[WIP] #[fused]

[GrigorenkoPV]

• A more granular take on -Zfused-futures #147129

TODO:

• TODOs in code
• Attribute validation
• mir tests
• support async blocks & async closures
• A proper tracking issue, if this does not get rejected

[rust-log-analyzer]

The job pr-check-2 failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

     | |
     | in this expansion of `find_attr!` (#1)
     | in this expansion of `$crate::find_attr!` (#2)
...
  81 |         $crate::find_attr!($attributes_list, $pattern $(if $guard)? => ()).is_some()
     |         ------------------------------------------------------------------ in this macro invocation (#2)
...
  89 |                 let i: &rustc_hir::Attribute = i;
     |                        ---------------------   ^ expected `rustc_hir::Attribute`, found `rustc_ast::Attribute`
     |                        |
     |                        expected due to this
     |
    ::: compiler/rustc_ast_lowering/src/expr/closure.rs:41:21
     |
  41 |                     find_attr!(&e.attrs, Fused(_)),
     |                     ------------------------------ in this macro invocation (#1)
     |
     = note: `rustc_ast::Attribute` and `rustc_hir::Attribute` have similar names, but are actually distinct types
note: `rustc_ast::Attribute` is defined in crate `rustc_ast`
    --> compiler/rustc_ast/src/ast.rs:3404:1
---
    | |
    | in this expansion of `find_attr!` (#1)
    | in this expansion of `$crate::find_attr!` (#2)
...
 81 |         $crate::find_attr!($attributes_list, $pattern $(if $guard)? => ()).is_some()
    |         ------------------------------------------------------------------ in this macro invocation (#2)
...
 89 |                 let i: &rustc_hir::Attribute = i;
    |                        ---------------------   ^ expected `&Attribute`, found `Attribute`
    |                        |
    |                        expected due to this
    |
   ::: compiler/rustc_ast_lowering/src/expr.rs:359:70
    |
359 | ...                   hir::CoroutineDesugaring::Async { fused: find_attr!(e.attrs, Fused(_)) }
    |                                                                ----------------------------- in this macro invocation (#1)

For more information about this error, try `rustc --explain E0308`.
[RUSTC-TIMING] rustc_ast_lowering test:false 1.470
error: could not compile `rustc_ast_lowering` (lib) due to 2 previous errors

[rust-bors]

☔ The latest upstream changes (presumably #156649) made this pull request unmergeable. Please resolve the merge conflicts.