Always parse 'x.y' as a prefixed identifier.

pkg/analyzer/lib/src/generated/parser.dart

Index: pkg/analyzer/lib/src/generated/parser.dart
diff --git a/pkg/analyzer/lib/src/generated/parser.dart b/pkg/analyzer/lib/src/generated/parser.dart
index e8bc7dd5d908187636ff18c9c417df3423376aa7..1ccc89f9ecd4cb8b8fbc2d7de39d1319a3b055c9 100644
--- a/pkg/analyzer/lib/src/generated/parser.dart
+++ b/pkg/analyzer/lib/src/generated/parser.dart
@@ -6357,11 +6357,6 @@ class Parser {
       Expression selectorExpression = parseAssignableSelector(
           expression, isOptional || (expression is PrefixedIdentifier));
       if (identical(selectorExpression, expression)) {
-        if (!isOptional && (expression is PrefixedIdentifier)) {
-          PrefixedIdentifier identifier = expression as PrefixedIdentifier;
-          expression = astFactory.propertyAccess(
-              identifier.prefix, identifier.period, identifier.identifier);
-        }
         return expression;
       }
       expression = selectorExpression;