deduplicate warnings (attempt 2)

Author: jdonszelmann

compiler/rustc_passes/src/stability.rs

@@ -5,15 +5,16 @@ use std::num::NonZero;
 
 use rustc_ast_lowering::stability::extern_abi_stability;
 use rustc_data_structures::fx::FxIndexMap;
+use rustc_data_structures::smallvec::SmallVec;
 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_id::{CRATE_DEF_ID, LOCAL_CRATE, LocalDefId, LocalModDefId};
+use rustc_hir::def::{CtorOf, DefKind, Res};
+use rustc_hir::def_id::{CRATE_DEF_ID, DefId, 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 +740,38 @@ 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 UsePath { segments, ref res, span } = *path;
+
+        // At most 3 (since there are 3 namespaces) so don't bother with
+        // a set, or allocating a vec.
+        let mut seen_dids = SmallVec::<[DefId; 3]>::new();
+
+        for res in res.present_items() {
+            // 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(did) = res.opt_def_id() {
+                // If it's a ctor, we need the parent did.
+                // The parent defid of a constructor is that of the struct it constructs.
+                let did = match self.tcx.def_kind(did) {
+                    DefKind::Ctor(CtorOf::Struct, _) => self.tcx.parent(did),
+                    _ => did,
+                };
+
+                // When we've already seen a defid, don't walk this path.
+                // This avoids the duplicate deprecation warnings.
+                if seen_dids.contains(&did) {
+                    continue;
+                }
+
+                seen_dids.push(did);
+            }
+
+            self.visit_path(&Path { segments, res, span }, 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

@@ -11,10 +11,8 @@ pub mod a {
 
 use a::Foo;
 //~^ ERROR use of deprecated 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`
 use a::Baz;
 //~^ ERROR use of deprecated struct `a::Baz`
 

tests/ui/deprecation/unit_and_tuple_struct.stderr

@@ -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