Implement AstBuilder support for top level variables and function literals.

pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart

Index: pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart b/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
index 849100a1c5cdf19c83674b42dcf77f815740d6b4..fd77898bd1b63fdbb164f733e8f850a20b300485 100644
--- a/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
+++ b/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
@@ -313,6 +313,10 @@ class AstBuilder extends ScopeListener {
     debugEvent("InitializedIdentifier");
     AstNode node = pop();
     VariableDeclaration variable;
+    // TODO(paulberry,ahe): This seems kludgy.  It would be preferable if we
+    // could respond to a "handleNoVariableInitializer" event by converting a
+    // SimpleIdentifier into a VariableDeclaration, and then when this code was
+    // reached, node would always be a VariableDeclaration.

[ahe, 2017/02/20 09:04:20]

Good idea. I've filed issue https://github.com/dart-lang/sdk/issues/28833.

However, now that I've filed that bug, I realize I can implement this event
without changing dart2js, so I should #justdoit.

[Paul Berry, 2017/02/20 15:01:36]

Thanks for doing that!  Now that the new event is in, I would like to try my
hand at cleaning up the kludge, so I've changed it to just "TODO(paulberry)" :)

     if (node is VariableDeclaration) {
       variable = node;
     } else if (node is SimpleIdentifier) {
@@ -626,6 +630,8 @@ class AstBuilder extends ScopeListener {
   }
 
   void endTopLevelMethod(Token beginToken, Token getOrSet, Token endToken) {
+    // TODO(paulberry): set up scopes properly to resolve parameters and type
+    // variables.
     debugEvent("TopLevelMethod");
     FunctionBody body = _endFunctionBody();
     FormalParameterList parameters = pop();
@@ -932,6 +938,48 @@ class AstBuilder extends ScopeListener {
         toAnalyzerToken(ofKeyword), uri, name, toAnalyzerToken(semicolon)));
     accumulateIdentifierComponents = false;
   }
+
+  void endUnnamedFunction(Token token) {
+    // TODO(paulberry): set up scopes properly to resolve parameters and type
+    // variables.

[ahe, 2017/02/20 09:04:20]

This is a bit tricky when it comes to handling initializers in constructors. So
we should make sure that this class and BodyBuilder shares most of this logic.

[Paul Berry, 2017/02/20 15:01:36]

Good point.  I've updated the TODO comment to make a note of this.

+    debugEvent("UnnamedFunction");
+    var body = _endFunctionBody();
+    FormalParameterList parameters = pop();
+    TypeParameterList typeParameters = pop();
+    push(ast.functionExpression(typeParameters, parameters, body));
+  }
+
+  @override
+  void handleNoFieldInitializer(Token token) {
+    debugEvent("NoFieldInitializer");
+    SimpleIdentifier name = pop();
+    push(ast.variableDeclaration(name, null, null));
+  }
+
+  void endFieldInitializer(Token assignment) {
+    debugEvent("FieldInitializer");
+    Expression initializer = pop();
+    SimpleIdentifier name = pop();
+    push(ast.variableDeclaration(
+        name, toAnalyzerToken(assignment), initializer));
+  }
+
+  void endTopLevelFields(int count, Token beginToken, Token endToken) {
+    debugEvent("TopLevelFields");
+    List<VariableDeclaration> variables = popList(count);
+    TypeAnnotation type = pop();
+    // TODO(paulberry,ahe): the parser needs to pass the var/const/final keyword

[ahe, 2017/02/20 09:04:20]

Those should be available in beginToken. Another option is building a different
object to represent modifiers.

[Paul Berry, 2017/02/20 15:01:36]

Oh, ok.  I misread the parser code and thought "beginToken" included metadata. 
I've updated the TODO comment and I will fix in a follow-up CL.

+    // to the listener.
+    var keyword = null; // TODO(paulberry)
+    var variableList = ast.variableDeclarationList(
+        null, null, toAnalyzerToken(keyword), type, variables);
+    var modifiers = pop();
+    assert(modifiers == null); // TODO(paulberry)
+    List<Annotation> metadata = pop();
+    Comment comment = null; // TODO(paulberry)
+    push(ast.topLevelVariableDeclaration(
+        comment, metadata, variableList, toAnalyzerToken(endToken)));
+  }
 }
 
 /// Data structure placed on the stack to represent a class body.