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//! lint on inherent implementations
use rustc::hir::*;
use rustc::lint::*;
use std::collections::HashMap;
use std::default::Default;
use syntax_pos::Span;
/// **What it does:** Checks for multiple inherent implementations of a struct
///
/// **Why is this bad?** Splitting the implementation of a type makes the code harder to navigate.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// struct X;
/// impl X {
/// fn one() {}
/// }
/// impl X {
/// fn other() {}
/// }
/// ```
///
/// Could be written:
///
/// ```rust
/// struct X;
/// impl X {
/// fn one() {}
/// fn other() {}
/// }
/// ```
declare_clippy_lint! {
pub MULTIPLE_INHERENT_IMPL,
restriction,
"Multiple inherent impl that could be grouped"
}
pub struct Pass {
impls: HashMap<def_id::DefId, (Span, Generics)>,
}
impl Default for Pass {
fn default() -> Self {
Pass { impls: HashMap::new() }
}
}
impl LintPass for Pass {
fn get_lints(&self) -> LintArray {
lint_array!(MULTIPLE_INHERENT_IMPL)
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
fn check_item(&mut self, _: &LateContext<'a, 'tcx>, item: &'tcx Item) {
if let Item_::ItemImpl(_, _, _, ref generics, None, _, _) = item.node {
// Remember for each inherent implementation encoutered its span and generics
self.impls
.insert(item.hir_id.owner_def_id(), (item.span, generics.clone()));
}
}
fn check_crate_post(&mut self, cx: &LateContext<'a, 'tcx>, krate: &'tcx Crate) {
if let Some(item) = krate.items.values().nth(0) {
// Retrieve all inherent implementations from the crate, grouped by type
for impls in cx
.tcx
.crate_inherent_impls(item.hir_id.owner_def_id().krate)
.inherent_impls
.values()
{
// Filter out implementations that have generic params (type or lifetime)
let mut impl_spans = impls
.iter()
.filter_map(|impl_def| self.impls.get(impl_def))
.filter(|(_, generics)| generics.params.len() == 0)
.map(|(span, _)| span);
if let Some(initial_span) = impl_spans.nth(0) {
impl_spans.for_each(|additional_span| {
cx.span_lint_note(
MULTIPLE_INHERENT_IMPL,
*additional_span,
"Multiple implementations of this structure",
*initial_span,
"First implementation here",
)
})
}
}
}
}
}