Merge #10979

10979: fix: Don't show trait flyimports for impl trait and placeholders r=Veykril a=Veykril

cc #8539
bors r+

Co-authored-by: Lukas Wirth <lukastw97@gmail.com>

crates/hir/src/lib.rs

@@ -2623,13 +2623,15 @@ impl Type {
     }
 
     pub fn autoderef<'a>(&'a self, db: &'a dyn HirDatabase) -> impl Iterator<Item = Type> + 'a {
+        self.autoderef_(db).map(move |ty| self.derived(ty))
+    }
+
+    pub fn autoderef_<'a>(&'a self, db: &'a dyn HirDatabase) -> impl Iterator<Item = Ty> + 'a {
         // There should be no inference vars in types passed here
         let canonical = hir_ty::replace_errors_with_variables(&self.ty);
         let environment = self.env.env.clone();
         let ty = InEnvironment { goal: canonical, environment };
-        autoderef(db, Some(self.krate), ty)
-            .map(|canonical| canonical.value)
-            .map(move |ty| self.derived(ty))
+        autoderef(db, Some(self.krate), ty).map(|canonical| canonical.value)
     }
 
     // This would be nicer if it just returned an iterator, but that runs into
@@ -2808,22 +2810,32 @@ impl Type {
         db: &'a dyn HirDatabase,
     ) -> impl Iterator<Item = Trait> + 'a {
         let _p = profile::span("applicable_inherent_traits");
-        self.autoderef(db)
-            .filter_map(|derefed_type| derefed_type.ty.dyn_trait())
+        self.autoderef_(db)
+            .filter_map(|ty| ty.dyn_trait())
             .flat_map(move |dyn_trait_id| hir_ty::all_super_traits(db.upcast(), dyn_trait_id))
             .map(Trait::from)
     }
 
-    pub fn as_impl_traits(&self, db: &dyn HirDatabase) -> Option<Vec<Trait>> {
+    pub fn env_traits<'a>(&'a self, db: &'a dyn HirDatabase) -> impl Iterator<Item = Trait> + 'a {
+        let _p = profile::span("env_traits");
+        self.autoderef_(db)
+            .filter(|ty| matches!(ty.kind(&Interner), TyKind::Placeholder(_)))
+            .flat_map(|ty| {
+                self.env
+                    .traits_in_scope_from_clauses(ty)
+                    .flat_map(|t| hir_ty::all_super_traits(db.upcast(), t))
+            })
+            .map(Trait::from)
+    }
+
+    pub fn as_impl_traits(&self, db: &dyn HirDatabase) -> Option<impl Iterator<Item = Trait>> {
         self.ty.impl_trait_bounds(db).map(|it| {
-            it.into_iter()
-                .filter_map(|pred| match pred.skip_binders() {
+            it.into_iter().filter_map(|pred| match pred.skip_binders() {
                 hir_ty::WhereClause::Implemented(trait_ref) => {
                     Some(Trait::from(trait_ref.hir_trait_id()))
                 }
                 _ => None,
             })
-                .collect()
         })
     }
 

crates/hir_ty/src/method_resolution.rs

@@ -719,7 +719,7 @@ fn iterate_trait_method_candidates(
     let env_traits = match self_ty.value.kind(&Interner) {
         TyKind::Placeholder(_) => {
             // if we have `T: Trait` in the param env, the trait doesn't need to be in scope
-            env.traits_in_scope_from_clauses(&self_ty.value)
+            env.traits_in_scope_from_clauses(self_ty.value.clone())
                 .flat_map(|t| all_super_traits(db.upcast(), t))
                 .collect()
         }

crates/hir_ty/src/traits.rs

@@ -54,17 +54,13 @@ impl TraitEnvironment {
         }
     }
 
-    pub(crate) fn traits_in_scope_from_clauses<'a>(
+    pub fn traits_in_scope_from_clauses<'a>(
         &'a self,
-        ty: &'a Ty,
+        ty: Ty,
     ) -> impl Iterator<Item = TraitId> + 'a {
-        self.traits_from_clauses.iter().filter_map(move |(self_ty, trait_id)| {
-            if self_ty == ty {
-                Some(*trait_id)
-            } else {
-                None
-            }
-        })
+        self.traits_from_clauses
+            .iter()
+            .filter_map(move |(self_ty, trait_id)| (*self_ty == ty).then(|| *trait_id))
     }
 }
 

crates/ide/src/goto_type_definition.rs

@@ -75,7 +75,7 @@ pub(crate) fn goto_type_definition(
                 } else if let Some(trait_) = t.as_dyn_trait() {
                     push(trait_.into());
                 } else if let Some(traits) = t.as_impl_traits(db) {
-                    traits.into_iter().for_each(|it| push(it.into()));
+                    traits.for_each(|it| push(it.into()));
                 } else if let Some(trait_) = t.as_associated_type_parent_trait(db) {
                     push(trait_.into());
                 }

crates/ide/src/hover.rs

@@ -337,7 +337,7 @@ fn walk_and_push_ty(
         } else if let Some(trait_) = t.as_dyn_trait() {
             push_new_def(trait_.into());
         } else if let Some(traits) = t.as_impl_traits(db) {
-            traits.into_iter().for_each(|it| push_new_def(it.into()));
+            traits.for_each(|it| push_new_def(it.into()));
         } else if let Some(trait_) = t.as_associated_type_parent_trait(db) {
             push_new_def(trait_.into());
         }

crates/ide_assists/src/utils/suggest_name.rs

@@ -243,7 +243,7 @@ fn name_of_type(ty: &hir::Type, db: &RootDatabase) -> Option<String> {
     } else if let Some(trait_) = ty.as_dyn_trait() {
         trait_name(&trait_, db)?
     } else if let Some(traits) = ty.as_impl_traits(db) {
-        let mut iter = traits.into_iter().filter_map(|t| trait_name(&t, db));
+        let mut iter = traits.filter_map(|t| trait_name(&t, db));
         let name = iter.next()?;
         if iter.next().is_some() {
             return None;

crates/ide_completion/src/completions/pattern.rs

@@ -1,5 +1,7 @@
 //! Completes constants and paths in unqualified patterns.
 
+use hir::db::DefDatabase;
+
 use crate::{
     context::{PatternContext, PatternRefutability},
     CompletionContext, Completions,
@@ -13,11 +15,12 @@ pub(crate) fn complete_pattern(acc: &mut Completions, ctx: &CompletionContext) {
         }
         _ => return,
     };
+    let single_variant_enum = |enum_: hir::Enum| ctx.db.enum_data(enum_.into()).variants.len() == 1;
 
-    if refutable {
     if let Some(hir::Adt::Enum(e)) =
         ctx.expected_type.as_ref().and_then(|ty| ty.strip_references().as_adt())
     {
+        if refutable || single_variant_enum(e) {
             super::enum_variants_with_paths(acc, ctx, e, |acc, ctx, variant, path| {
                 acc.add_qualified_variant_pat(ctx, variant, path.clone());
                 acc.add_qualified_enum_variant(ctx, variant, path);
@@ -28,20 +31,20 @@ pub(crate) fn complete_pattern(acc: &mut Completions, ctx: &CompletionContext) {
     // FIXME: ideally, we should look at the type we are matching against and
     // suggest variants + auto-imports
     ctx.process_all_names(&mut |name, res| {
-        let add_resolution = match &res {
+        let add_resolution = match res {
             hir::ScopeDef::ModuleDef(def) => match def {
                 hir::ModuleDef::Adt(hir::Adt::Struct(strukt)) => {
-                    acc.add_struct_pat(ctx, *strukt, Some(name.clone()));
+                    acc.add_struct_pat(ctx, strukt, Some(name.clone()));
                     true
                 }
-                hir::ModuleDef::Variant(variant) if refutable => {
-                    acc.add_variant_pat(ctx, *variant, Some(name.clone()));
+                hir::ModuleDef::Variant(variant)
+                    if refutable || single_variant_enum(variant.parent_enum(ctx.db)) =>
+                {
+                    acc.add_variant_pat(ctx, variant, Some(name.clone()));
                     true
                 }
-                hir::ModuleDef::Adt(hir::Adt::Enum(..))
-                | hir::ModuleDef::Variant(..)
-                | hir::ModuleDef::Const(..)
-                | hir::ModuleDef::Module(..) => refutable,
+                hir::ModuleDef::Adt(hir::Adt::Enum(e)) => refutable || single_variant_enum(e),
+                hir::ModuleDef::Const(..) | hir::ModuleDef::Module(..) => refutable,
                 _ => false,
             },
             hir::ScopeDef::MacroDef(mac) => mac.is_fn_like(),

crates/ide_completion/src/tests/flyimport.rs

@@ -924,6 +924,44 @@ mod bar {
             "#,
         expect![[r#""#]],
     );
+    check(
+        r#"
+mod baz {
+    pub trait DefDatabase {
+        fn method1(&self);
+    }
+    pub trait HirDatabase: DefDatabase {
+        fn method2(&self);
+    }
+}
+
+mod bar {
+    fn test(db: &impl crate::baz::HirDatabase) {
+        db.metho$0
+    }
+}
+"#,
+        expect![[r#""#]],
+    );
+    check(
+        r#"
+mod baz {
+    pub trait DefDatabase {
+        fn method1(&self);
+    }
+    pub trait HirDatabase: DefDatabase {
+        fn method2(&self);
+    }
+}
+
+mod bar {
+    fn test<T: crate::baz::HirDatabase>(db: T) {
+        db.metho$0
+    }
+}
+"#,
+        expect![[r#""#]],
+    );
 }
 
 #[test]

crates/ide_completion/src/tests/pattern.rs

@@ -130,6 +130,10 @@ fn foo() {
 fn irrefutable() {
     check(
         r#"
+enum SingleVariantEnum {
+    Variant
+}
+use SingleVariantEnum::Variant;
 fn foo() {
    let a$0
 }
@@ -140,6 +144,8 @@ fn foo() {
             st Record
             bn Tuple             Tuple($1)$0
             st Tuple
+            ev Variant
+            en SingleVariantEnum
             st Unit
             ma makro!(…)         #[macro_export] macro_rules! makro
         "##]],

crates/ide_db/src/helpers/import_assets.rs

@@ -454,8 +454,10 @@ fn trait_applicable_items(
 
     let db = sema.db;
 
-    let related_dyn_traits =
-        trait_candidate.receiver_ty.applicable_inherent_traits(db).collect::<FxHashSet<_>>();
+    let inherent_traits = trait_candidate.receiver_ty.applicable_inherent_traits(db);
+    let env_traits = trait_candidate.receiver_ty.env_traits(db);
+    let related_traits = inherent_traits.chain(env_traits).collect::<FxHashSet<_>>();
+
     let mut required_assoc_items = FxHashSet::default();
     let trait_candidates = items_locator::items_with_name(
         sema,
@@ -467,7 +469,7 @@ fn trait_applicable_items(
     .filter_map(|input| item_as_assoc(db, input))
     .filter_map(|assoc| {
         let assoc_item_trait = assoc.containing_trait(db)?;
-        if related_dyn_traits.contains(&assoc_item_trait) {
+        if related_traits.contains(&assoc_item_trait) {
             None
         } else {
             required_assoc_items.insert(assoc);