Deduplicate deprecation warning when using unit or tuple structs

compiler/rustc_passes/src/stability.rs

@@ -12,8 +12,8 @@ use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{CRATE_DEF_ID, LOCAL_CRATE, LocalDefId, LocalModDefId};
 use rustc_hir::intravisit::{self, Visitor, VisitorExt};
 use rustc_hir::{
-    self as hir, AmbigArg, ConstStability, DefaultBodyStability, FieldDef, Item, ItemKind,
-    Stability, StabilityLevel, StableSince, TraitRef, Ty, TyKind, UnstableReason,
+    self as hir, AmbigArg, ConstStability, DefaultBodyStability, FieldDef, HirId, Item, ItemKind,
+    Path, Stability, StabilityLevel, StableSince, TraitRef, Ty, TyKind, UnstableReason, UsePath,
     VERSION_PLACEHOLDER, Variant, find_attr,
 };
 use rustc_middle::hir::nested_filter;
@@ -739,6 +739,35 @@ impl<'tcx> Visitor<'tcx> for Checker<'tcx> {
         intravisit::walk_poly_trait_ref(self, t);
     }
 
+    fn visit_use(&mut self, path: &'tcx UsePath<'tcx>, hir_id: HirId) {
+        let res = path.res;
+
+        // A use item can import something from two namespaces at the same time.
+        // For deprecation/stability we don't want to warn twice.
+        // This specifically happens with constructors for unit/tuple structs.
+        if let Some(ty_ns_res) = res.type_ns
+            && let Some(value_ns_res) = res.value_ns
+            && let Some(type_ns_did) = ty_ns_res.opt_def_id()
+            && let Some(value_ns_did) = value_ns_res.opt_def_id()
+            && let DefKind::Ctor(.., _) = self.tcx.def_kind(value_ns_did)
+            && self.tcx.parent(value_ns_did) == type_ns_did
+        {
+            // Only visit the value namespace path when we've detected a duplicate,
+            // not the type namespace path.
+            let UsePath { segments, res: _, span } = *path;
+            self.visit_path(&Path { segments, res: value_ns_res, span }, hir_id);
+
+            // Though, visit the macro namespace if it exists,
+            // regardless of the checks above relating to constructors.
+            if let Some(res) = res.macro_ns {
+                self.visit_path(&Path { segments, res, span }, hir_id);
+            }
+        } else {
+            // if there's no duplicate, just walk as normal
+            intravisit::walk_use(self, path, hir_id)
+        }
+    }
+
     fn visit_path(&mut self, path: &hir::Path<'tcx>, id: hir::HirId) {
         if let Some(def_id) = path.res.opt_def_id() {
             let method_span = path.segments.last().map(|s| s.ident.span);

tests/ui/deprecation/unit_and_tuple_struct.rs

@@ -0,0 +1,45 @@
+#![deny(deprecated)]
+
+#[deprecated]
+pub mod a {
+    pub struct Foo;
+    pub struct Bar();
+    pub struct Baz {}
+
+    pub enum Enum {
+        VFoo,
+        VBar(),
+        VBaz {},
+    }
+}
+
+
+use a::Foo;
+//~^ ERROR use of deprecated unit struct `a::Foo`
+use a::Bar;
+//~^ ERROR use of deprecated tuple struct `a::Bar`
+use a::Baz;
+//~^ ERROR use of deprecated struct `a::Baz`
+
+use a::Enum::VFoo;
+//~^ ERROR use of deprecated unit variant `a::Enum::VFoo`
+use a::Enum::VBar;
+//~^ ERROR use of deprecated tuple variant `a::Enum::VBar`
+use a::Enum::VBaz;
+//~^ ERROR use of deprecated variant `a::Enum::VBaz`
+
+fn main() {
+  a::Foo;
+  //~^ ERROR use of deprecated unit struct `a::Foo`
+  a::Bar();
+  //~^ ERROR use of deprecated tuple struct `a::Bar`
+  a::Baz {};
+  //~^ ERROR use of deprecated struct `a::Baz`
+
+  a::Enum::VFoo;
+  //~^ ERROR use of deprecated unit variant `a::Enum::VFoo`
+  a::Enum::VBar();
+  //~^ ERROR use of deprecated tuple variant `a::Enum::VBar`
+  a::Enum::VBaz{};
+  //~^ ERROR use of deprecated variant `a::Enum::VBaz`
+}

tests/ui/deprecation/unit_and_tuple_struct.stderr

@@ -0,0 +1,80 @@
+error: use of deprecated unit struct `a::Foo`
+  --> $DIR/unit_and_tuple_struct.rs:17:8
+   |
+LL | use a::Foo;
+   |        ^^^
+   |
+note: the lint level is defined here
+  --> $DIR/unit_and_tuple_struct.rs:1:9
+   |
+LL | #![deny(deprecated)]
+   |         ^^^^^^^^^^
+
+error: use of deprecated tuple struct `a::Bar`
+  --> $DIR/unit_and_tuple_struct.rs:19:8
+   |
+LL | use a::Bar;
+   |        ^^^
+
+error: use of deprecated struct `a::Baz`
+  --> $DIR/unit_and_tuple_struct.rs:21:8
+   |
+LL | use a::Baz;
+   |        ^^^
+
+error: use of deprecated unit variant `a::Enum::VFoo`
+  --> $DIR/unit_and_tuple_struct.rs:24:14
+   |
+LL | use a::Enum::VFoo;
+   |              ^^^^
+
+error: use of deprecated tuple variant `a::Enum::VBar`
+  --> $DIR/unit_and_tuple_struct.rs:26:14
+   |
+LL | use a::Enum::VBar;
+   |              ^^^^
+
+error: use of deprecated variant `a::Enum::VBaz`
+  --> $DIR/unit_and_tuple_struct.rs:28:14
+   |
+LL | use a::Enum::VBaz;
+   |              ^^^^
+
+error: use of deprecated unit struct `a::Foo`
+  --> $DIR/unit_and_tuple_struct.rs:32:6
+   |
+LL |   a::Foo;
+   |      ^^^
+
+error: use of deprecated tuple struct `a::Bar`
+  --> $DIR/unit_and_tuple_struct.rs:34:6
+   |
+LL |   a::Bar();
+   |      ^^^
+
+error: use of deprecated struct `a::Baz`
+  --> $DIR/unit_and_tuple_struct.rs:36:6
+   |
+LL |   a::Baz {};
+   |      ^^^
+
+error: use of deprecated unit variant `a::Enum::VFoo`
+  --> $DIR/unit_and_tuple_struct.rs:39:12
+   |
+LL |   a::Enum::VFoo;
+   |            ^^^^
+
+error: use of deprecated tuple variant `a::Enum::VBar`
+  --> $DIR/unit_and_tuple_struct.rs:41:12
+   |
+LL |   a::Enum::VBar();
+   |            ^^^^
+
+error: use of deprecated variant `a::Enum::VBaz`
+  --> $DIR/unit_and_tuple_struct.rs:43:12
+   |
+LL |   a::Enum::VBaz{};
+   |            ^^^^
+
+error: aborting due to 12 previous errors
+