use crate::utils::{
- match_def_path, match_qpath, paths, snippet_with_applicability, span_help_and_lint, span_lint_and_sugg,
+ in_macro, match_def_path, match_qpath, paths, snippet, snippet_with_applicability, span_lint_and_help,
+ span_lint_and_sugg, span_lint_and_then,
};
use if_chain::if_chain;
-use rustc::declare_lint_pass;
-use rustc::hir::{BorrowKind, Expr, ExprKind, Mutability, QPath};
-use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
+use rustc::lint::in_external_macro;
use rustc_errors::Applicability;
-use rustc_session::declare_tool_lint;
+use rustc_hir::{BorrowKind, Expr, ExprKind, Mutability, QPath};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::source_map::Span;
declare_clippy_lint! {
/// **What it does:** Checks for `mem::replace()` on an `Option` with
"`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,
+ style,
+ "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_OPTION_WITH_NONE, MEM_REPLACE_WITH_UNINIT, MEM_REPLACE_WITH_DEFAULT]);
+
+fn check_replace_option_with_none(cx: &LateContext<'_, '_>, src: &Expr<'_>, dest: &Expr<'_>, expr_span: Span) {
+ if let ExprKind::Path(ref replacement_qpath) = src.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 dest.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,
+ );
+ }
+ }
+}
+
+fn check_replace_with_uninit(cx: &LateContext<'_, '_>, src: &Expr<'_>, expr_span: Span) {
+ if let ExprKind::Call(ref repl_func, ref repl_args) = src.kind {
+ if_chain! {
+ 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_lint_and_help(
+ 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(src).is_primitive() {
+ span_lint_and_help(
+ 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<'_, '_>, src: &Expr<'_>, dest: &Expr<'_>, expr_span: Span) {
+ if let ExprKind::Call(ref repl_func, _) = src.kind {
+ if_chain! {
+ if !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 {
+ span_lint_and_then(
+ cx,
+ MEM_REPLACE_WITH_DEFAULT,
+ expr_span,
+ "replacing a value of type `T` with `T::default()` is better expressed using `std::mem::take`",
+ |db| {
+ if !in_macro(expr_span) {
+ let suggestion = format!("std::mem::take({})", snippet(cx, dest.span, ""));
+
+ db.span_suggestion(
+ expr_span,
+ "consider using",
+ suggestion,
+ Applicability::MachineApplicable
+ );
+ }
+ }
+ );
+ }
+ }
+ }
+}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MemReplace {
- fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
+ 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);
-
- // Check that second argument is `Option::None`
+ if let [dest, src] = &**func_args;
then {
- if let ExprKind::Path(ref replacement_qpath) = func_args[1].kind {
- 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 func_args[0].kind {
- ExprKind::AddrOf(BorrowKind::Ref, Mutability::Mutable, 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,
- );
- }
- }
- if let ExprKind::Call(ref repl_func, ref repl_args) = func_args[1].kind {
- if_chain! {
- 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(&func_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",
- );
- }
- }
- }
- }
+ check_replace_option_with_none(cx, src, dest, expr.span);
+ check_replace_with_uninit(cx, src, expr.span);
+ check_replace_with_default(cx, src, dest, expr.span);
}
}
}
projects / rust.git / blobdiff