1 files changed, 337 insertions, 0 deletions

diff --git a/crates/ra_assists/src/assists/add_missing_impl_members.rs b/crates/ra_assists/src/assists/add_missing_impl_members.rs
new file mode 100644
index 000000000..2894bdd8a
--- /dev/null
+++ b/crates/ra_assists/src/assists/add_missing_impl_members.rs
@@ -0,0 +1,337 @@
+use hir::{db::HirDatabase, HasSource};
+use ra_syntax::{
+    ast::{self, AstNode, NameOwner},
+    SmolStr,
+};
+
+use crate::{ast_builder::AstBuilder, ast_editor::AstEditor, Assist, AssistCtx, AssistId};
+
+#[derive(PartialEq)]
+enum AddMissingImplMembersMode {
+    DefaultMethodsOnly,
+    NoDefaultMethods,
+}
+
+pub(crate) fn add_missing_impl_members(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+    add_missing_impl_members_inner(
+        ctx,
+        AddMissingImplMembersMode::NoDefaultMethods,
+        "add_impl_missing_members",
+        "add missing impl members",
+    )
+}
+
+pub(crate) fn add_missing_default_members(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+    add_missing_impl_members_inner(
+        ctx,
+        AddMissingImplMembersMode::DefaultMethodsOnly,
+        "add_impl_default_members",
+        "add impl default members",
+    )
+}
+
+fn add_missing_impl_members_inner(
+    mut ctx: AssistCtx<impl HirDatabase>,
+    mode: AddMissingImplMembersMode,
+    assist_id: &'static str,
+    label: &'static str,
+) -> Option<Assist> {
+    let impl_node = ctx.node_at_offset::<ast::ImplBlock>()?;
+    let impl_item_list = impl_node.item_list()?;
+
+    let trait_def = {
+        let file_id = ctx.frange.file_id;
+        let analyzer = hir::SourceAnalyzer::new(ctx.db, file_id, impl_node.syntax(), None);
+
+        resolve_target_trait_def(ctx.db, &analyzer, &impl_node)?
+    };
+
+    let def_name = |item: &ast::ImplItem| -> Option<SmolStr> {
+        match item {
+            ast::ImplItem::FnDef(def) => def.name(),
+            ast::ImplItem::TypeAliasDef(def) => def.name(),
+            ast::ImplItem::ConstDef(def) => def.name(),
+        }
+        .map(|it| it.text().clone())
+    };
+
+    let trait_items = trait_def.item_list()?.impl_items();
+    let impl_items = impl_item_list.impl_items().collect::<Vec<_>>();
+
+    let missing_items: Vec<_> = trait_items
+        .filter(|t| def_name(t).is_some())
+        .filter(|t| match t {
+            ast::ImplItem::FnDef(def) => match mode {
+                AddMissingImplMembersMode::DefaultMethodsOnly => def.body().is_some(),
+                AddMissingImplMembersMode::NoDefaultMethods => def.body().is_none(),
+            },
+            _ => mode == AddMissingImplMembersMode::NoDefaultMethods,
+        })
+        .filter(|t| impl_items.iter().all(|i| def_name(i) != def_name(t)))
+        .collect();
+    if missing_items.is_empty() {
+        return None;
+    }
+
+    ctx.add_action(AssistId(assist_id), label, |edit| {
+        let n_existing_items = impl_item_list.impl_items().count();
+        let items = missing_items.into_iter().map(|it| match it {
+            ast::ImplItem::FnDef(def) => strip_docstring(add_body(def).into()),
+            _ => strip_docstring(it),
+        });
+        let mut ast_editor = AstEditor::new(impl_item_list);
+
+        ast_editor.append_items(items);
+
+        let first_new_item = ast_editor.ast().impl_items().nth(n_existing_items).unwrap();
+        let cursor_position = first_new_item.syntax().text_range().start();
+        ast_editor.into_text_edit(edit.text_edit_builder());
+
+        edit.set_cursor(cursor_position);
+    });
+
+    ctx.build()
+}
+
+fn strip_docstring(item: ast::ImplItem) -> ast::ImplItem {
+    let mut ast_editor = AstEditor::new(item);
+    ast_editor.strip_attrs_and_docs();
+    ast_editor.ast().to_owned()
+}
+
+fn add_body(fn_def: ast::FnDef) -> ast::FnDef {
+    let mut ast_editor = AstEditor::new(fn_def.clone());
+    if fn_def.body().is_none() {
+        ast_editor.set_body(&AstBuilder::<ast::Block>::single_expr(
+            &AstBuilder::<ast::Expr>::unimplemented(),
+        ));
+    }
+    ast_editor.ast().to_owned()
+}
+
+/// Given an `ast::ImplBlock`, resolves the target trait (the one being
+/// implemented) to a `ast::TraitDef`.
+fn resolve_target_trait_def(
+    db: &impl HirDatabase,
+    analyzer: &hir::SourceAnalyzer,
+    impl_block: &ast::ImplBlock,
+) -> Option<ast::TraitDef> {
+    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.source(db).ast),
+        _ => None,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::helpers::{check_assist, check_assist_not_applicable};
+
+    #[test]
+    fn test_add_missing_impl_members() {
+        check_assist(
+            add_missing_impl_members,
+            "
+trait Foo {
+    type Output;
+
+    const CONST: usize = 42;
+
+    fn foo(&self);
+    fn bar(&self);
+    fn baz(&self);
+}
+
+struct S;
+
+impl Foo for S {
+    fn bar(&self) {}
+<|>
+}",
+            "
+trait Foo {
+    type Output;
+
+    const CONST: usize = 42;
+
+    fn foo(&self);
+    fn bar(&self);
+    fn baz(&self);
+}
+
+struct S;
+
+impl Foo for S {
+    fn bar(&self) {}
+    <|>type Output;
+    const CONST: usize = 42;
+    fn foo(&self) { unimplemented!() }
+    fn baz(&self) { unimplemented!() }
+
+}",
+        );
+    }
+
+    #[test]
+    fn test_copied_overriden_members() {
+        check_assist(
+            add_missing_impl_members,
+            "
+trait Foo {
+    fn foo(&self);
+    fn bar(&self) -> bool { true }
+    fn baz(&self) -> u32 { 42 }
+}
+
+struct S;
+
+impl Foo for S {
+    fn bar(&self) {}
+<|>
+}",
+            "
+trait Foo {
+    fn foo(&self);
+    fn bar(&self) -> bool { true }
+    fn baz(&self) -> u32 { 42 }
+}
+
+struct S;
+
+impl Foo for S {
+    fn bar(&self) {}
+    <|>fn foo(&self) { unimplemented!() }
+
+}",
+        );
+    }
+
+    #[test]
+    fn test_empty_impl_block() {
+        check_assist(
+            add_missing_impl_members,
+            "
+trait Foo { fn foo(&self); }
+struct S;
+impl Foo for S { <|> }",
+            "
+trait Foo { fn foo(&self); }
+struct S;
+impl Foo for S {
+    <|>fn foo(&self) { unimplemented!() }
+}",
+        );
+    }
+
+    #[test]
+    fn test_cursor_after_empty_impl_block() {
+        check_assist(
+            add_missing_impl_members,
+            "
+trait Foo { fn foo(&self); }
+struct S;
+impl Foo for S {}<|>",
+            "
+trait Foo { fn foo(&self); }
+struct S;
+impl Foo for S {
+    <|>fn foo(&self) { unimplemented!() }
+}",
+        )
+    }
+
+    #[test]
+    fn test_empty_trait() {
+        check_assist_not_applicable(
+            add_missing_impl_members,
+            "
+trait Foo;
+struct S;
+impl Foo for S { <|> }",
+        )
+    }
+
+    #[test]
+    fn test_ignore_unnamed_trait_members_and_default_methods() {
+        check_assist_not_applicable(
+            add_missing_impl_members,
+            "
+trait Foo {
+    fn (arg: u32);
+    fn valid(some: u32) -> bool { false }
+}
+struct S;
+impl Foo for S { <|> }",
+        )
+    }
+
+    #[test]
+    fn test_with_docstring_and_attrs() {
+        check_assist(
+            add_missing_impl_members,
+            r#"
+#[doc(alias = "test alias")]
+trait Foo {
+    /// doc string
+    type Output;
+
+    #[must_use]
+    fn foo(&self);
+}
+struct S;
+impl Foo for S {}<|>"#,
+            r#"
+#[doc(alias = "test alias")]
+trait Foo {
+    /// doc string
+    type Output;
+
+    #[must_use]
+    fn foo(&self);
+}
+struct S;
+impl Foo for S {
+    <|>type Output;
+    fn foo(&self) { unimplemented!() }
+}"#,
+        )
+    }
+
+    #[test]
+    fn test_default_methods() {
+        check_assist(
+            add_missing_default_members,
+            "
+trait Foo {
+    type Output;
+
+    const CONST: usize = 42;
+
+    fn valid(some: u32) -> bool { false }
+    fn foo(some: u32) -> bool;
+}
+struct S;
+impl Foo for S { <|> }",
+            "
+trait Foo {
+    type Output;
+
+    const CONST: usize = 42;
+
+    fn valid(some: u32) -> bool { false }
+    fn foo(some: u32) -> bool;
+}
+struct S;
+impl Foo for S {
+    <|>fn valid(some: u32) -> bool { false }
+}",
+        )
+    }
+
+}