[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)

    Checking rustc_passes v0.0.0 (/checkout/compiler/rustc_passes)
warning: unused variable: `hir_id`
    --> compiler/rustc_passes/src/check_attr.rs:1741:27
     |
1741 |     fn check_fused(&self, hir_id: HirId, attr_span: Span, target: Target) {
     |                           ^^^^^^ help: if this is intentional, prefix it with an underscore: `_hir_id`
     |
     = note: `#[warn(unused_variables)]` (part of `#[warn(unused)]`) on by default

warning: unused variable: `attr_span`
    --> compiler/rustc_passes/src/check_attr.rs:1741:42
     |
1741 |     fn check_fused(&self, hir_id: HirId, attr_span: Span, target: Target) {
     |                                          ^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_attr_span`

[RUSTC-TIMING] rustc_passes test:false 1.294
error: `rustc_passes` (lib) generated 2 warnings (run `cargo fix --lib -p rustc_passes` to apply 2 suggestions)
error: warnings are denied by `build.warnings` configuration
warning: build failed, waiting for other jobs to finish...