Fix false "never constructed" warnings for Self:: variant paths

Author: jakubadamw

src/librustc_passes/dead.rs

@@ -245,10 +245,6 @@ impl<'a, 'tcx> Visitor<'tcx> for MarkSymbolVisitor<'a, 'tcx> {
 
     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'tcx>) {
         match expr.kind {
-            hir::ExprKind::Path(ref qpath @ hir::QPath::TypeRelative(..)) => {
-                let res = self.tables.qpath_res(qpath, expr.hir_id);
-                self.handle_res(res);
-            }
             hir::ExprKind::MethodCall(..) => {
                 self.lookup_and_handle_method(expr.hir_id);
             }
@@ -282,10 +278,6 @@ impl<'a, 'tcx> Visitor<'tcx> for MarkSymbolVisitor<'a, 'tcx> {
                 let res = self.tables.qpath_res(path, pat.hir_id);
                 self.handle_field_pattern_match(pat, res, fields);
             }
-            PatKind::Path(ref qpath) => {
-                let res = self.tables.qpath_res(qpath, pat.hir_id);
-                self.handle_res(res);
-            }
             _ => (),
         }
 
@@ -294,9 +286,11 @@ impl<'a, 'tcx> Visitor<'tcx> for MarkSymbolVisitor<'a, 'tcx> {
         self.in_pat = false;
     }
 
-    fn visit_path(&mut self, path: &'tcx hir::Path<'tcx>, _: hir::HirId) {
-        self.handle_res(path.res);
-        intravisit::walk_path(self, path);
+    fn visit_qpath(&mut self, qpath: &'tcx hir::QPath<'tcx>,
+                   id: hir::HirId, span: rustc_span::Span) {
+        let res = self.tables.qpath_res(qpath, id);
+        self.handle_res(res);
+        intravisit::walk_qpath(self, qpath, id, span);
     }
 
     fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {

src/test/ui/lint/dead-code/lint-dead-code-5.rs

@@ -13,6 +13,23 @@ enum Enum2 {
     Variant5 { _x: isize }, //~ ERROR: variant is never constructed: `Variant5`
     Variant6(isize), //~ ERROR: variant is never constructed: `Variant6`
     _Variant7,
+    Variant8 { _field: bool },
+    Variant9,
+    Variant10(usize)
+}
+
+impl Enum2 {
+    fn new_variant8() -> Enum2 {
+        Self::Variant8 { _field: true }
+    }
+
+    fn new_variant9() -> Enum2 {
+        Self::Variant9
+    }
+
+    fn new_variant10() -> Enum2 {
+        Self::Variant10(10)
+    }
 }
 
 enum Enum3 { //~ ERROR: enum is never used
@@ -26,5 +43,8 @@ fn main() {
         Enum1::Variant1(_) => (),
         Enum1::Variant2 => ()
     }
-    let x = Enum2::Variant3(true);
+    let _ = Enum2::Variant3(true);
+    let _ = Enum2::new_variant8();
+    let _ = Enum2::new_variant9();
+    let _ = Enum2::new_variant10();
 }

src/test/ui/lint/dead-code/lint-dead-code-5.stderr

@@ -23,7 +23,7 @@ LL |     Variant6(isize),
    |     ^^^^^^^^^^^^^^^
 
 error: enum is never used: `Enum3`
-  --> $DIR/lint-dead-code-5.rs:18:6
+  --> $DIR/lint-dead-code-5.rs:35:6
    |
 LL | enum Enum3 {
    |      ^^^^^