-// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-use rustc::ty;
-use rustc::ty::adjustment;
-use util::nodemap::FxHashMap;
-use lint::{LateContext, EarlyContext, LintContext, LintArray};
-use lint::{LintPass, EarlyLintPass, LateLintPass};
-
-use std::collections::hash_map::Entry::{Occupied, Vacant};
-
-use syntax::ast;
-use syntax::attr;
-use syntax::feature_gate::{BUILTIN_ATTRIBUTES, AttributeType};
-use syntax::symbol::keywords;
-use syntax::ptr::P;
-use syntax_pos::Span;
-
-use rustc_back::slice;
-use rustc::hir;
-use rustc::hir::intravisit::FnKind;
+use crate::Lint;
+use crate::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
+use rustc_ast::ast;
+use rustc_ast::ast::{ExprKind, StmtKind};
+use rustc_ast::attr;
+use rustc_ast::util::parser;
+use rustc_ast_pretty::pprust;
+use rustc_data_structures::fx::FxHashMap;
+use rustc_errors::{pluralize, Applicability};
+use rustc_feature::{AttributeType, BuiltinAttribute, BUILTIN_ATTRIBUTE_MAP};
+use rustc_hir as hir;
+use rustc_hir::def::{DefKind, Res};
+use rustc_hir::def_id::DefId;
+use rustc_middle::ty::adjustment;
+use rustc_middle::ty::{self, Ty};
+use rustc_session::lint::builtin::UNUSED_ATTRIBUTES;
+use rustc_span::symbol::Symbol;
+use rustc_span::symbol::{kw, sym};
+use rustc_span::{BytePos, Span, DUMMY_SP};
+
+use log::debug;
declare_lint! {
- pub UNUSED_MUT,
+ pub UNUSED_MUST_USE,
Warn,
- "detect mut variables which don't need to be mutable"
+ "unused result of a type flagged as `#[must_use]`",
+ report_in_external_macro
}
-#[derive(Copy, Clone)]
-pub struct UnusedMut;
-
-impl UnusedMut {
- fn check_unused_mut_pat(&self, cx: &LateContext, pats: &[P<hir::Pat>]) {
- // collect all mutable pattern and group their NodeIDs by their Identifier to
- // avoid false warnings in match arms with multiple patterns
-
- let mut mutables = FxHashMap();
- for p in pats {
- p.each_binding(|mode, id, _, path1| {
- let name = path1.node;
- if let hir::BindByValue(hir::MutMutable) = mode {
- if !name.as_str().starts_with("_") {
- match mutables.entry(name) {
- Vacant(entry) => {
- entry.insert(vec![id]);
- }
- Occupied(mut entry) => {
- entry.get_mut().push(id);
- }
+declare_lint! {
+ pub UNUSED_RESULTS,
+ Allow,
+ "unused result of an expression in a statement"
+}
+
+declare_lint_pass!(UnusedResults => [UNUSED_MUST_USE, UNUSED_RESULTS]);
+
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedResults {
+ fn check_stmt(&mut self, cx: &LateContext<'_, '_>, s: &hir::Stmt<'_>) {
+ let expr = match s.kind {
+ hir::StmtKind::Semi(ref expr) => &**expr,
+ _ => return,
+ };
+
+ if let hir::ExprKind::Ret(..) = expr.kind {
+ return;
+ }
+
+ let ty = cx.tables.expr_ty(&expr);
+ let type_permits_lack_of_use = check_must_use_ty(cx, ty, &expr, s.span, "", "", 1);
+
+ let mut fn_warned = false;
+ let mut op_warned = false;
+ let maybe_def_id = match expr.kind {
+ hir::ExprKind::Call(ref callee, _) => {
+ match callee.kind {
+ hir::ExprKind::Path(ref qpath) => {
+ match cx.tables.qpath_res(qpath, callee.hir_id) {
+ Res::Def(DefKind::Fn | DefKind::AssocFn, def_id) => Some(def_id),
+ // `Res::Local` if it was a closure, for which we
+ // do not currently support must-use linting
+ _ => None,
}
}
+ _ => None,
}
- });
+ }
+ hir::ExprKind::MethodCall(..) => cx.tables.type_dependent_def_id(expr.hir_id),
+ _ => None,
+ };
+ if let Some(def_id) = maybe_def_id {
+ fn_warned = check_must_use_def(cx, def_id, s.span, "return value of ", "");
+ } else if type_permits_lack_of_use {
+ // We don't warn about unused unit or uninhabited types.
+ // (See https://github.com/rust-lang/rust/issues/43806 for details.)
+ return;
}
- let used_mutables = cx.tcx.used_mut_nodes.borrow();
- for (_, v) in &mutables {
- if !v.iter().any(|e| used_mutables.contains(e)) {
- cx.span_lint(UNUSED_MUT,
- cx.tcx.hir.span(v[0]),
- "variable does not need to be mutable");
- }
+ let must_use_op = match expr.kind {
+ // Hardcoding operators here seemed more expedient than the
+ // refactoring that would be needed to look up the `#[must_use]`
+ // attribute which does exist on the comparison trait methods
+ hir::ExprKind::Binary(bin_op, ..) => match bin_op.node {
+ hir::BinOpKind::Eq
+ | hir::BinOpKind::Lt
+ | hir::BinOpKind::Le
+ | hir::BinOpKind::Ne
+ | hir::BinOpKind::Ge
+ | hir::BinOpKind::Gt => Some("comparison"),
+ hir::BinOpKind::Add
+ | hir::BinOpKind::Sub
+ | hir::BinOpKind::Div
+ | hir::BinOpKind::Mul
+ | hir::BinOpKind::Rem => Some("arithmetic operation"),
+ hir::BinOpKind::And | hir::BinOpKind::Or => Some("logical operation"),
+ hir::BinOpKind::BitXor
+ | hir::BinOpKind::BitAnd
+ | hir::BinOpKind::BitOr
+ | hir::BinOpKind::Shl
+ | hir::BinOpKind::Shr => Some("bitwise operation"),
+ },
+ hir::ExprKind::Unary(..) => Some("unary operation"),
+ _ => None,
+ };
+
+ if let Some(must_use_op) = must_use_op {
+ cx.struct_span_lint(UNUSED_MUST_USE, expr.span, |lint| {
+ lint.build(&format!("unused {} that must be used", must_use_op)).emit()
+ });
+ op_warned = true;
}
- }
-}
-impl LintPass for UnusedMut {
- fn get_lints(&self) -> LintArray {
- lint_array!(UNUSED_MUT)
- }
-}
+ if !(type_permits_lack_of_use || fn_warned || op_warned) {
+ cx.struct_span_lint(UNUSED_RESULTS, s.span, |lint| lint.build("unused result").emit());
+ }
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedMut {
- fn check_expr(&mut self, cx: &LateContext, e: &hir::Expr) {
- if let hir::ExprMatch(_, ref arms, _) = e.node {
- for a in arms {
- self.check_unused_mut_pat(cx, &a.pats)
+ // Returns whether an error has been emitted (and thus another does not need to be later).
+ fn check_must_use_ty<'tcx>(
+ cx: &LateContext<'_, 'tcx>,
+ ty: Ty<'tcx>,
+ expr: &hir::Expr<'_>,
+ span: Span,
+ descr_pre: &str,
+ descr_post: &str,
+ plural_len: usize,
+ ) -> bool {
+ if ty.is_unit()
+ || cx.tcx.is_ty_uninhabited_from(
+ cx.tcx.parent_module(expr.hir_id).to_def_id(),
+ ty,
+ cx.param_env,
+ )
+ {
+ return true;
}
- }
- }
- fn check_stmt(&mut self, cx: &LateContext, s: &hir::Stmt) {
- if let hir::StmtDecl(ref d, _) = s.node {
- if let hir::DeclLocal(ref l) = d.node {
- self.check_unused_mut_pat(cx, slice::ref_slice(&l.pat));
+ let plural_suffix = pluralize!(plural_len);
+
+ match ty.kind {
+ ty::Adt(..) if ty.is_box() => {
+ let boxed_ty = ty.boxed_ty();
+ let descr_pre = &format!("{}boxed ", descr_pre);
+ check_must_use_ty(cx, boxed_ty, expr, span, descr_pre, descr_post, plural_len)
+ }
+ ty::Adt(def, _) => check_must_use_def(cx, def.did, span, descr_pre, descr_post),
+ ty::Opaque(def, _) => {
+ let mut has_emitted = false;
+ for (predicate, _) in cx.tcx.predicates_of(def).predicates {
+ if let ty::Predicate::Trait(ref poly_trait_predicate, _) = predicate {
+ let trait_ref = poly_trait_predicate.skip_binder().trait_ref;
+ let def_id = trait_ref.def_id;
+ let descr_pre =
+ &format!("{}implementer{} of ", descr_pre, plural_suffix,);
+ if check_must_use_def(cx, def_id, span, descr_pre, descr_post) {
+ has_emitted = true;
+ break;
+ }
+ }
+ }
+ has_emitted
+ }
+ ty::Dynamic(binder, _) => {
+ let mut has_emitted = false;
+ for predicate in binder.skip_binder().iter() {
+ if let ty::ExistentialPredicate::Trait(ref trait_ref) = predicate {
+ let def_id = trait_ref.def_id;
+ let descr_post =
+ &format!(" trait object{}{}", plural_suffix, descr_post,);
+ if check_must_use_def(cx, def_id, span, descr_pre, descr_post) {
+ has_emitted = true;
+ break;
+ }
+ }
+ }
+ has_emitted
+ }
+ ty::Tuple(ref tys) => {
+ let mut has_emitted = false;
+ let spans = if let hir::ExprKind::Tup(comps) = &expr.kind {
+ debug_assert_eq!(comps.len(), tys.len());
+ comps.iter().map(|e| e.span).collect()
+ } else {
+ vec![]
+ };
+ for (i, ty) in tys.iter().map(|k| k.expect_ty()).enumerate() {
+ let descr_post = &format!(" in tuple element {}", i);
+ let span = *spans.get(i).unwrap_or(&span);
+ if check_must_use_ty(cx, ty, expr, span, descr_pre, descr_post, plural_len)
+ {
+ has_emitted = true;
+ }
+ }
+ has_emitted
+ }
+ ty::Array(ty, len) => match len.try_eval_usize(cx.tcx, cx.param_env) {
+ // If the array is definitely non-empty, we can do `#[must_use]` checking.
+ Some(n) if n != 0 => {
+ let descr_pre = &format!("{}array{} of ", descr_pre, plural_suffix,);
+ check_must_use_ty(cx, ty, expr, span, descr_pre, descr_post, n as usize + 1)
+ }
+ // Otherwise, we don't lint, to avoid false positives.
+ _ => false,
+ },
+ _ => false,
}
}
- }
- fn check_fn(&mut self,
- cx: &LateContext,
- _: FnKind,
- _: &hir::FnDecl,
- body: &hir::Body,
- _: Span,
- _: ast::NodeId) {
- for a in &body.arguments {
- self.check_unused_mut_pat(cx, slice::ref_slice(&a.pat));
+ // Returns whether an error has been emitted (and thus another does not need to be later).
+ // FIXME: Args desc_{pre,post}_path could be made lazy by taking Fn() -> &str, but this
+ // would make calling it a big awkward. Could also take String (so args are moved), but
+ // this would still require a copy into the format string, which would only be executed
+ // when needed.
+ fn check_must_use_def(
+ cx: &LateContext<'_, '_>,
+ def_id: DefId,
+ span: Span,
+ descr_pre_path: &str,
+ descr_post_path: &str,
+ ) -> bool {
+ for attr in cx.tcx.get_attrs(def_id).iter() {
+ if attr.check_name(sym::must_use) {
+ cx.struct_span_lint(UNUSED_MUST_USE, span, |lint| {
+ let msg = format!(
+ "unused {}`{}`{} that must be used",
+ descr_pre_path,
+ cx.tcx.def_path_str(def_id),
+ descr_post_path
+ );
+ let mut err = lint.build(&msg);
+ // check for #[must_use = "..."]
+ if let Some(note) = attr.value_str() {
+ err.note(¬e.as_str());
+ }
+ err.emit();
+ });
+ return true;
+ }
+ }
+ false
}
}
}
declare_lint! {
- pub UNUSED_MUST_USE,
+ pub PATH_STATEMENTS,
Warn,
- "unused result of a type flagged as #[must_use]"
+ "path statements with no effect"
}
-declare_lint! {
- pub UNUSED_RESULTS,
- Allow,
- "unused result of an expression in a statement"
+declare_lint_pass!(PathStatements => [PATH_STATEMENTS]);
+
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for PathStatements {
+ fn check_stmt(&mut self, cx: &LateContext<'_, '_>, s: &hir::Stmt<'_>) {
+ if let hir::StmtKind::Semi(ref expr) = s.kind {
+ if let hir::ExprKind::Path(_) = expr.kind {
+ cx.struct_span_lint(PATH_STATEMENTS, s.span, |lint| {
+ lint.build("path statement with no effect").emit()
+ });
+ }
+ }
+ }
}
#[derive(Copy, Clone)]
-pub struct UnusedResults;
+pub struct UnusedAttributes {
+ builtin_attributes: &'static FxHashMap<Symbol, &'static BuiltinAttribute>,
+}
-impl LintPass for UnusedResults {
- fn get_lints(&self) -> LintArray {
- lint_array!(UNUSED_MUST_USE, UNUSED_RESULTS)
+impl UnusedAttributes {
+ pub fn new() -> Self {
+ UnusedAttributes { builtin_attributes: &*BUILTIN_ATTRIBUTE_MAP }
}
}
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedResults {
- fn check_stmt(&mut self, cx: &LateContext, s: &hir::Stmt) {
- let expr = match s.node {
- hir::StmtSemi(ref expr, _) => &**expr,
- _ => return,
- };
+impl_lint_pass!(UnusedAttributes => [UNUSED_ATTRIBUTES]);
- if let hir::ExprRet(..) = expr.node {
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedAttributes {
+ fn check_attribute(&mut self, cx: &LateContext<'_, '_>, attr: &ast::Attribute) {
+ debug!("checking attribute: {:?}", attr);
+
+ if attr.is_doc_comment() {
return;
}
- let t = cx.tables.expr_ty(&expr);
- let warned = match t.sty {
- ty::TyTuple(ref tys, _) if tys.is_empty() => return,
- ty::TyNever => return,
- ty::TyBool => return,
- ty::TyAdt(def, _) => {
- let attrs = cx.tcx.get_attrs(def.did);
- check_must_use(cx, &attrs, s.span)
+ let attr_info = attr.ident().and_then(|ident| self.builtin_attributes.get(&ident.name));
+
+ if let Some(&&(name, ty, ..)) = attr_info {
+ if let AttributeType::Whitelisted = ty {
+ debug!("{:?} is Whitelisted", name);
+ return;
}
- _ => false,
- };
- if !warned {
- cx.span_lint(UNUSED_RESULTS, s.span, "unused result");
}
- fn check_must_use(cx: &LateContext, attrs: &[ast::Attribute], sp: Span) -> bool {
- for attr in attrs {
- if attr.check_name("must_use") {
- let mut msg = "unused result which must be used".to_string();
- // check for #[must_use="..."]
- if let Some(s) = attr.value_str() {
- msg.push_str(": ");
- msg.push_str(&s.as_str());
- }
- cx.span_lint(UNUSED_MUST_USE, sp, &msg);
- return true;
- }
+ if !attr::is_used(attr) {
+ debug!("emitting warning for: {:?}", attr);
+ cx.struct_span_lint(UNUSED_ATTRIBUTES, attr.span, |lint| {
+ lint.build("unused attribute").emit()
+ });
+ // Is it a builtin attribute that must be used at the crate level?
+ if attr_info.map_or(false, |(_, ty, ..)| ty == &AttributeType::CrateLevel) {
+ cx.struct_span_lint(UNUSED_ATTRIBUTES, attr.span, |lint| {
+ let msg = match attr.style {
+ ast::AttrStyle::Outer => {
+ "crate-level attribute should be an inner attribute: add an exclamation \
+ mark: `#![foo]`"
+ }
+ ast::AttrStyle::Inner => "crate-level attribute should be in the root module",
+ };
+ lint.build(msg).emit()
+ });
}
- false
+ } else {
+ debug!("Attr was used: {:?}", attr);
}
}
}
-declare_lint! {
- pub UNUSED_UNSAFE,
- Warn,
- "unnecessary use of an `unsafe` block"
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+enum UnusedDelimsCtx {
+ FunctionArg,
+ MethodArg,
+ AssignedValue,
+ IfCond,
+ WhileCond,
+ ForIterExpr,
+ MatchScrutineeExpr,
+ ReturnValue,
+ BlockRetValue,
+ LetScrutineeExpr,
+ ArrayLenExpr,
+ AnonConst,
}
-#[derive(Copy, Clone)]
-pub struct UnusedUnsafe;
-
-impl LintPass for UnusedUnsafe {
- fn get_lints(&self) -> LintArray {
- lint_array!(UNUSED_UNSAFE)
+impl From<UnusedDelimsCtx> for &'static str {
+ fn from(ctx: UnusedDelimsCtx) -> &'static str {
+ match ctx {
+ UnusedDelimsCtx::FunctionArg => "function argument",
+ UnusedDelimsCtx::MethodArg => "method argument",
+ UnusedDelimsCtx::AssignedValue => "assigned value",
+ UnusedDelimsCtx::IfCond => "`if` condition",
+ UnusedDelimsCtx::WhileCond => "`while` condition",
+ UnusedDelimsCtx::ForIterExpr => "`for` iterator expression",
+ UnusedDelimsCtx::MatchScrutineeExpr => "`match` scrutinee expression",
+ UnusedDelimsCtx::ReturnValue => "`return` value",
+ UnusedDelimsCtx::BlockRetValue => "block return value",
+ UnusedDelimsCtx::LetScrutineeExpr => "`let` scrutinee expression",
+ UnusedDelimsCtx::ArrayLenExpr | UnusedDelimsCtx::AnonConst => "const expression",
+ }
}
}
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedUnsafe {
- fn check_expr(&mut self, cx: &LateContext, e: &hir::Expr) {
- /// Return the NodeId for an enclosing scope that is also `unsafe`
- fn is_enclosed(cx: &LateContext, id: ast::NodeId) -> Option<(String, ast::NodeId)> {
- let parent_id = cx.tcx.hir.get_parent_node(id);
- if parent_id != id {
- if cx.tcx.used_unsafe.borrow().contains(&parent_id) {
- Some(("block".to_string(), parent_id))
- } else if let Some(hir::map::NodeItem(&hir::Item {
- node: hir::ItemFn(_, hir::Unsafety::Unsafe, _, _, _, _),
- ..
- })) = cx.tcx.hir.find(parent_id) {
- Some(("fn".to_string(), parent_id))
+/// Used by both `UnusedParens` and `UnusedBraces` to prevent code duplication.
+trait UnusedDelimLint {
+ const DELIM_STR: &'static str;
+
+ /// Due to `ref` pattern, there can be a difference between using
+ /// `{ expr }` and `expr` in pattern-matching contexts. This means
+ /// that we should only lint `unused_parens` and not `unused_braces`
+ /// in this case.
+ ///
+ /// ```rust
+ /// let mut a = 7;
+ /// let ref b = { a }; // We actually borrow a copy of `a` here.
+ /// a += 1; // By mutating `a` we invalidate any borrows of `a`.
+ /// assert_eq!(b + 1, a); // `b` does not borrow `a`, so we can still use it here.
+ /// ```
+ const LINT_EXPR_IN_PATTERN_MATCHING_CTX: bool;
+
+ // this cannot be a constant is it refers to a static.
+ fn lint(&self) -> &'static Lint;
+
+ fn check_unused_delims_expr(
+ &self,
+ cx: &EarlyContext<'_>,
+ value: &ast::Expr,
+ ctx: UnusedDelimsCtx,
+ followed_by_block: bool,
+ left_pos: Option<BytePos>,
+ right_pos: Option<BytePos>,
+ );
+
+ fn is_expr_delims_necessary(inner: &ast::Expr, followed_by_block: bool) -> bool {
+ followed_by_block
+ && match inner.kind {
+ ExprKind::Ret(_) | ExprKind::Break(..) => true,
+ _ => parser::contains_exterior_struct_lit(&inner),
+ }
+ }
+
+ fn emit_unused_delims_expr(
+ &self,
+ cx: &EarlyContext<'_>,
+ value: &ast::Expr,
+ ctx: UnusedDelimsCtx,
+ left_pos: Option<BytePos>,
+ right_pos: Option<BytePos>,
+ ) {
+ let expr_text = if let Ok(snippet) = cx.sess().source_map().span_to_snippet(value.span) {
+ snippet
+ } else {
+ pprust::expr_to_string(value)
+ };
+ let keep_space = (
+ left_pos.map(|s| s >= value.span.lo()).unwrap_or(false),
+ right_pos.map(|s| s <= value.span.hi()).unwrap_or(false),
+ );
+ self.emit_unused_delims(cx, value.span, &expr_text, ctx.into(), keep_space);
+ }
+
+ fn emit_unused_delims(
+ &self,
+ cx: &EarlyContext<'_>,
+ span: Span,
+ pattern: &str,
+ msg: &str,
+ keep_space: (bool, bool),
+ ) {
+ // FIXME(flip1995): Quick and dirty fix for #70814. This should be fixed in rustdoc
+ // properly.
+ if span == DUMMY_SP {
+ return;
+ }
+
+ cx.struct_span_lint(self.lint(), span, |lint| {
+ let span_msg = format!("unnecessary {} around {}", Self::DELIM_STR, msg);
+ let mut err = lint.build(&span_msg);
+ let mut ate_left_paren = false;
+ let mut ate_right_paren = false;
+ let parens_removed = pattern.trim_matches(|c| match c {
+ '(' | '{' => {
+ if ate_left_paren {
+ false
+ } else {
+ ate_left_paren = true;
+ true
+ }
+ }
+ ')' | '}' => {
+ if ate_right_paren {
+ false
+ } else {
+ ate_right_paren = true;
+ true
+ }
+ }
+ _ => false,
+ });
+
+ let replace = {
+ let mut replace = if keep_space.0 {
+ let mut s = String::from(" ");
+ s.push_str(parens_removed);
+ s
} else {
- is_enclosed(cx, parent_id)
+ String::from(parens_removed)
+ };
+
+ if keep_space.1 {
+ replace.push(' ');
}
- } else {
- None
+ replace
+ };
+
+ let suggestion = format!("remove these {}", Self::DELIM_STR);
+
+ err.span_suggestion_short(span, &suggestion, replace, Applicability::MachineApplicable);
+ err.emit();
+ });
+ }
+
+ fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
+ use rustc_ast::ast::ExprKind::*;
+ let (value, ctx, followed_by_block, left_pos, right_pos) = match e.kind {
+ // Do not lint `unused_braces` in `if let` expressions.
+ If(ref cond, ref block, ..)
+ if !matches!(cond.kind, Let(_, _)) || Self::LINT_EXPR_IN_PATTERN_MATCHING_CTX =>
+ {
+ let left = e.span.lo() + rustc_span::BytePos(2);
+ let right = block.span.lo();
+ (cond, UnusedDelimsCtx::IfCond, true, Some(left), Some(right))
}
- }
- if let hir::ExprBlock(ref blk) = e.node {
- // Don't warn about generated blocks, that'll just pollute the output.
- if blk.rules == hir::UnsafeBlock(hir::UserProvided) &&
- !cx.tcx.used_unsafe.borrow().contains(&blk.id) {
-
- let mut db = cx.struct_span_lint(UNUSED_UNSAFE, blk.span,
- "unnecessary `unsafe` block");
-
- db.span_label(blk.span, "unnecessary `unsafe` block");
- if let Some((kind, id)) = is_enclosed(cx, blk.id) {
- db.span_note(cx.tcx.hir.span(id),
- &format!("because it's nested under this `unsafe` {}", kind));
+
+ While(ref cond, ref block, ..) => {
+ let left = e.span.lo() + rustc_span::BytePos(5);
+ let right = block.span.lo();
+ (cond, UnusedDelimsCtx::WhileCond, true, Some(left), Some(right))
+ }
+
+ ForLoop(_, ref cond, ref block, ..) => {
+ (cond, UnusedDelimsCtx::ForIterExpr, true, None, Some(block.span.lo()))
+ }
+
+ Match(ref head, _) if Self::LINT_EXPR_IN_PATTERN_MATCHING_CTX => {
+ let left = e.span.lo() + rustc_span::BytePos(5);
+ (head, UnusedDelimsCtx::MatchScrutineeExpr, true, Some(left), None)
+ }
+
+ Ret(Some(ref value)) => {
+ let left = e.span.lo() + rustc_span::BytePos(3);
+ (value, UnusedDelimsCtx::ReturnValue, false, Some(left), None)
+ }
+
+ Assign(_, ref value, _) | AssignOp(.., ref value) => {
+ (value, UnusedDelimsCtx::AssignedValue, false, None, None)
+ }
+ // either function/method call, or something this lint doesn't care about
+ ref call_or_other => {
+ let (args_to_check, ctx) = match *call_or_other {
+ Call(_, ref args) => (&args[..], UnusedDelimsCtx::FunctionArg),
+ // first "argument" is self (which sometimes needs delims)
+ MethodCall(_, ref args) => (&args[1..], UnusedDelimsCtx::MethodArg),
+ // actual catch-all arm
+ _ => {
+ return;
+ }
+ };
+ // Don't lint if this is a nested macro expansion: otherwise, the lint could
+ // trigger in situations that macro authors shouldn't have to care about, e.g.,
+ // when a parenthesized token tree matched in one macro expansion is matched as
+ // an expression in another and used as a fn/method argument (Issue #47775)
+ if e.span.ctxt().outer_expn_data().call_site.from_expansion() {
+ return;
}
- db.emit();
+ for arg in args_to_check {
+ self.check_unused_delims_expr(cx, arg, ctx, false, None, None);
+ }
+ return;
}
+ };
+ self.check_unused_delims_expr(cx, &value, ctx, followed_by_block, left_pos, right_pos);
+ }
+
+ fn check_stmt(&mut self, cx: &EarlyContext<'_>, s: &ast::Stmt) {
+ match s.kind {
+ StmtKind::Local(ref local) if Self::LINT_EXPR_IN_PATTERN_MATCHING_CTX => {
+ if let Some(ref value) = local.init {
+ self.check_unused_delims_expr(
+ cx,
+ &value,
+ UnusedDelimsCtx::AssignedValue,
+ false,
+ None,
+ None,
+ );
+ }
+ }
+ StmtKind::Expr(ref expr) => {
+ self.check_unused_delims_expr(
+ cx,
+ &expr,
+ UnusedDelimsCtx::BlockRetValue,
+ false,
+ None,
+ None,
+ );
+ }
+ _ => {}
+ }
+ }
+
+ fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
+ use ast::ItemKind::*;
+
+ if let Const(.., Some(expr)) | Static(.., Some(expr)) = &item.kind {
+ self.check_unused_delims_expr(
+ cx,
+ expr,
+ UnusedDelimsCtx::AssignedValue,
+ false,
+ None,
+ None,
+ );
}
}
}
declare_lint! {
- pub PATH_STATEMENTS,
+ pub(super) UNUSED_PARENS,
Warn,
- "path statements with no effect"
+ "`if`, `match`, `while` and `return` do not need parentheses"
}
-#[derive(Copy, Clone)]
-pub struct PathStatements;
+declare_lint_pass!(UnusedParens => [UNUSED_PARENS]);
-impl LintPass for PathStatements {
- fn get_lints(&self) -> LintArray {
- lint_array!(PATH_STATEMENTS)
+impl UnusedDelimLint for UnusedParens {
+ const DELIM_STR: &'static str = "parentheses";
+
+ const LINT_EXPR_IN_PATTERN_MATCHING_CTX: bool = true;
+
+ fn lint(&self) -> &'static Lint {
+ UNUSED_PARENS
}
-}
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for PathStatements {
- fn check_stmt(&mut self, cx: &LateContext, s: &hir::Stmt) {
- if let hir::StmtSemi(ref expr, _) = s.node {
- if let hir::ExprPath(_) = expr.node {
- cx.span_lint(PATH_STATEMENTS, s.span, "path statement with no effect");
+ fn check_unused_delims_expr(
+ &self,
+ cx: &EarlyContext<'_>,
+ value: &ast::Expr,
+ ctx: UnusedDelimsCtx,
+ followed_by_block: bool,
+ left_pos: Option<BytePos>,
+ right_pos: Option<BytePos>,
+ ) {
+ match value.kind {
+ ast::ExprKind::Paren(ref inner) => {
+ if !Self::is_expr_delims_necessary(inner, followed_by_block)
+ && value.attrs.is_empty()
+ && !value.span.from_expansion()
+ {
+ self.emit_unused_delims_expr(cx, value, ctx, left_pos, right_pos)
+ }
}
+ ast::ExprKind::Let(_, ref expr) => {
+ // FIXME(#60336): Properly handle `let true = (false && true)`
+ // actually needing the parenthesis.
+ self.check_unused_delims_expr(
+ cx,
+ expr,
+ UnusedDelimsCtx::LetScrutineeExpr,
+ followed_by_block,
+ None,
+ None,
+ );
+ }
+ _ => {}
}
}
}
-declare_lint! {
- pub UNUSED_ATTRIBUTES,
- Warn,
- "detects attributes that were not used by the compiler"
+impl UnusedParens {
+ fn check_unused_parens_pat(
+ &self,
+ cx: &EarlyContext<'_>,
+ value: &ast::Pat,
+ avoid_or: bool,
+ avoid_mut: bool,
+ ) {
+ use ast::{BindingMode, Mutability, PatKind};
+
+ if let PatKind::Paren(inner) = &value.kind {
+ match inner.kind {
+ // The lint visitor will visit each subpattern of `p`. We do not want to lint
+ // any range pattern no matter where it occurs in the pattern. For something like
+ // `&(a..=b)`, there is a recursive `check_pat` on `a` and `b`, but we will assume
+ // that if there are unnecessary parens they serve a purpose of readability.
+ PatKind::Range(..) => return,
+ // Avoid `p0 | .. | pn` if we should.
+ PatKind::Or(..) if avoid_or => return,
+ // Avoid `mut x` and `mut x @ p` if we should:
+ PatKind::Ident(BindingMode::ByValue(Mutability::Mut), ..) if avoid_mut => return,
+ // Otherwise proceed with linting.
+ _ => {}
+ }
+
+ let pattern_text =
+ if let Ok(snippet) = cx.sess().source_map().span_to_snippet(value.span) {
+ snippet
+ } else {
+ pprust::pat_to_string(value)
+ };
+ self.emit_unused_delims(cx, value.span, &pattern_text, "pattern", (false, false));
+ }
+ }
}
-#[derive(Copy, Clone)]
-pub struct UnusedAttributes;
+impl EarlyLintPass for UnusedParens {
+ fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
+ if let ExprKind::Let(ref pat, ..) | ExprKind::ForLoop(ref pat, ..) = e.kind {
+ self.check_unused_parens_pat(cx, pat, false, false);
+ }
-impl LintPass for UnusedAttributes {
- fn get_lints(&self) -> LintArray {
- lint_array!(UNUSED_ATTRIBUTES)
+ <Self as UnusedDelimLint>::check_expr(self, cx, e)
}
-}
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedAttributes {
- fn check_attribute(&mut self, cx: &LateContext, attr: &ast::Attribute) {
- debug!("checking attribute: {:?}", attr);
- let name = unwrap_or!(attr.name(), return);
-
- // Note that check_name() marks the attribute as used if it matches.
- for &(ref name, ty, _) in BUILTIN_ATTRIBUTES {
- match ty {
- AttributeType::Whitelisted if attr.check_name(name) => {
- debug!("{:?} is Whitelisted", name);
- break;
- }
- _ => (),
- }
+ fn check_pat(&mut self, cx: &EarlyContext<'_>, p: &ast::Pat) {
+ use ast::{Mutability, PatKind::*};
+ match &p.kind {
+ // Do not lint on `(..)` as that will result in the other arms being useless.
+ Paren(_)
+ // The other cases do not contain sub-patterns.
+ | Wild | Rest | Lit(..) | MacCall(..) | Range(..) | Ident(.., None) | Path(..) => {},
+ // These are list-like patterns; parens can always be removed.
+ TupleStruct(_, ps) | Tuple(ps) | Slice(ps) | Or(ps) => for p in ps {
+ self.check_unused_parens_pat(cx, p, false, false);
+ },
+ Struct(_, fps, _) => for f in fps {
+ self.check_unused_parens_pat(cx, &f.pat, false, false);
+ },
+ // Avoid linting on `i @ (p0 | .. | pn)` and `box (p0 | .. | pn)`, #64106.
+ Ident(.., Some(p)) | Box(p) => self.check_unused_parens_pat(cx, p, true, false),
+ // Avoid linting on `&(mut x)` as `&mut x` has a different meaning, #55342.
+ // Also avoid linting on `& mut? (p0 | .. | pn)`, #64106.
+ Ref(p, m) => self.check_unused_parens_pat(cx, p, true, *m == Mutability::Not),
}
+ }
- let plugin_attributes = cx.sess().plugin_attributes.borrow_mut();
- for &(ref name, ty) in plugin_attributes.iter() {
- if ty == AttributeType::Whitelisted && attr.check_name(&name) {
- debug!("{:?} (plugin attr) is whitelisted with ty {:?}", name, ty);
- break;
- }
+ fn check_anon_const(&mut self, cx: &EarlyContext<'_>, c: &ast::AnonConst) {
+ self.check_unused_delims_expr(cx, &c.value, UnusedDelimsCtx::AnonConst, false, None, None);
+ }
+
+ fn check_stmt(&mut self, cx: &EarlyContext<'_>, s: &ast::Stmt) {
+ if let StmtKind::Local(ref local) = s.kind {
+ self.check_unused_parens_pat(cx, &local.pat, false, false);
}
- if !attr::is_used(attr) {
- debug!("Emitting warning for: {:?}", attr);
- cx.span_lint(UNUSED_ATTRIBUTES, attr.span, "unused attribute");
- // Is it a builtin attribute that must be used at the crate level?
- let known_crate = BUILTIN_ATTRIBUTES.iter()
- .find(|&&(builtin, ty, _)| name == builtin && ty == AttributeType::CrateLevel)
- .is_some();
-
- // Has a plugin registered this attribute as one which must be used at
- // the crate level?
- let plugin_crate = plugin_attributes.iter()
- .find(|&&(ref x, t)| name == &**x && AttributeType::CrateLevel == t)
- .is_some();
- if known_crate || plugin_crate {
- let msg = match attr.style {
- ast::AttrStyle::Outer => {
- "crate-level attribute should be an inner attribute: add an exclamation \
- mark: #![foo]"
- }
- ast::AttrStyle::Inner => "crate-level attribute should be in the root module",
- };
- cx.span_lint(UNUSED_ATTRIBUTES, attr.span, msg);
+ <Self as UnusedDelimLint>::check_stmt(self, cx, s)
+ }
+
+ fn check_param(&mut self, cx: &EarlyContext<'_>, param: &ast::Param) {
+ self.check_unused_parens_pat(cx, ¶m.pat, true, false);
+ }
+
+ fn check_arm(&mut self, cx: &EarlyContext<'_>, arm: &ast::Arm) {
+ self.check_unused_parens_pat(cx, &arm.pat, false, false);
+ }
+
+ fn check_ty(&mut self, cx: &EarlyContext<'_>, ty: &ast::Ty) {
+ if let &ast::TyKind::Paren(ref r) = &ty.kind {
+ match &r.kind {
+ &ast::TyKind::TraitObject(..) => {}
+ &ast::TyKind::ImplTrait(_, ref bounds) if bounds.len() > 1 => {}
+ &ast::TyKind::Array(_, ref len) => {
+ self.check_unused_delims_expr(
+ cx,
+ &len.value,
+ UnusedDelimsCtx::ArrayLenExpr,
+ false,
+ None,
+ None,
+ );
+ }
+ _ => {
+ let pattern_text =
+ if let Ok(snippet) = cx.sess().source_map().span_to_snippet(ty.span) {
+ snippet
+ } else {
+ pprust::ty_to_string(ty)
+ };
+
+ self.emit_unused_delims(cx, ty.span, &pattern_text, "type", (false, false));
+ }
}
- } else {
- debug!("Attr was used: {:?}", attr);
}
}
+
+ fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
+ <Self as UnusedDelimLint>::check_item(self, cx, item)
+ }
}
declare_lint! {
- UNUSED_PARENS,
+ pub(super) UNUSED_BRACES,
Warn,
- "`if`, `match`, `while` and `return` do not need parentheses"
+ "unnecessary braces around an expression"
}
-#[derive(Copy, Clone)]
-pub struct UnusedParens;
+declare_lint_pass!(UnusedBraces => [UNUSED_BRACES]);
-impl UnusedParens {
- fn check_unused_parens_core(&self,
- cx: &EarlyContext,
- value: &ast::Expr,
- msg: &str,
- struct_lit_needs_parens: bool) {
- if let ast::ExprKind::Paren(ref inner) = value.node {
- let necessary = struct_lit_needs_parens && contains_exterior_struct_lit(&inner);
- if !necessary {
- cx.span_lint(UNUSED_PARENS,
- value.span,
- &format!("unnecessary parentheses around {}", msg))
- }
- }
+impl UnusedDelimLint for UnusedBraces {
+ const DELIM_STR: &'static str = "braces";
- /// Expressions that syntactically contain an "exterior" struct
- /// literal i.e. not surrounded by any parens or other
- /// delimiters, e.g. `X { y: 1 }`, `X { y: 1 }.method()`, `foo
- /// == X { y: 1 }` and `X { y: 1 } == foo` all do, but `(X {
- /// y: 1 }) == foo` does not.
- fn contains_exterior_struct_lit(value: &ast::Expr) -> bool {
- match value.node {
- ast::ExprKind::Struct(..) => true,
-
- ast::ExprKind::Assign(ref lhs, ref rhs) |
- ast::ExprKind::AssignOp(_, ref lhs, ref rhs) |
- ast::ExprKind::Binary(_, ref lhs, ref rhs) => {
- // X { y: 1 } + X { y: 2 }
- contains_exterior_struct_lit(&lhs) || contains_exterior_struct_lit(&rhs)
- }
- ast::ExprKind::Unary(_, ref x) |
- ast::ExprKind::Cast(ref x, _) |
- ast::ExprKind::Type(ref x, _) |
- ast::ExprKind::Field(ref x, _) |
- ast::ExprKind::TupField(ref x, _) |
- ast::ExprKind::Index(ref x, _) => {
- // &X { y: 1 }, X { y: 1 }.y
- contains_exterior_struct_lit(&x)
- }
+ const LINT_EXPR_IN_PATTERN_MATCHING_CTX: bool = false;
- ast::ExprKind::MethodCall(.., ref exprs) => {
- // X { y: 1 }.bar(...)
- contains_exterior_struct_lit(&exprs[0])
- }
+ fn lint(&self) -> &'static Lint {
+ UNUSED_BRACES
+ }
- _ => false,
+ fn check_unused_delims_expr(
+ &self,
+ cx: &EarlyContext<'_>,
+ value: &ast::Expr,
+ ctx: UnusedDelimsCtx,
+ followed_by_block: bool,
+ left_pos: Option<BytePos>,
+ right_pos: Option<BytePos>,
+ ) {
+ match value.kind {
+ ast::ExprKind::Block(ref inner, None)
+ if inner.rules == ast::BlockCheckMode::Default =>
+ {
+ // emit a warning under the following conditions:
+ //
+ // - the block does not have a label
+ // - the block is not `unsafe`
+ // - the block contains exactly one expression (do not lint `{ expr; }`)
+ // - `followed_by_block` is true and the internal expr may contain a `{`
+ // - the block is not multiline (do not lint multiline match arms)
+ // ```
+ // match expr {
+ // Pattern => {
+ // somewhat_long_expression
+ // }
+ // // ...
+ // }
+ // ```
+ // - the block has no attribute and was not created inside a macro
+ // - if the block is an `anon_const`, the inner expr must be a literal
+ // (do not lint `struct A<const N: usize>; let _: A<{ 2 + 3 }>;`)
+ //
+ // FIXME(const_generics): handle paths when #67075 is fixed.
+ if let [stmt] = inner.stmts.as_slice() {
+ if let ast::StmtKind::Expr(ref expr) = stmt.kind {
+ if !Self::is_expr_delims_necessary(expr, followed_by_block)
+ && (ctx != UnusedDelimsCtx::AnonConst
+ || matches!(expr.kind, ast::ExprKind::Lit(_)))
+ // array length expressions are checked during `check_anon_const` and `check_ty`,
+ // once as `ArrayLenExpr` and once as `AnonConst`.
+ //
+ // As we do not want to lint this twice, we do not emit an error for
+ // `ArrayLenExpr` if `AnonConst` would do the same.
+ && (ctx != UnusedDelimsCtx::ArrayLenExpr
+ || !matches!(expr.kind, ast::ExprKind::Lit(_)))
+ && !cx.sess().source_map().is_multiline(value.span)
+ && value.attrs.is_empty()
+ && !value.span.from_expansion()
+ {
+ self.emit_unused_delims_expr(cx, value, ctx, left_pos, right_pos)
+ }
+ }
+ }
+ }
+ ast::ExprKind::Let(_, ref expr) => {
+ // FIXME(#60336): Properly handle `let true = (false && true)`
+ // actually needing the parenthesis.
+ self.check_unused_delims_expr(
+ cx,
+ expr,
+ UnusedDelimsCtx::LetScrutineeExpr,
+ followed_by_block,
+ None,
+ None,
+ );
}
+ _ => {}
}
}
}
-impl LintPass for UnusedParens {
- fn get_lints(&self) -> LintArray {
- lint_array!(UNUSED_PARENS)
+impl EarlyLintPass for UnusedBraces {
+ fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
+ <Self as UnusedDelimLint>::check_expr(self, cx, e)
}
-}
-impl EarlyLintPass for UnusedParens {
- fn check_expr(&mut self, cx: &EarlyContext, e: &ast::Expr) {
- use syntax::ast::ExprKind::*;
- let (value, msg, struct_lit_needs_parens) = match e.node {
- If(ref cond, ..) => (cond, "`if` condition", true),
- While(ref cond, ..) => (cond, "`while` condition", true),
- IfLet(_, ref cond, ..) => (cond, "`if let` head expression", true),
- WhileLet(_, ref cond, ..) => (cond, "`while let` head expression", true),
- ForLoop(_, ref cond, ..) => (cond, "`for` head expression", true),
- Match(ref head, _) => (head, "`match` head expression", true),
- Ret(Some(ref value)) => (value, "`return` value", false),
- Assign(_, ref value) => (value, "assigned value", false),
- AssignOp(.., ref value) => (value, "assigned value", false),
- InPlace(_, ref value) => (value, "emplacement value", false),
- _ => return,
- };
- self.check_unused_parens_core(cx, &value, msg, struct_lit_needs_parens);
+ fn check_anon_const(&mut self, cx: &EarlyContext<'_>, c: &ast::AnonConst) {
+ self.check_unused_delims_expr(cx, &c.value, UnusedDelimsCtx::AnonConst, false, None, None);
}
- fn check_stmt(&mut self, cx: &EarlyContext, s: &ast::Stmt) {
- let (value, msg) = match s.node {
- ast::StmtKind::Local(ref local) => {
- match local.init {
- Some(ref value) => (value, "assigned value"),
- None => return,
- }
+ fn check_stmt(&mut self, cx: &EarlyContext<'_>, s: &ast::Stmt) {
+ <Self as UnusedDelimLint>::check_stmt(self, cx, s)
+ }
+
+ fn check_ty(&mut self, cx: &EarlyContext<'_>, ty: &ast::Ty) {
+ if let &ast::TyKind::Paren(ref r) = &ty.kind {
+ if let ast::TyKind::Array(_, ref len) = r.kind {
+ self.check_unused_delims_expr(
+ cx,
+ &len.value,
+ UnusedDelimsCtx::ArrayLenExpr,
+ false,
+ None,
+ None,
+ );
}
- _ => return,
- };
- self.check_unused_parens_core(cx, &value, msg, false);
+ }
+ }
+
+ fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
+ <Self as UnusedDelimLint>::check_item(self, cx, item)
}
}
"unnecessary braces around an imported item"
}
-#[derive(Copy, Clone)]
-pub struct UnusedImportBraces;
+declare_lint_pass!(UnusedImportBraces => [UNUSED_IMPORT_BRACES]);
+
+impl UnusedImportBraces {
+ fn check_use_tree(&self, cx: &EarlyContext<'_>, use_tree: &ast::UseTree, item: &ast::Item) {
+ if let ast::UseTreeKind::Nested(ref items) = use_tree.kind {
+ // Recursively check nested UseTrees
+ for &(ref tree, _) in items {
+ self.check_use_tree(cx, tree, item);
+ }
+
+ // Trigger the lint only if there is one nested item
+ if items.len() != 1 {
+ return;
+ }
-impl LintPass for UnusedImportBraces {
- fn get_lints(&self) -> LintArray {
- lint_array!(UNUSED_IMPORT_BRACES)
+ // Trigger the lint if the nested item is a non-self single item
+ let node_name = match items[0].0.kind {
+ ast::UseTreeKind::Simple(rename, ..) => {
+ let orig_ident = items[0].0.prefix.segments.last().unwrap().ident;
+ if orig_ident.name == kw::SelfLower {
+ return;
+ }
+ rename.unwrap_or(orig_ident).name
+ }
+ ast::UseTreeKind::Glob => Symbol::intern("*"),
+ ast::UseTreeKind::Nested(_) => return,
+ };
+
+ cx.struct_span_lint(UNUSED_IMPORT_BRACES, item.span, |lint| {
+ lint.build(&format!("braces around {} is unnecessary", node_name)).emit()
+ });
+ }
}
}
impl EarlyLintPass for UnusedImportBraces {
- fn check_item(&mut self, cx: &EarlyContext, item: &ast::Item) {
- if let ast::ItemKind::Use(ref view_path) = item.node {
- if let ast::ViewPathList(_, ref items) = view_path.node {
- if items.len() == 1 && items[0].node.name.name != keywords::SelfValue.name() {
- let msg = format!("braces around {} is unnecessary", items[0].node.name);
- cx.span_lint(UNUSED_IMPORT_BRACES, item.span, &msg);
- }
- }
+ fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
+ if let ast::ItemKind::Use(ref use_tree) = item.kind {
+ self.check_use_tree(cx, use_tree, item);
}
}
}
declare_lint! {
- UNUSED_ALLOCATION,
+ pub(super) UNUSED_ALLOCATION,
Warn,
"detects unnecessary allocations that can be eliminated"
}
-#[derive(Copy, Clone)]
-pub struct UnusedAllocation;
-
-impl LintPass for UnusedAllocation {
- fn get_lints(&self) -> LintArray {
- lint_array!(UNUSED_ALLOCATION)
- }
-}
+declare_lint_pass!(UnusedAllocation => [UNUSED_ALLOCATION]);
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedAllocation {
- fn check_expr(&mut self, cx: &LateContext, e: &hir::Expr) {
- match e.node {
- hir::ExprBox(_) => {}
+ fn check_expr(&mut self, cx: &LateContext<'_, '_>, e: &hir::Expr<'_>) {
+ match e.kind {
+ hir::ExprKind::Box(_) => {}
_ => return,
}
for adj in cx.tables.expr_adjustments(e) {
if let adjustment::Adjust::Borrow(adjustment::AutoBorrow::Ref(_, m)) = adj.kind {
- let msg = match m {
- hir::MutImmutable => "unnecessary allocation, use & instead",
- hir::MutMutable => "unnecessary allocation, use &mut instead"
- };
- cx.span_lint(UNUSED_ALLOCATION, e.span, msg);
+ cx.struct_span_lint(UNUSED_ALLOCATION, e.span, |lint| {
+ let msg = match m {
+ adjustment::AutoBorrowMutability::Not => {
+ "unnecessary allocation, use `&` instead"
+ }
+ adjustment::AutoBorrowMutability::Mut { .. } => {
+ "unnecessary allocation, use `&mut` instead"
+ }
+ };
+ lint.build(msg).emit()
+ });
}
}
}
projects / rustc.git / blobdiff