Fix missing_const_for_fn for impl trait methods
diff --git a/clippy_lints/src/missing_const_for_fn.rs b/clippy_lints/src/missing_const_for_fn.rs
index bd9e8ce..633105f 100644
--- a/clippy_lints/src/missing_const_for_fn.rs
+++ b/clippy_lints/src/missing_const_for_fn.rs
@@ -1,4 +1,5 @@
use crate::utils::{is_entrypoint_fn, span_lint};
+use if_chain::if_chain;
use rustc::hir;
use rustc::hir::intravisit::FnKind;
use rustc::hir::{Body, Constness, FnDecl, HirId};
@@ -95,7 +96,7 @@
}
},
FnKind::Method(_, sig, ..) => {
- if already_const(sig.header) {
+ if is_trait_method(cx, hir_id) || already_const(sig.header) {
return;
}
},
@@ -114,6 +115,18 @@
}
}
+fn is_trait_method(cx: &LateContext<'_, '_>, hir_id: HirId) -> bool {
+ // Get the implemented trait for the current function
+ let parent_impl = cx.tcx.hir().get_parent_item(hir_id);
+ if_chain! {
+ if parent_impl != hir::CRATE_HIR_ID;
+ if let hir::Node::Item(item) = cx.tcx.hir().get_by_hir_id(parent_impl);
+ if let hir::ItemKind::Impl(_, _, _, _, Some(_trait_ref), _, _) = &item.node;
+ then { return true; }
+ }
+ false
+}
+
// We don't have to lint on something that's already `const`
fn already_const(header: hir::FnHeader) -> bool {
header.constness == Constness::Const
diff --git a/tests/ui/missing_const_for_fn/cant_be_const.rs b/tests/ui/missing_const_for_fn/cant_be_const.rs
index 4a2e6ad..115cc95 100644
--- a/tests/ui/missing_const_for_fn/cant_be_const.rs
+++ b/tests/ui/missing_const_for_fn/cant_be_const.rs
@@ -59,3 +59,12 @@
// Don't lint in external macros (derive)
#[derive(PartialEq, Eq)]
struct Point(isize, isize);
+
+impl std::ops::Add for Point {
+ type Output = Self;
+
+ // Don't lint in trait impls of derived methods
+ fn add(self, other: Self) -> Self {
+ Point(self.0 + other.0, self.1 + other.1)
+ }
+}
