Tracking: upgrade to nightly-2020-05-26

[SimonSapin]

Blocked on:

• Installing the llvm-tools-preview component New rustc nightly with llvm-10 breaks script_plugins #26645 (comment), Partial preparations for upgrading to Rust nightly-2020-05-26 #26662
• Handling syn::Type::Group in derive_common::cg::map_type_params Partial preparations for upgrading to Rust nightly-2020-05-26 #26662
• rustfmt being available rustfmt no longer builds after rust-lang/rust#69659 rust-lang/rust#72232
• ICE in gfx-backend-metal Recent rustc nightlies panic when building gfx-backend-metal #26648, ICE in _match.rs:1184:21 when building "gfx-backend-metal" on Nightly rust-lang/rust#72467
• Upgrade parking-lot to 0.10 rustc nightlies break on any dependency that relies on parking_lot 0.9 #26644, Avoid parking_lot bustage with recent rustc nightlies. #26646. Work around: disable its nightly feature (which enables hardware lock elision)
• Exhaustiveness check regression Incorrect non-exhaustive pattern error rust-lang/rust#72476. Work around:

  --- ports/glutin/headed_window.rs
  +++ ports/glutin/headed_window.rs
  @@ -543,10 +543,14 @@ impl WindowMethods for Window {
   
           #[cfg(target_os = "linux")]
           return match native_context {
  -            NativeContext::Default(NativeContext::Default(native_context)) =>
  -                PlayerGLContext::Egl(native_context.egl_context as usize),
  -            NativeContext::Default(NativeContext::Alternate(native_context)) =>
  -                PlayerGLContext::Egl(native_context.egl_context as usize),
  +            NativeContext::Default(d) => match d {
  +                NativeContext::Default(native_context) => {
  +                    PlayerGLContext::Egl(native_context.egl_context as usize)
  +                },
  +                NativeContext::Alternate(native_context) => {
  +                    PlayerGLContext::Egl(native_context.egl_context as usize)
  +                },
  +            },
               NativeContext::Alternate(_) => unimplemented!(),
           };
   
  @@ -574,10 +578,10 @@ impl WindowMethods for Window {
   
           #[cfg(target_os = "linux")]
           return match native_connection {
  -            NativeConnection::Default(NativeConnection::Default(conn)) =>
  -                NativeDisplay::Egl(conn.0 as usize),
  -            NativeConnection::Default(NativeConnection::Alternate(conn)) =>
  -                NativeDisplay::X11(conn.x11_display as usize),
  +            NativeConnection::Default(d) => match d {
  +                NativeConnection::Default(conn) => NativeDisplay::Egl(conn.0 as usize),
  +                NativeConnection::Alternate(conn) => NativeDisplay::X11(conn.x11_display as usize),
  +            }
               NativeConnection::Alternate(_) => unimplemented!(),
           };

• TokenTree regression affecting syn Regression: spurious "error: expected ," in serde::Serialize on macro_rules-variable path enum discriminant rust-lang/rust#72608. Better work around: updating syn to 1.0.26: Regression: spurious "error: expected ," in serde::Serialize on macro_rules-variable path enum discriminant rust-lang/rust#72608 (comment), Parse macro metavariable in leading component of path dtolnay/syn#832. Work around:

  --- components/canvas_traits/webgl.rs
  +++ components/canvas_traits/webgl.rs
  @@ -932,7 +932,10 @@ macro_rules! gl_enums {
              #[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf)]
              #[derive(PartialEq, Serialize)]
              #[repr(u32)]
  -            pub enum $name { $($variant = $mod::$constant,)+ }
  +            pub enum $name { $(
  +                // FIXME https://github.com/rust-lang/rust/issues/72608
  +                $variant = { use $mod::$constant; $constant },
  +            )+ }
  

[SimonSapin]

rust-lang/rust#72671 and rust-lang/rust#72506 landed yesterday, fixing the remaining blockers. https://community-tc.services.mozilla.com/tasks/groups/G-mDKoxPROqJOjPiEkjBgw is green (enough) with today’s Nightly without any code change (beyond #26662), so closing.