> ## Documentation Index
> Fetch the complete documentation index at: https://companyname-a7d5b98e-ton-storage.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# FunC-to-Tolk converter

export const Aside = ({type = "note", title = "", icon = "", iconType = "regular", children}) => {
  const asideVariants = ["note", "tip", "caution", "danger"];
  const asideComponents = {
    note: {
      outerStyle: "border-sky-500/20 bg-sky-50/50 dark:border-sky-500/30 dark:bg-sky-500/10",
      innerStyle: "text-sky-900 dark:text-sky-200",
      calloutType: "note",
      icon: <svg width="14" height="14" viewBox="0 0 14 14" fill="currentColor" xmlns="http://www.w3.org/2000/svg" className="w-4 h-4 text-sky-500" aria-label="Note">
          <path fill-rule="evenodd" clip-rule="evenodd" d="M7 1.3C10.14 1.3 12.7 3.86 12.7 7C12.7 10.14 10.14 12.7 7 12.7C5.48908 12.6974 4.0408 12.096 2.97241 11.0276C1.90403 9.9592 1.30264 8.51092 1.3 7C1.3 3.86 3.86 1.3 7 1.3ZM7 0C3.14 0 0 3.14 0 7C0 10.86 3.14 14 7 14C10.86 14 14 10.86 14 7C14 3.14 10.86 0 7 0ZM8 3H6V8H8V3ZM8 9H6V11H8V9Z"></path>
        </svg>
    },
    tip: {
      outerStyle: "border-emerald-500/20 bg-emerald-50/50 dark:border-emerald-500/30 dark:bg-emerald-500/10",
      innerStyle: "text-emerald-900 dark:text-emerald-200",
      calloutType: "tip",
      icon: <svg width="11" height="14" viewBox="0 0 11 14" fill="currentColor" xmlns="http://www.w3.org/2000/svg" className="text-emerald-600 dark:text-emerald-400/80 w-3.5 h-auto" aria-label="Tip">
          <path d="M3.12794 12.4232C3.12794 12.5954 3.1776 12.7634 3.27244 12.907L3.74114 13.6095C3.88471 13.8248 4.21067 14 4.46964 14H6.15606C6.41415 14 6.74017 13.825 6.88373 13.6095L7.3508 12.9073C7.43114 12.7859 7.49705 12.569 7.49705 12.4232L7.50055 11.3513H3.12521L3.12794 12.4232ZM5.31288 0C2.52414 0.00875889 0.5 2.26889 0.5 4.78826C0.5 6.00188 0.949566 7.10829 1.69119 7.95492C2.14321 8.47011 2.84901 9.54727 3.11919 10.4557C3.12005 10.4625 3.12175 10.4698 3.12261 10.4771H7.50342C7.50427 10.4698 7.50598 10.463 7.50684 10.4557C7.77688 9.54727 8.48281 8.47011 8.93484 7.95492C9.67728 7.13181 10.1258 6.02703 10.1258 4.78826C10.1258 2.15486 7.9709 0.000106649 5.31288 0ZM7.94902 7.11267C7.52078 7.60079 6.99082 8.37878 6.6077 9.18794H4.02051C3.63739 8.37878 3.10743 7.60079 2.67947 7.11294C2.11997 6.47551 1.8126 5.63599 1.8126 4.78826C1.8126 3.09829 3.12794 1.31944 5.28827 1.3126C7.2435 1.3126 8.81315 2.88226 8.81315 4.78826C8.81315 5.63599 8.50688 6.47551 7.94902 7.11267ZM4.87534 2.18767C3.66939 2.18767 2.68767 3.16939 2.68767 4.37534C2.68767 4.61719 2.88336 4.81288 3.12521 4.81288C3.36705 4.81288 3.56274 4.61599 3.56274 4.37534C3.56274 3.6515 4.1515 3.06274 4.87534 3.06274C5.11719 3.06274 5.31288 2.86727 5.31288 2.62548C5.31288 2.38369 5.11599 2.18767 4.87534 2.18767Z"></path>
        </svg>
    },
    caution: {
      outerStyle: "border-amber-500/20 bg-amber-50/50 dark:border-amber-500/30 dark:bg-amber-500/10",
      innerStyle: "text-amber-900 dark:text-amber-200",
      calloutType: "warning",
      icon: <svg className="flex-none w-5 h-5 text-amber-400 dark:text-amber-300/80" fill="none" viewBox="0 0 24 24" stroke="currentColor" stroke-width="2" aria-label="Warning">
          <path stroke-linecap="round" stroke-linejoin="round" d="M12 9v2m0 4h.01m-6.938 4h13.856c1.54 0 2.502-1.667 1.732-3L13.732 4c-.77-1.333-2.694-1.333-3.464 0L3.34 16c-.77 1.333.192 3 1.732 3z"></path>
        </svg>
    },
    danger: {
      outerStyle: "border-red-500/20 bg-red-50/50 dark:border-red-500/30 dark:bg-red-500/10",
      innerStyle: "text-red-900 dark:text-red-200",
      calloutType: "danger",
      icon: <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512" fill="currentColor" className="text-red-600 dark:text-red-400/80 w-4 h-4" aria-label="Danger">
          <path d="M17.1 292c-12.9-22.3-12.9-49.7 0-72L105.4 67.1c12.9-22.3 36.6-36 62.4-36l176.6 0c25.7 0 49.5 13.7 62.4 36L494.9 220c12.9 22.3 12.9 49.7 0 72L406.6 444.9c-12.9 22.3-36.6 36-62.4 36l-176.6 0c-25.7 0-49.5-13.7-62.4-36L17.1 292zm41.6-48c-4.3 7.4-4.3 16.6 0 24l88.3 152.9c4.3 7.4 12.2 12 20.8 12l176.6 0c8.6 0 16.5-4.6 20.8-12L453.4 268c4.3-7.4 4.3-16.6 0-24L365.1 91.1c-4.3-7.4-12.2-12-20.8-12l-176.6 0c-8.6 0-16.5 4.6-20.8 12L58.6 244zM256 128c13.3 0 24 10.7 24 24l0 112c0 13.3-10.7 24-24 24s-24-10.7-24-24l0-112c0-13.3 10.7-24 24-24zM224 352a32 32 0 1 1 64 0 32 32 0 1 1 -64 0z"></path>
        </svg>
    }
  };
  let variant = type;
  let gotInvalidVariant = false;
  if (!asideVariants.includes(type)) {
    gotInvalidVariant = true;
    variant = "danger";
  }
  const iconVariants = ["regular", "solid", "light", "thin", "sharp-solid", "duotone", "brands"];
  if (!iconVariants.includes(iconType)) {
    iconType = "regular";
  }
  return <>
      <div className={`callout my-4 px-5 py-4 overflow-hidden rounded-2xl flex gap-3 border ${asideComponents[variant].outerStyle}`} data-callout-type={asideComponents[variant].calloutType}>
        <div className="mt-0.5 w-4" data-component-part="callout-icon">
          {}
          {icon === "" ? asideComponents[variant].icon : <Icon icon={icon} iconType={iconType} size={14} />}
        </div>
        <div className={`text-sm prose min-w-0 w-full ${asideComponents[variant].innerStyle}`} data-component-part="callout-content">
          {gotInvalidVariant ? <p>
              <span className="font-bold">
                Invalid <code>type</code> passed!
              </span>
              <br />
              <span className="font-bold">Received: </span>
              {type}
              <br />
              <span className="font-bold">Expected one of: </span>
              {asideVariants.join(", ")}
            </p> : <>
              {title && <p className="font-bold">{title}</p>}
              {children}
            </>}
        </div>
      </div>
    </>;
};

**The converter** may look like magic: any FunC project can be immediately transformed into Tolk with a single command:

```bash theme={null}
npx @ton/convert-func-to-tolk contracts
```

[GitHub repo](https://github.com/ton-blockchain/convert-func-to-tolk).

## Key idea: transform and gradually modernize

1. Take a FunC project and apply the converter<br />
   \=> get a contract that "looks and feels" like FunC.

2. Refactor it with modern features, step by step, keeping green tests<br />
   \=> resulting in an idiomatic Tolk project for further development.

## Step 1: convert and make it compile

This is a **syntax-level converter** that assists in migrating contracts to Tolk.
It rewrites FunC code with 1:1 semantics, — emitting a Tolk version of a contract that remains very close to the FunC original.

Example input: [jetton-minter.fc](https://github.com/ton-blockchain/convert-func-to-tolk/blob/master/tests/inout/jetton-minter.fc).<br />
Example output: [jetton-minter.tolk](https://github.com/ton-blockchain/convert-func-to-tolk/blob/master/tests/inout/jetton-minter.fc.tolk).

The converted contract won't use modern Tolk features like structures, auto-serialization, or clean message composition.
But after some manual fixes, it compiles, runs, and passes tests.

<Aside type="caution" title={"A contract does not compile after conversion?"}>
  Please, refer to a [GitHub repo](https://github.com/ton-blockchain/convert-func-to-tolk) — it contains common problems and provides ways to fix them.
</Aside>

**From there, the codebase can be gradually modernized** — step by step, while keeping it functional at every stage.

## Step 2: gradually refactor

* use the modern `onInternalMessage`, see [handling messages](/languages/tolk/features/message-handling)
* extract a `Storage` struct, with toCell/fromCell like in [examples](/languages/tolk/features/contract-storage)
* refactor incoming messages into [structs](/languages/tolk/syntax/structures-fields#serialization-prefixes-and-opcodes) with 32-bit opcodes — incrementally, one message at a time
* define a union of possible messages and [lazy](/languages/tolk/features/lazy-loading) match it
* extract outgoing messages into structs and [send](/languages/tolk/features/message-sending) them

<Aside type="tip" title={"Key idea: keep the tests running at every stage"}>
  This is what makes the approach safe — confidently refactor and modernize the codebase without breaking anything.
</Aside>

## Where to find examples?

Examples: [Tolk vs FunC benchmarks](https://github.com/ton-blockchain/tolk-bench).
This repository contains several contracts migrated from FunC — preserving original logic and passing the same tests.

Explore the Git history to see how each contract was gradually rewritten, step by step.