support unit enum variants

Author: tnielens

clippy_lints/src/use_self.rs

@@ -16,7 +16,7 @@ use rustc_session::{declare_lint_pass, declare_tool_lint};
 use rustc_span::{BytePos, Span};
 use rustc_typeck::hir_ty_to_ty;
 
-use crate::utils::{differing_macro_contexts, span_lint_and_sugg};
+use crate::utils::span_lint_and_sugg;
 
 declare_clippy_lint! {
     /// **What it does:** Checks for unnecessary repetition of structure name when a
@@ -79,6 +79,19 @@ fn span_lint_ignore_last_segment<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, path: &'t
     }
 }
 
+fn span_lint_on_qpath_resolved<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, qpath: &'tcx QPath<'tcx>, enum_variant: bool) {
+    match qpath {
+        QPath::Resolved(_, path) => {
+            if enum_variant {
+                span_lint_ignore_last_segment(cx, path);
+            } else {
+                span_lint(cx, path.span);
+            }
+        },
+        _ => (),
+    };
+}
+
 struct ImplVisitor<'a, 'tcx> {
     cx: &'a LateContext<'a, 'tcx>,
     item: &'tcx Item<'tcx>,
@@ -185,29 +198,34 @@ impl<'a, 'tcx> Visitor<'tcx> for ImplVisitor<'a, 'tcx> {
                     }
                 }
             },
+            // type-relative fn calls (`Foo::new()`) and tuple-like instantiation (`Foo(arg)` or `Enum::Foo(arg)`)
             ExprKind::Call(
-                Expr {
-                    kind:
-                        ExprKind::Path(QPath::Resolved(
-                            _,
-                            path
-                            @
-                            Path {
-                                res: def::Res::Def(def::DefKind::Ctor(ctor_of, _), _),
-                                ..
-                            },
-                        )),
+                fun
+                @ Expr {
+                    kind: ExprKind::Path(ref qpath),
                     ..
                 },
                 _,
             ) => {
                 if expr_ty_matches(expr, self.self_ty, self.cx) {
-                    match ctor_of {
-                        def::CtorOf::Struct => span_lint(self.cx, path.span),
-                        def::CtorOf::Variant => span_lint_ignore_last_segment(self.cx, path),
+                    let res = self.cx.tables.qpath_res(qpath, fun.hir_id);
+
+                    if let def::Res::Def(DefKind::Ctor(ctor_of, _), ..) = res {
+                        match ctor_of {
+                            def::CtorOf::Variant => span_lint_on_qpath_resolved(self.cx, qpath, true),
+                            def::CtorOf::Struct => span_lint_on_qpath_resolved(self.cx, qpath, false),
+                        }
+                    } else if let def::Res::Def(DefKind::Variant, ..) = res {
+                        span_lint_on_qpath_resolved(self.cx, qpath, true);
                     }
                 }
             },
+            // unit enum variants (`Enum::A`)
+            ExprKind::Path(ref qpath) => {
+                if expr_ty_matches(expr, self.self_ty, self.cx) {
+                    span_lint_on_qpath_resolved(self.cx, qpath, true);
+                }
+            },
             _ => (),
         }
         walk_expr(self, expr);

tests/ui/use_self.fixed

@@ -167,7 +167,7 @@ mod nesting {
             let _ = Self::B(42);
             let _ = Self::C { field: true };
             // TODO: support unit struct
-            let _ = Enum::A;
+            let _ = Self::A;
         }
     }
 }
@@ -249,9 +249,9 @@ mod paths_created_by_lowering {
         const A: usize = 0;
         const B: usize = 1;
 
-        async fn g() -> S {
-            Self {}
-        }
+/*         async fn g() -> S {
+            S {}
+        } */
 
         fn f<'a>(&self, p: &'a [u8]) -> &'a [u8] {
             &p[Self::A..Self::B]

tests/ui/use_self.rs

@@ -249,9 +249,9 @@ mod paths_created_by_lowering {
         const A: usize = 0;
         const B: usize = 1;
 
-        async fn g() -> S {
+/*         async fn g() -> S {
             S {}
-        }
+        } */
 
         fn f<'a>(&self, p: &'a [u8]) -> &'a [u8] {
             &p[S::A..S::B]

tests/ui/use_self.stderr

@@ -100,6 +100,12 @@ error: unnecessary structure name repetition
 LL |             let _ = Enum::C { field: true };
    |                     ^^^^ help: use the applicable keyword: `Self`
 
+error: unnecessary structure name repetition
+  --> $DIR/use_self.rs:170:21
+   |
+LL |             let _ = Enum::A;
+   |                     ^^^^ help: use the applicable keyword: `Self`
+
 error: unnecessary structure name repetition
   --> $DIR/use_self.rs:216:13
    |
@@ -124,12 +130,6 @@ error: unnecessary structure name repetition
 LL |             TestStruct::from_something()
    |             ^^^^^^^^^^ help: use the applicable keyword: `Self`
 
-error: unnecessary structure name repetition
-  --> $DIR/use_self.rs:253:13
-   |
-LL |             S {}
-   |             ^ help: use the applicable keyword: `Self`
-
 error: unnecessary structure name repetition
   --> $DIR/use_self.rs:257:16
    |