skills/ mcollina/skills

typescript-magician

Designs complex generic types, refactors `any` types to strict alternatives, creates type guards and utility types, and resolves TypeScript compiler errors. Use when the user asks about TypeScript (TS) types, generics, type inference, type guards, removing `any` types, strict typing, type errors, `i

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16 files scannedscanner v1.2.0Oct 11, 2026

Content sha256 a629165bbf9814c3… — run codexguild_scan_skills after installing to verify your local copy.

Static analysis is a first line of defense, not a guarantee. Read the source

SKILL.md

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When to use

Use this skill for:

  • TypeScript errors and type challenges
  • Eliminating any types from codebases
  • Complex generics and type inference issues
  • When strict typing is needed

Instructions

When invoked:

  1. Run tsc --noEmit to capture the full error output before making changes
  2. Identify the root cause of type issues (unsound inference, missing constraints, implicit any, etc.)
  3. Craft precise, type-safe solutions using advanced TypeScript features
  4. Eliminate all any types with proper typing — validate each replacement still satisfies call sites
  5. Confirm the fix compiles cleanly with a second tsc --noEmit pass

Capabilities include:

  • Advanced generics and conditional types
  • Template literal types and mapped types
  • Utility types and type manipulation
  • Brand types and nominal typing
  • Complex inference patterns
  • Variance and distribution rules
  • Module augmentation and declaration merging

For every TypeScript challenge:

  • Explain the type theory behind the problem
  • Provide multiple solution approaches when applicable
  • Show before/after type representations
  • Include comprehensive type tests
  • Ensure full IntelliSense support

Quick Examples

Eliminating any with generics

Before

function getProperty(obj: any, key: string): any {
  return obj[key];
}

After

function getProperty<T, K extends keyof T>(obj: T, key: K): T[K] {
  return obj[key];
}
// getProperty({ name: "Alice" }, "name") → inferred as string ✓

Narrowing an unknown API response

Before

async function fetchUser(): Promise<any> {
  const res = await fetch("/api/user");
  return res.json();
}

After

interface User { id: number; name: string }

function isUser(value: unknown): value is User {
  return (
    typeof value === "object" &&
    value !== null &&
    "id" in value &&
    "name" in value
  );
}

async function fetchUser(): Promise<User> {
  const res = await fetch("/api/user");
  const data: unknown = await res.json();
  if (!isUser(data)) throw new Error("Invalid user shape");
  return data;
}

Reference

Read individual rule files for detailed explanations and code examples:

Core Patterns

Advanced Generics

Type-Level Programming

Type Safety Patterns

Debugging

Files

16
101.8 KB

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