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Agent skill

Dart 3 Updates

by evanca in evanca/flutter-ai-rules

A skill your agent uses when writing switch statements, refactoring if-else chains, creating data classes, choosing records vs classes, destructuring values, or modernizing pre-Dart-3 code.

MITAuto-check passedDevelopment

Install Dart 3 Updates

skills CLI
$ npx skills add evanca/flutter-ai-rules --skill dart-3-updates -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install evanca/flutter-ai-rules dart-3-updates --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/evanca/flutter-ai-rules.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/dart-3-updates .claude/skills/dart-3-updates && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
dart-3-updates
GitHub stars
651
Token cost
~2k tokens
SKILL.md length
726 words
Files
1
Skills in repo
37
Repo updated
First seen
Licence
MIT

At a glance

A skill your agent uses when writing switch statements, refactoring if-else chains, creating data classes, choosing records vs classes, destructuring values, or modernizing pre-Dart-3 code.

  • Works in 5 steps: Branches → Patterns → Pattern Types → …
  • Writing switch statements
  • SKILL.md covers When to Use, 1. Branches, 2. Patterns and 3. Pattern Types, plus 2 more sections
  • Calls dart

What it does

Dart 3 Updates is an agent skill from evanca/flutter-ai-rules. Use when writing switch statements, refactoring if-else chains, creating data classes, choosing records vs classes, destructuring values, or modernizing pre-Dart-3 code.

Its SKILL.md is about 2k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Development, covering Cross-platform mobile apps and Refactoring. It works with Dart. The repository describes itself as: Flutter AI Skills and Rules for Claude, Codex, Cursor, and Other AI-Powered IDEs. The licence is MIT.

When your agent uses it

  • Writing switch statements
  • Refactoring if-else chains
  • Creating data classes
  • Choosing records vs classes

Example prompts

  • “/dart-3-updates”

Workflow steps

5 steps, taken from the step headings in SKILL.md.

  1. Branches
  2. Patterns
  3. Pattern Types
  4. Records
  5. Migration Workflow

What it can do on your machine

Read from SKILL.md and the folder at commit 30f908d. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Shell commands in SKILL.md call:

    • dart

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Dart 3 Updates loads about 2k tokens when it runs. Until then it costs about 46 tokens; SKILL.md has 726 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~46
When it runs · the whole SKILL.md, loaded when a task matches
~2k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from evanca/flutter-ai-rules at commit 30f908d, republished under its MIT licence (© evanca). 726 words, ~2,019 tokens.

Download SKILL.mdSave it as .claude/skills/dart-3-updates/SKILL.md (or your agent's skills folder).
name
dart-3-updates
description
Use when writing switch statements, refactoring if-else chains, creating data classes, choosing records vs classes, destructuring values, or modernizing pre-Dart-3 code.
license
MIT

Dart 3 Updates Skill

Apply Dart 3 language features — branches, patterns, pattern types, and records — correctly and idiomatically.

When to Use

Use this skill when:

  • Writing or refactoring switch statements or if-else chains.
  • Creating new data-holding classes and deciding between sealed classes, records, or plain classes.
  • Destructuring values from maps, lists, records, or objects.
  • Modernizing pre-Dart-3 code to use patterns, exhaustiveness checks, or switch expressions.

1. Branches

if / if-case
dart
// Standard if
if (score >= 90) {
  grade = 'A';
} else if (score >= 80) {
  grade = 'B';
} else {
  grade = 'C';
}

// if-case: match and destructure against a single pattern
if (pair case [int x, int y]) {
  print('$x, $y');
}
  • if conditions must evaluate to a bool.
  • In if-case, variables declared in the pattern are scoped to the matching branch.
  • If the pattern does not match, control flows to the else branch (if present).
switch statements
dart
switch (command) {
  case 'quit':
    quit();
  case 'start' || 'begin': // logical-or pattern
    startGame();
  default:
    print('Unknown command');
}
  • Each matched case body executes and jumps to the end — break is not required.
  • Non-empty cases can end with continue, throw, or return.
  • Use default or _ to handle unmatched values.
  • Empty cases fall through; use break to prevent fallthrough in an empty case.
  • Use continue with a label for non-sequential fallthrough.
  • Use logical-or patterns (case a || b) to share a body between cases.
switch expressions
dart
final color = switch (shape) {
  Circle() => 'red',
  Square() => 'blue',
  _ => 'unknown',
};
  • Omit case; use => for bodies; separate cases with commas.
  • Default must use _ (not default).
  • Produces a value.
Exhaustiveness
  • Dart checks exhaustiveness in switch statements and expressions at compile time.
  • Use default/_, enums, or sealed types to satisfy exhaustiveness.
dart
sealed class Shape {}
class Circle extends Shape {}
class Square extends Shape {}

// Dart knows all subtypes — no default needed:
String describe(Shape s) => switch (s) {
  Circle() => 'circle',
  Square() => 'square',
};
Guard clauses
dart
switch (point) {
  case (int x, int y) when x == y:
    print('Diagonal: $x');
  case (int x, int y):
    print('$x, $y');
}
  • Add when condition after a pattern to further constrain matching.
  • Usable in if-case, switch statements, and switch expressions.
  • If the guard is false, execution proceeds to the next case.

2. Patterns

Patterns represent the shape of a value for matching and destructuring.

Uses
dart
// Variable declaration
var (a, [b, c]) = ('str', [1, 2]);

// Variable assignment (swap)
(b, a) = (a, b);

// for-in loop destructuring
for (final MapEntry(:key, :value) in map.entries) { ... }

// switch / if-case (see Branches section)
  • Wildcard _ ignores parts of a matched value.
  • Rest elements (...) in list patterns ignore remaining elements.
  • Case patterns are refutable: if no match, execution continues to the next case.
  • Destructured values in a case become local variables scoped to that case body.
Object patterns
dart
var Foo(:one, :two) = myFoo;
JSON / nested data validation
dart
if (data case {'user': [String name, int age]}) {
  print('$name, $age');
}

3. Pattern Types

PatternSyntaxDescription
Logical-orp1 || p2Matches if any branch matches. All branches must bind the same variables.
Logical-andp1 && p2Matches if both match. Variable names must not overlap.
Relational== c, < c, >= cCompares value to a constant. Combine with && for ranges.
Castsubpattern as TypeAsserts type, then matches inner pattern. Throws if type mismatch.
Null-checksubpattern?Matches non-null; binds non-nullable type.
Null-assertsubpattern!Matches non-null or throws. Use in declarations to eliminate nulls.
Constant42, 'str', const Foo()Matches if value equals the constant.
Variablevar name, final Type nameBinds matched value to a new variable. Typed form only matches the declared type.
Wildcard_, Type _Matches any value without binding.
Parenthesized(subpattern)Controls precedence.
List[p1, p2]Matches lists by position. Length must match unless a rest element is used.
Rest element..., ...restMatches arbitrary-length tails or collects remaining elements.
Map{'key': subpattern}Matches maps by key. Missing keys throw StateError.
Record(p1, p2), (x: p1, y: p2)Matches records by shape; field names can be omitted if inferred.
ObjectClassName(field: p)Matches by type and destructures via getters. Extra fields ignored.
  • Use parentheses to group lower-precedence patterns.
  • All pattern types can be nested and combined.
Show full SKILL.md (223 more words)Show less

4. Records

dart
// Create
var record = ('first', a: 2, b: true, 'last');

// Type annotation
({int a, bool b}) namedRecord;

// Access
print(record.$1);   // positional: 'first'
print(record.a);    // named: 2
  • Records are anonymous, immutable, fixed-size aggregates.
  • Each field can have a different type (heterogeneous).
  • Fields are accessed via built-in getters ($1, $2, .name); no setters.
  • Two records are equal if they have the same shape and equal field values.
  • hashCode and == are automatically defined.
Multiple return values
dart
(String name, int age) userInfo(Map<String, dynamic> json) {
  return (json['name'] as String, json['age'] as int);
}

var (name, age) = userInfo(json);
// Named fields:
final (:name, :age) = userInfo(json);
Records vs. data classes

Use a record when:

  • Returning multiple values from a single function (small, one-time use).
  • Grouping a few values locally with no reuse across the codebase.
  • You need structural equality with no additional behavior.

Use a class when:

  • The type is reused across multiple files or features.
  • You need methods, encapsulation, inheritance, or copyWith.
  • The type is part of a public API or long-lived data model.
  • Changing the shape must be caught by the type system across the codebase.
Other best practices
  • Use typedef for record types to improve readability and maintainability.
  • Changing a record type alias does not guarantee type safety across the codebase — only classes provide full abstraction.

5. Migration Workflow

When modernizing pre-Dart-3 code, follow these steps:

Step 1 — Replace if-else chains with switch expressions
dart
// Before (pre-Dart 3)
String label;
if (status == Status.loading) {
  label = 'Loading...';
} else if (status == Status.success) {
  label = 'Done';
} else {
  label = 'Error';
}

// After (Dart 3)
final label = switch (status) {
  Status.loading => 'Loading...',
  Status.success => 'Done',
  Status.error => 'Error',
};
Step 2 — Convert abstract class hierarchies to sealed classes
dart
// Before
abstract class Result {}
class Success extends Result { final String data; Success(this.data); }
class Failure extends Result { final String error; Failure(this.error); }

// After — enables exhaustive switch
sealed class Result {}
final class Success extends Result { const Success(this.data); final String data; }
final class Failure extends Result { const Failure(this.error); final String error; }
Step 3 — Use destructuring for multiple return values

Replace wrapper classes used solely for returning multiple values with records.

Step 4 — Validate

Run dart analyze to confirm exhaustiveness and type safety after each change.

© evanca, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in skills/dart-3-updates of evanca/flutter-ai-rules.

Open the folder on GitHubat commit 30f908d

Compare with similar skills

Dart 3 Updates next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Dart 3 Updates compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Dart 3 Updates this skillevanca/flutter-ai-rules651—~2kAutomated safety check: PassMIT
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Squadron Workerd-markey/squadron138—~1.6kAutomated safety check: PassMIT
Dart Multiline Stringskevmoo/dash_skills147—~1.5kAutomated safety check: PassApache-2.0
Liquid Glass Widgetssdegenaar/liquid_glass_widgets730—~4.1kAutomated safety check: PassMIT
Test Guidelinesgetsentry/sentry-dart873—~3.1kAutomated safety check: PassMIT

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Works with

Categories

Questions about Dart 3 Updates

What does Dart 3 Updates do?

A skill your agent uses when writing switch statements, refactoring if-else chains, creating data classes, choosing records vs classes, destructuring values, or modernizing pre-Dart-3 code. Dart 3 Updates is an agent skill from evanca/flutter-ai-rules. Use when writing switch statements, refactoring if-else chains, creating data classes, choosing records vs classes, destructuring values, or modernizing pre-Dart-3 code.

When should I use Dart 3 Updates?

Dart 3 Updates fits situations like: writing switch statements; refactoring if-else chains; creating data classes; choosing records vs classes.

How do I install Dart 3 Updates in Claude Code?

Run `npx skills add evanca/flutter-ai-rules --skill dart-3-updates -a claude-code`. Or copy the skill folder (skills/dart-3-updates in evanca/flutter-ai-rules) into .claude/skills/dart-3-updates in your project. Claude Code loads it when a task matches its description.

How do I install Dart 3 Updates in Codex?

Run `npx skills add evanca/flutter-ai-rules --skill dart-3-updates -a codex`. Or copy the skill folder (skills/dart-3-updates in evanca/flutter-ai-rules) into .agents/skills/dart-3-updates in your project. Codex loads it when a task matches its description.

Can I use Dart 3 Updates in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add evanca/flutter-ai-rules --skill dart-3-updates -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/dart-3-updates, .gemini/skills/dart-3-updates, .github/skills/dart-3-updates and .opencode/skills/dart-3-updates in your project.

What does Dart 3 Updates need to run?

Going by SKILL.md and its folder, Dart 3 Updates needs the command-line tools its instructions call (dart).

Does Dart 3 Updates access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Dart 3 Updates safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Dart 3 Updates use?

Dart 3 Updates is published under the MIT licence (declared in SKILL.md). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Dart 3 Updates use?

About 2k tokens (SKILL.md is roughly 8.1k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Dart 3 Updates?

Skills that share tags, products or a category with Dart 3 Updates: Code Guidelines (getsentry/sentry-dart, 873 stars), Squadron Worker (d-markey/squadron, 138 stars), Dart Multiline Strings (kevmoo/dash_skills, 147 stars) and Liquid Glass Widgets (sdegenaar/liquid_glass_widgets, 730 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Dart 3 Updates?

evanca (a GitHub user) maintains it in evanca/flutter-ai-rules, which has 651 GitHub stars. The repository holds 37 skills in this directory. The repository was last updated on October 10, 2026.

Source: evanca/flutter-ai-rules on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.