Merge #505

505: Inherent methods r=matklad a=flodiebold

This adds resolution, type checking and completion for inherent methods.

The main open question here is the caching, I think. I'm not sure whether we should be caching method resolutions in a more fine grained way (currently we just build a hash map of types -> impl blocks, and iterate through all potential impl blocks when looking for a method).

Co-authored-by: Florian Diebold <flodiebold@gmail.com>

crates/ra_hir/src/code_model_api.rs

@@ -113,6 +113,11 @@ impl Module {
         self.child_impl(db, name)
     }
 
+    /// Iterates over all child modules.
+    pub fn children(&self, db: &impl HirDatabase) -> Cancelable<impl Iterator<Item = Module>> {
+        self.children_impl(db)
+    }
+
     /// Finds a parent module.
     pub fn parent(&self, db: &impl HirDatabase) -> Cancelable<Option<Module>> {
         self.parent_impl(db)
@@ -268,8 +273,11 @@ pub use crate::code_model_impl::function::ScopeEntryWithSyntax;
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct FnSignature {
     pub(crate) name: Name,
-    pub(crate) args: Vec<TypeRef>,
+    pub(crate) params: Vec<TypeRef>,
     pub(crate) ret_type: TypeRef,
+    /// True if the first param is `self`. This is relevant to decide whether this
+    /// can be called as a method.
+    pub(crate) has_self_param: bool,
 }
 
 impl FnSignature {
@@ -277,13 +285,19 @@ impl FnSignature {
         &self.name
     }
 
-    pub fn args(&self) -> &[TypeRef] {
+    pub fn params(&self) -> &[TypeRef] {
-        &self.args
+        &self.params
     }
 
     pub fn ret_type(&self) -> &TypeRef {
         &self.ret_type
     }
+
+    /// True if the first arg is `self`. This is relevant to decide whether this
+    /// can be called as a method.
+    pub fn has_self_param(&self) -> bool {
+        self.has_self_param
+    }
 }
 
 impl Function {

crates/ra_hir/src/code_model_impl/function.rs

@@ -42,7 +42,8 @@ impl FnSignature {
             .name()
             .map(|n| n.as_name())
             .unwrap_or_else(Name::missing);
-        let mut args = Vec::new();
+        let mut params = Vec::new();
+        let mut has_self_param = false;
         if let Some(param_list) = node.param_list() {
             if let Some(self_param) = param_list.self_param() {
                 let self_type = if let Some(type_ref) = self_param.type_ref() {
@@ -59,11 +60,12 @@ impl FnSignature {
                         }
                     }
                 };
-                args.push(self_type);
+                params.push(self_type);
+                has_self_param = true;
             }
             for param in param_list.params() {
                 let type_ref = TypeRef::from_ast_opt(param.type_ref());
-                args.push(type_ref);
+                params.push(type_ref);
             }
         }
         let ret_type = if let Some(type_ref) = node.ret_type().and_then(|rt| rt.type_ref()) {
@@ -73,8 +75,9 @@ impl FnSignature {
         };
         let sig = FnSignature {
             name,
-            args,
+            params,
             ret_type,
+            has_self_param,
         };
         Arc::new(sig)
     }

crates/ra_hir/src/code_model_impl/function/scope.rs

@@ -43,7 +43,7 @@ impl FnScopes {
             scope_for: FxHashMap::default(),
         };
         let root = scopes.root_scope();
-        scopes.add_params_bindings(root, body.args());
+        scopes.add_params_bindings(root, body.params());
         compute_expr_scopes(body.body_expr(), &body, &mut scopes, root);
         scopes
     }

crates/ra_hir/src/code_model_impl/module.rs

@@ -95,6 +95,21 @@ impl Module {
         Module::from_module_id(db, loc.source_root_id, child_id).map(Some)
     }
 
+    /// Iterates over all child modules.
+    pub fn children_impl(&self, db: &impl HirDatabase) -> Cancelable<impl Iterator<Item = Module>> {
+        // FIXME this should be implementable without collecting into a vec, but
+        // it's kind of hard since the iterator needs to keep a reference to the
+        // module tree.
+        let loc = self.def_id.loc(db);
+        let module_tree = db.module_tree(loc.source_root_id)?;
+        let children = loc
+            .module_id
+            .children(&module_tree)
+            .map(|(_, module_id)| Module::from_module_id(db, loc.source_root_id, module_id))
+            .collect::<Cancelable<Vec<_>>>()?;
+        Ok(children.into_iter())
+    }
+
     pub fn parent_impl(&self, db: &impl HirDatabase) -> Cancelable<Option<Module>> {
         let loc = self.def_id.loc(db);
         let module_tree = db.module_tree(loc.source_root_id)?;

crates/ra_hir/src/db.rs

@@ -5,13 +5,13 @@ use ra_db::{SourceRootId, LocationIntener, SyntaxDatabase, Cancelable};
 
 use crate::{
     DefLoc, DefId, MacroCallLoc, MacroCallId, Name, HirFileId,
-    SourceFileItems, SourceItemId,
+    SourceFileItems, SourceItemId, Crate,
     query_definitions,
     FnSignature, FnScopes,
     macros::MacroExpansion,
     module_tree::{ModuleId, ModuleTree},
     nameres::{ItemMap, InputModuleItems},
-    ty::{InferenceResult, Ty},
+    ty::{InferenceResult, Ty, method_resolution::CrateImplBlocks},
     adt::{StructData, EnumData, EnumVariantData},
     impl_block::ModuleImplBlocks,
 };
@@ -102,6 +102,11 @@ pub trait HirDatabase: SyntaxDatabase
         use fn crate::impl_block::impls_in_module;
     }
 
+    fn impls_in_crate(krate: Crate) -> Cancelable<Arc<CrateImplBlocks>> {
+        type ImplsInCrateQuery;
+        use fn crate::ty::method_resolution::CrateImplBlocks::impls_in_crate_query;
+    }
+
     fn body_hir(def_id: DefId) -> Cancelable<Arc<crate::expr::Body>> {
         type BodyHirQuery;
         use fn crate::expr::body_hir;

crates/ra_hir/src/expr.rs

@@ -18,13 +18,13 @@ impl_arena_id!(ExprId);
 pub struct Body {
     exprs: Arena<ExprId, Expr>,
     pats: Arena<PatId, Pat>,
-    /// The patterns for the function's arguments. While the argument types are
+    /// The patterns for the function's parameters. While the parameter types are
     /// part of the function signature, the patterns are not (they don't change
     /// the external type of the function).
     ///
     /// If this `Body` is for the body of a constant, this will just be
     /// empty.
-    args: Vec<PatId>,
+    params: Vec<PatId>,
     /// The `ExprId` of the actual body expression.
     body_expr: ExprId,
 }
@@ -44,8 +44,8 @@ pub struct BodySyntaxMapping {
 }
 
 impl Body {
-    pub fn args(&self) -> &[PatId] {
+    pub fn params(&self) -> &[PatId] {
-        &self.args
+        &self.params
     }
 
     pub fn body_expr(&self) -> ExprId {
@@ -699,11 +699,11 @@ impl ExprCollector {
         }
     }
 
-    fn into_body_syntax_mapping(self, args: Vec<PatId>, body_expr: ExprId) -> BodySyntaxMapping {
+    fn into_body_syntax_mapping(self, params: Vec<PatId>, body_expr: ExprId) -> BodySyntaxMapping {
         let body = Body {
             exprs: self.exprs,
             pats: self.pats,
-            args,
+            params,
             body_expr,
         };
         BodySyntaxMapping {
@@ -719,8 +719,8 @@ impl ExprCollector {
 pub(crate) fn collect_fn_body_syntax(node: &ast::FnDef) -> BodySyntaxMapping {
     let mut collector = ExprCollector::new();
 
-    let args = if let Some(param_list) = node.param_list() {
+    let params = if let Some(param_list) = node.param_list() {
-        let mut args = Vec::new();
+        let mut params = Vec::new();
 
         if let Some(self_param) = param_list.self_param() {
             let self_param = LocalSyntaxPtr::new(
@@ -729,13 +729,13 @@ pub(crate) fn collect_fn_body_syntax(node: &ast::FnDef) -> BodySyntaxMapping {
                     .expect("self param without self keyword")
                     .syntax(),
             );
-            let arg = collector.alloc_pat(
+            let param = collector.alloc_pat(
                 Pat::Bind {
                     name: Name::self_param(),
                 },
                 self_param,
             );
-            args.push(arg);
+            params.push(param);
         }
 
         for param in param_list.params() {
@@ -744,15 +744,15 @@ pub(crate) fn collect_fn_body_syntax(node: &ast::FnDef) -> BodySyntaxMapping {
             } else {
                 continue;
             };
-            args.push(collector.collect_pat(pat));
+            params.push(collector.collect_pat(pat));
         }
-        args
+        params
     } else {
         Vec::new()
     };
 
     let body = collector.collect_block_opt(node.body());
-    collector.into_body_syntax_mapping(args, body)
+    collector.into_body_syntax_mapping(params, body)
 }
 
 pub(crate) fn body_syntax_mapping(

crates/ra_hir/src/impl_block.rs

@@ -33,20 +33,27 @@ impl ImplBlock {
         })
     }
 
+    pub(crate) fn from_id(module_impl_blocks: Arc<ModuleImplBlocks>, impl_id: ImplId) -> ImplBlock {
+        ImplBlock {
+            module_impl_blocks,
+            impl_id,
+        }
+    }
+
     fn impl_data(&self) -> &ImplData {
         &self.module_impl_blocks.impls[self.impl_id]
     }
 
     pub fn target_trait(&self) -> Option<&TypeRef> {
-        self.impl_data().target_trait.as_ref()
+        self.impl_data().target_trait()
     }
 
     pub fn target_type(&self) -> &TypeRef {
-        &self.impl_data().target_type
+        self.impl_data().target_type()
     }
 
     pub fn items(&self) -> &[ImplItem] {
-        &self.impl_data().items
+        self.impl_data().items()
     }
 }
 
@@ -64,7 +71,7 @@ impl ImplData {
         module: &Module,
         node: &ast::ImplBlock,
     ) -> Self {
-        let target_trait = node.target_type().map(TypeRef::from_ast);
+        let target_trait = node.target_trait().map(TypeRef::from_ast);
         let target_type = TypeRef::from_ast_opt(node.target_type());
         let module_loc = module.def_id.loc(db);
         let items = if let Some(item_list) = node.item_list() {
@@ -103,6 +110,18 @@ impl ImplData {
             items,
         }
     }
+
+    pub fn target_trait(&self) -> Option<&TypeRef> {
+        self.target_trait.as_ref()
+    }
+
+    pub fn target_type(&self) -> &TypeRef {
+        &self.target_type
+    }
+
+    pub fn items(&self) -> &[ImplItem] {
+        &self.items
+    }
 }
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -133,11 +152,9 @@ impl_arena_id!(ImplId);
 /// This way, we avoid having to do this process for the whole crate whenever
 /// a file is changed; as long as the impl blocks in the file don't change,
 /// we don't need to do the second step again.
-///
-/// (The second step does not yet exist.)
 #[derive(Debug, PartialEq, Eq)]
 pub struct ModuleImplBlocks {
-    impls: Arena<ImplId, ImplData>,
+    pub(crate) impls: Arena<ImplId, ImplData>,
     impls_by_def: FxHashMap<DefId, ImplId>,
 }
 
@@ -153,7 +170,10 @@ impl ModuleImplBlocks {
         let (file_id, module_source) = module.definition_source(db)?;
         let node = match &module_source {
             ModuleSource::SourceFile(node) => node.syntax(),
-            ModuleSource::Module(node) => node.syntax(),
+            ModuleSource::Module(node) => node
+                .item_list()
+                .expect("inline module should have item list")
+                .syntax(),
         };
 
         let source_file_items = db.file_items(file_id.into());

crates/ra_hir/src/mock.rs

@@ -235,6 +235,7 @@ salsa::database_storage! {
             fn enum_data() for db::EnumDataQuery;
             fn enum_variant_data() for db::EnumVariantDataQuery;
             fn impls_in_module() for db::ImplsInModuleQuery;
+            fn impls_in_crate() for db::ImplsInCrateQuery;
             fn body_hir() for db::BodyHirQuery;
             fn body_syntax_mapping() for db::BodySyntaxMappingQuery;
             fn fn_signature() for db::FnSignatureQuery;

crates/ra_hir/src/ty.rs

@@ -17,6 +17,7 @@ mod autoderef;
 mod primitive;
 #[cfg(test)]
 mod tests;
+pub(crate) mod method_resolution;
 
 use std::borrow::Cow;
 use std::ops::Index;
@@ -431,7 +432,7 @@ fn type_for_fn(db: &impl HirDatabase, f: Function) -> Cancelable<Ty> {
     let impl_block = f.impl_block(db)?;
     // TODO we ignore type parameters for now
     let input = signature
-        .args()
+        .params()
         .iter()
         .map(|tr| Ty::from_hir(db, &module, impl_block.as_ref(), tr))
         .collect::<Cancelable<Vec<_>>>()?;
@@ -875,7 +876,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             }
             Expr::Call { callee, args } => {
                 let callee_ty = self.infer_expr(*callee, &Expectation::none())?;
-                let (arg_tys, ret_ty) = match &callee_ty {
+                let (param_tys, ret_ty) = match &callee_ty {
                     Ty::FnPtr(sig) => (&sig.input[..], sig.output.clone()),
                     _ => {
                         // not callable
@@ -886,19 +887,43 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 for (i, arg) in args.iter().enumerate() {
                     self.infer_expr(
                         *arg,
-                        &Expectation::has_type(arg_tys.get(i).cloned().unwrap_or(Ty::Unknown)),
+                        &Expectation::has_type(param_tys.get(i).cloned().unwrap_or(Ty::Unknown)),
                     )?;
                 }
                 ret_ty
             }
-            Expr::MethodCall { receiver, args, .. } => {
+            Expr::MethodCall {
-                let _receiver_ty = self.infer_expr(*receiver, &Expectation::none())?;
+                receiver,
-                // TODO resolve method...
+                args,
-                for (_i, arg) in args.iter().enumerate() {
+                method_name,
-                    // TODO unify / expect argument type
+            } => {
-                    self.infer_expr(*arg, &Expectation::none())?;
+                let receiver_ty = self.infer_expr(*receiver, &Expectation::none())?;
+                let resolved = receiver_ty.clone().lookup_method(self.db, method_name)?;
+                let method_ty = match resolved {
+                    Some(def_id) => self.db.type_for_def(def_id)?,
+                    None => Ty::Unknown,
+                };
+                let method_ty = self.insert_type_vars(method_ty);
+                let (expected_receiver_ty, param_tys, ret_ty) = match &method_ty {
+                    Ty::FnPtr(sig) => {
+                        if sig.input.len() > 0 {
+                            (&sig.input[0], &sig.input[1..], sig.output.clone())
+                        } else {
+                            (&Ty::Unknown, &[][..], sig.output.clone())
+                        }
+                    }
+                    _ => (&Ty::Unknown, &[][..], Ty::Unknown),
+                };
+                // TODO we would have to apply the autoderef/autoref steps here
+                // to get the correct receiver type to unify...
+                self.unify(expected_receiver_ty, &receiver_ty);
+                for (i, arg) in args.iter().enumerate() {
+                    self.infer_expr(
+                        *arg,
+                        &Expectation::has_type(param_tys.get(i).cloned().unwrap_or(Ty::Unknown)),
+                    )?;
                 }
-                Ty::Unknown
+                ret_ty
             }
             Expr::Match { expr, arms } => {
                 let _ty = self.infer_expr(*expr, &Expectation::none())?;
@@ -1068,7 +1093,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
 
     fn collect_fn_signature(&mut self, signature: &FnSignature) -> Cancelable<()> {
         let body = Arc::clone(&self.body); // avoid borrow checker problem
-        for (type_ref, pat) in signature.args().iter().zip(body.args()) {
+        for (type_ref, pat) in signature.params().iter().zip(body.params()) {
             let ty = self.make_ty(type_ref)?;
             let ty = self.insert_type_vars(ty);
             self.write_pat_ty(*pat, ty);

crates/ra_hir/src/ty/method_resolution.rs

@@ -0,0 +1,164 @@
+//! This module is concerned with finding methods that a given type provides.
+//! For details about how this works in rustc, see the method lookup page in the
+//! [rustc guide](https://rust-lang.github.io/rustc-guide/method-lookup.html)
+//! and the corresponding code mostly in librustc_typeck/check/method/probe.rs.
+use std::sync::Arc;
+
+use rustc_hash::FxHashMap;
+
+use ra_db::{Cancelable, SourceRootId};
+
+use crate::{HirDatabase, DefId, module_tree::ModuleId, Module, Crate, Name, Function, impl_block::{ImplId, ImplBlock, ImplItem}};
+use super::Ty;
+
+/// This is used as a key for indexing impls.
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+pub enum TyFingerprint {
+    Adt(DefId),
+    // we'll also want to index impls for primitive types etc.
+}
+
+impl TyFingerprint {
+    /// Creates a TyFingerprint for looking up an impl. Only certain types can
+    /// have impls: if we have some `struct S`, we can have an `impl S`, but not
+    /// `impl &S`. Hence, this will return `None` for reference types and such.
+    fn for_impl(ty: &Ty) -> Option<TyFingerprint> {
+        match ty {
+            Ty::Adt { def_id, .. } => Some(TyFingerprint::Adt(*def_id)),
+            _ => None,
+        }
+    }
+}
+
+#[derive(Debug, PartialEq, Eq)]
+pub struct CrateImplBlocks {
+    /// To make sense of the ModuleIds, we need the source root.
+    source_root_id: SourceRootId,
+    impls: FxHashMap<TyFingerprint, Vec<(ModuleId, ImplId)>>,
+}
+
+impl CrateImplBlocks {
+    pub fn lookup_impl_blocks<'a>(
+        &'a self,
+        db: &'a impl HirDatabase,
+        ty: &Ty,
+    ) -> impl Iterator<Item = Cancelable<ImplBlock>> + 'a {
+        let fingerprint = TyFingerprint::for_impl(ty);
+        fingerprint
+            .and_then(|f| self.impls.get(&f))
+            .into_iter()
+            .flat_map(|i| i.iter())
+            .map(move |(module_id, impl_id)| {
+                let module_impl_blocks = db.impls_in_module(self.source_root_id, *module_id)?;
+                Ok(ImplBlock::from_id(module_impl_blocks, *impl_id))
+            })
+    }
+
+    fn collect_recursive(&mut self, db: &impl HirDatabase, module: Module) -> Cancelable<()> {
+        let module_id = module.def_id.loc(db).module_id;
+        let module_impl_blocks = db.impls_in_module(self.source_root_id, module_id)?;
+
+        for (impl_id, impl_data) in module_impl_blocks.impls.iter() {
+            let impl_block = ImplBlock::from_id(Arc::clone(&module_impl_blocks), impl_id);
+
+            if let Some(_target_trait) = impl_data.target_trait() {
+                // ignore for now
+            } else {
+                let target_ty =
+                    Ty::from_hir(db, &module, Some(&impl_block), impl_data.target_type())?;
+                if let Some(target_ty_fp) = TyFingerprint::for_impl(&target_ty) {
+                    self.impls
+                        .entry(target_ty_fp)
+                        .or_insert_with(Vec::new)
+                        .push((module_id, impl_id));
+                }
+            }
+        }
+
+        for child in module.children(db)? {
+            self.collect_recursive(db, child)?;
+        }
+
+        Ok(())
+    }
+
+    pub(crate) fn impls_in_crate_query(
+        db: &impl HirDatabase,
+        krate: Crate,
+    ) -> Cancelable<Arc<CrateImplBlocks>> {
+        let crate_graph = db.crate_graph();
+        let file_id = crate_graph.crate_root(krate.crate_id);
+        let source_root_id = db.file_source_root(file_id);
+        let mut crate_impl_blocks = CrateImplBlocks {
+            source_root_id,
+            impls: FxHashMap::default(),
+        };
+        if let Some(module) = krate.root_module(db)? {
+            crate_impl_blocks.collect_recursive(db, module)?;
+        }
+        Ok(Arc::new(crate_impl_blocks))
+    }
+}
+
+fn def_crate(db: &impl HirDatabase, ty: &Ty) -> Cancelable<Option<Crate>> {
+    match ty {
+        Ty::Adt { def_id, .. } => def_id.krate(db),
+        _ => Ok(None),
+    }
+}
+
+impl Ty {
+    // TODO: cache this as a query?
+    // - if so, what signature? (TyFingerprint, Name)?
+    // - or maybe cache all names and def_ids of methods per fingerprint?
+    pub fn lookup_method(self, db: &impl HirDatabase, name: &Name) -> Cancelable<Option<DefId>> {
+        self.iterate_methods(db, |f| {
+            let sig = f.signature(db);
+            if sig.name() == name && sig.has_self_param() {
+                Ok(Some(f.def_id()))
+            } else {
+                Ok(None)
+            }
+        })
+    }
+
+    // This would be nicer if it just returned an iterator, but that's really
+    // complicated with all the cancelable operations
+    pub fn iterate_methods<T>(
+        self,
+        db: &impl HirDatabase,
+        mut callback: impl FnMut(Function) -> Cancelable<Option<T>>,
+    ) -> Cancelable<Option<T>> {
+        // For method calls, rust first does any number of autoderef, and then one
+        // autoref (i.e. when the method takes &self or &mut self). We just ignore
+        // the autoref currently -- when we find a method matching the given name,
+        // we assume it fits.
+
+        // Also note that when we've got a receiver like &S, even if the method we
+        // find in the end takes &self, we still do the autoderef step (just as
+        // rustc does an autoderef and then autoref again).
+
+        for derefed_ty in self.autoderef(db) {
+            let krate = match def_crate(db, &derefed_ty)? {
+                Some(krate) => krate,
+                None => continue,
+            };
+            let impls = db.impls_in_crate(krate)?;
+
+            for impl_block in impls.lookup_impl_blocks(db, &derefed_ty) {
+                let impl_block = impl_block?;
+                for item in impl_block.items() {
+                    match item {
+                        ImplItem::Method(f) => {
+                            if let Some(result) = callback(f.clone())? {
+                                return Ok(Some(result));
+                            }
+                        }
+                        _ => {}
+                    }
+                }
+            }
+        }
+        Ok(None)
+    }
+}

crates/ra_hir/src/ty/tests.rs

@@ -242,6 +242,32 @@ fn test() {
     );
 }
 
+#[test]
+fn infer_inherent_method() {
+    check_inference(
+        r#"
+struct A;
+
+impl A {
+    fn foo(self, x: u32) -> i32 {}
+}
+
+mod b {
+    impl super::A {
+        fn bar(&self, x: u64) -> i64 {}
+    }
+}
+
+fn test(a: A) {
+    a.foo(1);
+    (&a).bar(1);
+    a.bar(1);
+}
+"#,
+        "inherent_method.txt",
+    );
+}
+
 fn infer(content: &str) -> String {
     let (db, _, file_id) = MockDatabase::with_single_file(content);
     let source_file = db.source_file(file_id);

crates/ra_hir/src/ty/tests/data/inherent_method.txt

@@ -0,0 +1,18 @@
+[32; 36) 'self': A
+[38; 39) 'x': u32
+[53; 55) '{}': ()
+[103; 107) 'self': &A
+[109; 110) 'x': u64
+[124; 126) '{}': ()
+[144; 145) 'a': A
+[150; 198) '{     ...(1); }': ()
+[156; 157) 'a': A
+[156; 164) 'a.foo(1)': i32
+[162; 163) '1': u32
+[170; 181) '(&a).bar(1)': i64
+[171; 173) '&a': &A
+[172; 173) 'a': A
+[179; 180) '1': u64
+[187; 188) 'a': A
+[187; 195) 'a.bar(1)': i64
+[193; 194) '1': u64

crates/ra_ide_api/src/completion/complete_dot.rs

@@ -17,8 +17,9 @@ pub(super) fn complete_dot(acc: &mut Completions, ctx: &CompletionContext) -> Ca
     };
     let receiver_ty = infer_result[expr].clone();
     if !ctx.is_call {
-        complete_fields(acc, ctx, receiver_ty)?;
+        complete_fields(acc, ctx, receiver_ty.clone())?;
     }
+    complete_methods(acc, ctx, receiver_ty)?;
     Ok(())
 }
 
@@ -55,6 +56,24 @@ fn complete_fields(acc: &mut Completions, ctx: &CompletionContext, receiver: Ty)
     Ok(())
 }
 
+fn complete_methods(
+    acc: &mut Completions,
+    ctx: &CompletionContext,
+    receiver: Ty,
+) -> Cancelable<()> {
+    receiver.iterate_methods(ctx.db, |func| {
+        let sig = func.signature(ctx.db);
+        if sig.has_self_param() {
+            CompletionItem::new(CompletionKind::Reference, sig.name().to_string())
+                .from_function(ctx, func)
+                .kind(CompletionItemKind::Method)
+                .add_to(acc);
+        }
+        Ok(None::<()>)
+    })?;
+    Ok(())
+}
+
 #[cfg(test)]
 mod tests {
     use crate::completion::*;
@@ -87,7 +106,8 @@ mod tests {
                 }
             }
             ",
-            r#"the_field "(u32,)""#,
+            r#"the_field "(u32,)"
+               foo "foo($0)""#,
         );
     }
 
@@ -102,7 +122,8 @@ mod tests {
                 }
             }
             ",
-            r#"the_field "(u32, i32)""#,
+            r#"the_field "(u32, i32)"
+               foo "foo($0)""#,
         );
     }
 
@@ -118,4 +139,36 @@ mod tests {
             r#""#,
         );
     }
+
+    #[test]
+    fn test_method_completion() {
+        check_ref_completion(
+            r"
+            struct A {}
+            impl A {
+                fn the_method(&self) {}
+            }
+            fn foo(a: A) {
+               a.<|>
+            }
+            ",
+            r#"the_method "the_method($0)""#,
+        );
+    }
+
+    #[test]
+    fn test_no_non_self_method() {
+        check_ref_completion(
+            r"
+            struct A {}
+            impl A {
+                fn the_method() {}
+            }
+            fn foo(a: A) {
+               a.<|>
+            }
+            ",
+            r#""#,
+        );
+    }
 }

crates/ra_ide_api/src/completion/completion_item.rs

@@ -37,6 +37,7 @@ pub enum CompletionItemKind {
     Const,
     Trait,
     TypeAlias,
+    Method,
 }
 
 #[derive(Debug, PartialEq, Eq)]
@@ -183,10 +184,14 @@ impl Builder {
         self
     }
 
-    fn from_function(mut self, ctx: &CompletionContext, function: hir::Function) -> Builder {
+    pub(super) fn from_function(
+        mut self,
+        ctx: &CompletionContext,
+        function: hir::Function,
+    ) -> Builder {
         // If not an import, add parenthesis automatically.
         if ctx.use_item_syntax.is_none() && !ctx.is_call {
-            if function.signature(ctx.db).args().is_empty() {
+            if function.signature(ctx.db).params().is_empty() {
                 self.snippet = Some(format!("{}()$0", self.label));
             } else {
                 self.snippet = Some(format!("{}($0)", self.label));

crates/ra_ide_api/src/db.rs

@@ -124,6 +124,7 @@ salsa::database_storage! {
             fn enum_data() for hir::db::EnumDataQuery;
             fn enum_variant_data() for hir::db::EnumVariantDataQuery;
             fn impls_in_module() for hir::db::ImplsInModuleQuery;
+            fn impls_in_crate() for hir::db::ImplsInCrateQuery;
             fn body_hir() for hir::db::BodyHirQuery;
             fn body_syntax_mapping() for hir::db::BodySyntaxMappingQuery;
             fn fn_signature() for hir::db::FnSignatureQuery;

crates/ra_lsp_server/src/conv.rs

@@ -69,6 +69,7 @@ impl Conv for CompletionItemKind {
             CompletionItemKind::TypeAlias => Struct,
             CompletionItemKind::Const => Constant,
             CompletionItemKind::Static => Value,
+            CompletionItemKind::Method => Method,
         }
     }
 }