clippy fixes and code simplification

Author: hkBst

compiler/rustc_hir_typeck/src/fn_ctxt/adjust_fulfillment_errors.rs

@@ -94,20 +94,16 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let find_param_matching = |matches: &dyn Fn(ParamTerm) -> bool| {
             predicate_args.iter().find_map(|arg| {
-                arg.walk().find_map(|arg| {
-                    if let ty::GenericArgKind::Type(ty) = arg.kind()
-                        && let ty::Param(param_ty) = *ty.kind()
-                        && matches(ParamTerm::Ty(param_ty))
-                    {
-                        Some(arg)
-                    } else if let ty::GenericArgKind::Const(ct) = arg.kind()
-                        && let ty::ConstKind::Param(param_ct) = ct.kind()
-                        && matches(ParamTerm::Const(param_ct))
+                arg.walk().find(|arg| match arg.kind() {
+                    ty::GenericArgKind::Type(ty) if let ty::Param(param_ty) = ty.kind() => {
+                        matches(ParamTerm::Ty(*param_ty))
+                    }
+                    ty::GenericArgKind::Const(ct)
+                        if let ty::ConstKind::Param(param_ct) = ct.kind() =>
                     {
-                        Some(arg)
-                    } else {
-                        None
+                        matches(ParamTerm::Const(param_ct))
                     }
+                    _ => false,
                 })
             })
         };
@@ -162,7 +158,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 .into_iter()
                 .flatten()
                 {
-                    if self.point_at_path_if_possible(error, def_id, param, &qpath) {
+                    if self.point_at_path_if_possible(error, def_id, param, qpath) {
                         return true;
                     }
                 }
@@ -194,7 +190,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 args,
             ) => {
                 if let Some(param) = predicate_self_type_to_point_at
-                    && self.point_at_path_if_possible(error, callee_def_id, param, &qpath)
+                    && self.point_at_path_if_possible(error, callee_def_id, param, qpath)
                 {
                     return true;
                 }
@@ -225,7 +221,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     .into_iter()
                     .flatten()
                 {
-                    if self.point_at_path_if_possible(error, callee_def_id, param, &qpath) {
+                    if self.point_at_path_if_possible(error, callee_def_id, param, qpath) {
                         return true;
                     }
                 }
@@ -544,10 +540,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     }
 
     /// - `blame_specific_*` means that the function will recursively traverse the expression,
-    /// looking for the most-specific-possible span to blame.
+    ///   looking for the most-specific-possible span to blame.
     ///
     /// - `point_at_*` means that the function will only go "one level", pointing at the specific
-    /// expression mentioned.
+    ///   expression mentioned.
     ///
     /// `blame_specific_arg_if_possible` will find the most-specific expression anywhere inside
     /// the provided function call expression, and mark it as responsible for the fulfillment
@@ -607,9 +603,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     /**
      * Recursively searches for the most-specific blameable expression.
      * For example, if you have a chain of constraints like:
-     * - want `Vec<i32>: Copy`
-     * - because `Option<Vec<i32>>: Copy` needs `Vec<i32>: Copy` because `impl <T: Copy> Copy for Option<T>`
-     * - because `(Option<Vec<i32>, bool)` needs `Option<Vec<i32>>: Copy` because `impl <A: Copy, B: Copy> Copy for (A, B)`
+     *  - want `Vec<i32>: Copy`
+     *  - because `Option<Vec<i32>>: Copy` needs `Vec<i32>: Copy` because `impl <T: Copy> Copy for Option<T>`
+     *  - because `(Option<Vec<i32>, bool)` needs `Option<Vec<i32>>: Copy` because `impl <A: Copy, B: Copy> Copy for (A, B)`
+     *
      * then if you pass in `(Some(vec![1, 2, 3]), false)`, this helper `point_at_specific_expr_if_possible`
      * will find the expression `vec![1, 2, 3]` as the "most blameable" reason for this missing constraint.
      *
@@ -747,9 +744,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
     /// Drills into `expr` to arrive at the equivalent location of `find_generic_param` in `in_ty`.
     /// For example, given
-    /// - expr: `(Some(vec![1, 2, 3]), false)`
-    /// - param: `T`
-    /// - in_ty: `(Option<Vec<T>, bool)`
+    ///  - expr: `(Some(vec![1, 2, 3]), false)`
+    ///  - param: `T`
+    ///  - in_ty: `(Option<Vec<T>, bool)`
+    ///
     /// we would drill until we arrive at `vec![1, 2, 3]`.
     ///
     /// If successful, we return `Ok(refined_expr)`. If unsuccessful, we return `Err(partially_refined_expr`),
@@ -1017,7 +1015,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     .variant_with_id(variant_def_id)
                     .fields
                     .iter()
-                    .map(|field| field.ty(self.tcx, *in_ty_adt_generic_args))
+                    .map(|field| field.ty(self.tcx, in_ty_adt_generic_args))
                     .enumerate()
                     .filter(|(_index, field_type)| find_param_in_ty((*field_type).into(), param)),
             ) else {

compiler/rustc_hir_typeck/src/fn_ctxt/arg_matrix.rs

@@ -174,7 +174,7 @@ impl<'tcx> ArgMatrix<'tcx> {
                 return Some(Issue::Missing(next_unmatched_idx));
             }
             // If we eliminate the last column, any left-over inputs are extra
-            if mat[i].len() == 0 {
+            if mat[i].is_empty() {
                 return Some(Issue::Extra(next_unmatched_idx));
             }
 
@@ -187,28 +187,18 @@ impl<'tcx> ArgMatrix<'tcx> {
                 continue;
             }
 
-            let mut useless = true;
-            let mut unsatisfiable = true;
-            if is_arg {
-                for j in 0..ii.len() {
-                    // If we find at least one input this argument could satisfy
-                    // this argument isn't unsatisfiable
-                    if matches!(mat[j][i], Compatibility::Compatible) {
-                        unsatisfiable = false;
-                        break;
-                    }
-                }
-            }
-            if is_input {
-                for j in 0..ai.len() {
-                    // If we find at least one argument that could satisfy this input
-                    // this input isn't useless
-                    if matches!(mat[i][j], Compatibility::Compatible) {
-                        useless = false;
-                        break;
-                    }
-                }
-            }
+            // If this argument can satisfy some input, then this argument is satisfiable
+            let unsatisfiable = if is_arg {
+                !mat.iter().take(ii.len()).any(|c| matches!(c[i], Compatibility::Compatible))
+            } else {
+                true
+            };
+            // If this input can be satisfied by some argument, then this input is useful
+            let useless = if is_input {
+                !mat[i].iter().take(ai.len()).any(|c| matches!(c, Compatibility::Compatible))
+            } else {
+                true
+            };
 
             match (is_input, is_arg, useless, unsatisfiable) {
                 // If an argument is unsatisfied, and the input in its position is useless

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -780,10 +780,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 }
                 _ => bug!("unexpected type: {:?}", ty.normalized),
             },
-            Res::Def(
-                DefKind::Struct | DefKind::Union | DefKind::TyAlias { .. } | DefKind::AssocTy,
-                _,
-            )
+            Res::Def(DefKind::Struct | DefKind::Union | DefKind::TyAlias | DefKind::AssocTy, _)
             | Res::SelfTyParam { .. }
             | Res::SelfTyAlias { .. } => match ty.normalized.ty_adt_def() {
                 Some(adt) if !adt.is_enum() => {
@@ -871,7 +868,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let decl_ty = self.local_ty(decl.span, decl.hir_id);
 
         // Type check the initializer.
-        if let Some(ref init) = decl.init {
+        if let Some(init) = decl.init {
             let init_ty = self.check_decl_initializer(decl.hir_id, decl.pat, init);
             self.overwrite_local_ty_if_err(decl.hir_id, decl.pat, init_ty);
         }
@@ -935,7 +932,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
             // Ignore for now.
             hir::StmtKind::Item(_) => {}
-            hir::StmtKind::Expr(ref expr) => {
+            hir::StmtKind::Expr(expr) => {
                 // Check with expected type of `()`.
                 self.check_expr_has_type_or_error(expr, self.tcx.types.unit, |err| {
                     if self.is_next_stmt_expr_continuation(stmt.hir_id)
@@ -1774,10 +1771,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 let params =
                     params.get(is_method as usize..params.len() - sig.decl.c_variadic as usize)?;
                 debug_assert_eq!(params.len(), fn_inputs.len());
-                Some((
-                    fn_inputs.zip(params.iter().map(|param| FnParam::Param(param))).collect(),
-                    generics,
-                ))
+                Some((fn_inputs.zip(params.iter().map(FnParam::Param)).collect(), generics))
             }
             (None, Some(params)) => {
                 let params =
@@ -2639,7 +2633,7 @@ impl<'a, 'b, 'tcx> FnCallDiagCtxt<'a, 'b, 'tcx> {
         suggestions: Vec<(Span, String)>,
         suggestion_text: SuggestionText,
     ) -> Option<String> {
-        let suggestion_text = match suggestion_text {
+        match suggestion_text {
             SuggestionText::None => None,
             SuggestionText::Provide(plural) => {
                 Some(format!("provide the argument{}", if plural { "s" } else { "" }))
@@ -2655,8 +2649,7 @@ impl<'a, 'b, 'tcx> FnCallDiagCtxt<'a, 'b, 'tcx> {
             SuggestionText::Swap => Some("swap these arguments".to_string()),
             SuggestionText::Reorder => Some("reorder these arguments".to_string()),
             SuggestionText::DidYouMean => Some("did you mean".to_string()),
-        };
-        suggestion_text
+        }
     }
 
     fn arguments_formatting(&self, suggestion_span: Span) -> ArgumentsFormatting {
@@ -2954,7 +2947,7 @@ impl<'a, 'b, 'tcx> ArgsCtxt<'a, 'b, 'tcx> {
                     .fn_ctxt
                     .typeck_results
                     .borrow()
-                    .expr_ty_adjusted_opt(*expr)
+                    .expr_ty_adjusted_opt(expr)
                     .unwrap_or_else(|| Ty::new_misc_error(self.call_ctxt.fn_ctxt.tcx));
                 (
                     self.call_ctxt.fn_ctxt.resolve_vars_if_possible(ty),

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -1132,7 +1132,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             })
             .collect::<Vec<String>>();
 
-        if all_matching_bounds_strs.len() == 0 {
+        if all_matching_bounds_strs.is_empty() {
             return;
         }
 
@@ -1336,7 +1336,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     expected_ty = *inner_expected_ty;
                 }
                 (hir::ExprKind::Block(blk, _), _, _) => {
-                    self.suggest_block_to_brackets(diag, *blk, expr_ty, expected_ty);
+                    self.suggest_block_to_brackets(diag, blk, expr_ty, expected_ty);
                     break true;
                 }
                 _ => break false,
@@ -1463,7 +1463,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         {
             let span = expr
                 .span
-                .find_ancestor_not_from_extern_macro(&self.tcx.sess.source_map())
+                .find_ancestor_not_from_extern_macro(self.tcx.sess.source_map())
                 .unwrap_or(expr.span);
 
             let mut sugg = if self.precedence(expr) >= ExprPrecedence::Unambiguous {
@@ -2133,7 +2133,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         let span = expr
             .span
-            .find_ancestor_not_from_extern_macro(&self.tcx.sess.source_map())
+            .find_ancestor_not_from_extern_macro(self.tcx.sess.source_map())
             .unwrap_or(expr.span);
         err.span_suggestion_verbose(span.shrink_to_hi(), msg, sugg, Applicability::HasPlaceholders);
         true
@@ -2246,7 +2246,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
             let src_map = tcx.sess.source_map();
             let suggestion = if src_map.is_multiline(expr.span) {
-                let indentation = src_map.indentation_before(span).unwrap_or_else(String::new);
+                let indentation = src_map.indentation_before(span).unwrap_or_default();
                 format!("\n{indentation}/* {suggestion} */")
             } else {
                 // If the entire expr is on a single line
@@ -2278,7 +2278,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // Check if `expr` is contained in array of two elements
         if let hir::Node::Expr(array_expr) = self.tcx.parent_hir_node(expr.hir_id)
             && let hir::ExprKind::Array(elements) = array_expr.kind
-            && let [first, second] = &elements[..]
+            && let [first, second] = elements
             && second.hir_id == expr.hir_id
         {
             // Span between the two elements of the array

compiler/rustc_hir_typeck/src/gather_locals.rs

@@ -135,7 +135,7 @@ impl<'a, 'tcx> GatherLocalsVisitor<'a, 'tcx> {
     /// again during type checking by querying [`FnCtxt::local_ty`] for the same hir_id.
     fn declare(&mut self, decl: Declaration<'tcx>) {
         let local_ty = match decl.ty {
-            Some(ref ty) => {
+            Some(ty) => {
                 let o_ty = self.fcx.lower_ty(ty);
 
                 let c_ty = self.fcx.infcx.canonicalize_user_type_annotation(

compiler/rustc_hir_typeck/src/loops.rs

@@ -147,17 +147,15 @@ impl<'hir> Visitor<'hir> for CheckLoopVisitor<'hir> {
                     }
                 }
             }
-            hir::ExprKind::Loop(ref b, _, source, _) => {
+            hir::ExprKind::Loop(b, _, source, _) => {
                 let cx = match self.is_loop_match(e, b) {
                     Some(labeled_block) => LoopMatch { labeled_block },
                     None => Loop(source),
                 };
 
                 self.with_context(cx, |v| v.visit_block(b));
             }
-            hir::ExprKind::Closure(&hir::Closure {
-                ref fn_decl, body, fn_decl_span, kind, ..
-            }) => {
+            hir::ExprKind::Closure(&hir::Closure { fn_decl, body, fn_decl_span, kind, .. }) => {
                 let cx = match kind {
                     hir::ClosureKind::Coroutine(hir::CoroutineKind::Desugared(kind, source)) => {
                         Coroutine { coroutine_span: fn_decl_span, kind, source }
@@ -167,16 +165,16 @@ impl<'hir> Visitor<'hir> for CheckLoopVisitor<'hir> {
                 self.visit_fn_decl(fn_decl);
                 self.with_context(cx, |v| v.visit_nested_body(body));
             }
-            hir::ExprKind::Block(ref b, Some(_label)) => {
+            hir::ExprKind::Block(b, Some(_label)) => {
                 self.with_context(LabeledBlock, |v| v.visit_block(b));
             }
-            hir::ExprKind::Block(ref b, None)
+            hir::ExprKind::Block(b, None)
                 if matches!(self.cx_stack.last(), Some(&Fn) | Some(&ConstBlock)) =>
             {
                 self.with_context(Normal, |v| v.visit_block(b));
             }
             hir::ExprKind::Block(
-                ref b @ hir::Block { rules: hir::BlockCheckMode::DefaultBlock, .. },
+                b @ hir::Block { rules: hir::BlockCheckMode::DefaultBlock, .. },
                 None,
             ) if matches!(
                 self.cx_stack.last(),
@@ -431,10 +429,7 @@ impl<'hir> CheckLoopVisitor<'hir> {
 
         // Accept either `state = expr` or `state = expr;`.
         let loop_body_expr = match body.stmts {
-            [] => match body.expr {
-                Some(expr) => expr,
-                None => return None,
-            },
+            [] => body.expr?,
             [single] if body.expr.is_none() => match single.kind {
                 hir::StmtKind::Expr(expr) | hir::StmtKind::Semi(expr) => expr,
                 _ => return None,

compiler/rustc_index/src/bit_set.rs

@@ -1409,7 +1409,7 @@ impl<R: Idx, C: Idx> BitMatrix<R, C> {
         BitMatrix {
             num_rows,
             num_columns,
-            words: iter::repeat(&row.words).take(num_rows).flatten().cloned().collect(),
+            words: iter::repeat_n(&row.words, num_rows).flatten().cloned().collect(),
             marker: PhantomData,
         }
     }

compiler/rustc_mir_transform/src/impossible_predicates.rs

@@ -20,11 +20,11 @@
 //! parameters, so this filtering serves two purposes:
 //!
 //! 1. We skip evaluating any predicates that we would
-//! never be able prove are unsatisfiable (e.g. `<T as Foo>`
+//!    never be able prove are unsatisfiable (e.g. `<T as Foo>`
 //! 2. We avoid trying to normalize predicates involving generic
-//! parameters (e.g. `<T as Foo>::MyItem`). This can confuse
-//! the normalization code (leading to cycle errors), since
-//! it's usually never invoked in this way.
+//!    parameters (e.g. `<T as Foo>::MyItem`). This can confuse
+//!    the normalization code (leading to cycle errors), since
+//!    it's usually never invoked in this way.
 
 use rustc_middle::mir::{Body, START_BLOCK, TerminatorKind};
 use rustc_middle::ty::{TyCtxt, TypeFlags, TypeVisitableExt};

compiler/rustc_mir_transform/src/inline.rs

@@ -635,7 +635,7 @@ fn try_inlining<'tcx, I: Inliner<'tcx>>(
 
     // Normally, this shouldn't be required, but trait normalization failure can create a
     // validation ICE.
-    if !validate_types(tcx, inliner.typing_env(), &callee_body, &caller_body).is_empty() {
+    if !validate_types(tcx, inliner.typing_env(), &callee_body, caller_body).is_empty() {
         debug!("failed to validate callee body");
         return Err("implementation limitation -- callee body failed validation");
     }