Auto merge of #124187 - compiler-errors:self-ctor, r=petrochenkov

Warn (or error) when `Self` ctor from outer item is referenced in inner nested item

This implements a warning `SELF_CONSTRUCTOR_FROM_OUTER_ITEM` when a self constructor from an outer impl is referenced in an inner nested item. This is a proper fix mentioned https://github.com/rust-lang/rust/pull/117246#discussion_r1374648388.

This warning is additionally bumped to a hard error when the self type references generic parameters, since it's almost always going to ICE, and is basically *never* correct to do.

This also reverts part of https://github.com/rust-lang/rust/pull/117246, since I believe this is the proper fix and we shouldn't need the helper functions (`opt_param_at`/`opt_type_param`) any longer, since they shouldn't really ever be used in cases where we don't have this problem.

1 files changed, 0 insertions, 28 deletions

diff --git a/compiler/rustc_middle/src/ty/generics.rs b/compiler/rustc_middle/src/ty/generics.rs
index 870e4865aea..1c4462fc1dc 100644
--- a/compiler/rustc_middle/src/ty/generics.rs
+++ b/compiler/rustc_middle/src/ty/generics.rs
@@ -245,20 +245,6 @@ impl<'tcx> Generics {
         }
     }
 
-    /// Returns the `GenericParamDef` with the given index if available.
-    pub fn opt_param_at(
-        &'tcx self,
-        param_index: usize,
-        tcx: TyCtxt<'tcx>,
-    ) -> Option<&'tcx GenericParamDef> {
-        if let Some(index) = param_index.checked_sub(self.parent_count) {
-            self.own_params.get(index)
-        } else {
-            tcx.generics_of(self.parent.expect("parent_count > 0 but no parent?"))
-                .opt_param_at(param_index, tcx)
-        }
-    }
-
     pub fn params_to(&'tcx self, param_index: usize, tcx: TyCtxt<'tcx>) -> &'tcx [GenericParamDef] {
         if let Some(index) = param_index.checked_sub(self.parent_count) {
             &self.own_params[..index]
@@ -290,20 +276,6 @@ impl<'tcx> Generics {
         }
     }
 
-    /// Returns the `GenericParamDef` associated with this `ParamTy` if it belongs to this
-    /// `Generics`.
-    pub fn opt_type_param(
-        &'tcx self,
-        param: ParamTy,
-        tcx: TyCtxt<'tcx>,
-    ) -> Option<&'tcx GenericParamDef> {
-        let param = self.opt_param_at(param.index as usize, tcx)?;
-        match param.kind {
-            GenericParamDefKind::Type { .. } => Some(param),
-            _ => None,
-        }
-    }
-
     /// Returns the `GenericParamDef` associated with this `ParamConst`.
     pub fn const_param(&'tcx self, param: ParamConst, tcx: TyCtxt<'tcx>) -> &GenericParamDef {
         let param = self.param_at(param.index as usize, tcx);