I&#x27;ve been playing around with type mapping like this in a highly experimental crate. The ability to map, filter and reduce types is insanely powerful but it&#x27;s tough to get ergonomic syntax.<p><a href="https:&#x2F;&#x2F;docs.rs&#x2F;tuplemagic&#x2F;latest&#x2F;tuplemagic&#x2F;index.html" rel="nofollow">https:&#x2F;&#x2F;docs.rs&#x2F;tuplemagic&#x2F;latest&#x2F;tuplemagic&#x2F;index.html</a>

I also hit a funny compiler end-of-the road last month when I wanted to try out generic_const_exprs for my RFC8366 implementation:<p><pre><code>  pub struct VoucherDetails&lt;C&gt;
    where
      C: CapacityConfig,
      [(); C::SERIAL_NUMBER_MAX]:,
      [(); C::MANUFACTURER_PRIVATE_MAX]:,
      [(); C::IDEVID_ISSUER_MAX]:,
      &#x2F;&#x2F; &lt;imagine a dozen more properties here&gt;
      [(); C::NONCE_B64_MAX]:,
  { ... }
</code></pre>
The heavy const eval + trait resolution was too much even for my M2 Pro.

This was incredible, even as it rapidly outpaced my PL and mathematics knowledge.

HN

Torturing Rustc by Emulating HKTs

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