lint new_without_default on const fns too

Author: Centri3

clippy_lints/src/new_without_default.rs

@@ -75,10 +75,6 @@ impl<'tcx> LateLintPass<'tcx> for NewWithoutDefault {
  if let hir::ImplItemKind::Fn(ref sig, _) = impl_item.kind {
  let name = impl_item.ident.name;
  let id = impl_item.owner_id;
- if sig.header.constness == hir::Constness::Const {
- // can't be implemented by default
- return;
- }
  if sig.header.unsafety == hir::Unsafety::Unsafe {
  // can't be implemented for unsafe new
  return;

tests/ui/new_without_default.fixed

@@ -132,12 +132,18 @@ impl PrivateItem {
  } // We don't lint private items on public structs
 }
 
-struct Const;
+pub struct Const;
+
+impl Default for Const {
+ fn default() -> Self {
+ Self::new()
+ }
+}
 
 impl Const {
  pub const fn new() -> Const {
  Const
- } // const fns can't be implemented via Default
+ } // While Default is not const, it can still call const functions, so we should lint this
 }
 
 pub struct IgnoreGenericNew;

tests/ui/new_without_default.rs

@@ -114,12 +114,12 @@ impl PrivateItem {
  } // We don't lint private items on public structs
 }
 
-struct Const;
+pub struct Const;
 
 impl Const {
  pub const fn new() -> Const {
  Const
- } // const fns can't be implemented via Default
+ } // While Default is not const, it can still call const functions, so we should lint this
 }
 
 pub struct IgnoreGenericNew;

tests/ui/new_without_default.stderr

@@ -55,6 +55,23 @@ LL + }
 LL + }
  |
 
+error: you should consider adding a `Default` implementation for `Const`
+ --> $DIR/new_without_default.rs:120:5
+ |
+LL | / pub const fn new() -> Const {
+LL | | Const
+LL | | } // While Default is not const, it can still call const functions, so we should lint this
+ | |_____^
+ |
+help: try adding this
+ |
+LL + impl Default for Const {
+LL + fn default() -> Self {
+LL + Self::new()
+LL + }
+LL + }
+ |
+
 error: you should consider adding a `Default` implementation for `NewNotEqualToDerive`
  --> $DIR/new_without_default.rs:180:5
  |
@@ -149,5 +166,5 @@ LL + }
 LL + }
  |
 
-error: aborting due to 8 previous errors
+error: aborting due to 9 previous errors