Rollup merge of #5226 - ThibsG:DerefExplicit1566, r=flip1995
Add lint for explicit deref and deref_mut method calls This PR adds the lint `explicit_deref_method` that suggests replacing `deref()` and `deref_mut()` with `&*a` and `&mut *a`. It doesn't lint inside macros. This PR is the continuation of #3258. changelog: Add lint `explicit_deref_method`. Fixes: #1566
This commit is contained in:
commit
3481bf4102
7 changed files with 381 additions and 0 deletions
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@ -1256,6 +1256,7 @@ Released 2018-09-13
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[`expect_fun_call`]: https://rust-lang.github.io/rust-clippy/master/index.html#expect_fun_call
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[`expl_impl_clone_on_copy`]: https://rust-lang.github.io/rust-clippy/master/index.html#expl_impl_clone_on_copy
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[`explicit_counter_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#explicit_counter_loop
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[`explicit_deref_methods`]: https://rust-lang.github.io/rust-clippy/master/index.html#explicit_deref_methods
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[`explicit_into_iter_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#explicit_into_iter_loop
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[`explicit_iter_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#explicit_iter_loop
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[`explicit_write`]: https://rust-lang.github.io/rust-clippy/master/index.html#explicit_write
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113
clippy_lints/src/dereference.rs
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113
clippy_lints/src/dereference.rs
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@ -0,0 +1,113 @@
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use crate::utils::{get_parent_expr, implements_trait, snippet, span_lint_and_sugg};
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use if_chain::if_chain;
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use rustc_ast::util::parser::{ExprPrecedence, PREC_POSTFIX, PREC_PREFIX};
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use rustc_errors::Applicability;
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use rustc_hir::{Expr, ExprKind};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::source_map::Span;
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declare_clippy_lint! {
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/// **What it does:** Checks for explicit `deref()` or `deref_mut()` method calls.
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///
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/// **Why is this bad?** Derefencing by `&*x` or `&mut *x` is clearer and more concise,
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/// when not part of a method chain.
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///
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/// **Example:**
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/// ```rust
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/// use std::ops::Deref;
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/// let a: &mut String = &mut String::from("foo");
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/// let b: &str = a.deref();
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/// ```
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/// Could be written as:
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/// ```rust
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/// let a: &mut String = &mut String::from("foo");
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/// let b = &*a;
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/// ```
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///
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/// This lint excludes
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/// ```rust,ignore
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/// let _ = d.unwrap().deref();
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/// ```
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pub EXPLICIT_DEREF_METHODS,
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pedantic,
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"Explicit use of deref or deref_mut method while not in a method chain."
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}
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declare_lint_pass!(Dereferencing => [
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EXPLICIT_DEREF_METHODS
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]);
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Dereferencing {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
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if_chain! {
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if !expr.span.from_expansion();
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if let ExprKind::MethodCall(ref method_name, _, ref args) = &expr.kind;
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if args.len() == 1;
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then {
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if let Some(parent_expr) = get_parent_expr(cx, expr) {
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// Check if we have the whole call chain here
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if let ExprKind::MethodCall(..) = parent_expr.kind {
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return;
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}
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// Check for Expr that we don't want to be linted
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let precedence = parent_expr.precedence();
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match precedence {
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// Lint a Call is ok though
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ExprPrecedence::Call | ExprPrecedence::AddrOf => (),
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_ => {
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if precedence.order() >= PREC_PREFIX && precedence.order() <= PREC_POSTFIX {
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return;
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}
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}
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}
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}
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let name = method_name.ident.as_str();
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lint_deref(cx, &*name, &args[0], args[0].span, expr.span);
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}
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}
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}
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}
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fn lint_deref(cx: &LateContext<'_, '_>, method_name: &str, call_expr: &Expr<'_>, var_span: Span, expr_span: Span) {
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match method_name {
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"deref" => {
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if cx
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.tcx
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.lang_items()
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.deref_trait()
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.map_or(false, |id| implements_trait(cx, cx.tables.expr_ty(&call_expr), id, &[]))
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{
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span_lint_and_sugg(
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cx,
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EXPLICIT_DEREF_METHODS,
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expr_span,
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"explicit deref method call",
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"try this",
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format!("&*{}", &snippet(cx, var_span, "..")),
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Applicability::MachineApplicable,
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);
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}
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},
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"deref_mut" => {
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if cx
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.tcx
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.lang_items()
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.deref_mut_trait()
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.map_or(false, |id| implements_trait(cx, cx.tables.expr_ty(&call_expr), id, &[]))
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{
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span_lint_and_sugg(
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cx,
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EXPLICIT_DEREF_METHODS,
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expr_span,
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"explicit deref_mut method call",
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"try this",
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format!("&mut *{}", &snippet(cx, var_span, "..")),
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Applicability::MachineApplicable,
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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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@ -191,6 +191,7 @@ mod copies;
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mod copy_iterator;
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mod dbg_macro;
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mod default_trait_access;
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mod dereference;
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mod derive;
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mod doc;
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mod double_comparison;
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@ -513,6 +514,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
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©_iterator::COPY_ITERATOR,
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&dbg_macro::DBG_MACRO,
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&default_trait_access::DEFAULT_TRAIT_ACCESS,
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&dereference::EXPLICIT_DEREF_METHODS,
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&derive::DERIVE_HASH_XOR_EQ,
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&derive::EXPL_IMPL_CLONE_ON_COPY,
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&doc::DOC_MARKDOWN,
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@ -1039,6 +1041,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
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store.register_late_pass(|| box verbose_file_reads::VerboseFileReads);
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store.register_late_pass(|| box redundant_pub_crate::RedundantPubCrate::default());
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store.register_late_pass(|| box unnamed_address::UnnamedAddress);
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store.register_late_pass(|| box dereference::Dereferencing);
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store.register_group(true, "clippy::restriction", Some("clippy_restriction"), vec![
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LintId::of(&arithmetic::FLOAT_ARITHMETIC),
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@ -1089,6 +1092,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
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LintId::of(&copies::SAME_FUNCTIONS_IN_IF_CONDITION),
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LintId::of(©_iterator::COPY_ITERATOR),
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LintId::of(&default_trait_access::DEFAULT_TRAIT_ACCESS),
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LintId::of(&dereference::EXPLICIT_DEREF_METHODS),
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LintId::of(&derive::EXPL_IMPL_CLONE_ON_COPY),
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LintId::of(&doc::DOC_MARKDOWN),
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LintId::of(&doc::MISSING_ERRORS_DOC),
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@ -528,6 +528,13 @@ pub static ref ALL_LINTS: Vec<Lint> = vec![
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deprecation: None,
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module: "loops",
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},
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Lint {
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name: "explicit_deref_methods",
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group: "pedantic",
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desc: "Explicit use of deref or deref_mut method while not in a method chain.",
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deprecation: None,
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module: "dereference",
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},
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Lint {
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name: "explicit_into_iter_loop",
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group: "pedantic",
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93
tests/ui/dereference.fixed
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93
tests/ui/dereference.fixed
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// run-rustfix
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#![allow(unused_variables, clippy::many_single_char_names, clippy::clone_double_ref)]
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#![warn(clippy::explicit_deref_methods)]
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use std::ops::{Deref, DerefMut};
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fn concat(deref_str: &str) -> String {
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format!("{}bar", deref_str)
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}
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fn just_return(deref_str: &str) -> &str {
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deref_str
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}
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struct CustomVec(Vec<u8>);
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impl Deref for CustomVec {
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type Target = Vec<u8>;
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fn deref(&self) -> &Vec<u8> {
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&self.0
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}
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}
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fn main() {
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let a: &mut String = &mut String::from("foo");
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// these should require linting
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let b: &str = &*a;
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let b: &mut str = &mut *a;
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// both derefs should get linted here
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let b: String = format!("{}, {}", &*a, &*a);
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println!("{}", &*a);
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#[allow(clippy::match_single_binding)]
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match &*a {
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_ => (),
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}
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let b: String = concat(&*a);
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let b = &*just_return(a);
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let b: String = concat(&*just_return(a));
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let b: &str = &*a.deref();
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let opt_a = Some(a.clone());
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let b = &*opt_a.unwrap();
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// following should not require linting
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let cv = CustomVec(vec![0, 42]);
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let c = cv.deref()[0];
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let b: &str = &*a.deref();
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let b: String = a.deref().clone();
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let b: usize = a.deref_mut().len();
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let b: &usize = &a.deref().len();
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let b: &str = &*a;
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let b: &mut str = &mut *a;
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macro_rules! expr_deref {
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($body:expr) => {
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$body.deref()
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};
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}
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let b: &str = expr_deref!(a);
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// The struct does not implement Deref trait
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#[derive(Copy, Clone)]
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struct NoLint(u32);
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impl NoLint {
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pub fn deref(self) -> u32 {
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self.0
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}
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pub fn deref_mut(self) -> u32 {
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self.0
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}
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}
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let no_lint = NoLint(42);
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let b = no_lint.deref();
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let b = no_lint.deref_mut();
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}
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93
tests/ui/dereference.rs
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93
tests/ui/dereference.rs
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@ -0,0 +1,93 @@
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// run-rustfix
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#![allow(unused_variables, clippy::many_single_char_names, clippy::clone_double_ref)]
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#![warn(clippy::explicit_deref_methods)]
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use std::ops::{Deref, DerefMut};
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fn concat(deref_str: &str) -> String {
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format!("{}bar", deref_str)
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}
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fn just_return(deref_str: &str) -> &str {
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deref_str
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}
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struct CustomVec(Vec<u8>);
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impl Deref for CustomVec {
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type Target = Vec<u8>;
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fn deref(&self) -> &Vec<u8> {
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&self.0
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}
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}
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fn main() {
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let a: &mut String = &mut String::from("foo");
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// these should require linting
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let b: &str = a.deref();
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let b: &mut str = a.deref_mut();
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// both derefs should get linted here
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let b: String = format!("{}, {}", a.deref(), a.deref());
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println!("{}", a.deref());
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#[allow(clippy::match_single_binding)]
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match a.deref() {
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_ => (),
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}
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let b: String = concat(a.deref());
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let b = just_return(a).deref();
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let b: String = concat(just_return(a).deref());
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let b: &str = a.deref().deref();
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let opt_a = Some(a.clone());
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let b = opt_a.unwrap().deref();
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// following should not require linting
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let cv = CustomVec(vec![0, 42]);
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let c = cv.deref()[0];
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let b: &str = &*a.deref();
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let b: String = a.deref().clone();
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let b: usize = a.deref_mut().len();
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let b: &usize = &a.deref().len();
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let b: &str = &*a;
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let b: &mut str = &mut *a;
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macro_rules! expr_deref {
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($body:expr) => {
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$body.deref()
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};
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}
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let b: &str = expr_deref!(a);
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// The struct does not implement Deref trait
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#[derive(Copy, Clone)]
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struct NoLint(u32);
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impl NoLint {
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pub fn deref(self) -> u32 {
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self.0
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}
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pub fn deref_mut(self) -> u32 {
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self.0
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}
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}
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let no_lint = NoLint(42);
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let b = no_lint.deref();
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let b = no_lint.deref_mut();
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}
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70
tests/ui/dereference.stderr
Normal file
70
tests/ui/dereference.stderr
Normal file
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@ -0,0 +1,70 @@
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error: explicit deref method call
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--> $DIR/dereference.rs:30:19
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LL | let b: &str = a.deref();
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| ^^^^^^^^^ help: try this: `&*a`
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= note: `-D clippy::explicit-deref-methods` implied by `-D warnings`
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error: explicit deref_mut method call
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--> $DIR/dereference.rs:32:23
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LL | let b: &mut str = a.deref_mut();
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| ^^^^^^^^^^^^^ help: try this: `&mut *a`
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error: explicit deref method call
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--> $DIR/dereference.rs:35:39
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LL | let b: String = format!("{}, {}", a.deref(), a.deref());
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| ^^^^^^^^^ help: try this: `&*a`
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error: explicit deref method call
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--> $DIR/dereference.rs:35:50
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|
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LL | let b: String = format!("{}, {}", a.deref(), a.deref());
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| ^^^^^^^^^ help: try this: `&*a`
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error: explicit deref method call
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--> $DIR/dereference.rs:37:20
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|
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LL | println!("{}", a.deref());
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| ^^^^^^^^^ help: try this: `&*a`
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error: explicit deref method call
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--> $DIR/dereference.rs:40:11
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|
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LL | match a.deref() {
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| ^^^^^^^^^ help: try this: `&*a`
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error: explicit deref method call
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--> $DIR/dereference.rs:44:28
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|
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LL | let b: String = concat(a.deref());
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| ^^^^^^^^^ help: try this: `&*a`
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error: explicit deref method call
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--> $DIR/dereference.rs:46:13
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|
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LL | let b = just_return(a).deref();
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| ^^^^^^^^^^^^^^^^^^^^^^ help: try this: `&*just_return(a)`
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error: explicit deref method call
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--> $DIR/dereference.rs:48:28
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|
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LL | let b: String = concat(just_return(a).deref());
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| ^^^^^^^^^^^^^^^^^^^^^^ help: try this: `&*just_return(a)`
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error: explicit deref method call
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--> $DIR/dereference.rs:50:19
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|
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LL | let b: &str = a.deref().deref();
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| ^^^^^^^^^^^^^^^^^ help: try this: `&*a.deref()`
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error: explicit deref method call
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--> $DIR/dereference.rs:53:13
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|
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LL | let b = opt_a.unwrap().deref();
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| ^^^^^^^^^^^^^^^^^^^^^^ help: try this: `&*opt_a.unwrap()`
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error: aborting due to 11 previous errors
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