Installation

1. 1
   Make sure Claude is on your device and in your terminal.

   Skills load from ~/.claude/skills/ when Claude Code starts up — so you need it on your machine first. If you don't have it yet, install it once with the command below, then run claude in any terminal to verify.

   One-time setup

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   npm i -g @anthropic-ai/claude-code

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2. 2
   Paste into Claude Code or into your terminal.

   Install

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   git clone ht••••••••••••••••••••••••••••••• •••••••••••••••• •• ••••• •• ••••••••••••••••••••••••••••••••••••••••••• •• •• •• ••••••••••••••••••••••••••••••••••••••••••••••••••••• ••••••••••••••••••••••••••••••••••••••••••••

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   This copies the whole skill folder into ~/.claude/skills/ast-visitor-pattern-prisma/ — the SKILL.md plus any scripts, reference docs, or templates the skill ships with. Safe default: works for every skill.

   Faster alternative (instruction-only skills)

   Skips the clone and grabs only the SKILL.md file. Don't use this if the skill ships Python scripts, reference markdowns, or asset templates — they won't be downloaded and the skill will fail when it tries to load them.

   Quick install (SKILL.md only)

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   mkdir -p ~/.•••••••••••••••••••••••••••••••••••••••• •• •••• ••••• ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••• •• ••••••••••••••••••••••••••••••••••••••••••••••••••••

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3. 3
   Restart Claude Code.

   Quit and reopen Claude Code (or any other agent that loads from ~/.claude/skills/). New skills are picked up on startup.

4. 4
   Just ask Claude.

   Skills auto-activate when your request matches the skill's description — no slash command needed. Trigger phrases live in the skill's own frontmatter; you can read them in the “What this skill does” section above.

Prefer to read the source first? Open on GitHub.

When Claude uses it

Use the frozen-class/visitor pattern for discriminated unions that have multiple dispatch sites. Use when creating a new set of variants (commands, IR nodes, factory calls) that will be switched over in 2+ places, or when refactoring an existing union type that has grown multiple switch sites.

What this skill does

// 1. Abstract base (not exported — consumers use the union type)
abstract class FooNode {
  abstract readonly kind: string;
  abstract accept<R>(visitor: FooVisitor<R>): R;
  protected freeze(): void { Object.freeze(this); }
}

// 2. Visitor interface
export interface FooVisitor<R> {
  bar(node: BarNode): R;
  baz(node: BazNode): R;
}

// 3. Concrete subclasses — readonly fields, freeze() in constructor
export class BarNode extends FooNode {
  readonly kind = 'bar' as const;
  readonly value: string;
  constructor(value: string) {
    super();
    this.value = value;
    this.freeze();
  }
  accept<R>(visitor: FooVisitor<R>): R { return visitor.bar(this); }
}

export class BazNode extends FooNode {
  readonly kind = 'baz' as const;
  readonly count: number;
  constructor(count: number) {
    super();
    this.count = count;
    this.freeze();
  }
  accept<R>(visitor: FooVisitor<R>): R { return visitor.baz(this); }
}

// 4. Union type
export type Foo = BarNode | BazNode;

const renderVisitor: FooVisitor<string> = {
  bar(node) { return node.value; },
  baz(node) { return String(node.count); },
};

function render(node: Foo): string {
  return node.accept(renderVisitor);
}

// ✅
const call = new BarNode('x');
export function bar(value: string): BarNode { return new BarNode(value); }

// ❌
const call: Foo = { kind: 'bar', value: 'x' };
export function bar(value: string): Foo { return Object.freeze({ kind: 'bar', value }); }