Updated parser to produce error when trying to reinitialize final variables in class constructors. …

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
diff --git a/runtime/vm/parser.cc b/runtime/vm/parser.cc
index f96c1a3ec17e9fb14636824aff397baba1ee81ab..2eb8912ae71a1a9b972509e7b7a98a6c9c711c8e 100644
--- a/runtime/vm/parser.cc
+++ b/runtime/vm/parser.cc
@@ -3021,6 +3021,15 @@ AstNode* Parser::CheckDuplicateFieldInit(
     if (initialized_field == NULL) {
       break;
     }
+
+    const String& initialized_name =
+        String::ZoneHandle(initialized_field->name());
+    const String& field_name = String::ZoneHandle(field->name());
+    if (initialized_name.Equals(field_name) && field->IsFinalAndInitialized()) {
+      ReportError(init_pos, "final field '%s' is already initialized.",
+                  field_name.ToCString());
+    }
+
     if (initialized_field->raw() == field->raw()) {
       // This final field has been initialized by an inlined
       // initializer expression. This is a runtime error.
@@ -4495,6 +4504,37 @@ void Parser::CheckMemberNameConflict(ClassDesc* members, MemberDesc* member) {
 }
 
 
+void Parser::CheckMemberAlreadyInitializedConflicts(ClassDesc* members,
+                                                    MemberDesc* member) {
+  if (!member->IsConstructor()) {
+    return;
+  }
+  ParamList* params = &member->params;
+  if (!params->has_field_initializer) {
+    return;
+  }
+  const ZoneGrowableArray<ParamDesc>& parameters = *params->parameters;
+  for (intptr_t p = 0; p < parameters.length(); p++) {
+    const ParamDesc& current_param = parameters[p];
+    if (!current_param.is_field_initializer) {
+      continue;
+    }
+    const String& name = *current_param.name;
+    for (intptr_t i = 0; i < members->members().length(); i++) {
+      MemberDesc* existing_member = &members->members()[i];
+      if (existing_member->has_final &&
+          name.Equals(*existing_member->DictName()) &&
+          (existing_member->field_ != NULL) &&
+          existing_member->field_->IsFinalAndInitialized()) {

[siva, 2017/06/13 22:37:57]

The correct check here is to use field_->has_initializer() as we have delayed
initialization of fields if the expression is not a simple literal.

[bkonyi, 2017/06/15 22:32:48]

Ah, don't know how I missed that... done.

+        ReportError(current_param.name_pos,
+                    "final field '%s' is already initialized.",
+                    existing_member->DictName()->ToCString());
+      }
+    }
+  }
+}
+
+
 void Parser::ParseClassMemberDefinition(ClassDesc* members,
                                         TokenPosition metadata_pos) {
   TRACE_PARSER("ParseClassMemberDefinition");
@@ -4707,6 +4747,7 @@ void Parser::ParseClassMemberDefinition(ClassDesc* members,
   }
   current_member_ = NULL;
   CheckMemberNameConflict(members, &member);
+  CheckMemberAlreadyInitializedConflicts(members, &member);

[siva, 2017/06/13 22:37:56]

I don't think this is quite correct, consider this example where the final field
comes after the constructor.

class Foo {
  Foo(this.x);
  final int x = 10;
}

[bkonyi, 2017/06/15 22:32:48]

This seemed to work, but it probably makes more sense to do this after the
entire class is processed anyways.

   members->AddMember(member);
 }