feat: Go to implementation of trait methods

crates/hir-ty/src/method_resolution.rs

@@ -8,8 +8,9 @@ use arrayvec::ArrayVec;
 use base_db::{CrateId, Edition};
 use chalk_ir::{cast::Cast, Mutability, UniverseIndex};
 use hir_def::{
-    item_scope::ItemScope, nameres::DefMap, AssocItemId, BlockId, ConstId, FunctionId,
-    GenericDefId, HasModule, ImplId, ItemContainerId, Lookup, ModuleDefId, ModuleId, TraitId,
+    data::ImplData, item_scope::ItemScope, nameres::DefMap, AssocItemId, BlockId, ConstId,
+    FunctionId, GenericDefId, HasModule, ImplId, ItemContainerId, Lookup, ModuleDefId, ModuleId,
+    TraitId,
 };
 use hir_expand::name::Name;
 use rustc_hash::{FxHashMap, FxHashSet};
@@ -247,7 +248,7 @@ impl TraitImpls {
         self.map
             .get(&trait_)
             .into_iter()
-            .flat_map(move |map| map.get(&None).into_iter().chain(map.get(&Some(self_ty))))
+            .flat_map(move |map| map.get(&Some(self_ty)).into_iter().chain(map.get(&None)))
             .flat_map(|v| v.iter().copied())
     }
 
@@ -575,6 +576,59 @@ pub(crate) fn iterate_method_candidates<T>(
     slot
 }
 
+pub fn lookup_impl_method(
+    self_ty: &Ty,
+    db: &dyn HirDatabase,
+    env: Arc<TraitEnvironment>,
+    trait_: TraitId,
+    name: &Name,
+) -> Option<FunctionId> {
+    let self_ty_fp = TyFingerprint::for_trait_impl(self_ty)?;
+    let trait_impls = TraitImpls::trait_impls_in_deps_query(db, env.krate);
+    let impls = trait_impls.for_trait_and_self_ty(trait_, self_ty_fp);
+    let mut table = InferenceTable::new(db, env.clone());
+    find_matching_impl(impls, &mut table, &self_ty).and_then(|data| {
+        data.items.iter().find_map(|it| match it {
+            AssocItemId::FunctionId(f) => (db.function_data(*f).name == *name).then(|| *f),
+            _ => None,
+        })
+    })
+}
+
+fn find_matching_impl(
+    mut impls: impl Iterator<Item = ImplId>,
+    table: &mut InferenceTable,
+    self_ty: &Ty,
+) -> Option<Arc<ImplData>> {
+    let db = table.db;
+    loop {
+        let impl_ = impls.next()?;
+        let r = table.run_in_snapshot(|table| {
+            let impl_data = db.impl_data(impl_);
+            let substs =
+                TyBuilder::subst_for_def(db, impl_).fill_with_inference_vars(table).build();
+            let impl_ty = db.impl_self_ty(impl_).substitute(Interner, &substs);
+
+            table
+                .unify(self_ty, &impl_ty)
+                .then(|| {
+                    let wh_goals =
+                        crate::chalk_db::convert_where_clauses(db, impl_.into(), &substs)
+                            .into_iter()
+                            .map(|b| b.into_well_formed_goal(Interner).cast(Interner));
+
+                    let goal = crate::Goal::all(Interner, wh_goals);
+
+                    table.try_obligation(goal).map(|_| impl_data)
+                })
+                .flatten()
+        });
+        if r.is_some() {
+            break r;
+        }
+    }
+}
+
 pub fn iterate_path_candidates(
     ty: &Canonical<Ty>,
     db: &dyn HirDatabase,
@@ -970,18 +1024,31 @@ fn is_valid_candidate(
     self_ty: &Ty,
     visible_from_module: Option<ModuleId>,
 ) -> bool {
+    macro_rules! check_that {
+        ($cond:expr) => {
+            if !$cond {
+                return false;
+            }
+        };
+    }
+
     let db = table.db;
     match item {
         AssocItemId::FunctionId(m) => {
             let data = db.function_data(m);
-            if let Some(name) = name {
-                if &data.name != name {
-                    return false;
+
+            check_that!(name.map_or(true, |n| n == &data.name));
+            check_that!(visible_from_module.map_or(true, |from_module| {
+                let v = db.function_visibility(m).is_visible_from(db.upcast(), from_module);
+                if !v {
+                    cov_mark::hit!(autoderef_candidate_not_visible);
                 }
-            }
+                v
+            }));
+
             table.run_in_snapshot(|table| {
                 let subst = TyBuilder::subst_for_def(db, m).fill_with_inference_vars(table).build();
-                let expected_self_ty = match m.lookup(db.upcast()).container {
+                let expect_self_ty = match m.lookup(db.upcast()).container {
                     ItemContainerId::TraitId(_) => {
                         subst.at(Interner, 0).assert_ty_ref(Interner).clone()
                     }
@@ -993,49 +1060,31 @@ fn is_valid_candidate(
                         unreachable!()
                     }
                 };
-                if !table.unify(&expected_self_ty, &self_ty) {
-                    return false;
-                }
+                check_that!(table.unify(&expect_self_ty, self_ty));
                 if let Some(receiver_ty) = receiver_ty {
-                    if !data.has_self_param() {
-                        return false;
-                    }
+                    check_that!(data.has_self_param());
 
                     let sig = db.callable_item_signature(m.into());
                     let expected_receiver =
                         sig.map(|s| s.params()[0].clone()).substitute(Interner, &subst);
-                    let receiver_matches = table.unify(&receiver_ty, &expected_receiver);
 
-                    if !receiver_matches {
-                        return false;
-                    }
+                    check_that!(table.unify(&receiver_ty, &expected_receiver));
                 }
-                if let Some(from_module) = visible_from_module {
-                    if !db.function_visibility(m).is_visible_from(db.upcast(), from_module) {
-                        cov_mark::hit!(autoderef_candidate_not_visible);
-                        return false;
-                    }
-                }
-
                 true
             })
         }
         AssocItemId::ConstId(c) => {
             let data = db.const_data(c);
-            if receiver_ty.is_some() {
-                return false;
-            }
-            if let Some(name) = name {
-                if data.name.as_ref() != Some(name) {
-                    return false;
-                }
-            }
-            if let Some(from_module) = visible_from_module {
-                if !db.const_visibility(c).is_visible_from(db.upcast(), from_module) {
+            check_that!(receiver_ty.is_none());
+
+            check_that!(name.map_or(true, |n| data.name.as_ref() == Some(n)));
+            check_that!(visible_from_module.map_or(true, |from_module| {
+                let v = db.const_visibility(c).is_visible_from(db.upcast(), from_module);
+                if !v {
                     cov_mark::hit!(const_candidate_not_visible);
-                    return false;
                 }
-            }
+                v
+            }));
             if let ItemContainerId::ImplId(impl_id) = c.lookup(db.upcast()).container {
                 let self_ty_matches = table.run_in_snapshot(|table| {
                     let subst =

crates/hir/src/semantics.rs

@@ -16,7 +16,6 @@ use hir_expand::{
     name::{known, AsName},
     ExpansionInfo, MacroCallId,
 };
-use hir_ty::Interner;
 use itertools::Itertools;
 use rustc_hash::{FxHashMap, FxHashSet};
 use smallvec::{smallvec, SmallVec};
@@ -975,18 +974,11 @@ impl<'db> SemanticsImpl<'db> {
     }
 
     fn resolve_method_call(&self, call: &ast::MethodCallExpr) -> Option<FunctionId> {
-        self.analyze(call.syntax())?.resolve_method_call(self.db, call).map(|(id, _)| id)
+        self.analyze(call.syntax())?.resolve_method_call(self.db, call)
     }
 
     fn resolve_method_call_as_callable(&self, call: &ast::MethodCallExpr) -> Option<Callable> {
-        let source_analyzer = self.analyze(call.syntax())?;
-        let (func, subst) = source_analyzer.resolve_method_call(self.db, call)?;
-        let ty = self.db.value_ty(func.into()).substitute(Interner, &subst);
-        let resolver = source_analyzer.resolver;
-        let ty = Type::new_with_resolver(self.db, &resolver, ty);
-        let mut res = ty.as_callable(self.db)?;
-        res.is_bound_method = true;
-        Some(res)
+        self.analyze(call.syntax())?.resolve_method_call_as_callable(self.db, call)
     }
 
     fn resolve_field(&self, field: &ast::FieldExpr) -> Option<Field> {

crates/hir/src/source_analyzer.rs

@@ -21,7 +21,8 @@ use hir_def::{
     path::{ModPath, Path, PathKind},
     resolver::{resolver_for_scope, Resolver, TypeNs, ValueNs},
     type_ref::Mutability,
-    AsMacroCall, DefWithBodyId, FieldId, FunctionId, LocalFieldId, Lookup, ModuleDefId, VariantId,
+    AsMacroCall, AssocItemId, DefWithBodyId, FieldId, FunctionId, ItemContainerId, LocalFieldId,
+    Lookup, ModuleDefId, VariantId,
 };
 use hir_expand::{
     builtin_fn_macro::BuiltinFnLikeExpander, hygiene::Hygiene, name::AsName, HirFileId, InFile,
@@ -31,8 +32,8 @@ use hir_ty::{
         record_literal_missing_fields, record_pattern_missing_fields, unsafe_expressions,
         UnsafeExpr,
     },
-    Adjust, Adjustment, AutoBorrow, InferenceResult, Interner, Substitution, TyExt,
-    TyLoweringContext,
+    method_resolution, Adjust, Adjustment, AutoBorrow, InferenceResult, Interner, Substitution,
+    TyExt, TyKind, TyLoweringContext,
 };
 use smallvec::SmallVec;
 use syntax::{
@@ -42,8 +43,8 @@ use syntax::{
 
 use crate::{
     db::HirDatabase, semantics::PathResolution, Adt, AssocItem, BindingMode, BuiltinAttr,
-    BuiltinType, Const, Field, Function, Local, Macro, ModuleDef, Static, Struct, ToolModule,
-    Trait, Type, TypeAlias, Variant,
+    BuiltinType, Callable, Const, Field, Function, Local, Macro, ModuleDef, Static, Struct,
+    ToolModule, Trait, Type, TypeAlias, Variant,
 };
 
 /// `SourceAnalyzer` is a convenience wrapper which exposes HIR API in terms of
@@ -238,13 +239,29 @@ impl SourceAnalyzer {
         )
     }
 
+    pub(crate) fn resolve_method_call_as_callable(
+        &self,
+        db: &dyn HirDatabase,
+        call: &ast::MethodCallExpr,
+    ) -> Option<Callable> {
+        let expr_id = self.expr_id(db, &call.clone().into())?;
+        let (func, substs) = self.infer.as_ref()?.method_resolution(expr_id)?;
+        let ty = db.value_ty(func.into()).substitute(Interner, &substs);
+        let ty = Type::new_with_resolver(db, &self.resolver, ty);
+        let mut res = ty.as_callable(db)?;
+        res.is_bound_method = true;
+        Some(res)
+    }
+
     pub(crate) fn resolve_method_call(
         &self,
         db: &dyn HirDatabase,
         call: &ast::MethodCallExpr,
-    ) -> Option<(FunctionId, Substitution)> {
+    ) -> Option<FunctionId> {
         let expr_id = self.expr_id(db, &call.clone().into())?;
-        self.infer.as_ref()?.method_resolution(expr_id)
+        let (f_in_trait, substs) = self.infer.as_ref()?.method_resolution(expr_id)?;
+        let f_in_impl = self.resolve_impl_method(db, f_in_trait, &substs);
+        f_in_impl.or(Some(f_in_trait))
     }
 
     pub(crate) fn resolve_field(
@@ -342,6 +359,25 @@ impl SourceAnalyzer {
                 let expr_id = self.expr_id(db, &path_expr.into())?;
                 let infer = self.infer.as_ref()?;
                 if let Some(assoc) = infer.assoc_resolutions_for_expr(expr_id) {
+                    let assoc = match assoc {
+                        AssocItemId::FunctionId(f_in_trait) => {
+                            match infer.type_of_expr.get(expr_id) {
+                                None => assoc,
+                                Some(func_ty) => {
+                                    if let TyKind::FnDef(_fn_def, subs) = func_ty.kind(Interner) {
+                                        self.resolve_impl_method(db, f_in_trait, subs)
+                                            .map(AssocItemId::FunctionId)
+                                            .unwrap_or(assoc)
+                                    } else {
+                                        assoc
+                                    }
+                                }
+                            }
+                        }
+
+                        _ => assoc,
+                    };
+
                     return Some(PathResolution::Def(AssocItem::from(assoc).into()));
                 }
                 if let Some(VariantId::EnumVariantId(variant)) =
@@ -567,6 +603,30 @@ impl SourceAnalyzer {
         }
         false
     }
+
+    fn resolve_impl_method(
+        &self,
+        db: &dyn HirDatabase,
+        func: FunctionId,
+        substs: &Substitution,
+    ) -> Option<FunctionId> {
+        let impled_trait = match func.lookup(db.upcast()).container {
+            ItemContainerId::TraitId(trait_id) => trait_id,
+            _ => return None,
+        };
+        if substs.is_empty(Interner) {
+            return None;
+        }
+        let self_ty = substs.at(Interner, 0).ty(Interner)?;
+        let krate = self.resolver.krate();
+        let trait_env = self.resolver.body_owner()?.as_generic_def_id().map_or_else(
+            || Arc::new(hir_ty::TraitEnvironment::empty(krate)),
+            |d| db.trait_environment(d),
+        );
+
+        let fun_data = db.function_data(func);
+        method_resolution::lookup_impl_method(self_ty, db, trait_env, impled_trait, &fun_data.name)
+    }
 }
 
 fn scope_for(

crates/ide-assists/src/handlers/qualify_method_call.rs

@@ -1,8 +1,5 @@
-use hir::{ItemInNs, ModuleDef};
-use ide_db::{
-    assists::{AssistId, AssistKind},
-    imports::import_assets::item_for_path_search,
-};
+use hir::{db::HirDatabase, AsAssocItem, AssocItem, AssocItemContainer, ItemInNs, ModuleDef};
+use ide_db::assists::{AssistId, AssistKind};
 use syntax::{ast, AstNode};
 
 use crate::{
@@ -67,6 +64,26 @@ pub(crate) fn qualify_method_call(acc: &mut Assists, ctx: &AssistContext) -> Opt
     Some(())
 }
 
+fn item_for_path_search(db: &dyn HirDatabase, item: ItemInNs) -> Option<ItemInNs> {
+    Some(match item {
+        ItemInNs::Types(_) | ItemInNs::Values(_) => match item_as_assoc(db, item) {
+            Some(assoc_item) => match assoc_item.container(db) {
+                AssocItemContainer::Trait(trait_) => ItemInNs::from(ModuleDef::from(trait_)),
+                AssocItemContainer::Impl(impl_) => match impl_.trait_(db) {
+                    None => ItemInNs::from(ModuleDef::from(impl_.self_ty(db).as_adt()?)),
+                    Some(trait_) => ItemInNs::from(ModuleDef::from(trait_)),
+                },
+            },
+            None => item,
+        },
+        ItemInNs::Macros(_) => item,
+    })
+}
+
+fn item_as_assoc(db: &dyn HirDatabase, item: ItemInNs) -> Option<AssocItem> {
+    item.as_module_def().and_then(|module_def| module_def.as_assoc_item(db))
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

crates/ide-assists/src/utils/suggest_name.rs

@@ -450,6 +450,21 @@ fn foo() { S.bar($01$0, 2) }
         );
     }
 
+    #[test]
+    fn method_on_impl_trait() {
+        check(
+            r#"
+struct S;
+trait T {
+    fn bar(&self, n: i32, m: u32);
+}
+impl T for S { fn bar(&self, n: i32, m: u32); }
+fn foo() { S.bar($01$0, 2) }
+"#,
+            "n",
+        );
+    }
+
     #[test]
     fn method_ufcs() {
         check(

crates/ide-db/src/imports/import_assets.rs

@@ -401,7 +401,7 @@ fn import_for_item(
     })
 }
 
-pub fn item_for_path_search(db: &RootDatabase, item: ItemInNs) -> Option<ItemInNs> {
+fn item_for_path_search(db: &RootDatabase, item: ItemInNs) -> Option<ItemInNs> {
     Some(match item {
         ItemInNs::Types(_) | ItemInNs::Values(_) => match item_as_assoc(db, item) {
             Some(assoc_item) => match assoc_item.container(db) {