-// Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution.
-//
-// 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 crate::rustc::hir::{Expr, ExprKind, MutMutable, QPath};
-use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
-use crate::rustc::{declare_tool_lint, lint_array};
-use crate::utils::{match_def_path, match_qpath, opt_def_id, paths, snippet, span_lint_and_sugg};
+use crate::utils::{
+ in_macro, match_def_path, match_qpath, paths, snippet_with_applicability, span_help_and_lint, span_lint_and_sugg,
+};
use if_chain::if_chain;
+use rustc::declare_lint_pass;
+use rustc::hir::{BorrowKind, Expr, ExprKind, HirVec, Mutability, QPath};
+use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintPass};
+use rustc_errors::Applicability;
+use rustc_session::declare_tool_lint;
-/// **What it does:** Checks for `mem::replace()` on an `Option` with
-/// `None`.
-///
-/// **Why is this bad?** `Option` already has the method `take()` for
-/// taking its current value (Some(..) or None) and replacing it with
-/// `None`.
-///
-/// **Known problems:** None.
-///
-/// **Example:**
-/// ```rust
-/// let mut an_option = Some(0);
-/// let replaced = mem::replace(&mut an_option, None);
-/// ```
-/// Is better expressed with:
-/// ```rust
-/// let mut an_option = Some(0);
-/// let taken = an_option.take();
-/// ```
declare_clippy_lint! {
+ /// **What it does:** Checks for `mem::replace()` on an `Option` with
+ /// `None`.
+ ///
+ /// **Why is this bad?** `Option` already has the method `take()` for
+ /// taking its current value (Some(..) or None) and replacing it with
+ /// `None`.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// use std::mem;
+ ///
+ /// let mut an_option = Some(0);
+ /// let replaced = mem::replace(&mut an_option, None);
+ /// ```
+ /// Is better expressed with:
+ /// ```rust
+ /// let mut an_option = Some(0);
+ /// let taken = an_option.take();
+ /// ```
pub MEM_REPLACE_OPTION_WITH_NONE,
style,
"replacing an `Option` with `None` instead of `take()`"
}
-pub struct MemReplace;
+declare_clippy_lint! {
+ /// **What it does:** Checks for `mem::replace(&mut _, mem::uninitialized())`
+ /// and `mem::replace(&mut _, mem::zeroed())`.
+ ///
+ /// **Why is this bad?** This will lead to undefined behavior even if the
+ /// value is overwritten later, because the uninitialized value may be
+ /// observed in the case of a panic.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ ///
+ /// ```
+ /// use std::mem;
+ ///# fn may_panic(v: Vec<i32>) -> Vec<i32> { v }
+ ///
+ /// #[allow(deprecated, invalid_value)]
+ /// fn myfunc (v: &mut Vec<i32>) {
+ /// let taken_v = unsafe { mem::replace(v, mem::uninitialized()) };
+ /// let new_v = may_panic(taken_v); // undefined behavior on panic
+ /// mem::forget(mem::replace(v, new_v));
+ /// }
+ /// ```
+ ///
+ /// The [take_mut](https://docs.rs/take_mut) crate offers a sound solution,
+ /// at the cost of either lazily creating a replacement value or aborting
+ /// on panic, to ensure that the uninitialized value cannot be observed.
+ pub MEM_REPLACE_WITH_UNINIT,
+ correctness,
+ "`mem::replace(&mut _, mem::uninitialized())` or `mem::replace(&mut _, mem::zeroed())`"
+}
+
+declare_clippy_lint! {
+ /// **What it does:** Checks for `std::mem::replace` on a value of type
+ /// `T` with `T::default()`.
+ ///
+ /// **Why is this bad?** `std::mem` module already has the method `take` to
+ /// take the current value and replace it with the default value of that type.
+ ///
+ /// **Known problems:** None.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// let mut text = String::from("foo");
+ /// let replaced = std::mem::replace(&mut text, String::default());
+ /// ```
+ /// Is better expressed with:
+ /// ```rust
+ /// let mut text = String::from("foo");
+ /// let taken = std::mem::take(&mut text);
+ /// ```
+ pub MEM_REPLACE_WITH_DEFAULT,
+ nursery,
+ "replacing a value of type `T` with `T::default()` instead of using `std::mem::take`"
+}
+
+declare_lint_pass!(MemReplace =>
+ [MEM_REPLACE_OPTION_WITH_NONE, MEM_REPLACE_WITH_UNINIT, MEM_REPLACE_WITH_DEFAULT]);
-impl LintPass for MemReplace {
- fn get_lints(&self) -> LintArray {
- lint_array![MEM_REPLACE_OPTION_WITH_NONE]
+fn check_replace_option_with_none(cx: &LateContext<'_, '_>, expr: &'_ Expr, args: &HirVec<Expr>) {
+ if let ExprKind::Path(ref replacement_qpath) = args[1].kind {
+ // Check that second argument is `Option::None`
+ if match_qpath(replacement_qpath, &paths::OPTION_NONE) {
+ // Since this is a late pass (already type-checked),
+ // and we already know that the second argument is an
+ // `Option`, we do not need to check the first
+ // argument's type. All that's left is to get
+ // replacee's path.
+ let replaced_path = match args[0].kind {
+ ExprKind::AddrOf(BorrowKind::Ref, Mutability::Mut, ref replaced) => {
+ if let ExprKind::Path(QPath::Resolved(None, ref replaced_path)) = replaced.kind {
+ replaced_path
+ } else {
+ return;
+ }
+ },
+ ExprKind::Path(QPath::Resolved(None, ref replaced_path)) => replaced_path,
+ _ => return,
+ };
+
+ let mut applicability = Applicability::MachineApplicable;
+ span_lint_and_sugg(
+ cx,
+ MEM_REPLACE_OPTION_WITH_NONE,
+ expr.span,
+ "replacing an `Option` with `None`",
+ "consider `Option::take()` instead",
+ format!(
+ "{}.take()",
+ snippet_with_applicability(cx, replaced_path.span, "", &mut applicability)
+ ),
+ applicability,
+ );
+ }
}
}
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MemReplace {
- fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
+fn check_replace_with_uninit(cx: &LateContext<'_, '_>, expr: &'_ Expr, args: &HirVec<Expr>) {
+ if let ExprKind::Call(ref repl_func, ref repl_args) = args[1].kind {
if_chain! {
- // Check that `expr` is a call to `mem::replace()`
- if let ExprKind::Call(ref func, ref func_args) = expr.node;
- if func_args.len() == 2;
- if let ExprKind::Path(ref func_qpath) = func.node;
- if let Some(def_id) = opt_def_id(cx.tables.qpath_def(func_qpath, func.hir_id));
- if match_def_path(cx.tcx, def_id, &paths::MEM_REPLACE);
-
- // Check that second argument is `Option::None`
- if let ExprKind::Path(ref replacement_qpath) = func_args[1].node;
- if match_qpath(replacement_qpath, &paths::OPTION_NONE);
+ if repl_args.is_empty();
+ if let ExprKind::Path(ref repl_func_qpath) = repl_func.kind;
+ if let Some(repl_def_id) = cx.tables.qpath_res(repl_func_qpath, repl_func.hir_id).opt_def_id();
+ then {
+ if match_def_path(cx, repl_def_id, &paths::MEM_UNINITIALIZED) {
+ span_help_and_lint(
+ cx,
+ MEM_REPLACE_WITH_UNINIT,
+ expr.span,
+ "replacing with `mem::uninitialized()`",
+ "consider using the `take_mut` crate instead",
+ );
+ } else if match_def_path(cx, repl_def_id, &paths::MEM_ZEROED) &&
+ !cx.tables.expr_ty(&args[1]).is_primitive() {
+ span_help_and_lint(
+ cx,
+ MEM_REPLACE_WITH_UNINIT,
+ expr.span,
+ "replacing with `mem::zeroed()`",
+ "consider using a default value or the `take_mut` crate instead",
+ );
+ }
+ }
+ }
+ }
+}
+fn check_replace_with_default(cx: &LateContext<'_, '_>, expr: &'_ Expr, args: &HirVec<Expr>) {
+ if let ExprKind::Call(ref repl_func, _) = args[1].kind {
+ if_chain! {
+ if !in_macro(expr.span) && !in_external_macro(cx.tcx.sess, expr.span);
+ if let ExprKind::Path(ref repl_func_qpath) = repl_func.kind;
+ if let Some(repl_def_id) = cx.tables.qpath_res(repl_func_qpath, repl_func.hir_id).opt_def_id();
+ if match_def_path(cx, repl_def_id, &paths::DEFAULT_TRAIT_METHOD);
then {
- // Since this is a late pass (already type-checked),
- // and we already know that the second argument is an
- // `Option`, we do not need to check the first
- // argument's type. All that's left is to get
- // replacee's path.
- let replaced_path = match func_args[0].node {
- ExprKind::AddrOf(MutMutable, ref replaced) => {
- if let ExprKind::Path(QPath::Resolved(None, ref replaced_path)) = replaced.node {
- replaced_path
- } else {
- return
- }
- },
- ExprKind::Path(QPath::Resolved(None, ref replaced_path)) => replaced_path,
- _ => return,
- };
+ let mut applicability = Applicability::MachineApplicable;
span_lint_and_sugg(
cx,
- MEM_REPLACE_OPTION_WITH_NONE,
+ MEM_REPLACE_WITH_DEFAULT,
expr.span,
- "replacing an `Option` with `None`",
- "consider `Option::take()` instead",
- format!("{}.take()", snippet(cx, replaced_path.span, ""))
+ "replacing a value of type `T` with `T::default()` is better expressed using `std::mem::take`",
+ "consider using",
+ format!(
+ "std::mem::take({})",
+ snippet_with_applicability(cx, args[0].span, "", &mut applicability)
+ ),
+ applicability,
);
}
}
}
}
+
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MemReplace {
+ fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
+ if_chain! {
+ // Check that `expr` is a call to `mem::replace()`
+ if let ExprKind::Call(ref func, ref func_args) = expr.kind;
+ if func_args.len() == 2;
+ if let ExprKind::Path(ref func_qpath) = func.kind;
+ if let Some(def_id) = cx.tables.qpath_res(func_qpath, func.hir_id).opt_def_id();
+ if match_def_path(cx, def_id, &paths::MEM_REPLACE);
+
+ then {
+ check_replace_option_with_none(cx, expr, &func_args);
+ check_replace_with_uninit(cx, expr, &func_args);
+ check_replace_with_default(cx, expr, &func_args);
+ }
+ }
+ }
+}
projects / rust.git / blobdiff