Merge pull request #778 from mcarton/fix-new_without_default

Fix `new_without_default` with lts and generics

src/new_without_default.rs

@@ -51,6 +51,7 @@ impl LateLintPass for NewWithoutDefault {
                 let self_ty = cx.tcx.lookup_item_type(cx.tcx.map.local_def_id(cx.tcx.map.get_parent(id))).ty;
 
                 if_let_chain!{[
+                    self_ty.walk_shallow().next().is_none(), // implements_trait does not work with generics
                     let Some(ret_ty) = return_ty(cx.tcx.node_id_to_type(id)),
                     same_tys(cx, self_ty, ret_ty),
                     let Some(default_trait_id) = get_trait_def_id(cx, &DEFAULT_TRAIT_PATH),

src/utils/mod.rs

@@ -270,6 +270,7 @@ pub fn implements_trait<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, ty: ty::Ty<'tcx>,
                                   -> bool {
     cx.tcx.populate_implementations_for_trait_if_necessary(trait_id);
 
+    let ty = cx.tcx.erase_regions(&ty);
     let infcx = infer::new_infer_ctxt(cx.tcx, &cx.tcx.tables, None, ProjectionMode::Any);
     let obligation = traits::predicate_for_trait_def(cx.tcx,
                                                      traits::ObligationCause::dummy(),

tests/compile-fail/new_without_default.rs

@@ -32,13 +32,36 @@ impl Params {
     fn new(_: u32) -> Self { Params }
 }
 
-struct Generics<'a, T> {
-    foo: &'a bool,
+struct GenericsOk<T> {
     bar: T,
 }
 
-impl<'c, V> Generics<'c, V> {
-    fn new<'b>() -> Generics<'b, V> { unimplemented!() } //~ERROR: you should consider adding a `Default` implementation for
+impl<U> Default for GenericsOk<U> {
+    fn default() -> Self { unimplemented!(); }
+}
+
+impl<'c, V> GenericsOk<V> {
+    fn new() -> GenericsOk<V> { unimplemented!() }
+}
+
+struct LtOk<'a> {
+    foo: &'a bool,
+}
+
+impl<'b> Default for LtOk<'b> {
+    fn default() -> Self { unimplemented!(); }
+}
+
+impl<'c> LtOk<'c> {
+    fn new() -> LtOk<'c> { unimplemented!() }
+}
+
+struct LtKo<'a> {
+    foo: &'a bool,
+}
+
+impl<'c> LtKo<'c> {
+    fn new() -> LtKo<'c> { unimplemented!() } //~ERROR: you should consider adding a `Default` implementation for
 }
 
 fn main() {}