Add tree shaker support for setters and field writes.

pkg/analyzer2dart/lib/src/tree_shaker.dart

Index: pkg/analyzer2dart/lib/src/tree_shaker.dart
diff --git a/pkg/analyzer2dart/lib/src/tree_shaker.dart b/pkg/analyzer2dart/lib/src/tree_shaker.dart
index bdf94c5809b26c0b03d3a481821d25968724f4a8..6b55396cfa6171e23bbb2eabfa3d020e78f434d2 100644
--- a/pkg/analyzer2dart/lib/src/tree_shaker.dart
+++ b/pkg/analyzer2dart/lib/src/tree_shaker.dart
@@ -137,6 +137,19 @@ class LocalReachabilityComputer {
           }
         }
       }
+    } else if (selector.kind == SelectorKind.SETTER) {
+      for (PropertyAccessorElement accessor in classElement.accessors) {
+        // accessor.name uses the convention that setter names end in '='.
+        if (accessor.isSetter && '${selector.name}=' == accessor.name) {

[scheglov, 2014/10/21 14:58:21]

We could probably make it slightly faster by computing '${selector.name}='
outside of the loop.

[Paul Berry, 2014/10/21 15:14:04]

Done.

+          if (accessor.isSynthetic) {
+            // This accessor is implied by the corresponding field declaration.
+            // TODO(paulberry): should we distinguish reads and writes?
+            fields.add(accessor.variable);
+          } else {
+            accessors.add(accessor);
+          }
+        }
+      }
     }
   }
 }
@@ -294,8 +307,10 @@ class TreeShakingVisitor extends SemanticVisitor {
           new Selector.getter(semantics.identifier.name, null));
     }
     if (semantics.isWrite) {
-      // TODO(paulberry): implement.
-      return giveUp(node, '_handlePropertyAccess of ${semantics}.');
+      // Selector.setter constructor uses the convention that setter names
+      // don't end in '='.
+      analysis.invokes.add(
+          new Selector.setter(semantics.identifier.name, null));
     }
   }