Added a utility function that can be used to determine the missing impl items.

crates/ra_assists/src/lib.rs

@@ -9,7 +9,7 @@ mod assist_ctx;
 mod marks;
 #[cfg(test)]
 mod doc_tests;
-mod utils;
+pub mod utils;
 pub mod ast_transform;
 
 use ra_db::FileRange;

crates/ra_assists/src/utils.rs

@@ -1,10 +1,83 @@
 //! Assorted functions shared by several assists.
 
 use ra_syntax::{
-    ast::{self, make},
+    ast::{self, make, NameOwner},
-    T,
+    AstNode, T,
 };
 
+use hir::db::HirDatabase;
+
+use rustc_hash::FxHashSet;
+
+pub fn get_missing_impl_items(
+    db: &impl HirDatabase,
+    analyzer: &hir::SourceAnalyzer,
+    impl_block: &ast::ImplBlock,
+) -> Vec<hir::AssocItem> {
+    // since the names are unique only to each associated type (fn/type/const),
+    // create buckets of each already implemented type that we'll use in the
+    // lookup later.
+    let mut impl_fns = FxHashSet::default();
+    let mut impl_type = FxHashSet::default();
+    let mut impl_const = FxHashSet::default();
+
+    if let Some(item_list) = impl_block.item_list() {
+        for item in item_list.impl_items() {
+            match item {
+                ast::ImplItem::FnDef(f) => {
+                    if let Some(n) = f.name() {
+                        impl_fns.insert(n.syntax().to_string());
+                    }
+                }
+
+                ast::ImplItem::TypeAliasDef(t) => {
+                    if let Some(n) = t.name() {
+                        impl_type.insert(n.syntax().to_string());
+                    }
+                }
+
+                ast::ImplItem::ConstDef(c) => {
+                    if let Some(n) = c.name() {
+                        impl_const.insert(n.syntax().to_string());
+                    }
+                }
+            }
+        }
+    }
+
+    resolve_target_trait(db, analyzer, impl_block).map_or(vec![], |target_trait| {
+        target_trait
+            .items(db)
+            .iter()
+            .filter(|i| match i {
+                hir::AssocItem::Function(f) => !impl_fns.contains(&f.name(db).to_string()),
+                hir::AssocItem::TypeAlias(t) => !impl_type.contains(&t.name(db).to_string()),
+                hir::AssocItem::Const(c) => {
+                    c.name(db).map(|n| !impl_const.contains(&n.to_string())).unwrap_or_default()
+                }
+            })
+            .map(|i| i.clone())
+            .collect()
+    })
+}
+
+fn resolve_target_trait(
+    db: &impl HirDatabase,
+    analyzer: &hir::SourceAnalyzer,
+    impl_block: &ast::ImplBlock,
+) -> Option<hir::Trait> {
+    let ast_path = impl_block
+        .target_trait()
+        .map(|it| it.syntax().clone())
+        .and_then(ast::PathType::cast)?
+        .path()?;
+
+    match analyzer.resolve_path(db, &ast_path) {
+        Some(hir::PathResolution::Def(hir::ModuleDef::Trait(def))) => Some(def),
+        _ => None,
+    }
+}
+
 pub(crate) fn invert_boolean_expression(expr: ast::Expr) -> ast::Expr {
     if let Some(expr) = invert_special_case(&expr) {
         return expr;

crates/ra_ide/src/completion/complete_trait_impl.rs

@@ -1,127 +1,30 @@
-use crate::completion::{CompletionContext, Completions, CompletionItem, CompletionKind, CompletionItemKind};
+use crate::completion::{
+    CompletionContext, CompletionItem, CompletionItemKind, CompletionKind, Completions,
+};
 
-use ra_syntax::ast::{self, NameOwner, AstNode};
+use hir::{self, Docs};
-
-use hir::{self, db::HirDatabase, Docs};
 
+use ra_assists::utils::get_missing_impl_items;
 
 pub(crate) fn complete_trait_impl(acc: &mut Completions, ctx: &CompletionContext) {
     let impl_block = ctx.impl_block.as_ref();
     let item_list = impl_block.and_then(|i| i.item_list());
 
-    if item_list.is_none() 
+    if item_list.is_none() || impl_block.is_none() || ctx.function_syntax.is_some() {
-    || impl_block.is_none() 
-    || ctx.function_syntax.is_some() {
         return;
     }
 
-    let item_list = item_list.unwrap();
     let impl_block = impl_block.unwrap();
 
-    let target_trait = resolve_target_trait(ctx.db, &ctx.analyzer, &impl_block);
+    for item in get_missing_impl_items(ctx.db, &ctx.analyzer, impl_block) {
-    if target_trait.is_none() {
-        return;
-    }
-
-    let target_trait = target_trait.unwrap();
-
-    let trait_items = target_trait.items(ctx.db);
-    let missing_items = trait_items
-        .iter()
-        .filter(|i| {
-            match i {
-                hir::AssocItem::Function(f) => {
-                    let f_name = f.name(ctx.db).to_string();
-
-                    item_list
-                        .impl_items()
-                        .find(|impl_item| {
-                            match impl_item {
-                                ast::ImplItem::FnDef(impl_f) => {
-                                    if let Some(n) = impl_f.name() { 
-                                        f_name == n.syntax().to_string()
-                                    } else { 
-                                        false
-                                    }
-                                },
-                                _ => false
-                            }
-                        }).is_none()
-                },
-                hir::AssocItem::Const(c) => {
-                    let c_name = c.name(ctx.db)
-                        .map(|f| f.to_string());
-
-                    if c_name.is_none() {
-                        return false;
-                    }
-
-                    let c_name = c_name.unwrap();
-
-                    item_list
-                        .impl_items()
-                        .find(|impl_item| {
-                            match impl_item {
-                                ast::ImplItem::ConstDef(c) => {
-                                    if let Some(n) = c.name() { 
-                                        c_name == n.syntax().to_string()
-                                    } else { 
-                                        false
-                                    }
-                                },
-                                _ => false
-                            }
-                        }).is_none()
-                },
-                hir::AssocItem::TypeAlias(t) => {
-                    let t_name = t.name(ctx.db).to_string();
-
-                    item_list
-                        .impl_items()
-                        .find(|impl_item| {
-                            match impl_item {
-                                ast::ImplItem::TypeAliasDef(t) => {
-                                    if let Some(n) = t.name() { 
-                                        t_name == n.syntax().to_string()
-                                    } else { 
-                                        false
-                                    }
-                                },
-                                _ => false
-                            }
-                        }).is_none()
-                }
-            }
-        });
-
-    for item in missing_items {
         match item {
-            hir::AssocItem::Function(f) => add_function_impl(acc, ctx, f),
+            hir::AssocItem::Function(f) => add_function_impl(acc, ctx, &f),
-            hir::AssocItem::TypeAlias(t) => add_type_alias_impl(acc, ctx, t),
+            hir::AssocItem::TypeAlias(t) => add_type_alias_impl(acc, ctx, &t),
-            _ => {},
+            _ => {}
         }
     }
 }
 
-fn resolve_target_trait(
-    db: &impl HirDatabase,
-    analyzer: &hir::SourceAnalyzer,
-    impl_block: &ast::ImplBlock
-) -> Option<hir::Trait> {
-    let ast_path = impl_block
-        .target_trait()
-        .map(|it| it.syntax().clone())
-        .and_then(ast::PathType::cast)?
-        .path()?;
-
-    match analyzer.resolve_path(db, &ast_path) {
-        Some(hir::PathResolution::Def(hir::ModuleDef::Trait(def))) => {
-            Some(def)
-        }
-        _ => None,
-    }
-}
-
 fn add_function_impl(acc: &mut Completions, ctx: &CompletionContext, func: &hir::Function) {
     use crate::display::FunctionSignature;
 
@@ -151,13 +54,14 @@ fn add_function_impl(acc: &mut Completions, ctx: &CompletionContext, func: &hir:
         s
     };
 
-    builder
+    builder.insert_text(snippet).kind(completion_kind).add_to(acc);
-        .insert_text(snippet)
-        .kind(completion_kind)
-        .add_to(acc);
 }
 
-fn add_type_alias_impl(acc: &mut Completions, ctx: &CompletionContext, type_alias: &hir::TypeAlias) {
+fn add_type_alias_impl(
+    acc: &mut Completions,
+    ctx: &CompletionContext,
+    type_alias: &hir::TypeAlias,
+) {
     let snippet = format!("type {} = ", type_alias.name(ctx.db).to_string());
 
     CompletionItem::new(CompletionKind::Magic, ctx.source_range(), snippet.clone())