1 files changed, 608 insertions, 0 deletions

diff --git a/crates/ra_assists/src/handlers/add_missing_impl_members.rs b/crates/ra_assists/src/handlers/add_missing_impl_members.rs
new file mode 100644
index 000000000..448697d31
--- /dev/null
+++ b/crates/ra_assists/src/handlers/add_missing_impl_members.rs
@@ -0,0 +1,608 @@
+use hir::{db::HirDatabase, HasSource, InFile};
+use ra_syntax::{
+    ast::{self, edit, make, AstNode, NameOwner},
+    SmolStr,
+};
+
+use crate::{
+    ast_transform::{self, AstTransform, QualifyPaths, SubstituteTypeParams},
+    Assist, AssistCtx, AssistId,
+};
+
+#[derive(PartialEq)]
+enum AddMissingImplMembersMode {
+    DefaultMethodsOnly,
+    NoDefaultMethods,
+}
+
+// Assist: add_impl_missing_members
+//
+// Adds scaffold for required impl members.
+//
+// ```
+// trait Trait<T> {
+//     Type X;
+//     fn foo(&self) -> T;
+//     fn bar(&self) {}
+// }
+//
+// impl Trait<u32> for () {<|>
+//
+// }
+// ```
+// ->
+// ```
+// trait Trait<T> {
+//     Type X;
+//     fn foo(&self) -> T;
+//     fn bar(&self) {}
+// }
+//
+// impl Trait<u32> for () {
+//     fn foo(&self) -> u32 { unimplemented!() }
+//
+// }
+// ```
+pub(crate) fn add_missing_impl_members(ctx: AssistCtx) -> Option<Assist> {
+    add_missing_impl_members_inner(
+        ctx,
+        AddMissingImplMembersMode::NoDefaultMethods,
+        "add_impl_missing_members",
+        "Implement missing members",
+    )
+}
+
+// Assist: add_impl_default_members
+//
+// Adds scaffold for overriding default impl members.
+//
+// ```
+// trait Trait {
+//     Type X;
+//     fn foo(&self);
+//     fn bar(&self) {}
+// }
+//
+// impl Trait for () {
+//     Type X = ();
+//     fn foo(&self) {}<|>
+//
+// }
+// ```
+// ->
+// ```
+// trait Trait {
+//     Type X;
+//     fn foo(&self);
+//     fn bar(&self) {}
+// }
+//
+// impl Trait for () {
+//     Type X = ();
+//     fn foo(&self) {}
+//     fn bar(&self) {}
+//
+// }
+// ```
+pub(crate) fn add_missing_default_members(ctx: AssistCtx) -> Option<Assist> {
+    add_missing_impl_members_inner(
+        ctx,
+        AddMissingImplMembersMode::DefaultMethodsOnly,
+        "add_impl_default_members",
+        "Implement default members",
+    )
+}
+
+fn add_missing_impl_members_inner(
+    ctx: AssistCtx,
+    mode: AddMissingImplMembersMode,
+    assist_id: &'static str,
+    label: &'static str,
+) -> Option<Assist> {
+    let _p = ra_prof::profile("add_missing_impl_members_inner");
+    let impl_node = ctx.find_node_at_offset::<ast::ImplBlock>()?;
+    let impl_item_list = impl_node.item_list()?;
+
+    let (trait_, trait_def) = {
+        let analyzer = ctx.source_analyzer(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;
+    }
+
+    let db = ctx.db;
+    let file_id = ctx.frange.file_id;
+    let trait_file_id = trait_.source(db).file_id;
+
+    ctx.add_assist(AssistId(assist_id), label, |edit| {
+        let n_existing_items = impl_item_list.impl_items().count();
+        let module = hir::SourceAnalyzer::new(
+            db,
+            hir::InFile::new(file_id.into(), impl_node.syntax()),
+            None,
+        )
+        .module();
+        let ast_transform = QualifyPaths::new(db, module)
+            .or(SubstituteTypeParams::for_trait_impl(db, trait_, impl_node));
+        let items = missing_items
+            .into_iter()
+            .map(|it| ast_transform::apply(&*ast_transform, InFile::new(trait_file_id, it)))
+            .map(|it| match it {
+                ast::ImplItem::FnDef(def) => ast::ImplItem::FnDef(add_body(def)),
+                _ => it,
+            })
+            .map(|it| edit::strip_attrs_and_docs(&it));
+        let new_impl_item_list = impl_item_list.append_items(items);
+        let cursor_position = {
+            let first_new_item = new_impl_item_list.impl_items().nth(n_existing_items).unwrap();
+            first_new_item.syntax().text_range().start()
+        };
+
+        edit.replace_ast(impl_item_list, new_impl_item_list);
+        edit.set_cursor(cursor_position);
+    })
+}
+
+fn add_body(fn_def: ast::FnDef) -> ast::FnDef {
+    if fn_def.body().is_none() {
+        fn_def.with_body(make::block_from_expr(make::expr_unimplemented()))
+    } else {
+        fn_def
+    }
+}
+
+/// 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<(hir::Trait, 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, def.source(db).value))
+        }
+        _ => 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 fill_in_type_params_1() {
+        check_assist(
+            add_missing_impl_members,
+            "
+trait Foo<T> { fn foo(&self, t: T) -> &T; }
+struct S;
+impl Foo<u32> for S { <|> }",
+            "
+trait Foo<T> { fn foo(&self, t: T) -> &T; }
+struct S;
+impl Foo<u32> for S {
+    <|>fn foo(&self, t: u32) -> &u32 { unimplemented!() }
+}",
+        );
+    }
+
+    #[test]
+    fn fill_in_type_params_2() {
+        check_assist(
+            add_missing_impl_members,
+            "
+trait Foo<T> { fn foo(&self, t: T) -> &T; }
+struct S;
+impl<U> Foo<U> for S { <|> }",
+            "
+trait Foo<T> { fn foo(&self, t: T) -> &T; }
+struct S;
+impl<U> Foo<U> for S {
+    <|>fn foo(&self, t: U) -> &U { 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_qualify_path_1() {
+        check_assist(
+            add_missing_impl_members,
+            "
+mod foo {
+    pub struct Bar;
+    trait Foo { fn foo(&self, bar: Bar); }
+}
+struct S;
+impl foo::Foo for S { <|> }",
+            "
+mod foo {
+    pub struct Bar;
+    trait Foo { fn foo(&self, bar: Bar); }
+}
+struct S;
+impl foo::Foo for S {
+    <|>fn foo(&self, bar: foo::Bar) { unimplemented!() }
+}",
+        );
+    }
+
+    #[test]
+    fn test_qualify_path_generic() {
+        check_assist(
+            add_missing_impl_members,
+            "
+mod foo {
+    pub struct Bar<T>;
+    trait Foo { fn foo(&self, bar: Bar<u32>); }
+}
+struct S;
+impl foo::Foo for S { <|> }",
+            "
+mod foo {
+    pub struct Bar<T>;
+    trait Foo { fn foo(&self, bar: Bar<u32>); }
+}
+struct S;
+impl foo::Foo for S {
+    <|>fn foo(&self, bar: foo::Bar<u32>) { unimplemented!() }
+}",
+        );
+    }
+
+    #[test]
+    fn test_qualify_path_and_substitute_param() {
+        check_assist(
+            add_missing_impl_members,
+            "
+mod foo {
+    pub struct Bar<T>;
+    trait Foo<T> { fn foo(&self, bar: Bar<T>); }
+}
+struct S;
+impl foo::Foo<u32> for S { <|> }",
+            "
+mod foo {
+    pub struct Bar<T>;
+    trait Foo<T> { fn foo(&self, bar: Bar<T>); }
+}
+struct S;
+impl foo::Foo<u32> for S {
+    <|>fn foo(&self, bar: foo::Bar<u32>) { unimplemented!() }
+}",
+        );
+    }
+
+    #[test]
+    fn test_substitute_param_no_qualify() {
+        // when substituting params, the substituted param should not be qualified!
+        check_assist(
+            add_missing_impl_members,
+            "
+mod foo {
+    trait Foo<T> { fn foo(&self, bar: T); }
+    pub struct Param;
+}
+struct Param;
+struct S;
+impl foo::Foo<Param> for S { <|> }",
+            "
+mod foo {
+    trait Foo<T> { fn foo(&self, bar: T); }
+    pub struct Param;
+}
+struct Param;
+struct S;
+impl foo::Foo<Param> for S {
+    <|>fn foo(&self, bar: Param) { unimplemented!() }
+}",
+        );
+    }
+
+    #[test]
+    fn test_qualify_path_associated_item() {
+        check_assist(
+            add_missing_impl_members,
+            "
+mod foo {
+    pub struct Bar<T>;
+    impl Bar<T> { type Assoc = u32; }
+    trait Foo { fn foo(&self, bar: Bar<u32>::Assoc); }
+}
+struct S;
+impl foo::Foo for S { <|> }",
+            "
+mod foo {
+    pub struct Bar<T>;
+    impl Bar<T> { type Assoc = u32; }
+    trait Foo { fn foo(&self, bar: Bar<u32>::Assoc); }
+}
+struct S;
+impl foo::Foo for S {
+    <|>fn foo(&self, bar: foo::Bar<u32>::Assoc) { unimplemented!() }
+}",
+        );
+    }
+
+    #[test]
+    fn test_qualify_path_nested() {
+        check_assist(
+            add_missing_impl_members,
+            "
+mod foo {
+    pub struct Bar<T>;
+    pub struct Baz;
+    trait Foo { fn foo(&self, bar: Bar<Baz>); }
+}
+struct S;
+impl foo::Foo for S { <|> }",
+            "
+mod foo {
+    pub struct Bar<T>;
+    pub struct Baz;
+    trait Foo { fn foo(&self, bar: Bar<Baz>); }
+}
+struct S;
+impl foo::Foo for S {
+    <|>fn foo(&self, bar: foo::Bar<foo::Baz>) { unimplemented!() }
+}",
+        );
+    }
+
+    #[test]
+    fn test_qualify_path_fn_trait_notation() {
+        check_assist(
+            add_missing_impl_members,
+            "
+mod foo {
+    pub trait Fn<Args> { type Output; }
+    trait Foo { fn foo(&self, bar: dyn Fn(u32) -> i32); }
+}
+struct S;
+impl foo::Foo for S { <|> }",
+            "
+mod foo {
+    pub trait Fn<Args> { type Output; }
+    trait Foo { fn foo(&self, bar: dyn Fn(u32) -> i32); }
+}
+struct S;
+impl foo::Foo for S {
+    <|>fn foo(&self, bar: dyn Fn(u32) -> i32) { 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 }
+}",
+        )
+    }
+}