[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)

    --> compiler/rustc_passes/src/check_attr.rs:1760:9
     |
1759 |           return;
     |           ------ any code following this expression is unreachable
1760 | /         match target {
1761 | |             Target::Fn => todo!("Check that the fn is async"),
1762 | |             Target::Closure => todo!("Check that the closure is async"),
1763 | |             Target::Expression => todo!("Check that this is an async block"),
...    |
1767 | |             _ => bug!("This should not be accepted by rustc_attr_parsing"),
1768 | |         }
     | |_________^ unreachable expression
     |
     = note: `#[warn(unreachable_code)]` (part of `#[warn(unused)]`) on by default

warning: unused variable: `hir_id`
    --> compiler/rustc_passes/src/check_attr.rs:1758:27
     |
1758 |     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:1758:42
     |
1758 |     fn check_fused(&self, hir_id: HirId, attr_span: Span, target: Target) {
     |                                          ^^^^^^^^^ help: if this is intentional, prefix it with an underscore: `_attr_span`

warning: unused variable: `target`
    --> compiler/rustc_passes/src/check_attr.rs:1758:59
     |
1758 |     fn check_fused(&self, hir_id: HirId, attr_span: Span, target: Target) {
     |                                                           ^^^^^^ help: if this is intentional, prefix it with an underscore: `_target`

[RUSTC-TIMING] rustc_passes test:false 1.437
error: `rustc_passes` (lib) generated 4 warnings (run `cargo fix --lib -p rustc_passes` to apply 3 suggestions)
error: warnings are denied by `build.warnings` configuration
warning: build failed, waiting for other jobs to finish...