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Dart: several type positions create no reference (extension on type, field types, generic arguments in expressions and top-level initializers) #2327
Description
Version: 1.6.2 (also current main, 6560052)
Summary
In Dart, callers / impact for a class only see parameter types, return types (including their generic arguments), and instantiations. A type named in these positions is never recorded as a reference:
| Position | Example | Referenced? |
|---|---|---|
| parameter type | int score(Report r) |
yes |
| return type generic argument | Future<Report?> load() |
yes |
| extension target | extension ReportX on Report {} |
no |
| class field type | final Report report; |
no |
| generic argument in a top-level initializer | final p = Family<Report?, String>(); |
no |
| generic argument in an expression | Future<Report?>.value(null); |
no |
In Flutter apps these are the common shapes for model extensions, generated API models (fields of other models), and Riverpod providers (FutureProvider.family<Report?, String>(…)), so model-to-UI impact is substantially incomplete. In one app, these positions account for most of the missed usages of shared API types. (Distinct from #1784, which is about extension type members.)
Reproduction
Run with CODEGRAPH=/path/to/codegraph bash repro.sh (creates and deletes a temporary project):
set -euo pipefail
CODEGRAPH="${CODEGRAPH:-codegraph}"
export DO_NOT_TRACK=1 CODEGRAPH_TELEMETRY=0 CODEGRAPH_NO_UPDATE_CHECK=1
proj="$(mktemp -d)"
trap 'rm -rf "$proj"' EXIT
index_project() { (cd "$proj" && git init -q && "$CODEGRAPH" init . >/dev/null 2>&1); }
callers_of() { (cd "$proj" && "$CODEGRAPH" callers "$1" 2>&1); }
mkdir -p "$proj/lib"
printf 'name: repro\nenvironment:\n sdk: ">=3.0.0 <4.0.0"\n' >"$proj/pubspec.yaml"
cat >"$proj/lib/report.dart" <<'T'
class Report {
final int score;
const Report(this.score);
}
T
cat >"$proj/lib/a_parameter.dart" <<'T'
import 'report.dart';
int score(Report r) => r.score;
T
cat >"$proj/lib/b_return_generic.dart" <<'T'
import 'report.dart';
Future<Report?> load() async => null;
T
cat >"$proj/lib/c_extension_on.dart" <<'T'
import 'report.dart';
extension ReportX on Report {
bool get high => score > 5;
}
T
cat >"$proj/lib/d_field_type.dart" <<'T'
import 'report.dart';
class Holder {
final Report report;
const Holder(this.report);
}
T
cat >"$proj/lib/e_toplevel_initializer_generic.dart" <<'T'
import 'report.dart';
class Family<T, A> {
const Family();
}
final reportProvider = Family<Report?, String>();
T
cat >"$proj/lib/f_expression_generic.dart" <<'T'
import 'report.dart';
void run() {
Future<Report?>.value(null);
}
T
index_project
echo "== callers Report (expected: files a through f)"; callers_of ReportActual
Callers of "Report" (2):
function load [references]
lib/b_return_generic.dart:3
function score [references]
lib/a_parameter.dart:3
Expected
Files c through f are also listed (the extension ReportX, the class Holder or its field, reportProvider, and run).
Activity
Phase 4: resolution and extraction accuracy
fix(dart): link getter reads, enum-extension members and more type po…
colbymchenry commentedon Oct 5, 2026
Thanks @mg-mg-mg for the position-by-position table and the repro script. The fix was written straight against them.
Fixed on
mainin #2360. Dart type references used to come only from function and method signatures. They now also come from:on(extension ReportX on Report)final Report report;), attributed to the class, since Dart fields have no symbols of their own, and enum fieldsfinal/constinitializers (final reportProvider = Family<Report?, String>();)Future<Report?>.value(null)), casts,ischecks andon X catchConstructor class names, import prefixes, built-in types and a class's references to itself are skipped. On your script,
callers Reportnow listsReportX,Holder,reportProviderandrunalongsideloadandscore. On bloc, riverpod and flutter/samples this added about 1,350, 4,870 and 670 type references and removed none.Still not covered: generic arguments in
extends Bloc<E, S>, and calls inside top-level andstaticinitializers, such as the bodies of Riverpod providers.This ships in the next release. Re-index after upgrading (
codegraph index) to pick it up. You're credited in the changelog.