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Use Option<Ident> for lowered param names.

Parameter patterns are lowered to an `Ident` by
`lower_fn_params_to_names`, which is used when lowering bare function
types, trait methods, and foreign functions. Currently, there are two
exceptional cases where the lowered param can become an empty `Ident`.

- If the incoming pattern is an empty `Ident`. This occurs if the
  parameter is anonymous, e.g. in a bare function type.

- If the incoming pattern is neither an ident nor an underscore. Any
  such parameter will have triggered a compile error (hence the
  `span_delayed_bug`), but lowering still occurs.

This commit replaces these empty `Ident` results with `None`, which
eliminates a number of `kw::Empty` uses, and makes it impossible to fail
to check for these exceptional cases.

Note: the `FIXME` comment in `is_unwrap_or_empty_symbol` is removed. It
actually should have been removed in #138482, the precursor to this PR.
That PR changed the lowering of wild patterns to `_` symbols instead of
empty symbols, which made the mentioned underscore check load-bearing.
This commit is contained in:
Nicholas Nethercote 2025-03-14 09:03:23 +11:00
parent 75530e9f72
commit f27cab806e
20 changed files with 125 additions and 87 deletions

View file

@ -1034,7 +1034,13 @@ fn report_trait_method_mismatch<'tcx>(
let span = tcx
.hir_body_param_names(body)
.zip(sig.decl.inputs.iter())
.map(|(param, ty)| param.span.to(ty.span))
.map(|(param_name, ty)| {
if let Some(param_name) = param_name {
param_name.span.to(ty.span)
} else {
ty.span
}
})
.next()
.unwrap_or(impl_err_span);

View file

@ -49,10 +49,12 @@ pub(crate) fn validate_cmse_abi<'tcx>(
Ok(Err(index)) => {
// fn(x: u32, u32, u32, u16, y: u16) -> u32,
// ^^^^^^
let span = bare_fn_ty.param_names[index]
.span
.to(bare_fn_ty.decl.inputs[index].span)
.to(bare_fn_ty.decl.inputs.last().unwrap().span);
let span = if let Some(ident) = bare_fn_ty.param_names[index] {
ident.span.to(bare_fn_ty.decl.inputs[index].span)
} else {
bare_fn_ty.decl.inputs[index].span
}
.to(bare_fn_ty.decl.inputs.last().unwrap().span);
let plural = bare_fn_ty.param_names.len() - index != 1;
dcx.emit_err(errors::CmseInputsStackSpill { span, plural, abi });
}