06f1f027ab Make `hash_newtype` evocative of the output (Martin Habovstiak)
b018f3e90b Remove the `$len` argument from `hash_newtype` (Martin Habovstiak)
752817e20d Stop using `$len` in `hash_newtype` (Martin Habovstiak)
Pull request description:
The API guidelines say macro input should be evocative of the output.
`hash_newtype` didn't have this property.
This change makes it look exactly like the resulting struct, `$len`
parameter was removed since it's not needed, reversing is controlled
using an attribute. The macro is also better documented and ready to be
extended in the future.
The tagged SHA256 newtype is not yet modified because it has a more
complicated input parameters.
Closes#1648
ACKs for top commit:
apoelstra:
ACK 06f1f027ab
Tree-SHA512: 9762db1eca9cd749980e5d68ca286f6c926620295a602f62365f199c7b333334b976db25ba25c64e56403cd1ba046b21b99e1c73cc528ad95612ef8901f216e5