rust-clippy/clippy_lints/src/needless_borrowed_ref.rs

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use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::source::snippet_with_applicability;
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use if_chain::if_chain;
use rustc_errors::Applicability;
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use rustc_hir::{BindingAnnotation, Mutability, Node, Pat, PatKind};
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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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declare_clippy_lint! {
/// ### What it does
/// Checks for bindings that destructure a reference and borrow the inner
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/// value with `&ref`.
///
/// ### Why is this bad?
/// This pattern has no effect in almost all cases.
///
/// ### Known problems
/// In some cases, `&ref` is needed to avoid a lifetime mismatch error.
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/// Example:
/// ```rust
/// fn foo(a: &Option<String>, b: &Option<String>) {
/// match (a, b) {
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/// (None, &ref c) | (&ref c, None) => (),
/// (&Some(ref c), _) => (),
/// };
/// }
/// ```
///
/// ### Example
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/// Bad:
/// ```rust
/// let mut v = Vec::<String>::new();
/// let _ = v.iter_mut().filter(|&ref a| a.is_empty());
/// ```
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///
/// Good:
/// ```rust
/// let mut v = Vec::<String>::new();
/// let _ = v.iter_mut().filter(|a| a.is_empty());
/// ```
Added `clippy::version` attribute to all normal lints So, some context for this, well, more a story. I'm not used to scripting, I've never really scripted anything, even if it's a valuable skill. I just never really needed it. Now, `@flip1995` correctly suggested using a script for this in `rust-clippy#7813`... And I decided to write a script using nushell because why not? This was a mistake... I spend way more time on this than I would like to admit. It has definitely been more than 4 hours. It shouldn't take that long, but me being new to scripting and nushell just wasn't a good mixture... Anyway, here is the script that creates another script which adds the versions. Fun... Just execute this on the `gh-pages` branch and the resulting `replacer.sh` in `clippy_lints` and it should all work. ```nu mv v0.0.212 rust-1.00.0; mv beta rust-1.57.0; mv master rust-1.58.0; let paths = (open ./rust-1.58.0/lints.json | select id id_span | flatten | select id path); let versions = ( ls | where name =~ "rust-" | select name | format {name}/lints.json | each { open $it | select id | insert version $it | str substring "5,11" version} | group-by id | rotate counter-clockwise id version | update version {get version | first 1} | flatten | select id version); $paths | each { |row| let version = ($versions | where id == ($row.id) | format {version}) let idu = ($row.id | str upcase) $"sed -i '0,/($idu),/{s/pub ($idu),/#[clippy::version = "($version)"]\n pub ($idu),/}' ($row.path)" } | str collect ";" | str find-replace --all '1.00.0' 'pre 1.29.0' | save "replacer.sh"; ``` And this still has some problems, but at this point I just want to be done -.-
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#[clippy::version = "pre 1.29.0"]
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pub NEEDLESS_BORROWED_REFERENCE,
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complexity,
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"destructuring a reference and borrowing the inner value"
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}
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declare_lint_pass!(NeedlessBorrowedRef => [NEEDLESS_BORROWED_REFERENCE]);
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impl<'tcx> LateLintPass<'tcx> for NeedlessBorrowedRef {
fn check_pat(&mut self, cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>) {
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if pat.span.from_expansion() {
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// OK, simple enough, lints doesn't check in macro.
return;
}
if_chain! {
// Only lint immutable refs, because `&mut ref T` may be useful.
if let PatKind::Ref(sub_pat, Mutability::Not) = pat.kind;
// Check sub_pat got a `ref` keyword (excluding `ref mut`).
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if let PatKind::Binding(BindingAnnotation::Ref, .., spanned_name, _) = sub_pat.kind;
let parent_id = cx.tcx.hir().get_parent_node(pat.hir_id);
if let Some(parent_node) = cx.tcx.hir().find(parent_id);
then {
// do not recurse within patterns, as they may have other references
// XXXManishearth we can relax this constraint if we only check patterns
// with a single ref pattern inside them
if let Node::Pat(_) = parent_node {
return;
}
let mut applicability = Applicability::MachineApplicable;
span_lint_and_then(cx, NEEDLESS_BORROWED_REFERENCE, pat.span,
"this pattern takes a reference on something that is being de-referenced",
|diag| {
let hint = snippet_with_applicability(cx, spanned_name.span, "..", &mut applicability).into_owned();
diag.span_suggestion(
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pat.span,
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"try removing the `&ref` part and just keep",
hint,
applicability,
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);
});
}
}
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}
}