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

src/librustc_passes/dead.rs

@@ -255,7 +255,9 @@ impl<'a, 'tcx> Visitor<'tcx> for MarkSymbolVisitor<'a, 'tcx> {
             hir::ExprKind::Field(ref lhs, ..) => {
                 self.handle_field_access(&lhs, expr.hir_id);
             }
-            hir::ExprKind::Struct(_, ref fields, _) => {
+            hir::ExprKind::Struct(ref qpath, ref fields, _) => {
+                let res = self.tables.qpath_res(qpath, expr.hir_id);
+                self.handle_res(res);
                 if let ty::Adt(ref adt, _) = self.tables.expr_ty(expr).kind {
                     self.mark_as_used_if_union(adt, fields);
                 }

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
@@ -27,4 +44,7 @@ fn main() {
         Enum1::Variant2 => ()
     }
     let x = 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 {
    |      ^^^^^