deduplicate warnings (attempt 2)

Author: jdonszelmann

compiler/rustc_passes/src/stability.rs

@@ -8,12 +8,12 @@ use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::unord::{ExtendUnord, UnordMap, UnordSet};
 use rustc_feature::{EnabledLangFeature, EnabledLibFeature};
 use rustc_hir::attrs::{AttributeKind, DeprecatedSince};
-use rustc_hir::def::{DefKind, Res};
+use rustc_hir::def::{CtorOf, 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 +739,28 @@ 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(CtorOf::Struct, _) = 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
+            let UsePath { segments, res: _, span } = *path;
+            self.visit_path(&Path { segments, res: value_ns_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

@@ -10,11 +10,9 @@ pub mod a {
 
 
 use a::Foo;
-//~^ ERROR use of deprecated struct `a::Foo`
-//~| ERROR use of deprecated unit struct `a::Foo`
+//~^ ERROR use of deprecated unit struct `a::Foo`
 use a::Bar;
-//~^ ERROR use of deprecated struct `a::Bar`
-//~| ERROR use of deprecated tuple struct `a::Bar`
+//~^ ERROR use of deprecated tuple struct `a::Bar`
 use a::Baz;
 //~^ ERROR use of deprecated struct `a::Baz`
 

tests/ui/deprecation/unit_and_tuple_struct.stderr

@@ -1,4 +1,4 @@
-error: use of deprecated struct `a::Foo`
+error: use of deprecated unit struct `a::Foo`
   --> $DIR/unit_and_tuple_struct.rs:12:8
    |
 LL | use a::Foo;
@@ -10,47 +10,35 @@ note: the lint level is defined here
 LL | #![deny(deprecated)]
    |         ^^^^^^^^^^
 
-error: use of deprecated unit struct `a::Foo`
-  --> $DIR/unit_and_tuple_struct.rs:12:8
-   |
-LL | use a::Foo;
-   |        ^^^
-
-error: use of deprecated struct `a::Bar`
-  --> $DIR/unit_and_tuple_struct.rs:15:8
-   |
-LL | use a::Bar;
-   |        ^^^
-
 error: use of deprecated tuple struct `a::Bar`
-  --> $DIR/unit_and_tuple_struct.rs:15:8
+  --> $DIR/unit_and_tuple_struct.rs:14:8
    |
 LL | use a::Bar;
    |        ^^^
 
 error: use of deprecated struct `a::Baz`
-  --> $DIR/unit_and_tuple_struct.rs:18:8
+  --> $DIR/unit_and_tuple_struct.rs:16:8
    |
 LL | use a::Baz;
    |        ^^^
 
 error: use of deprecated unit struct `a::Foo`
-  --> $DIR/unit_and_tuple_struct.rs:22:6
+  --> $DIR/unit_and_tuple_struct.rs:20:6
    |
 LL |   a::Foo;
    |      ^^^
 
 error: use of deprecated tuple struct `a::Bar`
-  --> $DIR/unit_and_tuple_struct.rs:24:6
+  --> $DIR/unit_and_tuple_struct.rs:22:6
    |
 LL |   a::Bar();
    |      ^^^
 
 error: use of deprecated struct `a::Baz`
-  --> $DIR/unit_and_tuple_struct.rs:26:6
+  --> $DIR/unit_and_tuple_struct.rs:24:6
    |
 LL |   a::Baz {};
    |      ^^^
 
-error: aborting due to 8 previous errors
+error: aborting due to 6 previous errors