Introduce FieldParameterElement.

frog/leg/compile_time_constants.dart

Index: frog/leg/compile_time_constants.dart
diff --git a/frog/leg/compile_time_constants.dart b/frog/leg/compile_time_constants.dart
index cefe2f5f2a70f8d0f44862a181f09597555c33cf..56a8a91d68c4cad2c93953686eb207968701ef46 100644
--- a/frog/leg/compile_time_constants.dart
+++ b/frog/leg/compile_time_constants.dart
@@ -486,7 +486,8 @@ class ConstantHandler extends CompilerTask {
    */
   void compileWorkItem(WorkItem work) {
     assert(work.element.kind == ElementKind.FIELD
-           || work.element.kind == ElementKind.PARAMETER);
+           || work.element.kind == ElementKind.PARAMETER
+           || work.element.kind == ElementKind.FIELD_PARAMETER);
     VariableElement element = work.element;
     // Shortcut if it has already been compiled.
     if (initialVariableValues.containsKey(element)) return;
@@ -932,7 +933,12 @@ class CompileTimeConstantEvaluator extends AbstractVisitor {
       }
       int index = 0;
       parameters.forEachParameter((Element parameter) {
-        constructorDefinitions[parameter] = arguments[index++];
+        Constant argument = arguments[index++];
+        constructorDefinitions[parameter] = argument;
+        if (parameter.kind == ElementKind.FIELD_PARAMETER) {
+          FieldParameterElement fieldParameterElement = parameter;
+          constructorDefinitions[fieldParameterElement.fieldElement] = argument;
+        }
       });
     }