Auto merge of rust-lang#120619 - compiler-errors:param, r=lcnr

Assert that params with the same *index* have the same *name*

Found this bug when trying to build libcore with the new solver, since it will canonicalize two params with the same index into *different* placeholders if those params differ by name.

Author: bors

clippy_lints/src/default.rs

@@ -131,7 +131,7 @@ impl<'tcx> LateLintPass<'tcx> for Default {
                 // only when assigning `... = Default::default()`
                 && is_expr_default(expr, cx)
                 && let binding_type = cx.typeck_results().node_type(binding_id)
-                && let Some(adt) = binding_type.ty_adt_def()
+                && let ty::Adt(adt, args) = *binding_type.kind()
                 && adt.is_struct()
                 && let variant = adt.non_enum_variant()
                 && (adt.did().is_local() || !variant.is_field_list_non_exhaustive())
@@ -144,7 +144,7 @@ impl<'tcx> LateLintPass<'tcx> for Default {
                     .fields
                     .iter()
                     .all(|field| {
-                        is_copy(cx, cx.tcx.type_of(field.did).instantiate_identity())
+                        is_copy(cx, cx.tcx.type_of(field.did).instantiate(cx.tcx, args))
                     })
                 && (!has_drop(cx, binding_type) || all_fields_are_copy)
             {

clippy_lints/src/useless_conversion.rs

@@ -86,7 +86,6 @@ fn into_iter_bound<'tcx>(
     param_index: u32,
     node_args: GenericArgsRef<'tcx>,
 ) -> Option<Span> {
-    let param_env = cx.tcx.param_env(fn_did);
     let mut into_iter_span = None;
 
     for (pred, span) in cx.tcx.explicit_predicates_of(fn_did).predicates {
@@ -111,7 +110,7 @@ fn into_iter_bound<'tcx>(
                     }));
 
                     let predicate = EarlyBinder::bind(tr).instantiate(cx.tcx, args);
-                    let obligation = Obligation::new(cx.tcx, ObligationCause::dummy(), param_env, predicate);
+                    let obligation = Obligation::new(cx.tcx, ObligationCause::dummy(), cx.param_env, predicate);
                     if !cx
                         .tcx
                         .infer_ctxt()