bors 0132f8258a Auto merge of #87064 - Aaron1011:new-closure-track-caller, r=estebank ... Support `#[track_caller]` on closures and generators ## Lang team summary This PR adds support for placing the `#[track_caller]` attribute on closure and generator expressions. This attribute's addition behaves identically (from a users perspective) to the attribute being placed on the method in impl Fn/FnOnce/FnMut for ... generated by compiler. The attribute is currently "double" feature gated -- both `stmt_expr_attributes` (preexisting) and `closure_track_caller` (newly added) must be enabled in order to place these attributes on closures. As the Fn* traits lack a `#[track_caller]` attribute in their definition, caller information does not propagate when invoking closures through dyn Fn*. There is no limitation that this PR adds in supporting this; it can be added in the future. # Implementation details This is implemented in the same way as for functions - an extra location argument is appended to the end of the ABI. For closures, this argument is *not* part of the 'tupled' argument storing the parameters - the final closure argument for `#[track_caller]` closures is no longer a tuple. For direct (monomorphized) calls, the necessary support was already implemented - we just needeed to adjust some assertions around checking the ABI and argument count to take closures into account. For calls through a trait object, more work was needed. When creating a `ReifyShim`, we need to create a shim for the trait method (e.g. `FnOnce::call_mut`) - unlike normal functions, closures are never invoked directly, and always go through a trait method. Additional handling was needed for `InstanceDef::ClosureOnceShim`. In order to pass location information throgh a direct (monomorphized) call to `FnOnce::call_once` on an `FnMut` closure, we need to make `ClosureOnceShim` aware of `#[tracked_caller]`. A new field `track_caller` is added to `ClosureOnceShim` - this is used by `InstanceDef::requires_caller` location, allowing codegen to pass through the extra location argument. Since `ClosureOnceShim.track_caller` is only used by codegen, we end up generating two identical MIR shims - one for `track_caller == true`, and one for `track_caller == false`. However, these two shims are used by the entire crate (i.e. it's two shims total, not two shims per unique closure), so this shouldn't a big deal.		2021-09-23 12:26:51 +00:00
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src	Auto merge of #87064 - Aaron1011:new-closure-track-caller, r=estebank	2021-09-23 12:26:51 +00:00
Cargo.toml	Migrate to 2021	2021-09-20 22:21:42 -04:00