-// 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::hir::def::Def;
-use rustc::hir::def_id::DefId;
-use rustc::ty;
-use rustc::ty::adjustment;
-use lint::{LateContext, EarlyContext, LintContext, LintArray};
-use lint::{LintPass, EarlyLintPass, LateLintPass};
-
-use syntax::ast;
-use syntax::attr;
-use syntax::feature_gate::{BUILTIN_ATTRIBUTES, AttributeType};
-use syntax::print::pprust;
-use syntax::symbol::keywords;
-use syntax::util::parser;
-use syntax_pos::Span;
-
-use rustc::hir;
+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_MUST_USE,
Warn,
- "unused result of a type flagged as #[must_use]"
+ "unused result of a type flagged as `#[must_use]`",
+ report_in_external_macro
}
declare_lint! {
"unused result of an expression in a statement"
}
-#[derive(Copy, Clone)]
-pub struct UnusedResults;
-
-impl LintPass for UnusedResults {
- fn get_lints(&self) -> LintArray {
- lint_array!(UNUSED_MUST_USE, UNUSED_RESULTS)
- }
-}
+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.node {
- hir::StmtSemi(ref expr, _) => &**expr,
+ 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::ExprRet(..) = expr.node {
+ if let hir::ExprKind::Ret(..) = expr.kind {
return;
}
- let t = cx.tables.expr_ty(&expr);
- let ty_warned = match t.sty {
- ty::TyTuple(ref tys) if tys.is_empty() => return,
- ty::TyNever => return,
- ty::TyAdt(def, _) => {
- if def.variants.is_empty() {
- return;
- } else {
- check_must_use(cx, def.did, s.span, "")
- }
- },
- _ => false,
- };
+ 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 = match expr.node {
- hir::ExprCall(ref callee, _) => {
- match callee.node {
- hir::ExprPath(ref qpath) => {
- let def = cx.tables.qpath_def(qpath, callee.hir_id);
- if let Def::Fn(_) = def {
- Some(def)
- } else { // `Def::Local` if it was a closure, for which we
- None // do not currently support must-use linting
+ 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
+ }
+ _ => None,
}
- },
- hir::ExprMethodCall(..) => {
- cx.tables.type_dependent_defs().get(expr.hir_id).cloned()
- },
- _ => None
+ }
+ hir::ExprKind::MethodCall(..) => cx.tables.type_dependent_def_id(expr.hir_id),
+ _ => None,
};
- if let Some(def) = maybe_def {
- let def_id = def.def_id();
- fn_warned = check_must_use(cx, def_id, s.span, "return value of ");
+ 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 must_use_op = match expr.node {
+
+ 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::ExprBinary(bin_op, ..) => {
- match bin_op.node {
- hir::BiEq | hir::BiLt | hir::BiLe | hir::BiNe | hir::BiGe | hir::BiGt => {
- Some("comparison")
- },
- hir::BiAdd | hir::BiSub | hir::BiDiv | hir::BiMul | hir::BiRem => {
- Some("arithmetic operation")
- },
- hir::BiAnd | hir::BiOr => {
- Some("logical operation")
- },
- hir::BiBitXor | hir::BiBitAnd | hir::BiBitOr | hir::BiShl | hir::BiShr => {
- Some("bitwise operation")
- },
- }
+ 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::ExprUnary(..) => Some("unary operation"),
- _ => None
+ hir::ExprKind::Unary(..) => Some("unary operation"),
+ _ => None,
};
if let Some(must_use_op) = must_use_op {
- cx.span_lint(UNUSED_MUST_USE, expr.span,
- &format!("unused {} which must be used", 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;
}
- if !(ty_warned || fn_warned || op_warned) {
- cx.span_lint(UNUSED_RESULTS, s.span, "unused result");
+ if !(type_permits_lack_of_use || fn_warned || op_warned) {
+ cx.struct_span_lint(UNUSED_RESULTS, s.span, |lint| lint.build("unused result").emit());
}
- fn check_must_use(cx: &LateContext, def_id: DefId, sp: Span, describe_path: &str) -> bool {
- for attr in cx.tcx.get_attrs(def_id).iter() {
- if attr.check_name("must_use") {
- let mut msg = format!("unused {}`{}` which must be used",
- describe_path, cx.tcx.item_path_str(def_id));
- let mut err = cx.struct_span_lint(UNUSED_MUST_USE, sp, &msg);
- // check for #[must_use = "..."]
- if let Some(note) = attr.value_str() {
- err.note(¬e.as_str());
+ // 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;
+ }
+
+ 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)
}
- err.emit();
+ // Otherwise, we don't lint, to avoid false positives.
+ _ => false,
+ },
+ _ => false,
+ }
+ }
+
+ // 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;
}
}
"path statements with no effect"
}
-#[derive(Copy, Clone)]
-pub struct PathStatements;
-
-impl LintPass for PathStatements {
- fn get_lints(&self) -> LintArray {
- lint_array!(PATH_STATEMENTS)
- }
-}
+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::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_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()
+ });
}
}
}
}
-declare_lint! {
- pub UNUSED_ATTRIBUTES,
- Warn,
- "detects attributes that were not used by the compiler"
-}
-
#[derive(Copy, Clone)]
-pub struct UnusedAttributes;
+pub struct UnusedAttributes {
+ builtin_attributes: &'static FxHashMap<Symbol, &'static BuiltinAttribute>,
+}
-impl LintPass for UnusedAttributes {
- fn get_lints(&self) -> LintArray {
- lint_array!(UNUSED_ATTRIBUTES)
+impl UnusedAttributes {
+ pub fn new() -> Self {
+ UnusedAttributes { builtin_attributes: &*BUILTIN_ATTRIBUTE_MAP }
}
}
+impl_lint_pass!(UnusedAttributes => [UNUSED_ATTRIBUTES]);
+
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedAttributes {
- fn check_attribute(&mut self, cx: &LateContext, attr: &ast::Attribute) {
+ fn check_attribute(&mut self, cx: &LateContext<'_, '_>, attr: &ast::Attribute) {
debug!("checking attribute: {:?}", attr);
- // 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;
- }
- _ => (),
- }
+
+ if attr.is_doc_comment() {
+ return;
}
- 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;
+ 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;
}
}
- let name = attr.name();
if !attr::is_used(attr) {
- debug!("Emitting warning for: {:?}", attr);
- cx.span_lint(UNUSED_ATTRIBUTES, attr.span, "unused attribute");
+ 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?
- 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);
+ 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()
+ });
}
} else {
debug!("Attr was used: {:?}", attr);
}
}
-declare_lint! {
- pub(super) UNUSED_PARENS,
- Warn,
- "`if`, `match`, `while` and `return` do not need parentheses"
+#[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 UnusedParens;
-
-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 &&
- parser::contains_exterior_struct_lit(&inner);
- if !necessary {
- let span_msg = format!("unnecessary parentheses around {}", msg);
- let mut err = cx.struct_span_lint(UNUSED_PARENS,
- value.span,
- &span_msg);
- // Remove exactly one pair of parentheses (rather than naïvely
- // stripping all paren characters)
- let mut ate_left_paren = false;
- let mut ate_right_paren = false;
- let parens_removed = pprust::expr_to_string(value)
- .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,
- }
- }).to_owned();
- err.span_suggestion_short(value.span,
- "remove these parentheses",
- parens_removed);
- err.emit();
- }
+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 LintPass for UnusedParens {
- fn get_lints(&self) -> LintArray {
- lint_array!(UNUSED_PARENS)
+/// 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),
+ }
}
-}
-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),
+ 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 {
+ String::from(parens_removed)
+ };
+
+ if keep_space.1 {
+ replace.push(' ');
+ }
+ 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))
+ }
+
+ 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;
- let call_kind;
- match *call_or_other {
- Call(_, ref args) => {
- call_kind = "function";
- args_to_check = &args[..];
- },
- MethodCall(_, ref args) => {
- call_kind = "method";
- // first "argument" is self (which sometimes needs parens)
- args_to_check = &args[1..];
- }
+ 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; }
- }
+ _ => {
+ 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_info()
- .map_or(false, |info| info.call_site.ctxt().outer()
- .expn_info().is_some()) {
- return;
+ if e.span.ctxt().outer_expn_data().call_site.from_expansion() {
+ return;
}
- let msg = format!("{} argument", call_kind);
for arg in args_to_check {
- self.check_unused_parens_core(cx, arg, &msg, false);
+ self.check_unused_delims_expr(cx, arg, ctx, false, None, None);
}
return;
}
};
- self.check_unused_parens_core(cx, &value, msg, struct_lit_needs_parens);
+ 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) {
- 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) {
+ 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,
+ );
}
}
- _ => return,
- };
- self.check_unused_parens_core(cx, &value, msg, false);
+ 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(super) UNUSED_PARENS,
+ Warn,
+ "`if`, `match`, `while` and `return` do not need parentheses"
+}
+
+declare_lint_pass!(UnusedParens => [UNUSED_PARENS]);
+
+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
+ }
+
+ 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,
+ );
+ }
+ _ => {}
+ }
+ }
+}
+
+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));
+ }
+ }
+}
+
+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);
+ }
+
+ <Self as UnusedDelimLint>::check_expr(self, cx, e)
+ }
+
+ 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),
+ }
+ }
+
+ 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);
+ }
+
+ <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));
+ }
+ }
+ }
+ }
+
+ fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
+ <Self as UnusedDelimLint>::check_item(self, cx, item)
+ }
+}
+
+declare_lint! {
+ pub(super) UNUSED_BRACES,
+ Warn,
+ "unnecessary braces around an expression"
+}
+
+declare_lint_pass!(UnusedBraces => [UNUSED_BRACES]);
+
+impl UnusedDelimLint for UnusedBraces {
+ const DELIM_STR: &'static str = "braces";
+
+ const LINT_EXPR_IN_PATTERN_MATCHING_CTX: bool = false;
+
+ fn lint(&self) -> &'static Lint {
+ UNUSED_BRACES
+ }
+
+ 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 EarlyLintPass for UnusedBraces {
+ fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
+ <Self as UnusedDelimLint>::check_expr(self, cx, e)
+ }
+
+ 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) {
+ <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,
+ );
+ }
+ }
+ }
+
+ 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) {
+ 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 {
}
// Trigger the lint if the nested item is a non-self single item
- let node_ident;
- match items[0].0.kind {
+ 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 == keywords::SelfValue.name() {
+ if orig_ident.name == kw::SelfLower {
return;
- } else {
- node_ident = rename.unwrap_or(orig_ident);
}
+ rename.unwrap_or(orig_ident).name
}
- ast::UseTreeKind::Glob => {
- node_ident = ast::Ident::from_str("*");
- }
- ast::UseTreeKind::Nested(_) => {
- return;
- }
- }
+ ast::UseTreeKind::Glob => Symbol::intern("*"),
+ ast::UseTreeKind::Nested(_) => return,
+ };
- let msg = format!("braces around {} is unnecessary", node_ident.name);
- cx.span_lint(UNUSED_IMPORT_BRACES, item.span, &msg);
+ cx.struct_span_lint(UNUSED_IMPORT_BRACES, item.span, |lint| {
+ lint.build(&format!("braces around {} is unnecessary", node_name)).emit()
+ });
}
}
}
-impl LintPass for UnusedImportBraces {
- fn get_lints(&self) -> LintArray {
- lint_array!(UNUSED_IMPORT_BRACES)
- }
-}
-
impl EarlyLintPass for UnusedImportBraces {
- fn check_item(&mut self, cx: &EarlyContext, item: &ast::Item) {
- if let ast::ItemKind::Use(ref use_tree) = item.node {
+ 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);
}
}
"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 {
- adjustment::AutoBorrowMutability::Immutable =>
- "unnecessary allocation, use & instead",
- adjustment::AutoBorrowMutability::Mutable { .. }=>
- "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()
+ });
}
}
}