuedFormalParameter");
-    Expression initializer = popForValue();
+    Expression initializer = popForValue() as Expression;
     Identifier name = pop();
     push(new InitializedIdentifier(name.name, initializer));
   }
@@ -1554,14 +1574,14 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   void handleIndexedExpression(
       Token openCurlyBracket, Token closeCurlyBracket) {
     debugEvent("IndexedExpression");
-    Expression index = popForValue();
+    Expression index = popForValue() as Expression;
     var receiver = pop();
     if (receiver is ThisAccessor && receiver.isSuper) {
       push(new SuperIndexAccessor(this, receiver.charOffset, index,
           lookupSuperMember(indexGetName), lookupSuperMember(indexSetName)));
     } else {
       push(IndexAccessor.make(this, openCurlyBracket.charOffset,
-          toValue(receiver), index, null, null));
+          toValue(receiver) as Expression, index, null, null));
     }
   }
 
@@ -1570,7 +1590,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
     debugEvent("UnaryPrefixExpression");
     var receiver = pop();
     if (optional("!", token)) {
-      push(new Not(toValue(receiver)));
+      push(new Not(toValue(receiver) as Expression));
     } else {
       String operator = token.stringValue;
       if (optional("-", token)) {
@@ -1583,8 +1603,8 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
             new Arguments.empty(),
             token.charOffset)));
       } else {
-        push(buildMethodInvocation(toValue(receiver), new Name(operator),
-            new Arguments.empty(), token.charOffset));
+        push(buildMethodInvocation(toValue(receiver) as Expression,
+            new Name(operator), new Arguments.empty(), token.charOffset));
       }
     }
   }
@@ -1603,7 +1623,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
       push(accessor.buildPrefixIncrement(
           incrementOperator(token), token.charOffset));
     } else {
-      push(wrapInvalid(toValue(accessor)));
+      push(wrapInvalid(toValue(accessor) as Expression));
     }
   }
 
@@ -1615,7 +1635,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
       push(new DelayedPostfixIncrement(
           this, token.charOffset, accessor, incrementOperator(token), null));
     } else {
-      push(wrapInvalid(toValue(accessor)));
+      push(wrapInvalid(toValue(accessor) as Expression));
     }
   }
 
@@ -1683,7 +1703,8 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
       typeParameters = target.enclosingClass.typeParameters;
     }
     if (!checkArguments(target.function, arguments, typeParameters)) {
-      return throwNoSuchMethodError(target.name.name, arguments, charOffset);
+      return throwNoSuchMethodError(target.name.name, arguments, charOffset)
+          as Expression;
     }
     if (target is Constructor) {
       return new ConstructorInvocation(target, arguments)
@@ -1844,7 +1865,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   @override
   void handleNamedArgument(Token colon) {
     debugEvent("NamedArgument");
-    Expression value = popForValue();
+    Expression value = popForValue() as Expression;
     Identifier identifier = pop();
     push(new NamedExpression(identifier.name, value));
   }
@@ -1863,7 +1884,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
     enterLocalScope();
   }
 
-  void enterFunction() {
+  void enterFunction(bool isNamed) {
     debugEvent("enterFunction");
     functionNestingLevel++;
     push(switchScope ?? NullValue.SwitchScope);
@@ -1879,13 +1900,13 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   @override
   void beginFunction(Token token) {
     debugEvent("beginFunction");
-    enterFunction();
+    enterFunction(true);
   }
 
   @override
   void beginUnnamedFunction(Token token) {
     debugEvent("beginUnnamedFunction");
-    enterFunction();
+    enterFunction(false);
   }
 
   @override
@@ -1931,14 +1952,15 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
         typeParameters: typeParameters, asyncMarker: asyncModifier)
       ..fileOffset = beginToken.charOffset
       ..fileEndOffset = token.charOffset);
-    push(new FunctionExpression(function)..fileOffset = beginToken.charOffset);
+    push(new KernelFunctionExpression(function)
+      ..fileOffset = beginToken.charOffset);
   }
 
   @override
   void endDoWhileStatement(
       Token doKeyword, Token whileKeyword, Token endToken) {
     debugEvent("DoWhileStatement");
-    Expression condition = popForValue();
+    Expression condition = popForValue() as Expression;
     Statement body = popStatement();
     JumpTarget continueTarget = exitContinueTarget();
     JumpTarget breakTarget = exitBreakTarget();
@@ -1962,7 +1984,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   @override
   void endForInExpression(Token token) {
     debugEvent("ForInExpression");
-    Expression expression = popForValue();
+    Expression expression = popForValue() as Expression;
     exitLocalScope();
     push(expression ?? NullValue.Expression);
   }
@@ -1972,7 +1994,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
       Token inKeyword, Token rightParenthesis, Token endToken) {
     debugEvent("ForIn");
     Statement body = popStatement();
-    Expression expression = popForValue();
+    Expression expression = popForValue() as Expression;
     var lvalue = pop();
     exitLocalScope();
     JumpTarget continueTarget = exitContinueTarget();
@@ -2002,7 +2024,8 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
           body);
     } else {
       variable = new VariableDeclaration.forValue(buildCompileTimeError(
-          "Expected lvalue, but got ${lvalue}", forToken.next.next.charOffset));
+          "Expected lvalue, but got ${lvalue}",
+          forToken.next.next.charOffset) as Expression);
     }
     Statement result = new ForInStatement(variable, expression, body,
         isAsync: awaitToken != null)..fileOffset = body.fileOffset;
@@ -2071,7 +2094,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   void endWhileStatement(Token whileKeyword, Token endToken) {
     debugEvent("WhileStatement");
     Statement body = popStatement();
-    Expression condition = popForValue();
+    Expression condition = popForValue() as Expression;
     JumpTarget continueTarget = exitContinueTarget();
     JumpTarget breakTarget = exitBreakTarget();
     if (continueTarget.hasUsers) {
@@ -2096,16 +2119,16 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   void handleAssertStatement(Token assertKeyword, Token leftParenthesis,
       Token commaToken, Token rightParenthesis, Token semicolonToken) {
     debugEvent("AssertStatement");
-    Expression message = popForValueIfNotNull(commaToken);
-    Expression condition = popForValue();
+    Expression message = popForValueIfNotNull(commaToken) as Expression;
+    Expression condition = popForValue() as Expression;
     push(new AssertStatement(condition, message));
   }
 
   @override
   void endYieldStatement(Token yieldToken, Token starToken, Token endToken) {
     debugEvent("YieldStatement");
-    push(new YieldStatement(popForValue(), isYieldStar: starToken != null)
-      ..fileOffset = yieldToken.charOffset);
+    push(new YieldStatement(popForValue() as Expression,
+        isYieldStar: starToken != null)..fileOffset = yieldToken.charOffset);
   }
 
   @override
@@ -2127,7 +2150,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
         if (labelOrExpression is Label) {
           labels.add(labelOrExpression);
         } else {
-          expressions.add(toValue(labelOrExpression));
+          expressions.add(toValue(labelOrExpression) as Expression);
         }
       }
     }
@@ -2154,7 +2177,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
       Token firstToken,
       Token endToken) {
     debugEvent("SwitchCase");
-    Block block = popBlock(statementCount, firstToken.charOffset);
+    Block block = popBlock(statementCount, firstToken.charOffset) as Block;
     exitLocalScope();
     List<Label> labels = pop();
     List<Expression> expressions = pop();
@@ -2192,7 +2215,7 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
     JumpTarget target = exitBreakTarget();
     exitSwitchScope();
     exitLocalScope();
-    Expression expression = popForValue();
+    Expression expression = popForValue() as Expression;
     Statement result = new SwitchStatement(expression, cases);
     if (target.hasUsers) {
       result = new LabeledStatement(result);
@@ -2345,27 +2368,30 @@ class BodyBuilder extends ScopeListener<JumpTarget> implements BuilderHelper {
   }
 
   @override
-  Expression buildCompileTimeError(error, [int charOffset = -1]) {
+  ShadowExpression buildCompileTimeError(error, [int charOffset = -1]) {
     addCompileTimeError(charOffset, error);
     String message = formatUnexpected(uri, charOffset, error);
     Builder constructor = library.loader.getCompileTimeError();
     return new Throw(buildStaticInvocation(constructor.target,
-        new Arguments(<Expression>[new StringLiteral(message)]),
-        isConst: false)); // TODO(ahe): Make this const.
+            new Arguments(<Expression>[new StringLiteral(message)]),
+            isConst: false) as Expression)
+        as ShadowExpression; // TODO(ahe): Make this const.
   }
 
   Statement buildCompileTimeErrorStatement(error, [int charOffset = -1]) {
-    return new ExpressionStatement(buildCompileTimeError(error, charOffset));
+    return new ExpressionStatement(
+        buildCompileTimeError(error, charOffset) as Expression);
   }
 
   @override
   Initializer buildCompileTimeErrorIntializer(error, [int charOffset = -1]) {
     return new LocalInitializer(new VariableDeclaration.forValue(
-        buildCompileTimeError(error, charOffset)));
+        buildCompileTimeError(error, charOffset) as Expression));
   }
 
   @override
-  Expression buildProblemExpression(ProblemBuilder builder, int charOffset) {
+  ShadowExpression buildProblemExpression(
+      ProblemBuilder builder, int charOffset) {
     return buildCompileTimeError(builder.message, charOffset);
   }
 
@@ -2500,9 +2526,9 @@ abstract class ContextAccessor extends BuilderAccessor {
     return internalError("Unhandled: ${runtimeType}", uri, charOffset);
   }
 
-  Expression buildSimpleRead();
+  ShadowExpression buildSimpleRead();
 
-  Expression buildForEffect();
+  ShadowExpression buildForEffect();
 
   Expression buildAssignment(Expression value, {bool voidContext: false}) {
     return makeInvalidWrite(value);
@@ -2533,7 +2559,8 @@ abstract class ContextAccessor extends BuilderAccessor {
 
   Expression makeInvalidWrite(Expression value) {
     return helper.buildCompileTimeError(
-        "Can't be used as left-hand side of assignment.", charOffset);
+            "Can't be used as left-hand side of assignment.", charOffset)
+        as Expression;
   }
 }
 
@@ -2546,12 +2573,12 @@ class DelayedAssignment extends ContextAccessor {
       BuilderAccessor accessor, this.value, this.assignmentOperator)
       : super(helper, charOffset, accessor);
 
-  Expression buildSimpleRead() {
-    return handleAssignment(false);
+  ShadowExpression buildSimpleRead() {
+    return handleAssignment(false) as ShadowExpression;
   }
 
-  Expression buildForEffect() {
-    return handleAssignment(true);
+  ShadowExpression buildForEffect() {
+    return handleAssignment(true) as ShadowExpression;
   }
 
   Expression handleAssignment(bool voidContext) {
@@ -2624,14 +2651,16 @@ class DelayedPostfixIncrement extends ContextAccessor {
       BuilderAccessor accessor, this.binaryOperator, this.interfaceTarget)
       : super(helper, charOffset, accessor);
 
-  Expression buildSimpleRead() {
+  ShadowExpression buildSimpleRead() {
     return accessor.buildPostfixIncrement(binaryOperator, charOffset,
-        voidContext: false, interfaceTarget: interfaceTarget);
+        voidContext: false,
+        interfaceTarget: interfaceTarget) as ShadowExpression;
   }
 
-  Expression buildForEffect() {
+  ShadowExpression buildForEffect() {
     return accessor.buildPostfixIncrement(binaryOperator, charOffset,
-        voidContext: true, interfaceTarget: interfaceTarget);
+        voidContext: true,
+        interfaceTarget: interfaceTarget) as ShadowExpression;
   }
 }