//!
//! This lint is **warn** by default
-use rustc::lint::*;
-use rustc::hir::{MutImmutable, Pat, PatKind, BindingMode};
-use rustc::ty;
-use utils::{span_lint, in_macro};
+use crate::utils::{snippet_with_applicability, span_lint_and_then};
+use if_chain::if_chain;
+use rustc::declare_lint_pass;
+use rustc::hir::{BindingAnnotation, Mutability, Node, Pat, PatKind};
+use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
+use rustc_errors::Applicability;
+use rustc_session::declare_tool_lint;
-/// **What it does:** Checks for useless borrowed references.
-///
-/// **Why is this bad?** It is completely useless and make the code look more complex than it
-/// actually is.
-///
-/// **Known problems:** None.
-///
-/// **Example:**
-/// ```rust
-/// let mut v = Vec::<String>::new();
-/// let _ = v.iter_mut().filter(|&ref a| a.is_empty());
-/// ```
-/// This clojure takes a reference on something that has been matched as a reference and
-/// de-referenced.
-/// As such, it could just be |a| a.is_empty()
-declare_lint! {
+declare_clippy_lint! {
+ /// **What it does:** Checks for useless borrowed references.
+ ///
+ /// **Why is this bad?** It is mostly useless and make the code look more
+ /// complex than it
+ /// actually is.
+ ///
+ /// **Known problems:** It seems that the `&ref` pattern is sometimes useful.
+ /// For instance in the following snippet:
+ /// ```rust,ignore
+ /// enum Animal {
+ /// Cat(u64),
+ /// Dog(u64),
+ /// }
+ ///
+ /// fn foo(a: &Animal, b: &Animal) {
+ /// match (a, b) {
+ /// (&Animal::Cat(v), k) | (k, &Animal::Cat(v)) => (), // lifetime mismatch error
+ /// (&Animal::Dog(ref c), &Animal::Dog(_)) => ()
+ /// }
+ /// }
+ /// ```
+ /// There is a lifetime mismatch error for `k` (indeed a and b have distinct
+ /// lifetime).
+ /// This can be fixed by using the `&ref` pattern.
+ /// However, the code can also be fixed by much cleaner ways
+ ///
+ /// **Example:**
+ /// ```rust
+ /// let mut v = Vec::<String>::new();
+ /// let _ = v.iter_mut().filter(|&ref a| a.is_empty());
+ /// ```
+ /// This closure takes a reference on something that has been matched as a
+ /// reference and
+ /// de-referenced.
+ /// As such, it could just be |a| a.is_empty()
pub NEEDLESS_BORROWED_REFERENCE,
- Warn,
+ complexity,
"taking a needless borrowed reference"
}
-#[derive(Copy, Clone)]
-pub struct NeedlessBorrowedRef;
-
-impl LintPass for NeedlessBorrowedRef {
- fn get_lints(&self) -> LintArray {
- lint_array!(NEEDLESS_BORROWED_REFERENCE)
- }
-}
+declare_lint_pass!(NeedlessBorrowedRef => [NEEDLESS_BORROWED_REFERENCE]);
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NeedlessBorrowedRef {
fn check_pat(&mut self, cx: &LateContext<'a, 'tcx>, pat: &'tcx Pat) {
- if in_macro(pat.span) {
+ if pat.span.from_expansion() {
// OK, simple enough, lints doesn't check in macro.
return;
}
- if_let_chain! {[
- // Pat is a pattern whose node
- // is a binding which "involves" a immutable reference...
- let PatKind::Binding(BindingMode::BindByRef(MutImmutable), ..) = pat.node,
- // Pattern's type is a reference. Get the type and mutability of referenced value (tam: TypeAndMut).
- let ty::TyRef(_, ref tam) = cx.tables.pat_ty(pat).sty,
- // This is an immutable reference.
- tam.mutbl == MutImmutable,
- ], {
- span_lint(cx, NEEDLESS_BORROWED_REFERENCE, pat.span, "this pattern takes a reference on something that is being de-referenced")
- }}
+ if_chain! {
+ // Only lint immutable refs, because `&mut ref T` may be useful.
+ if let PatKind::Ref(ref sub_pat, Mutability::Immutable) = pat.kind;
+
+ // Check sub_pat got a `ref` keyword (excluding `ref mut`).
+ 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",
+ |db| {
+ let hint = snippet_with_applicability(cx, spanned_name.span, "..", &mut applicability).into_owned();
+ db.span_suggestion(
+ pat.span,
+ "try removing the `&ref` part and just keep",
+ hint,
+ applicability,
+ );
+ });
+ }
+ }
}
}
projects / rust.git / blobdiff