new_ret_no_self correct linting of tuple return types

Author: JoshMcguigan

clippy_lints/src/methods/mod.rs

@@ -936,6 +936,9 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
         if let hir::ImplItemKind::Method(_, _) = implitem.node {
             let ret_ty = return_ty(cx, implitem.id);
 
+//            println!("ret_ty: {:?}", ret_ty);
+//            println!("ret_ty.sty {:?}", ret_ty.sty);
+
             // if return type is impl trait
             if let TyKind::Opaque(def_id, _) = ret_ty.sty {
 
@@ -955,6 +958,14 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
                 }
             }
 
+            // if return type is tuple
+            if let TyKind::Tuple(list) = ret_ty.sty {
+                // then at least one of the types in the tuple must be Self
+                for ret_type in list {
+                    if same_tys(cx, ty, ret_type) { return; }
+                }
+            }
+
             if name == "new" && !same_tys(cx, ret_ty, ty) {
                 span_lint(cx,
                           NEW_RET_NO_SELF,

tests/ui/new_ret_no_self.rs

@@ -91,3 +91,31 @@ impl V {
         unimplemented!();
     }
 }
+
+struct TupleReturnerOk;
+
+impl TupleReturnerOk {
+    // should not trigger lint
+    pub fn new() -> (Self, u32) { unimplemented!(); }
+}
+
+struct TupleReturnerOk2;
+
+impl TupleReturnerOk2 {
+    // should not trigger lint (it doesn't matter which element in the tuple is Self)
+    pub fn new() -> (u32, Self) { unimplemented!(); }
+}
+
+struct TupleReturnerOk3;
+
+impl TupleReturnerOk3 {
+    // should not trigger lint (tuple can contain multiple Self)
+    pub fn new() -> (Self, Self) { unimplemented!(); }
+}
+
+struct TupleReturnerBad;
+
+impl TupleReturnerBad {
+    // should trigger lint
+    pub fn new() -> (u32, u32) { unimplemented!(); }
+}

tests/ui/new_ret_no_self.stderr

@@ -24,5 +24,11 @@ error: methods called `new` usually return `Self`
 92 | |     }
    | |_____^
 
-error: aborting due to 3 previous errors
+error: methods called `new` usually return `Self`
+   --> $DIR/new_ret_no_self.rs:120:5
+    |
+120 |     pub fn new() -> (u32, u32) { unimplemented!(); }
+    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 4 previous errors