Add AstBuilder support for DottedName and ConditionalUri.

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 5e9603f95a2ab007f6baf4c911d04bb776198cd0..c93ca97812a3010cc0dd92e7abdd6ff879a1b56b 100644
--- a/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
+++ b/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
@@ -700,7 +700,6 @@ class AstBuilder extends ScopeListener {
     SimpleIdentifier prefix;
     if (asKeyword != null) prefix = pop();
     List<Configuration> configurations = pop();
-    assert(configurations == null); // TODO(paulberry)
     StringLiteral uri = pop();
     List<Annotation> metadata = pop();
     assert(metadata == null);
@@ -723,7 +722,6 @@ class AstBuilder extends ScopeListener {
     debugEvent("Export");
     List<Combinator> combinators = pop();
     List<Configuration> configurations = pop();
-    assert(configurations == null); // TODO(paulberry)
     StringLiteral uri = pop();
     List<Annotation> metadata = pop();
     assert(metadata == null);
@@ -734,6 +732,39 @@ class AstBuilder extends ScopeListener {
   }
 
   @override
+  void endDottedName(int count, Token firstIdentifier) {
+    debugEvent("DottedName");
+    List<SimpleIdentifier> components = popList(count);
+    push(ast.dottedName(components));
+  }
+
+  void endConditionalUri(Token ifKeyword, Token equalitySign) {
+    debugEvent("ConditionalUri");
+    StringLiteral libraryUri = pop();
+    // TODO(paulberry,ahe): the parser should report the right paren token to
+    // the listener.

[ahe, 2017/02/22 05:58:53]

That would be ifKeyword.next.endGroup.

+    Token rightParen = null;
+    StringLiteral value;
+    if (equalitySign != null) {
+      value = pop();
+    }
+    DottedName name = pop();
+    // TODO(paulberry,ahe): what if there is no `(` token due to an error in the
+    // file being parsed?  It seems like we need the parser to do adequate error
+    // recovery and then report both the ifKeyword and leftParen tokens to the
+    // listener.
+    Token leftParen = ifKeyword.next;

[ahe, 2017/02/22 05:58:53]

The scanner should have set up the token stream so that there's a synthetic
endGroup token for the right parenthesis.

The next token of the endGroup will be an error token. The parser may not
recover from this situation.

[Paul Berry, 2017/02/22 21:20:13]

I think you're answering the question "what if there is no ')' token due to an
error in the file being parsed?"  My question is "what if there is no '('
token?"

Currently, the parser calls expect() to consume the '(' token, and expect()
calls reportUnrecoverableError(), which calls handleUnrecoverableError(), which
throws an exception.  So the question is moot for now.

But in the long run we're going to have to change things so that when the parser
is invoked by analyzer, the error can be recovered from, at which point we're
going to have to decide what should happen here.  I don't know whether we'll
wind up introducing a synthetic '(' token or doing something else.  We'll have
to make sure completion does the right thing.

Leaving the code as is for now.

[ahe, 2017/02/23 17:51:52]

Yes. I answered "what if there's no close parenthesis".
 
Yes, it is moot for now.

However, handleUnrecoverableError may recover. Take a look at handleError in
pkg/compiler/lib/src/parser/element_listener.dart.
I have been thinking that one should start by introducing a synthetic version of
whatever is missing, however, it's more complicated than that.
Yes. I'm just using your todos as an opportunity to provide some additional
details.

+    push(ast.configuration(
+        toAnalyzerToken(ifKeyword),
+        toAnalyzerToken(leftParen),
+        name,
+        toAnalyzerToken(equalitySign),
+        value,
+        toAnalyzerToken(rightParen),
+        libraryUri));
+  }
+
+  @override
   void endConditionalUris(int count) {
     debugEvent("ConditionalUris");
     push(popList(count) ?? NullValue.ConditionalUris);