Fix clippy::useless_conversion

compiler/rustc_ast/src/ast.rs

@@ -3475,7 +3475,7 @@ impl From<ForeignItemKind> for ItemKind {
     fn from(foreign_item_kind: ForeignItemKind) -> ItemKind {
         match foreign_item_kind {
             ForeignItemKind::Static(box static_foreign_item) => {
-                ItemKind::Static(Box::new(static_foreign_item.into()))
+                ItemKind::Static(Box::new(static_foreign_item))
             }
             ForeignItemKind::Fn(fn_kind) => ItemKind::Fn(fn_kind),
             ForeignItemKind::TyAlias(ty_alias_kind) => ItemKind::TyAlias(ty_alias_kind),
@@ -3489,9 +3489,7 @@ impl TryFrom<ItemKind> for ForeignItemKind {
 
     fn try_from(item_kind: ItemKind) -> Result<ForeignItemKind, ItemKind> {
         Ok(match item_kind {
-            ItemKind::Static(box static_item) => {
-                ForeignItemKind::Static(Box::new(static_item.into()))
-            }
+            ItemKind::Static(box static_item) => ForeignItemKind::Static(Box::new(static_item)),
             ItemKind::Fn(fn_kind) => ForeignItemKind::Fn(fn_kind),
             ItemKind::TyAlias(ty_alias_kind) => ForeignItemKind::TyAlias(ty_alias_kind),
             ItemKind::MacCall(a) => ForeignItemKind::MacCall(a),

compiler/rustc_const_eval/src/const_eval/eval_queries.rs

@@ -75,12 +75,7 @@ fn eval_body_using_ecx<'tcx, R: InterpretationResult<'tcx>>(
 
     // This can't use `init_stack_frame` since `body` is not a function,
     // so computing its ABI would fail. It's also not worth it since there are no arguments to pass.
-    ecx.push_stack_frame_raw(
-        cid.instance,
-        body,
-        &ret.clone().into(),
-        StackPopCleanup::Root { cleanup: false },
-    )?;
+    ecx.push_stack_frame_raw(cid.instance, body, &ret, StackPopCleanup::Root { cleanup: false })?;
     ecx.storage_live_for_always_live_locals()?;
 
     // The main interpreter loop.

compiler/rustc_const_eval/src/interpret/call.rs

@@ -823,7 +823,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
             (Abi::Rust, fn_abi),
             &[FnArg::Copy(arg.into())],
             false,
-            &ret.into(),
+            &ret,
             Some(target),
             unwind,
         )

compiler/rustc_errors/src/diagnostic.rs

@@ -681,10 +681,10 @@ impl<'a, G: EmissionGuarantee> Diag<'a, G> {
             " ".repeat(expected_padding),
             expected_label
         ))];
-        msg.extend(expected.0.into_iter());
+        msg.extend(expected.0);
         msg.push(StringPart::normal(format!("`{expected_extra}\n")));
         msg.push(StringPart::normal(format!("{}{} `", " ".repeat(found_padding), found_label)));
-        msg.extend(found.0.into_iter());
+        msg.extend(found.0);
         msg.push(StringPart::normal(format!("`{found_extra}")));
 
         // For now, just attach these as notes.

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -1602,7 +1602,7 @@ fn check_fn_or_method<'tcx>(
                     function: def_id,
                     // Note that the `param_idx` of the output type is
                     // one greater than the index of the last input type.
-                    param_idx: idx.try_into().unwrap(),
+                    param_idx: idx,
                 }),
                 ty,
             )
@@ -1611,7 +1611,7 @@ fn check_fn_or_method<'tcx>(
     for (idx, ty) in sig.inputs_and_output.iter().enumerate() {
         wfcx.register_wf_obligation(
             arg_span(idx),
-            Some(WellFormedLoc::Param { function: def_id, param_idx: idx.try_into().unwrap() }),
+            Some(WellFormedLoc::Param { function: def_id, param_idx: idx }),
             ty.into(),
         );
     }

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -2565,7 +2565,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     other_generic_param.name.ident() == generic_param.name.ident()
                 },
             ) {
-                idxs_matched.push(other_idx.into());
+                idxs_matched.push(other_idx);
             }
 
             if idxs_matched.is_empty() {

compiler/rustc_middle/src/ty/consts.rs

@@ -396,7 +396,7 @@ impl<'tcx> Const<'tcx> {
                         Ok((tcx.type_of(unevaluated.def).instantiate(tcx, unevaluated.args), c))
                     }
                     Ok(Err(bad_ty)) => Err(Either::Left(bad_ty)),
-                    Err(err) => Err(Either::Right(err.into())),
+                    Err(err) => Err(Either::Right(err)),
                 }
             }
             ConstKind::Value(ty, val) => Ok((ty, val)),

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -1526,7 +1526,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
 
                 let precedence = |binop: rustc_middle::mir::BinOp| {
                     use rustc_ast::util::parser::AssocOp;
-                    AssocOp::from_ast_binop(binop.to_hir_binop().into()).precedence()
+                    AssocOp::from_ast_binop(binop.to_hir_binop()).precedence()
                 };
                 let op_precedence = precedence(op);
                 let formatted_op = op.to_hir_binop().as_str();

compiler/rustc_next_trait_solver/src/solve/trait_goals.rs

@@ -883,7 +883,6 @@ where
             .into_iter()
             .chain(a_data.principal_def_id().into_iter().flat_map(|principal_def_id| {
                 elaborate::supertrait_def_ids(self.cx(), principal_def_id)
-                    .into_iter()
                     .filter(|def_id| self.cx().trait_is_auto(*def_id))
             }))
             .collect();

compiler/rustc_parse/src/parser/attr_wrapper.rs

@@ -383,7 +383,7 @@ impl<'a> Parser<'a> {
             self.capture_state
                 .parser_replacements
                 .drain(parser_replacements_start..parser_replacements_end)
-                .chain(inner_attr_parser_replacements.into_iter())
+                .chain(inner_attr_parser_replacements)
                 .map(|(parser_range, data)| {
                     (NodeRange::new(parser_range, collect_pos.start_pos), data)
                 })

compiler/rustc_parse/src/parser/item.rs

@@ -1588,7 +1588,7 @@ impl<'a> Parser<'a> {
                             (thin_vec![], Recovered::Yes(guar))
                         }
                     };
-                VariantData::Struct { fields, recovered: recovered.into() }
+                VariantData::Struct { fields, recovered }
             } else if this.check(&token::OpenDelim(Delimiter::Parenthesis)) {
                 let body = match this.parse_tuple_struct_body() {
                     Ok(body) => body,
@@ -1672,7 +1672,7 @@ impl<'a> Parser<'a> {
                     class_name.span,
                     generics.where_clause.has_where_token,
                 )?;
-                VariantData::Struct { fields, recovered: recovered.into() }
+                VariantData::Struct { fields, recovered }
             }
         // No `where` so: `struct Foo<T>;`
         } else if self.eat(&token::Semi) {
@@ -1684,7 +1684,7 @@ impl<'a> Parser<'a> {
                 class_name.span,
                 generics.where_clause.has_where_token,
             )?;
-            VariantData::Struct { fields, recovered: recovered.into() }
+            VariantData::Struct { fields, recovered }
         // Tuple-style struct definition with optional where-clause.
         } else if self.token == token::OpenDelim(Delimiter::Parenthesis) {
             let body = VariantData::Tuple(self.parse_tuple_struct_body()?, DUMMY_NODE_ID);
@@ -1713,14 +1713,14 @@ impl<'a> Parser<'a> {
                 class_name.span,
                 generics.where_clause.has_where_token,
             )?;
-            VariantData::Struct { fields, recovered: recovered.into() }
+            VariantData::Struct { fields, recovered }
         } else if self.token == token::OpenDelim(Delimiter::Brace) {
             let (fields, recovered) = self.parse_record_struct_body(
                 "union",
                 class_name.span,
                 generics.where_clause.has_where_token,
             )?;
-            VariantData::Struct { fields, recovered: recovered.into() }
+            VariantData::Struct { fields, recovered }
         } else {
             let token_str = super::token_descr(&self.token);
             let msg = format!("expected `where` or `{{` after union name, found {token_str}");

compiler/rustc_symbol_mangling/src/v0.rs

@@ -381,7 +381,7 @@ impl<'tcx> Printer<'tcx> for SymbolMangler<'tcx> {
                     let consts = [
                         start.unwrap_or(self.tcx.consts.unit),
                         end.unwrap_or(self.tcx.consts.unit),
-                        ty::Const::from_bool(self.tcx, include_end).into(),
+                        ty::Const::from_bool(self.tcx, include_end),
                     ];
                     // HACK: Represent as tuple until we have something better.
                     // HACK: constants are used in arrays, even if the types don't match.

compiler/rustc_trait_selection/src/traits/project.rs

@@ -408,7 +408,7 @@ pub(super) fn opt_normalize_projection_term<'a, 'b, 'tcx>(
             debug!("opt_normalize_projection_type: found error");
             let result = normalize_to_error(selcx, param_env, projection_term, cause, depth);
             obligations.extend(result.obligations);
-            return Ok(Some(result.value.into()));
+            return Ok(Some(result.value));
         }
     }
 
@@ -478,7 +478,7 @@ pub(super) fn opt_normalize_projection_term<'a, 'b, 'tcx>(
             }
             let result = normalize_to_error(selcx, param_env, projection_term, cause, depth);
             obligations.extend(result.obligations);
-            Ok(Some(result.value.into()))
+            Ok(Some(result.value))
         }
     }
 }