Fix: The method 'getInvocation' isn't defined for the type 'DartObjectImpl'

build_runner is failing to compile its own build script, not your code. source_gen 3.1.0 and 4.0.0 call DartObjectImpl.getInvocation(), which analyzer 8.4.0 deleted, and both packages declare constraints loose enough for pub to pair them. Fix it by upgrading whichever code generator in your pubspec.yaml pins source_gen below 4.0.1. If you cannot upgrade today, add dependency_overrides: analyzer: 8.3.0 as a stopgap.

The error, in full

You run dart run build_runner build (or flutter pub run build_runner build) and get a Dart front-end compile error pointing into your pub cache:

[INFO] Generating build script...
../../.pub-cache/hosted/pub.dev/source_gen-3.1.0/lib/src/constants/revive.dart:82:40:
Error: The method 'getInvocation' isn't defined for the type 'DartObjectImpl'.
 - 'DartObjectImpl' is from 'package:analyzer/src/dart/constant/value.dart'
   ('../../.pub-cache/hosted/pub.dev/analyzer-8.4.1/lib/src/dart/constant/value.dart').
Try correcting the name to the name of an existing method, or defining a method
named 'getInvocation'.
  final i = (object as DartObjectImpl).getInvocation();
                                       ^^^^^^^^^^^^^
[SEVERE] Failed to compile build script. Check builder definitions and generated
script .dart_tool/build/entrypoint/build.dart.

Two details in that output do the diagnostic work for you. The failing file is in source_gen, not in your project. And the version numbers on those two cache paths are the whole bug: source_gen-3.1.0 against analyzer-8.4.1.

Everything below was verified against pub.dev package archives and holds for Flutter 3.47.0 with Dart 3.13.0, the stable channel as of August 2026, as well as for any older Dart 3.x project that resolves the same pair.

Why analyzer 8.4.0 removed the method

source_gen has to answer a question for every annotation it sees: given a const object the analyzer already evaluated, what source code would recreate it? That is what reviveInstance in source_gen/lib/src/constants/revive.dart does, and it is how @JsonSerializable(fieldRename: FieldRename.snake) becomes usable configuration inside a builder.

To do that, source_gen needed the constructor and the argument values behind a DartObject. For years the only way to get them was an implementation import:

// source_gen 3.1.0, lib/src/constants/revive.dart
// ignore: implementation_imports
import 'package:analyzer/src/dart/constant/value.dart' show DartObjectImpl;

// ...
final i = (object as DartObjectImpl).getInvocation();

That // ignore: implementation_imports comment is the analyzer’s own lint telling source_gen it is reaching into a src/ directory that carries no API stability promise.

The analyzer team fixed the underlying gap. Version 8.1.0, published 7 August 2025, added DartObject.constructorInvocation to the public package:analyzer/dart/constant/value.dart surface, returning a ConstructorInvocation with constructor, positionalArguments and namedArguments. In 8.3.0 the old entry point was still present and marked for removal:

// analyzer 8.3.0, lib/src/dart/constant/value.dart
@Deprecated('Use constructorInvocation instead')
ConstructorInvocationImpl? getInvocation() {
  return constructorInvocation;
}

Analyzer 8.4.0, published 15 October 2025, dropped that method. constructorInvocation remains, but nothing named getInvocation exists anywhere in the package. Any code still calling it stops compiling the moment that version is resolved.

source_gen had already moved. Version 4.0.1, published 4 September 2025, switched to the public getter and tightened its own constraint to analyzer: ^8.1.1:

// source_gen 4.0.1 and later, lib/src/constants/revive.dart
final i = object.constructorInvocation;
if (i != null) {
  url = Uri.parse(urlOfElement(i.constructor.enclosingElement));
  // ...
}

Note the missing implementation import. That is the actual fix, and it is why every version of source_gen from 4.0.1 onward is immune.

The version-solver hole that pairs the broken versions

If source_gen 4.0.1 fixed this in September and analyzer 8.4.0 landed in October, why does anyone hit it? Because the broken versions never declared the incompatibility, and pub only reads declarations.

Here are the constraints that matter:

source_gen 3.1.0 and 4.0.0 are the only two published versions that both call the removed method and permit analyzer 8.4.x. Their upper bound of <9.0.0 was a guess that a major bump would carry any breaking change. The analyzer team removed a deprecated member in a minor release, which is normal for something that was never public API in the first place.

Pub prefers the newest version that satisfies every constraint, so a project with no other pressure resolves source_gen 4.3.0 and never sees this. The failure needs something in your graph to hold source_gen down. That something is almost always a code generator with a caret pin. objectbox_generator 5.0.0, published 1 October 2025, declared source_gen: ^3.1.0, which resolves to exactly one version, 3.1.0, because 3.1.0 is the last release in the 3.x line. Two weeks later analyzer 8.4.0 shipped, and every ObjectBox project that ran dart pub upgrade got a build script that would not compile.

The ObjectBox changelog for 5.0.1 names the failure directly: “Generator: migrate to analyzer 8 APIs. Require at least analyzer 8.1.1 and source_gen 4.0.1. Resolves Error: The method 'getInvocation' isn't defined when running the generator using analyzer 8.4.0”.

ObjectBox was not alone. json_serializable 6.11.0 shipped source_gen: ^3.1.0 and widened it to >=3.1.0 <5.0.0 in 6.11.1. retrofit_generator 10.0.2, chopper_generator 8.3.1, built_value_generator 8.11.1 and envied_generator 1.2.1 all carried the same shape of pin in the same window. Because source_gen is a single shared node in the dependency graph, one stale generator drags every other generator in your project down to 3.1.0 with it. A project that uses freezed, json_serializable and one unmaintained builder will blame the wrong package every time.

Reproducing it from a clean pubspec

# pubspec.yaml
# Dart 3.9.x. Any SDK that admits analyzer 8.4.x reproduces this.
name: repro
environment:
  sdk: ^3.9.0

dependencies:
  objectbox: 5.0.0

dev_dependencies:
  build_runner: ^2.9.0
  objectbox_generator: 5.0.0

Run dart pub get and then read what was actually chosen:

dart pub deps --style=compact | grep -E 'source_gen|analyzer'

You will see source_gen 3.1.0 and analyzer 8.4.1. That pair is the bug. dart run build_runner build then fails with the error at the top of this post, before a single line of your code is analyzed.

Fix 1: upgrade the generator that pins source_gen

This is the correct fix and it is usually one line. Find the constraint that is capping source_gen, then raise it.

Ask pub to identify the culprit by demanding a version it cannot give you:

dart pub add dev:source_gen:^4.0.1

Version solving fails, and the explanation names the package holding the pin:

Because objectbox_generator 5.0.0 depends on source_gen ^3.1.0 and no versions
        of objectbox_generator match >5.0.0 <6.0.0, objectbox_generator 5.0.0
        requires source_gen ^3.1.0.
So, because repro depends on both objectbox_generator 5.0.0 and
source_gen ^4.0.1, version solving failed.

Read that from the bottom up, the same way you would read any pub version solving failure. The top line is the fact you have to change.

Then bump the named package and let the fix flow through:

dart pub upgrade objectbox objectbox_generator
dart run build_runner build --delete-conflicting-outputs

Known-good floors, if you would rather set them explicitly:

• objectbox_generator 5.0.1 or later
• json_serializable 6.11.1 or later
• chopper_generator 8.5.0 or later
• envied_generator 1.3.2 or later
• retrofit_generator 10.2.3 or later
• built_value_generator 8.11.2 or later

Do not add source_gen to your own dev_dependencies as the fix. It is a transitive dependency of your generators, and pinning it in your pubspec only moves the conflict into your file where it will rot.

Fix 2: pin analyzer as a stopgap

If the offending generator is abandoned or you are mid-release and cannot take an upgrade, hold the analyzer at the last version that still carries the deprecated method:

# pubspec.yaml
# Temporary. Delete once the generator is upgraded.
dependency_overrides:
  analyzer: 8.3.0

Analyzer 8.3.0 (10 October 2025) is the last release with getInvocation present. This works because the deprecated method was a one-line forwarder to constructorInvocation, so behaviour is identical.

Two costs, both real. dependency_overrides silences the solver for every package in the graph, so a second package that genuinely needs analyzer 8.4+ will now fail at compile time instead of at pub get. And overrides are ignored when your package is consumed as a dependency, so a published package cannot ship this as a fix for its own users. Treat it as a branch-level unblock with a dated TODO, and pair it with a CI job that builds without the override so you find out when it becomes unnecessary. If you maintain more than one branch on different SDKs, targeting multiple Flutter versions from one CI pipeline is the pattern for keeping both honest.

Fix 3: if the call is in your own builder

If the failing path in the error is your own package rather than source_gen, you wrote the call and you own the migration. It is a direct swap:

// Before. Requires the implementation import of DartObjectImpl.
// ignore: implementation_imports
import 'package:analyzer/src/dart/constant/value.dart' show DartObjectImpl;

final invocation = (object as DartObjectImpl).getInvocation();

// After. analyzer 8.1.0 and later. Public API, no src/ import.
import 'package:analyzer/dart/constant/value.dart';

final invocation = object.constructorInvocation;
if (invocation != null) {
  final ctor = invocation.constructor;
  final positional = invocation.positionalArguments;
  final named = invocation.namedArguments;
}

Delete the implementation_imports ignore along with it. Then set your own floor to analyzer: '>=8.1.1' so pub cannot hand your code an analyzer that lacks the getter. That lower bound is the part people skip, and it is what turns a fixed package back into a broken one for somebody on an older SDK.

While you are there, note that ConstructorInvocation.constructor2 exists and is deprecated in favour of constructor. Migrate both in the same pass rather than trading one removal for the next.

Gotchas and lookalikes

flutter clean does not fix this and never did. The most-repeated advice for build_runner failures is to delete .dart_tool and rebuild. Here that only reruns the same compile against the same resolved versions. If the error mentions a file inside .pub-cache, the resolution is wrong and no amount of cache clearing changes it.

--delete-conflicting-outputs does not fix it either. That flag handles a build that produced a file another builder wants to write. It runs after the build script compiles, and here the build script never compiles.

The lockfile is the usual trigger. Nothing in your pubspec changed; a dart pub upgrade, a fresh CI checkout without a committed pubspec.lock, or a teammate’s pub get moved analyzer to 8.4.x while source_gen stayed pinned at 3.1.0. If a colleague’s machine still builds, diff the two lockfiles before anything else.

Sibling errors, identical cause. The getter 'name' isn't defined for the class 'NamedType', The getter 'tmp' isn't defined for the class 'Diagnostic', and DotShorthandConstructorInvocation isn't defined are all the same failure mode: a builder compiled against an analyzer API that moved. The diagnosis is unchanged. Read the two versions off the cache paths in the error, find the package that pins the older one, upgrade it. This is the same shape of breakage as a plugin removing its unnamed constructor, except the API belongs to a package you never wrote down.

Analyzer 9.0.0 is not the boundary you want. It shipped 23 October 2025, eight days after 8.4.0. Setting analyzer: <9.0.0 does not protect you, because 8.4.x is already below it. The only safe floors are source_gen: '>=4.0.1' on the generator side and analyzer: '>=8.1.1' on yours.

Related

• Reading pub’s proof of failure is the core skill here: Version solving failed in pubspec.yaml walks the PubGrub output line by line.
• freezed is a source_gen builder like any other, so this failure can hit a project that only uses it for data classes. Dart records vs Freezed classes covers when you need the code generation at all.
• Riverpod’s generator sits on the same stack: migrating from Riverpod 2.x to Riverpod 3.0 includes the codegen bump.
• A package upgrade that removes a constructor rather than a method: The class ‘GoogleSignIn’ doesn’t have an unnamed constructor.
• To keep a project building while a generator upgrade lands, see targeting multiple Flutter versions from one CI pipeline.

Sources

• source_gen changelog, for the 4.0.1 move to analyzer: ^8.1.1. Version constraints and publish dates were read from the pub.dev package archives for 3.1.0, 4.0.0 and 4.0.1.
• analyzer changelog, for 8.1.0 adding DartObject.constructorInvocation. The presence of the deprecated getInvocation() in 8.3.0 and its absence in 8.4.0 were confirmed against the published archives of both versions.
• objectbox changelog, version 5.0.1, published 29 October 2025, which names this exact error and its fix.
• build_runner on pub.dev. The “Failed to compile build script” message comes from lib/src/bootstrap/bootstrapper.dart.
• dart pub deps and the PubGrub solver documentation for the diagnosis commands.