Don't warn on pub fields of pub(restricted) structs

Author: Urgau

compiler/rustc_lint/src/builtin.rs

@@ -1424,8 +1424,24 @@ impl<'tcx> LateLintPass<'tcx> for UnreachablePub {
     }
 
     fn check_field_def(&mut self, cx: &LateContext<'_>, field: &hir::FieldDef<'_>) {
-        if matches!(cx.tcx.parent_hir_node(field.hir_id), Node::Variant(_)) {
-            return;
+        match cx.tcx.parent_hir_node(field.hir_id) {
+            Node::Variant(_) => return,
+            // We don't want to lint on struct/union fields whose parent def is
+            // not public. We therefore check if the parent is a struct/union and
+            // if it `pub` we ignore the field.
+            //
+            // ```
+            // pub(crate) struct Hydrogen {
+            //     pub neutrons: usize, // should not lint
+            // }
+            // ```
+            Node::Item(item)
+                if item.is_struct_or_union()
+                    && !cx.tcx.visibility(item.owner_id.def_id).is_public() =>
+            {
+                return;
+            }
+            _ => {}
         }
         self.perform_lint(cx, "field", field.def_id, field.vis_span, false);
     }

tests/ui/lint/unreachable_pub.rs

@@ -15,6 +15,10 @@ mod private_mod {
         // (... but not more-restricted fields)
         pub(crate) electrons: usize
     }
+    pub(crate) struct Calcium {
+        pub neutrons: usize, // the visibility is clearly defined by the struct above
+                             // no need to cluter the field definition
+    }
     impl Hydrogen {
         // impls, too
         pub fn count_neutrons(&self) -> usize { self.neutrons } //~ WARNING unreachable_pub

tests/ui/lint/unreachable_pub.stderr

@@ -42,15 +42,15 @@ LL |         pub neutrons: usize,
    |         help: consider restricting its visibility: `pub(crate)`
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:20:9
+  --> $DIR/unreachable_pub.rs:24:9
    |
 LL |         pub fn count_neutrons(&self) -> usize { self.neutrons }
    |         ---^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |         |
    |         help: consider restricting its visibility: `pub(crate)`
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:29:5
+  --> $DIR/unreachable_pub.rs:33:5
    |
 LL |     pub enum Helium {}
    |     ---^^^^^^^^^^^^
@@ -60,7 +60,7 @@ LL |     pub enum Helium {}
    = help: or consider exporting it for use by other crates
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:30:5
+  --> $DIR/unreachable_pub.rs:34:5
    |
 LL |     pub union Lithium { c1: usize, c2: u8 }
    |     ---^^^^^^^^^^^^^^
@@ -70,7 +70,7 @@ LL |     pub union Lithium { c1: usize, c2: u8 }
    = help: or consider exporting it for use by other crates
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:31:5
+  --> $DIR/unreachable_pub.rs:35:5
    |
 LL |     pub fn beryllium() {}
    |     ---^^^^^^^^^^^^^^^
@@ -80,7 +80,7 @@ LL |     pub fn beryllium() {}
    = help: or consider exporting it for use by other crates
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:32:5
+  --> $DIR/unreachable_pub.rs:36:5
    |
 LL |     pub trait Boron {}
    |     ---^^^^^^^^^^^^
@@ -90,7 +90,7 @@ LL |     pub trait Boron {}
    = help: or consider exporting it for use by other crates
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:33:5
+  --> $DIR/unreachable_pub.rs:37:5
    |
 LL |     pub const CARBON: usize = 1;
    |     ---^^^^^^^^^^^^^^^^^^^^
@@ -100,7 +100,7 @@ LL |     pub const CARBON: usize = 1;
    = help: or consider exporting it for use by other crates
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:34:5
+  --> $DIR/unreachable_pub.rs:38:5
    |
 LL |     pub static NITROGEN: usize = 2;
    |     ---^^^^^^^^^^^^^^^^^^^^^^^
@@ -110,7 +110,7 @@ LL |     pub static NITROGEN: usize = 2;
    = help: or consider exporting it for use by other crates
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:35:5
+  --> $DIR/unreachable_pub.rs:39:5
    |
 LL |     pub type Oxygen = bool;
    |     ---^^^^^^^^^^^^
@@ -120,7 +120,7 @@ LL |     pub type Oxygen = bool;
    = help: or consider exporting it for use by other crates
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:38:47
+  --> $DIR/unreachable_pub.rs:42:47
    |
 LL |         ($visibility: vis, $name: ident) => { $visibility struct $name {} }
    |                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -135,7 +135,7 @@ LL |     define_empty_struct_with_visibility!(pub, Fluorine);
    = note: this warning originates in the macro `define_empty_struct_with_visibility` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:44:9
+  --> $DIR/unreachable_pub.rs:48:9
    |
 LL |         pub fn catalyze() -> bool;
    |         ---^^^^^^^^^^^^^^^^^^^^^^