217 lines
8.5 KiB
Rust
217 lines
8.5 KiB
Rust
// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use crate::rustc::hir::*;
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use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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use crate::rustc::ty;
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use crate::rustc::{declare_tool_lint, lint_array};
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use crate::rustc_errors::Applicability;
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use crate::utils::sugg::Sugg;
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use crate::utils::{
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differing_macro_contexts, match_type, paths, snippet, span_lint_and_then, walk_ptrs_ty, SpanlessEq,
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};
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use if_chain::if_chain;
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use matches::matches;
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/// **What it does:** Checks for manual swapping.
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///
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/// **Why is this bad?** The `std::mem::swap` function exposes the intent better
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/// without deinitializing or copying either variable.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust,ignore
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/// let t = b;
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/// b = a;
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/// a = t;
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/// ```
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/// Use std::mem::swap():
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/// ```rust
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/// std::mem::swap(&mut a, &mut b);
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/// ```
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declare_clippy_lint! {
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pub MANUAL_SWAP,
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complexity,
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"manual swap of two variables"
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}
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/// **What it does:** Checks for `foo = bar; bar = foo` sequences.
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///
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/// **Why is this bad?** This looks like a failed attempt to swap.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust,ignore
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/// a = b;
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/// b = a;
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/// ```
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declare_clippy_lint! {
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pub ALMOST_SWAPPED,
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correctness,
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"`foo = bar; bar = foo` sequence"
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}
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#[derive(Copy, Clone)]
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pub struct Swap;
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impl LintPass for Swap {
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fn get_lints(&self) -> LintArray {
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lint_array![MANUAL_SWAP, ALMOST_SWAPPED]
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Swap {
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fn check_block(&mut self, cx: &LateContext<'a, 'tcx>, block: &'tcx Block) {
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check_manual_swap(cx, block);
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check_suspicious_swap(cx, block);
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}
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}
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/// Implementation of the `MANUAL_SWAP` lint.
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fn check_manual_swap(cx: &LateContext<'_, '_>, block: &Block) {
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for w in block.stmts.windows(3) {
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if_chain! {
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// let t = foo();
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if let StmtKind::Decl(ref tmp, _) = w[0].node;
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if let DeclKind::Local(ref tmp) = tmp.node;
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if let Some(ref tmp_init) = tmp.init;
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if let PatKind::Binding(_, _, ident, None) = tmp.pat.node;
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// foo() = bar();
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if let StmtKind::Semi(ref first, _) = w[1].node;
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if let ExprKind::Assign(ref lhs1, ref rhs1) = first.node;
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// bar() = t;
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if let StmtKind::Semi(ref second, _) = w[2].node;
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if let ExprKind::Assign(ref lhs2, ref rhs2) = second.node;
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if let ExprKind::Path(QPath::Resolved(None, ref rhs2)) = rhs2.node;
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if rhs2.segments.len() == 1;
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if ident.as_str() == rhs2.segments[0].ident.as_str();
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if SpanlessEq::new(cx).ignore_fn().eq_expr(tmp_init, lhs1);
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if SpanlessEq::new(cx).ignore_fn().eq_expr(rhs1, lhs2);
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then {
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fn check_for_slice<'a>(
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cx: &LateContext<'_, '_>,
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lhs1: &'a Expr,
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lhs2: &'a Expr,
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) -> Option<(&'a Expr, &'a Expr, &'a Expr)> {
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if let ExprKind::Index(ref lhs1, ref idx1) = lhs1.node {
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if let ExprKind::Index(ref lhs2, ref idx2) = lhs2.node {
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if SpanlessEq::new(cx).ignore_fn().eq_expr(lhs1, lhs2) {
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let ty = walk_ptrs_ty(cx.tables.expr_ty(lhs1));
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if matches!(ty.sty, ty::Slice(_)) ||
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matches!(ty.sty, ty::Array(_, _)) ||
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match_type(cx, ty, &paths::VEC) ||
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match_type(cx, ty, &paths::VEC_DEQUE) {
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return Some((lhs1, idx1, idx2));
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}
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}
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}
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}
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None
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}
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let (replace, what, sugg) = if let Some((slice, idx1, idx2)) = check_for_slice(cx, lhs1, lhs2) {
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if let Some(slice) = Sugg::hir_opt(cx, slice) {
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(false,
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format!(" elements of `{}`", slice),
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format!("{}.swap({}, {})",
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slice.maybe_par(),
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snippet(cx, idx1.span, ".."),
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snippet(cx, idx2.span, "..")))
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} else {
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(false, String::new(), String::new())
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}
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} else if let (Some(first), Some(second)) = (Sugg::hir_opt(cx, lhs1), Sugg::hir_opt(cx, rhs1)) {
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(true, format!(" `{}` and `{}`", first, second),
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format!("std::mem::swap({}, {})", first.mut_addr(), second.mut_addr()))
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} else {
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(true, String::new(), String::new())
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};
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let span = w[0].span.to(second.span);
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span_lint_and_then(cx,
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MANUAL_SWAP,
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span,
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&format!("this looks like you are swapping{} manually", what),
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|db| {
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if !sugg.is_empty() {
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db.span_suggestion_with_applicability(
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span,
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"try",
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sugg,
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Applicability::Unspecified,
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);
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if replace {
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db.note("or maybe you should use `std::mem::replace`?");
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}
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}
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});
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}
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}
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}
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}
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/// Implementation of the `ALMOST_SWAPPED` lint.
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fn check_suspicious_swap(cx: &LateContext<'_, '_>, block: &Block) {
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for w in block.stmts.windows(2) {
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if_chain! {
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if let StmtKind::Semi(ref first, _) = w[0].node;
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if let StmtKind::Semi(ref second, _) = w[1].node;
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if !differing_macro_contexts(first.span, second.span);
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if let ExprKind::Assign(ref lhs0, ref rhs0) = first.node;
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if let ExprKind::Assign(ref lhs1, ref rhs1) = second.node;
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if SpanlessEq::new(cx).ignore_fn().eq_expr(lhs0, rhs1);
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if SpanlessEq::new(cx).ignore_fn().eq_expr(lhs1, rhs0);
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then {
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let lhs0 = Sugg::hir_opt(cx, lhs0);
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let rhs0 = Sugg::hir_opt(cx, rhs0);
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let (what, lhs, rhs) = if let (Some(first), Some(second)) = (lhs0, rhs0) {
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(
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format!(" `{}` and `{}`", first, second),
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first.mut_addr().to_string(),
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second.mut_addr().to_string(),
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)
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} else {
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(String::new(), String::new(), String::new())
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};
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let span = first.span.to(second.span);
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span_lint_and_then(cx,
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ALMOST_SWAPPED,
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span,
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&format!("this looks like you are trying to swap{}", what),
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|db| {
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if !what.is_empty() {
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db.span_suggestion_with_applicability(
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span,
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"try",
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format!(
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"std::mem::swap({}, {})",
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lhs,
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rhs,
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),
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Applicability::MaybeIncorrect,
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);
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db.note("or maybe you should use `std::mem::replace`?");
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}
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});
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}
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}
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}
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}
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