This PR adds “sparse casesOn” constructions. They are similar to
`.casesOn`, but have arms only for some constructors and a catch-all
(providing `t.ctorIdx ≠ 42` assumptions). The compiler has native
support for these constructors and now (because of the similarity) also
the per-constructor elimination principles.
This PR splits some low-hanging fruit out of `Init.Data.String.Basic`:
basic material about `String.Pos.Raw`, `String.Substrig`, and
`String.Iterator`.
More splitting required and the remaining material is quite unorganized,
but it's a start.
This PR removes the auto-generated `binductionOn` and `ibelow`
implementations for inductive types in favor of the improved `brecOn`
implementation from #7639.
this is a first step towards porting the code `constructions.cpp` to
Lean: It leaves the construction of the `Declaration` untouched, but
moves adding the declarations to the environment, and setting various
attributes, to the Lean world.
This allows the remaining logic (the construction of the `Declaration`)
to be implemented in Lean separately and easily compared to the C++
implementation, before we replace that too.
To that end, `Declaraion` gains an `BEq` instance.
---------
Co-authored-by: Leonardo de Moura <leomoura@amazon.com>
Co-authored-by: Arthur Adjedj <arthur.adjedj@ens-paris-saclay.fr>
This coercion caused difficult-to-diagnose bugs sometimes. Because there
are some situations where converting a string to a name should be done
by parsing the string, and others where it should not, an explicit
choice seems better here.
---------
Co-authored-by: Mac Malone <tydeu@hatpress.net>
