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Auto merge of #86164 - FabianWolff:issue-86053, r=davidtwco

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Handle C-variadic arguments properly when reporting region errors

This pull request fixes #86053. The issue is that for a C-variadic function
```rust
#![feature(c_variadic)]
unsafe extern "C" fn foo(_: (), ...) {}
```
`foo`'s signature will contain only the first parameter (and have `c_variadic` set to `true`), whereas its body has a second argument (a `hir::Pat` for the `...`).

The code for reporting region errors iterates over the body's parameters and tries to fetch the corresponding parameter from the signature; this causes an out-of-bounds ICE for the `...` (though not in the example above, because there are no region errors to report).

I have simply restricted the iteration over the body parameters to exclude `...`, which is fine because `...` cannot cause a region error.
This commit is contained in:
bors 2021-06-17 06:34:12 +00:00
commit cb3c4ee718
10 changed files with 218 additions and 69 deletions
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61
compiler/rustc_infer/src/infer/error_reporting/nice_region_error/util.rs
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@ -56,33 +56,42 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
let fn_decl = hir.fn_decl_by_hir_id(owner_id).unwrap();
let poly_fn_sig = self.tcx().fn_sig(id);
let fn_sig = self.tcx().liberate_late_bound_regions(id, poly_fn_sig);
body.params.iter().enumerate().find_map(|(index, param)| {
// May return None; sometimes the tables are not yet populated.
let ty = fn_sig.inputs()[index];
let mut found_anon_region = false;
let new_param_ty = self.tcx().fold_regions(ty, &mut false, |r, _| {
if *r == *anon_region {
found_anon_region = true;
replace_region
} else {
r
}
});
if found_anon_region {
let ty_hir_id = fn_decl.inputs[index].hir_id;
let param_ty_span = hir.span(ty_hir_id);
let is_first = index == 0;
Some(AnonymousParamInfo {
param,
param_ty: new_param_ty,
param_ty_span,
bound_region,
is_first,
})
body.params
.iter()
.take(if fn_sig.c_variadic {
fn_sig.inputs().len()
} else {
None
}
})
assert_eq!(fn_sig.inputs().len(), body.params.len());
body.params.len()
})
.enumerate()
.find_map(|(index, param)| {
// May return None; sometimes the tables are not yet populated.
let ty = fn_sig.inputs()[index];
let mut found_anon_region = false;
let new_param_ty = self.tcx().fold_regions(ty, &mut false, |r, _| {
if *r == *anon_region {
found_anon_region = true;
replace_region
} else {
r
}
});
if found_anon_region {
let ty_hir_id = fn_decl.inputs[index].hir_id;
let param_ty_span = hir.span(ty_hir_id);
let is_first = index == 0;
Some(AnonymousParamInfo {
param,
param_ty: new_param_ty,
param_ty_span,
bound_region,
is_first,
})
} else {
None
}
})
}
pub(super) fn future_return_type(