compiler: fix few unused_peekable and needless_pass_by_ref_mut clippy lints

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -1552,7 +1552,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
 /// When encountering an equality constraint in a `where` clause, emit an error. If the code seems
 /// like it's setting an associated type, provide an appropriate suggestion.
 fn deny_equality_constraints(
-    this: &mut AstValidator<'_>,
+    this: &AstValidator<'_>,
     predicate: &WhereEqPredicate,
     generics: &Generics,
 ) {

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -337,7 +337,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     }
 
     fn suggest_ref_or_clone(
-        &mut self,
+        &self,
         mpi: MovePathIndex,
         move_span: Span,
         err: &mut Diag<'tcx>,
@@ -1125,7 +1125,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     }
 
     pub(crate) fn report_use_while_mutably_borrowed(
-        &mut self,
+        &self,
         location: Location,
         (place, _span): (Place<'tcx>, Span),
         borrow: &BorrowData<'tcx>,
@@ -1174,7 +1174,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     }
 
     pub(crate) fn report_conflicting_borrow(
-        &mut self,
+        &self,
         location: Location,
         (place, span): (Place<'tcx>, Span),
         gen_borrow_kind: BorrowKind,
@@ -2463,7 +2463,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     }
 
     fn report_local_value_does_not_live_long_enough(
-        &mut self,
+        &self,
         location: Location,
         name: &str,
         borrow: &BorrowData<'tcx>,
@@ -2642,7 +2642,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     }
 
     fn report_thread_local_value_does_not_live_long_enough(
-        &mut self,
+        &self,
         drop_span: Span,
         borrow_span: Span,
     ) -> Diag<'tcx> {
@@ -2663,7 +2663,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
     #[instrument(level = "debug", skip(self))]
     fn report_temporary_value_does_not_live_long_enough(
-        &mut self,
+        &self,
         location: Location,
         borrow: &BorrowData<'tcx>,
         drop_span: Span,
@@ -2921,7 +2921,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
 
     #[instrument(level = "debug", skip(self))]
     fn report_escaping_closure_capture(
-        &mut self,
+        &self,
         use_span: UseSpans<'tcx>,
         var_span: Span,
         fr_name: &RegionName,
@@ -3031,7 +3031,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     }
 
     fn report_escaping_data(
-        &mut self,
+        &self,
         borrow_span: Span,
         name: &Option<String>,
         upvar_span: Span,
@@ -3065,7 +3065,7 @@ impl<'cx, 'tcx> MirBorrowckCtxt<'cx, 'tcx> {
     }
 
     fn get_moved_indexes(
-        &mut self,
+        &self,
         location: Location,
         mpi: MovePathIndex,
     ) -> (Vec<MoveSite>, Vec<Location>) {
@@ -3854,7 +3854,7 @@ enum AnnotatedBorrowFnSignature<'tcx> {
 impl<'tcx> AnnotatedBorrowFnSignature<'tcx> {
     /// Annotate the provided diagnostic with information about borrow from the fn signature that
     /// helps explain.
-    pub(crate) fn emit(&self, cx: &mut MirBorrowckCtxt<'_, 'tcx>, diag: &mut Diag<'_>) -> String {
+    pub(crate) fn emit(&self, cx: &MirBorrowckCtxt<'_, 'tcx>, diag: &mut Diag<'_>) -> String {
         match self {
             &AnnotatedBorrowFnSignature::Closure { argument_ty, argument_span } => {
                 diag.span_label(

compiler/rustc_borrowck/src/type_check/liveness/polonius.rs

@@ -87,6 +87,8 @@ pub(super) fn populate_access_facts<'a, 'tcx>(
     body: &Body<'tcx>,
     location_table: &LocationTable,
     move_data: &MoveData<'tcx>,
+    //FIXME: this is not mutated, but expected to be modified as
+    // out param, bug?
     dropped_at: &mut Vec<(Local, Location)>,
 ) {
     debug!("populate_access_facts()");

compiler/rustc_borrowck/src/type_check/liveness/trace.rs

@@ -200,7 +200,7 @@ impl<'me, 'typeck, 'flow, 'tcx> LivenessResults<'me, 'typeck, 'flow, 'tcx> {
         for local in boring_locals {
             let local_ty = self.cx.body.local_decls[local].ty;
             let drop_data = self.cx.drop_data.entry(local_ty).or_insert_with({
-                let typeck = &mut self.cx.typeck;
+                let typeck = &self.cx.typeck;
                 move || LivenessContext::compute_drop_data(typeck, local_ty)
             });
 
@@ -542,7 +542,7 @@ impl<'tcx> LivenessContext<'_, '_, '_, 'tcx> {
         );
 
         let drop_data = self.drop_data.entry(dropped_ty).or_insert_with({
-            let typeck = &mut self.typeck;
+            let typeck = &self.typeck;
             move || Self::compute_drop_data(typeck, dropped_ty)
         });
 
@@ -597,10 +597,7 @@ impl<'tcx> LivenessContext<'_, '_, '_, 'tcx> {
         });
     }
 
-    fn compute_drop_data(
-        typeck: &mut TypeChecker<'_, 'tcx>,
-        dropped_ty: Ty<'tcx>,
-    ) -> DropData<'tcx> {
+    fn compute_drop_data(typeck: &TypeChecker<'_, 'tcx>, dropped_ty: Ty<'tcx>) -> DropData<'tcx> {
         debug!("compute_drop_data(dropped_ty={:?})", dropped_ty,);
 
         match typeck

compiler/rustc_builtin_macros/src/asm.rs

@@ -29,7 +29,7 @@ pub struct AsmArgs {
 }
 
 fn parse_args<'a>(
-    ecx: &mut ExtCtxt<'a>,
+    ecx: &ExtCtxt<'a>,
     sp: Span,
     tts: TokenStream,
     is_global_asm: bool,
@@ -303,7 +303,7 @@ pub fn parse_asm_args<'a>(
 ///
 /// This function must be called immediately after the option token is parsed.
 /// Otherwise, the suggestion will be incorrect.
-fn err_duplicate_option(p: &mut Parser<'_>, symbol: Symbol, span: Span) {
+fn err_duplicate_option(p: &Parser<'_>, symbol: Symbol, span: Span) {
     // Tool-only output
     let full_span = if p.token.kind == token::Comma { span.to(p.token.span) } else { span };
     p.psess.dcx.emit_err(errors::AsmOptAlreadyprovided { span, symbol, full_span });
@@ -315,7 +315,7 @@ fn err_duplicate_option(p: &mut Parser<'_>, symbol: Symbol, span: Span) {
 /// This function must be called immediately after the option token is parsed.
 /// Otherwise, the error will not point to the correct spot.
 fn try_set_option<'a>(
-    p: &mut Parser<'a>,
+    p: &Parser<'a>,
     args: &mut AsmArgs,
     symbol: Symbol,
     option: ast::InlineAsmOptions,

compiler/rustc_builtin_macros/src/assert.rs

@@ -111,7 +111,7 @@ fn expr_if_not(
     cx.expr_if(span, cx.expr(span, ExprKind::Unary(UnOp::Not, cond)), then, els)
 }
 
-fn parse_assert<'a>(cx: &mut ExtCtxt<'a>, sp: Span, stream: TokenStream) -> PResult<'a, Assert> {
+fn parse_assert<'a>(cx: &ExtCtxt<'a>, sp: Span, stream: TokenStream) -> PResult<'a, Assert> {
     let mut parser = cx.new_parser_from_tts(stream);
 
     if parser.token == token::Eof {

compiler/rustc_builtin_macros/src/cfg.rs

@@ -35,7 +35,7 @@ pub fn expand_cfg(
     })
 }
 
-fn parse_cfg<'a>(cx: &mut ExtCtxt<'a>, span: Span, tts: TokenStream) -> PResult<'a, ast::MetaItem> {
+fn parse_cfg<'a>(cx: &ExtCtxt<'a>, span: Span, tts: TokenStream) -> PResult<'a, ast::MetaItem> {
     let mut p = cx.new_parser_from_tts(tts);
 
     if p.token == token::Eof {

compiler/rustc_builtin_macros/src/cfg_accessible.rs

@@ -10,7 +10,7 @@ use rustc_span::Span;
 
 pub(crate) struct Expander;
 
-fn validate_input<'a>(ecx: &mut ExtCtxt<'_>, mi: &'a ast::MetaItem) -> Option<&'a ast::Path> {
+fn validate_input<'a>(ecx: &ExtCtxt<'_>, mi: &'a ast::MetaItem) -> Option<&'a ast::Path> {
     use errors::CfgAccessibleInvalid::*;
     match mi.meta_item_list() {
         None => {}

compiler/rustc_builtin_macros/src/concat_bytes.rs

@@ -8,7 +8,7 @@ use crate::errors;
 
 /// Emits errors for literal expressions that are invalid inside and outside of an array.
 fn invalid_type_err(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     token_lit: token::Lit,
     span: Span,
     is_nested: bool,
@@ -65,7 +65,7 @@ fn invalid_type_err(
 /// Otherwise, returns `None`, and either pushes the `expr`'s span to `missing_literals` or
 /// updates `guar` accordingly.
 fn handle_array_element(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     guar: &mut Option<ErrorGuaranteed>,
     missing_literals: &mut Vec<rustc_span::Span>,
     expr: &P<rustc_ast::Expr>,

compiler/rustc_builtin_macros/src/deriving/bounds.rs

@@ -6,7 +6,7 @@ use rustc_expand::base::{Annotatable, ExtCtxt};
 use rustc_span::Span;
 
 pub fn expand_deriving_copy(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     span: Span,
     mitem: &MetaItem,
     item: &Annotatable,
@@ -29,7 +29,7 @@ pub fn expand_deriving_copy(
 }
 
 pub fn expand_deriving_const_param_ty(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     span: Span,
     mitem: &MetaItem,
     item: &Annotatable,

compiler/rustc_builtin_macros/src/deriving/clone.rs

@@ -9,7 +9,7 @@ use rustc_span::Span;
 use thin_vec::{thin_vec, ThinVec};
 
 pub fn expand_deriving_clone(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     span: Span,
     mitem: &MetaItem,
     item: &Annotatable,
@@ -94,7 +94,7 @@ pub fn expand_deriving_clone(
 
 fn cs_clone_simple(
     name: &str,
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     trait_span: Span,
     substr: &Substructure<'_>,
     is_union: bool,
@@ -157,14 +157,14 @@ fn cs_clone_simple(
 
 fn cs_clone(
     name: &str,
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     trait_span: Span,
     substr: &Substructure<'_>,
 ) -> BlockOrExpr {
     let ctor_path;
     let all_fields;
     let fn_path = cx.std_path(&[sym::clone, sym::Clone, sym::clone]);
-    let subcall = |cx: &mut ExtCtxt<'_>, field: &FieldInfo| {
+    let subcall = |cx: &ExtCtxt<'_>, field: &FieldInfo| {
         let args = thin_vec![field.self_expr.clone()];
         cx.expr_call_global(field.span, fn_path.clone(), args)
     };

compiler/rustc_builtin_macros/src/deriving/cmp/eq.rs

@@ -10,7 +10,7 @@ use rustc_span::Span;
 use thin_vec::{thin_vec, ThinVec};
 
 pub fn expand_deriving_eq(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     span: Span,
     mitem: &MetaItem,
     item: &Annotatable,
@@ -49,7 +49,7 @@ pub fn expand_deriving_eq(
 }
 
 fn cs_total_eq_assert(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     trait_span: Span,
     substr: &Substructure<'_>,
 ) -> BlockOrExpr {

compiler/rustc_builtin_macros/src/deriving/cmp/ord.rs

@@ -8,7 +8,7 @@ use rustc_span::Span;
 use thin_vec::thin_vec;
 
 pub fn expand_deriving_ord(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     span: Span,
     mitem: &MetaItem,
     item: &Annotatable,
@@ -39,7 +39,7 @@ pub fn expand_deriving_ord(
     trait_def.expand(cx, mitem, item, push)
 }
 
-pub fn cs_cmp(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> BlockOrExpr {
+pub fn cs_cmp(cx: &ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> BlockOrExpr {
     let test_id = Ident::new(sym::cmp, span);
     let equal_path = cx.path_global(span, cx.std_path(&[sym::cmp, sym::Ordering, sym::Equal]));
     let cmp_path = cx.std_path(&[sym::cmp, sym::Ord, sym::cmp]);

compiler/rustc_builtin_macros/src/deriving/cmp/partial_eq.rs

@@ -9,14 +9,14 @@ use rustc_span::Span;
 use thin_vec::thin_vec;
 
 pub fn expand_deriving_partial_eq(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     span: Span,
     mitem: &MetaItem,
     item: &Annotatable,
     push: &mut dyn FnMut(Annotatable),
     is_const: bool,
 ) {
-    fn cs_eq(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> BlockOrExpr {
+    fn cs_eq(cx: &ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> BlockOrExpr {
         let base = true;
         let expr = cs_fold(
             true, // use foldl

compiler/rustc_builtin_macros/src/deriving/cmp/partial_ord.rs

@@ -8,7 +8,7 @@ use rustc_span::Span;
 use thin_vec::thin_vec;
 
 pub fn expand_deriving_partial_ord(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     span: Span,
     mitem: &MetaItem,
     item: &Annotatable,
@@ -69,7 +69,7 @@ pub fn expand_deriving_partial_ord(
 }
 
 fn cs_partial_cmp(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     span: Span,
     substr: &Substructure<'_>,
     tag_then_data: bool,

compiler/rustc_builtin_macros/src/deriving/debug.rs

@@ -9,7 +9,7 @@ use rustc_span::Span;
 use thin_vec::{thin_vec, ThinVec};
 
 pub fn expand_deriving_debug(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     span: Span,
     mitem: &MetaItem,
     item: &Annotatable,
@@ -45,7 +45,7 @@ pub fn expand_deriving_debug(
     trait_def.expand(cx, mitem, item, push)
 }
 
-fn show_substructure(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> BlockOrExpr {
+fn show_substructure(cx: &ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> BlockOrExpr {
     // We want to make sure we have the ctxt set so that we can use unstable methods
     let span = cx.with_def_site_ctxt(span);
 
@@ -209,7 +209,7 @@ fn show_substructure(cx: &mut ExtCtxt<'_>, span: Span, substr: &Substructure<'_>
 /// }
 /// ```
 fn show_fieldless_enum(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     span: Span,
     def: &EnumDef,
     substr: &Substructure<'_>,

compiler/rustc_builtin_macros/src/deriving/decodable.rs

@@ -11,7 +11,7 @@ use rustc_span::Span;
 use thin_vec::{thin_vec, ThinVec};
 
 pub fn expand_deriving_rustc_decodable(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     span: Span,
     mitem: &MetaItem,
     item: &Annotatable,
@@ -63,7 +63,7 @@ pub fn expand_deriving_rustc_decodable(
 }
 
 fn decodable_substructure(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     trait_span: Span,
     substr: &Substructure<'_>,
     krate: Symbol,
@@ -186,14 +186,14 @@ fn decodable_substructure(
 /// - `outer_pat_path` is the path to this enum variant/struct
 /// - `getarg` should retrieve the `usize`-th field with name `@str`.
 fn decode_static_fields<F>(
-    cx: &mut ExtCtxt<'_>,
+    cx: &ExtCtxt<'_>,
     trait_span: Span,
     outer_pat_path: ast::Path,
     fields: &StaticFields,
     mut getarg: F,
 ) -> P<Expr>
 where
-    F: FnMut(&mut ExtCtxt<'_>, Span, Symbol, usize) -> P<Expr>,
+    F: FnMut(&ExtCtxt<'_>, Span, Symbol, usize) -> P<Expr>,
 {
     match fields {
         Unnamed(fields, is_tuple) => {