new_ret_no_self fix false positive for impl trait return with associated type self

Author: JoshMcguigan

clippy_lints/src/methods/mod.rs

@@ -934,7 +934,8 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
         if let hir::ImplItemKind::Method(ref sig, id) = implitem.node {
             let ret_ty = return_ty(cx, implitem.id);
             if name == "new" &&
-                !ret_ty.walk().any(|t| same_tys(cx, t, ty)) {
+                !same_tys(cx, ret_ty, ty) &&
+                !ret_ty.is_impl_trait() {
                 span_lint(cx,
                           NEW_RET_NO_SELF,
                           implitem.span,

tests/ui/new_ret_no_self.rs

@@ -35,6 +35,19 @@ impl S2 {
     }
 }
 
+struct S3;
+
+impl R for S3 {
+    type Item = u32;
+}
+
+impl S3 {
+    // should trigger the lint, but currently does not
+    pub fn new(_: String) -> impl R<Item = u32> {
+        S3
+    }
+}
+
 struct T;
 
 impl T {

tests/ui/new_ret_no_self.stderr

@@ -1,17 +1,19 @@
 error: methods called `new` usually return `Self`
-  --> $DIR/new_ret_no_self.rs:51:5
+  --> $DIR/new_ret_no_self.rs:64:5
    |
-51 | /     pub fn new() -> u32 {
-52 | |         unimplemented!();
-53 | |     }
+64 | /     pub fn new() -> u32 {
+65 | |         unimplemented!();
+66 | |     }
    | |_____^
+   |
+   = note: `-D clippy::new-ret-no-self` implied by `-D warnings`
 
 error: methods called `new` usually return `Self`
-  --> $DIR/new_ret_no_self.rs:60:5
+  --> $DIR/new_ret_no_self.rs:73:5
    |
-60 | /     pub fn new(_: String) -> u32 {
-61 | |         unimplemented!();
-62 | |     }
+73 | /     pub fn new(_: String) -> u32 {
+74 | |         unimplemented!();
+75 | |     }
    | |_____^
 
 error: aborting due to 2 previous errors