bjoernager/rust
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Rollup merge of #89148 - estebank:used-type-param, r=oli-obk

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Suggest `_` in turbofish if param will be inferred from fn argument
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Jubilee 2021-09-23 17:31:43 -07:00 • committed by GitHub
commit 9e11d1cca4
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4 changed files with 57 additions and 1 deletions
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21
compiler/rustc_typeck/src/structured_errors/wrong_number_of_generic_args.rs
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@ -1,6 +1,7 @@
use crate::structured_errors::StructuredDiagnostic;
use rustc_errors::{pluralize, Applicability, DiagnosticBuilder, DiagnosticId};
use rustc_hir as hir;
use rustc_middle::hir::map::fn_sig;
use rustc_middle::middle::resolve_lifetime::LifetimeScopeForPath;
use rustc_middle::ty::{self as ty, TyCtxt};
use rustc_session::Session;
@ -292,12 +293,30 @@ impl<'a, 'tcx> WrongNumberOfGenericArgs<'a, 'tcx> {
&self,
num_params_to_take: usize,
) -> String {
let fn_sig = self.tcx.hir().get_if_local(self.def_id).and_then(|node| fn_sig(node));
let is_used_in_input = |def_id| {
fn_sig.map_or(false, |fn_sig| {
fn_sig.decl.inputs.iter().any(|ty| match ty.kind {
hir::TyKind::Path(hir::QPath::Resolved(
None,
hir::Path { res: hir::def::Res::Def(_, id), .. },
)) if *id == def_id => true,
_ => false,
})
})
};
self.gen_params
.params
.iter()
.skip(self.params_offset + self.num_provided_type_or_const_args())
.take(num_params_to_take)
.map(|param| param.name.to_string())
.map(|param| match param.kind {
// This is being infered from the item's inputs, no need to set it.
ty::GenericParamDefKind::Type { .. } if is_used_in_input(param.def_id) => {
"_".to_string()
}
_ => param.name.to_string(),
})
.collect::<Vec<_>>()
.join(", ")
}