58 lines
1.7 KiB
Rust
58 lines
1.7 KiB
Rust
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//! Checks for useless borrowed references in clojures.
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//!
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//! This lint is **warn** by default
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use rustc::lint::*;
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use rustc::hir::{MutImmutable, Pat, PatKind, BindingMode};
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use rustc::ty;
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use utils::{span_lint, in_macro};
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/// **What it does:** Checks for useless borrowed references in clojures.
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///
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/// **Why is this bad?** TODO
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// let mut v = Vec::<String>::new();
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/// let _ = v.iter_mut().filter(|&ref a| a.is_empty());
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/// ```
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/// It could just be |a| a.is_empty()
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declare_lint! {
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pub NEEDLESS_BORROWED_REFERENCE,
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Warn,
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"taking a needless borrowed reference"
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}
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#[derive(Copy, Clone)]
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pub struct NeedlessBorrowedRef;
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impl LintPass for NeedlessBorrowedRef {
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fn get_lints(&self) -> LintArray {
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lint_array!(NEEDLESS_BORROWED_REFERENCE)
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NeedlessBorrowedRef {
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fn check_pat(&mut self, cx: &LateContext<'a, 'tcx>, pat: &'tcx Pat) {
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if in_macro(pat.span) {
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// OK, simple enough, lints doesn't check in macro.
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return;
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}
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if_let_chain! {[
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// Pat is a pattern whose node
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// is a binding which "involves" a immutable reference...
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let PatKind::Binding(BindingMode::BindByRef(MutImmutable), ..) = pat.node,
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// Pattern's type is a reference. Get the type and mutability of referenced value (tam: TypeAndMut).
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let ty::TyRef(_, ref tam) = cx.tables.pat_ty(pat).sty,
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// This is an immutable reference.
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tam.mutbl == MutImmutable,
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], {
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span_lint(cx, NEEDLESS_BORROWED_REFERENCE, pat.span, "this pattern takes a needless borrowed reference")
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}}
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}
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}
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