This is the same approach taken in #24270, except that this
should not be a breaking change because it only changes the output
of hash functions, which nobody should be relying on.
derive: Avoid emitting provided PartialEq, PartialOrd methods for c-like enums
derive: Avoid emitting provided PartialEq, PartialOrd method for c-like enums
`ne` is completely symmetrical with the method `eq`, and we can save
rust code size and compilation time here if we only emit one of them
when possible.
One case where it's easy to recognize is when it's a C-like enum. Most
other cases can not omit ne, because any value field may have a custom
PartialEq implementation.
derive: use intrinsics::unreachable over unreachable!()
derive: use intrinsics::unreachable over unreachable!()
Fixes#31574.
Spawned from #32139.
r? @alexcrichton
When deriving Hash, RustcEncodable and RustcDecodable, the syntax extension
needs a type parameter to use in the inner method. They used to use __H, __S
and __D respectively. If this conflicts with a type parameter already declared
for the item, bad times result (see the test). There is no hygiene for type
parameters, but this commit introduces a better heuristic by concatenating the
names of all extant type parameters (and prepending __H).
This changes local variable names in all derives to remove leading
double-underscores. As far as I can tell, this doesn't break anything
because there is no user code in these generated functions except for
struct, field and type parameter names, and this doesn't cause shadowing
of those. But I am still a bit nervous.
This replaces some `if`s with `match`es. This was originally not possible
because using a global path in a match statement caused a "non-constant
path in constant expr" ICE. The issue is long since closed, though you still
hit it (as an error now, not an ICE) if you try to generate match patterns
using pat_lit(expr_path). But it works when constructing the patterns more
carefully.
Using the same logic as for `PartialEq`, when possible define only
`partial_cmp` and leave `lt, le, gt, ge` to their default
implementations. This works well for c-like enums.
`ne` is completely symmetrical with the method `eq`, and we can save
rust code size and compilation time here if we only emit one of them
when possible.
One case where it's easy to recognize is when it's a C-like enum. Most
other cases can not omit ne, because any value field may have a custom
PartialEq implementation.
