Auto merge of #49986 - zofrex:better-derived-argument-names, r=Manishearth

Provide better names for builtin deriving-generated attributes

First attempt at fixing #49967

Not in love with any choices here, don't be shy if you aren't happy with anything :)

I've tested that this produces nicer names in documentation, and that it no longer has issues conflicting with constants with the same name. (I guess we _could_ make a test for that... unsure if that would be valuable)

In all cases I took the names from the methods as declared in the relevant trait.

In some cases I had to prepend the names with _ otherwise there were errors about un-used variables. I'm uneasy with the inconsistency... do they all need to be like that? Is there a way to generate an alternate impl or use a different name (`_`?) in the cases where the arguments are not used?

Lastly the gensym addition to Ident I implemented largely as suggested, but I want to point out it's a little circuitous (at least, as far as I understand it). `cx.ident_of(name)` is just `Ident::from_str`, so we create an Ident then another Ident from it. `Ident::with_empty_ctxt(Symbol::gensym(string))` may or may not be equivalent, I don't know if it's important to intern it _then_ gensym it. It seems like either we could use that, or if we do want a new method to make this convenient, it could be on Ident instead (`from_str_gensymed`?)

2 files changed, 26 insertions, 1 deletions

diff --git a/src/test/run-pass-fulldeps/auxiliary/custom_derive_partial_eq.rs b/src/test/run-pass-fulldeps/auxiliary/custom_derive_partial_eq.rs
index f485982e2d3..6d5e82c68cc 100644
--- a/src/test/run-pass-fulldeps/auxiliary/custom_derive_partial_eq.rs
+++ b/src/test/run-pass-fulldeps/auxiliary/custom_derive_partial_eq.rs
@@ -58,7 +58,7 @@ fn expand_deriving_partial_eq(cx: &mut ExtCtxt, span: Span, mitem: &MetaItem, it
         name: "eq",
         generics: LifetimeBounds::empty(),
         explicit_self: borrowed_explicit_self(),
-        args: vec![borrowed_self()],
+        args: vec![(borrowed_self(), "other")],
         ret_ty: Literal(deriving::generic::ty::Path::new_local("bool")),
         attributes: attrs,
         is_unsafe: false,
diff --git a/src/test/run-pass-fulldeps/deriving-hygiene.rs b/src/test/run-pass-fulldeps/deriving-hygiene.rs
new file mode 100644
index 00000000000..532f2456599
--- /dev/null
+++ b/src/test/run-pass-fulldeps/deriving-hygiene.rs
@@ -0,0 +1,25 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(rustc_private)]
+extern crate serialize;
+
+pub const other: u8 = 1;
+pub const f: u8 = 1;
+pub const d: u8 = 1;
+pub const s: u8 = 1;
+pub const state: u8 = 1;
+pub const cmp: u8 = 1;
+
+#[derive(Ord,Eq,PartialOrd,PartialEq,Debug,Decodable,Encodable,Hash)]
+struct Foo {}
+
+fn main() {
+}