Prefer `pub(super)` in `unreachable_pub` lint suggestion

5 files changed, 307 insertions, 16 deletions

diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index 02d22ee49bd..130f3cb7c2a 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -1298,12 +1298,30 @@ impl UnreachablePub {
         let mut applicability = Applicability::MachineApplicable;
         if cx.tcx.visibility(def_id).is_public() && !cx.effective_visibilities.is_reachable(def_id)
         {
+            // prefer suggesting `pub(super)` instead of `pub(crate)` when possible,
+            // except when `pub(super) == pub(crate)`
+            let new_vis = if let Some(ty::Visibility::Restricted(restricted_did)) =
+                cx.effective_visibilities.effective_vis(def_id).map(|effective_vis| {
+                    effective_vis.at_level(rustc_middle::middle::privacy::Level::Reachable)
+                })
+                && let parent_parent = cx.tcx.parent_module_from_def_id(
+                    cx.tcx.parent_module_from_def_id(def_id.into()).into(),
+                )
+                && *restricted_did == parent_parent.to_local_def_id()
+                && !restricted_did.to_def_id().is_crate_root()
+            {
+                "pub(super)"
+            } else {
+                "pub(crate)"
+            };
+
             if vis_span.from_expansion() {
                 applicability = Applicability::MaybeIncorrect;
             }
             let def_span = cx.tcx.def_span(def_id);
             cx.emit_span_lint(UNREACHABLE_PUB, def_span, BuiltinUnreachablePub {
                 what,
+                new_vis,
                 suggestion: (vis_span, applicability),
                 help: exportable,
             });
diff --git a/compiler/rustc_lint/src/lints.rs b/compiler/rustc_lint/src/lints.rs
index 38e52570e53..352155729e5 100644
--- a/compiler/rustc_lint/src/lints.rs
+++ b/compiler/rustc_lint/src/lints.rs
@@ -254,7 +254,8 @@ impl<'a> LintDiagnostic<'a, ()> for BuiltinUngatedAsyncFnTrackCaller<'_> {
 #[diag(lint_builtin_unreachable_pub)]
 pub(crate) struct BuiltinUnreachablePub<'a> {
     pub what: &'a str,
-    #[suggestion(code = "pub(crate)")]
+    pub new_vis: &'a str,
+    #[suggestion(code = "{new_vis}")]
     pub suggestion: (Span, Applicability),
     #[help]
     pub help: bool,
diff --git a/tests/ui/lint/unreachable_pub.fixed b/tests/ui/lint/unreachable_pub.fixed
new file mode 100644
index 00000000000..163e8d24b32
--- /dev/null
+++ b/tests/ui/lint/unreachable_pub.fixed
@@ -0,0 +1,116 @@
+//@ check-pass
+//@ edition: 2018
+//@ run-rustfix
+
+#![allow(unused)]
+#![warn(unreachable_pub)]
+
+mod private_mod {
+    // non-leaked `pub` items in private module should be linted
+    pub(crate) use std::fmt; //~ WARNING unreachable_pub
+    pub(crate) use std::env::{Args}; // braced-use has different item spans than unbraced
+    //~^ WARNING unreachable_pub
+
+    // we lint on struct definition
+    pub(crate) struct Hydrogen { //~ WARNING unreachable_pub
+        // but not on fields, even if they are `pub` as putting `pub(crate)`
+        // it would clutter the source code for little value
+        pub neutrons: usize,
+        pub(crate) electrons: usize
+    }
+    pub(crate) struct Calcium {
+        pub neutrons: usize,
+    }
+    impl Hydrogen {
+        // impls, too
+        pub(crate) fn count_neutrons(&self) -> usize { self.neutrons } //~ WARNING unreachable_pub
+        pub(crate) fn count_electrons(&self) -> usize { self.electrons }
+    }
+    impl Clone for Hydrogen {
+        fn clone(&self) -> Hydrogen {
+            Hydrogen { neutrons: self.neutrons, electrons: self.electrons }
+        }
+    }
+
+    pub(crate) enum Helium {} //~ WARNING unreachable_pub
+    pub(crate) union Lithium { c1: usize, c2: u8 } //~ WARNING unreachable_pub
+    pub(crate) fn beryllium() {} //~ WARNING unreachable_pub
+    pub(crate) trait Boron {} //~ WARNING unreachable_pub
+    pub(crate) const CARBON: usize = 1; //~ WARNING unreachable_pub
+    pub(crate) static NITROGEN: usize = 2; //~ WARNING unreachable_pub
+    pub(crate) type Oxygen = bool; //~ WARNING unreachable_pub
+
+    macro_rules! define_empty_struct_with_visibility {
+        ($visibility: vis, $name: ident) => { $visibility struct $name {} }
+        //~^ WARNING unreachable_pub
+    }
+    define_empty_struct_with_visibility!(pub(crate), Fluorine);
+
+    extern "C" {
+        pub(crate) fn catalyze() -> bool; //~ WARNING unreachable_pub
+    }
+
+    mod private_in_private {
+        pub(super) enum Helium {} //~ WARNING unreachable_pub
+        pub(super) fn beryllium() {} //~ WARNING unreachable_pub
+    }
+
+    pub(crate) mod crate_in_private {
+        pub(crate) const CARBON: usize = 1; //~ WARNING unreachable_pub
+    }
+
+    pub(crate) mod pub_in_private { //~ WARNING unreachable_pub
+        pub(crate) static NITROGEN: usize = 2; //~ WARNING unreachable_pub
+    }
+
+    fn foo() {
+        const {
+            pub(crate) struct Foo; //~ WARNING unreachable_pub
+        };
+    }
+
+    enum Weird {
+        Variant = {
+            pub(crate) struct Foo; //~ WARNING unreachable_pub
+
+            mod tmp {
+                pub(crate) struct Bar; //~ WARNING unreachable_pub
+            }
+
+            let _ = tmp::Bar;
+
+            0
+        },
+    }
+
+    pub(crate) use fpu_precision::set_precision; //~ WARNING unreachable_pub
+
+    mod fpu_precision {
+        pub(crate) fn set_precision<T>() {} //~ WARNING unreachable_pub
+        pub(super) fn set_micro_precision<T>() {} //~ WARNING unreachable_pub
+    }
+
+    // items leaked through signatures (see `get_neon` below) are OK
+    pub struct Neon {}
+
+    // crate-visible items are OK
+    pub(crate) struct Sodium {}
+}
+
+pub mod public_mod {
+    // module is public: these are OK, too
+    pub struct Magnesium {}
+    pub(crate) struct Aluminum {}
+}
+
+pub fn get_neon() -> private_mod::Neon {
+    private_mod::Neon {}
+}
+
+fn main() {
+    let _ = get_neon();
+    let _ = private_mod::beryllium();
+    let _ = private_mod::crate_in_private::CARBON;
+    let _ = private_mod::pub_in_private::NITROGEN;
+    let _ = unsafe { private_mod::catalyze() };
+}
diff --git a/tests/ui/lint/unreachable_pub.rs b/tests/ui/lint/unreachable_pub.rs
index f21f6640342..8524820bcfb 100644
--- a/tests/ui/lint/unreachable_pub.rs
+++ b/tests/ui/lint/unreachable_pub.rs
@@ -1,4 +1,6 @@
 //@ check-pass
+//@ edition: 2018
+//@ run-rustfix
 
 #![allow(unused)]
 #![warn(unreachable_pub)]
@@ -48,6 +50,46 @@ mod private_mod {
         pub fn catalyze() -> bool; //~ WARNING unreachable_pub
     }
 
+    mod private_in_private {
+        pub enum Helium {} //~ WARNING unreachable_pub
+        pub fn beryllium() {} //~ WARNING unreachable_pub
+    }
+
+    pub(crate) mod crate_in_private {
+        pub const CARBON: usize = 1; //~ WARNING unreachable_pub
+    }
+
+    pub mod pub_in_private { //~ WARNING unreachable_pub
+        pub static NITROGEN: usize = 2; //~ WARNING unreachable_pub
+    }
+
+    fn foo() {
+        const {
+            pub struct Foo; //~ WARNING unreachable_pub
+        };
+    }
+
+    enum Weird {
+        Variant = {
+            pub struct Foo; //~ WARNING unreachable_pub
+
+            mod tmp {
+                pub struct Bar; //~ WARNING unreachable_pub
+            }
+
+            let _ = tmp::Bar;
+
+            0
+        },
+    }
+
+    pub use fpu_precision::set_precision; //~ WARNING unreachable_pub
+
+    mod fpu_precision {
+        pub fn set_precision<T>() {} //~ WARNING unreachable_pub
+        pub fn set_micro_precision<T>() {} //~ WARNING unreachable_pub
+    }
+
     // items leaked through signatures (see `get_neon` below) are OK
     pub struct Neon {}
 
@@ -67,4 +109,8 @@ pub fn get_neon() -> private_mod::Neon {
 
 fn main() {
     let _ = get_neon();
+    let _ = private_mod::beryllium();
+    let _ = private_mod::crate_in_private::CARBON;
+    let _ = private_mod::pub_in_private::NITROGEN;
+    let _ = unsafe { private_mod::catalyze() };
 }
diff --git a/tests/ui/lint/unreachable_pub.stderr b/tests/ui/lint/unreachable_pub.stderr
index 65f45fbd816..5173ff1f026 100644
--- a/tests/ui/lint/unreachable_pub.stderr
+++ b/tests/ui/lint/unreachable_pub.stderr
@@ -1,5 +1,5 @@
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:8:13
+  --> $DIR/unreachable_pub.rs:10:13
    |
 LL |     pub use std::fmt;
    |     ---     ^^^^^^^^
@@ -8,13 +8,13 @@ LL |     pub use std::fmt;
    |
    = help: or consider exporting it for use by other crates
 note: the lint level is defined here
-  --> $DIR/unreachable_pub.rs:4:9
+  --> $DIR/unreachable_pub.rs:6:9
    |
 LL | #![warn(unreachable_pub)]
    |         ^^^^^^^^^^^^^^^
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:9:24
+  --> $DIR/unreachable_pub.rs:11:24
    |
 LL |     pub use std::env::{Args}; // braced-use has different item spans than unbraced
    |     ---                ^^^^
@@ -24,7 +24,7 @@ LL |     pub use std::env::{Args}; // braced-use has different item spans than u
    = help: or consider exporting it for use by other crates
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:13:5
+  --> $DIR/unreachable_pub.rs:15:5
    |
 LL |     pub struct Hydrogen {
    |     ---^^^^^^^^^^^^^^^^
@@ -34,7 +34,7 @@ LL |     pub struct Hydrogen {
    = help: or consider exporting it for use by other crates
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:24:9
+  --> $DIR/unreachable_pub.rs:26:9
    |
 LL |         pub fn count_neutrons(&self) -> usize { self.neutrons }
    |         ---^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -42,7 +42,7 @@ LL |         pub fn count_neutrons(&self) -> usize { self.neutrons }
    |         help: consider restricting its visibility: `pub(crate)`
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:33:5
+  --> $DIR/unreachable_pub.rs:35:5
    |
 LL |     pub enum Helium {}
    |     ---^^^^^^^^^^^^
@@ -52,7 +52,7 @@ LL |     pub enum Helium {}
    = help: or consider exporting it for use by other crates
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:34:5
+  --> $DIR/unreachable_pub.rs:36:5
    |
 LL |     pub union Lithium { c1: usize, c2: u8 }
    |     ---^^^^^^^^^^^^^^
@@ -62,7 +62,7 @@ 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:35:5
+  --> $DIR/unreachable_pub.rs:37:5
    |
 LL |     pub fn beryllium() {}
    |     ---^^^^^^^^^^^^^^^
@@ -72,7 +72,7 @@ LL |     pub fn beryllium() {}
    = help: or consider exporting it for use by other crates
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:36:5
+  --> $DIR/unreachable_pub.rs:38:5
    |
 LL |     pub trait Boron {}
    |     ---^^^^^^^^^^^^
@@ -82,7 +82,7 @@ LL |     pub trait Boron {}
    = help: or consider exporting it for use by other crates
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:37:5
+  --> $DIR/unreachable_pub.rs:39:5
    |
 LL |     pub const CARBON: usize = 1;
    |     ---^^^^^^^^^^^^^^^^^^^^
@@ -92,7 +92,7 @@ LL |     pub const CARBON: usize = 1;
    = help: or consider exporting it for use by other crates
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:38:5
+  --> $DIR/unreachable_pub.rs:40:5
    |
 LL |     pub static NITROGEN: usize = 2;
    |     ---^^^^^^^^^^^^^^^^^^^^^^^
@@ -102,7 +102,7 @@ LL |     pub static NITROGEN: usize = 2;
    = help: or consider exporting it for use by other crates
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:39:5
+  --> $DIR/unreachable_pub.rs:41:5
    |
 LL |     pub type Oxygen = bool;
    |     ---^^^^^^^^^^^^
@@ -112,7 +112,7 @@ LL |     pub type Oxygen = bool;
    = help: or consider exporting it for use by other crates
 
 warning: unreachable `pub` item
-  --> $DIR/unreachable_pub.rs:42:47
+  --> $DIR/unreachable_pub.rs:44:47
    |
 LL |         ($visibility: vis, $name: ident) => { $visibility struct $name {} }
    |                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -127,7 +127,7 @@ 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:48:9
+  --> $DIR/unreachable_pub.rs:50:9
    |
 LL |         pub fn catalyze() -> bool;
    |         ---^^^^^^^^^^^^^^^^^^^^^^^
@@ -136,5 +136,115 @@ LL |         pub fn catalyze() -> bool;
    |
    = help: or consider exporting it for use by other crates
 
-warning: 13 warnings emitted
+warning: unreachable `pub` item
+  --> $DIR/unreachable_pub.rs:62:5
+   |
+LL |     pub mod pub_in_private {
+   |     ---^^^^^^^^^^^^^^^^^^^
+   |     |
+   |     help: consider restricting its visibility: `pub(crate)`
+   |
+   = help: or consider exporting it for use by other crates
+
+warning: unreachable `pub` item
+  --> $DIR/unreachable_pub.rs:68:13
+   |
+LL |             pub struct Foo;
+   |             ---^^^^^^^^^^^
+   |             |
+   |             help: consider restricting its visibility: `pub(crate)`
+   |
+   = help: or consider exporting it for use by other crates
+
+warning: unreachable `pub` item
+  --> $DIR/unreachable_pub.rs:74:13
+   |
+LL |             pub struct Foo;
+   |             ---^^^^^^^^^^^
+   |             |
+   |             help: consider restricting its visibility: `pub(crate)`
+   |
+   = help: or consider exporting it for use by other crates
+
+warning: unreachable `pub` item
+  --> $DIR/unreachable_pub.rs:86:13
+   |
+LL |     pub use fpu_precision::set_precision;
+   |     ---     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |     |
+   |     help: consider restricting its visibility: `pub(crate)`
+   |
+   = help: or consider exporting it for use by other crates
+
+warning: unreachable `pub` item
+  --> $DIR/unreachable_pub.rs:54:9
+   |
+LL |         pub enum Helium {}
+   |         ---^^^^^^^^^^^^
+   |         |
+   |         help: consider restricting its visibility: `pub(super)`
+   |
+   = help: or consider exporting it for use by other crates
+
+warning: unreachable `pub` item
+  --> $DIR/unreachable_pub.rs:55:9
+   |
+LL |         pub fn beryllium() {}
+   |         ---^^^^^^^^^^^^^^^
+   |         |
+   |         help: consider restricting its visibility: `pub(super)`
+   |
+   = help: or consider exporting it for use by other crates
+
+warning: unreachable `pub` item
+  --> $DIR/unreachable_pub.rs:59:9
+   |
+LL |         pub const CARBON: usize = 1;
+   |         ---^^^^^^^^^^^^^^^^^^^^
+   |         |
+   |         help: consider restricting its visibility: `pub(crate)`
+   |
+   = help: or consider exporting it for use by other crates
+
+warning: unreachable `pub` item
+  --> $DIR/unreachable_pub.rs:63:9
+   |
+LL |         pub static NITROGEN: usize = 2;
+   |         ---^^^^^^^^^^^^^^^^^^^^^^^
+   |         |
+   |         help: consider restricting its visibility: `pub(crate)`
+   |
+   = help: or consider exporting it for use by other crates
+
+warning: unreachable `pub` item
+  --> $DIR/unreachable_pub.rs:77:17
+   |
+LL |                 pub struct Bar;
+   |                 ---^^^^^^^^^^^
+   |                 |
+   |                 help: consider restricting its visibility: `pub(crate)`
+   |
+   = help: or consider exporting it for use by other crates
+
+warning: unreachable `pub` item
+  --> $DIR/unreachable_pub.rs:89:9
+   |
+LL |         pub fn set_precision<T>() {}
+   |         ---^^^^^^^^^^^^^^^^^^^^^^
+   |         |
+   |         help: consider restricting its visibility: `pub(crate)`
+   |
+   = help: or consider exporting it for use by other crates
+
+warning: unreachable `pub` item
+  --> $DIR/unreachable_pub.rs:90:9
+   |
+LL |         pub fn set_micro_precision<T>() {}
+   |         ---^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |         |
+   |         help: consider restricting its visibility: `pub(super)`
+   |
+   = help: or consider exporting it for use by other crates
+
+warning: 24 warnings emitted