4 files changed, 262 insertions, 58 deletions

diff --git a/crates/ra_assists/src/assists/add_custom_impl.rs b/crates/ra_assists/src/assists/add_custom_impl.rs
new file mode 100644
index 000000000..037306fd6
--- /dev/null
+++ b/crates/ra_assists/src/assists/add_custom_impl.rs
@@ -0,0 +1,206 @@
+//! FIXME: write short doc here
+
+use crate::{Assist, AssistCtx, AssistId};
+use hir::db::HirDatabase;
+use join_to_string::join;
+use ra_syntax::{
+    ast::{self, AstNode},
+    Direction, SmolStr,
+    SyntaxKind::{IDENT, WHITESPACE},
+    TextRange, TextUnit,
+};
+
+const DERIVE_TRAIT: &'static str = "derive";
+
+// Assist: add_custom_impl
+//
+// Adds impl block for derived trait.
+//
+// ```
+// #[derive(Deb<|>ug, Display)]
+// struct S;
+// ```
+// ->
+// ```
+// #[derive(Display)]
+// struct S;
+//
+// impl Debug for S {
+//
+// }
+// ```
+pub(crate) fn add_custom_impl(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
+    let input = ctx.find_node_at_offset::<ast::AttrInput>()?;
+    let attr = input.syntax().parent().and_then(ast::Attr::cast)?;
+
+    let attr_name = attr
+        .syntax()
+        .descendants_with_tokens()
+        .filter(|t| t.kind() == IDENT)
+        .find_map(|i| i.into_token())
+        .filter(|t| *t.text() == DERIVE_TRAIT)?
+        .text()
+        .clone();
+
+    let trait_token =
+        ctx.token_at_offset().filter(|t| t.kind() == IDENT && *t.text() != attr_name).next()?;
+
+    let annotated = attr.syntax().siblings(Direction::Next).find_map(|s| ast::Name::cast(s))?;
+    let annotated_name = annotated.syntax().text().to_string();
+    let start_offset = annotated.syntax().parent()?.text_range().end();
+
+    ctx.add_assist(AssistId("add_custom_impl"), "add custom impl", |edit| {
+        edit.target(attr.syntax().text_range());
+
+        let new_attr_input = input
+            .syntax()
+            .descendants_with_tokens()
+            .filter(|t| t.kind() == IDENT)
+            .filter_map(|t| t.into_token().map(|t| t.text().clone()))
+            .filter(|t| t != trait_token.text())
+            .collect::<Vec<SmolStr>>();
+        let has_more_derives = new_attr_input.len() > 0;
+        let new_attr_input =
+            join(new_attr_input.iter()).separator(", ").surround_with("(", ")").to_string();
+        let new_attr_input_len = new_attr_input.len();
+
+        let mut buf = String::new();
+        buf.push_str("\n\nimpl ");
+        buf.push_str(trait_token.text().as_str());
+        buf.push_str(" for ");
+        buf.push_str(annotated_name.as_str());
+        buf.push_str(" {\n");
+
+        let cursor_delta = if has_more_derives {
+            edit.replace(input.syntax().text_range(), new_attr_input);
+            input.syntax().text_range().len() - TextUnit::from_usize(new_attr_input_len)
+        } else {
+            let attr_range = attr.syntax().text_range();
+            edit.delete(attr_range);
+
+            let line_break_range = attr
+                .syntax()
+                .next_sibling_or_token()
+                .filter(|t| t.kind() == WHITESPACE)
+                .map(|t| t.text_range())
+                .unwrap_or(TextRange::from_to(TextUnit::from(0), TextUnit::from(0)));
+            edit.delete(line_break_range);
+
+            attr_range.len() + line_break_range.len()
+        };
+
+        edit.set_cursor(start_offset + TextUnit::of_str(&buf) - cursor_delta);
+        buf.push_str("\n}");
+        edit.insert(start_offset, buf);
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::helpers::{check_assist, check_assist_not_applicable};
+
+    #[test]
+    fn add_custom_impl_for_unique_input() {
+        check_assist(
+            add_custom_impl,
+            "
+#[derive(Debu<|>g)]
+struct Foo {
+    bar: String,
+}
+            ",
+            "
+struct Foo {
+    bar: String,
+}
+
+impl Debug for Foo {
+<|>
+}
+            ",
+        )
+    }
+
+    #[test]
+    fn add_custom_impl_for_with_visibility_modifier() {
+        check_assist(
+            add_custom_impl,
+            "
+#[derive(Debug<|>)]
+pub struct Foo {
+    bar: String,
+}
+            ",
+            "
+pub struct Foo {
+    bar: String,
+}
+
+impl Debug for Foo {
+<|>
+}
+            ",
+        )
+    }
+
+    #[test]
+    fn add_custom_impl_when_multiple_inputs() {
+        check_assist(
+            add_custom_impl,
+            "
+#[derive(Display, Debug<|>, Serialize)]
+struct Foo {}
+            ",
+            "
+#[derive(Display, Serialize)]
+struct Foo {}
+
+impl Debug for Foo {
+<|>
+}
+            ",
+        )
+    }
+
+    #[test]
+    fn test_ignore_derive_macro_without_input() {
+        check_assist_not_applicable(
+            add_custom_impl,
+            "
+#[derive(<|>)]
+struct Foo {}
+            ",
+        )
+    }
+
+    #[test]
+    fn test_ignore_if_cursor_on_param() {
+        check_assist_not_applicable(
+            add_custom_impl,
+            "
+#[derive<|>(Debug)]
+struct Foo {}
+            ",
+        );
+
+        check_assist_not_applicable(
+            add_custom_impl,
+            "
+#[derive(Debug)<|>]
+struct Foo {}
+            ",
+        )
+    }
+
+    #[test]
+    fn test_ignore_if_not_derive() {
+        check_assist_not_applicable(
+            add_custom_impl,
+            "
+#[allow(non_camel_<|>case_types)]
+struct Foo {}
+            ",
+        )
+    }
+}
diff --git a/crates/ra_assists/src/assists/add_import.rs b/crates/ra_assists/src/assists/add_import.rs
index 363ade016..b8752cbad 100644
--- a/crates/ra_assists/src/assists/add_import.rs
+++ b/crates/ra_assists/src/assists/add_import.rs
@@ -578,17 +578,21 @@ fn apply_auto_import(
 
 fn collect_hir_path_segments(path: &hir::Path) -> Option<Vec<SmolStr>> {
     let mut ps = Vec::<SmolStr>::with_capacity(10);
-    match path.kind {
+    match path.kind() {
         hir::PathKind::Abs => ps.push("".into()),
         hir::PathKind::Crate => ps.push("crate".into()),
         hir::PathKind::Plain => {}
-        hir::PathKind::Self_ => ps.push("self".into()),
-        hir::PathKind::Super => ps.push("super".into()),
-        hir::PathKind::Type(_) | hir::PathKind::DollarCrate(_) => return None,
-    }
-    for s in path.segments.iter() {
-        ps.push(s.name.to_string().into());
+        hir::PathKind::Super(0) => ps.push("self".into()),
+        hir::PathKind::Super(lvl) => {
+            let mut chain = "super".to_string();
+            for _ in 0..*lvl {
+                chain += "::super";
+            }
+            ps.push(chain.into());
+        }
+        hir::PathKind::DollarCrate(_) => return None,
     }
+    ps.extend(path.segments().iter().map(|it| it.name.to_string().into()));
     Some(ps)
 }
 
diff --git a/crates/ra_assists/src/assists/add_new.rs b/crates/ra_assists/src/assists/add_new.rs
index 8f68bd5fb..b2f946fac 100644
--- a/crates/ra_assists/src/assists/add_new.rs
+++ b/crates/ra_assists/src/assists/add_new.rs
@@ -1,5 +1,5 @@
 use format_buf::format;
-use hir::{db::HirDatabase, FromSource};
+use hir::{db::HirDatabase, FromSource, InFile};
 use join_to_string::join;
 use ra_syntax::{
     ast::{
@@ -56,42 +56,39 @@ pub(crate) fn add_new(ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
         let vis = vis.as_ref().map(String::as_str).unwrap_or("");
         write!(&mut buf, "    {}fn new(", vis).unwrap();
 
-        join(field_list.fields().map(|f| {
-            format!(
-                "{}: {}",
-                f.name().unwrap().syntax().text(),
-                f.ascribed_type().unwrap().syntax().text()
-            )
+        join(field_list.fields().filter_map(|f| {
+            Some(format!("{}: {}", f.name()?.syntax().text(), f.ascribed_type()?.syntax().text()))
         }))
         .separator(", ")
         .to_buf(&mut buf);
 
         buf.push_str(") -> Self { Self {");
 
-        join(field_list.fields().map(|f| f.name().unwrap().syntax().text()))
+        join(field_list.fields().filter_map(|f| Some(f.name()?.syntax().text())))
             .separator(", ")
             .surround_with(" ", " ")
             .to_buf(&mut buf);
 
         buf.push_str("} }");
 
-        let (start_offset, end_offset) = if let Some(impl_block) = impl_block {
-            buf.push('\n');
-            let start = impl_block
-                .syntax()
-                .descendants_with_tokens()
-                .find(|t| t.kind() == T!['{'])
-                .unwrap()
-                .text_range()
-                .end();
-
-            (start, TextUnit::from_usize(1))
-        } else {
-            buf = generate_impl_text(&strukt, &buf);
-            let start = strukt.syntax().text_range().end();
-
-            (start, TextUnit::from_usize(3))
-        };
+        let (start_offset, end_offset) = impl_block
+            .and_then(|impl_block| {
+                buf.push('\n');
+                let start = impl_block
+                    .syntax()
+                    .descendants_with_tokens()
+                    .find(|t| t.kind() == T!['{'])?
+                    .text_range()
+                    .end();
+
+                Some((start, TextUnit::from_usize(1)))
+            })
+            .unwrap_or_else(|| {
+                buf = generate_impl_text(&strukt, &buf);
+                let start = strukt.syntax().text_range().end();
+
+                (start, TextUnit::from_usize(3))
+            });
 
         edit.set_cursor(start_offset + TextUnit::of_str(&buf) - end_offset);
         edit.insert(start_offset, buf);
@@ -141,44 +138,41 @@ fn find_struct_impl(
     })?;
 
     let struct_ty = {
-        let src = hir::Source { file_id: ctx.frange.file_id.into(), value: strukt.clone() };
-        hir::Struct::from_source(db, src).unwrap().ty(db)
+        let src = InFile { file_id: ctx.frange.file_id.into(), value: strukt.clone() };
+        hir::Struct::from_source(db, src)?.ty(db)
     };
 
-    let mut found_new_fn = false;
-
-    let block = module.descendants().filter_map(ast::ImplBlock::cast).find(|impl_blk| {
-        if found_new_fn {
-            return false;
-        }
-
-        let src = hir::Source { file_id: ctx.frange.file_id.into(), value: impl_blk.clone() };
-        let blk = hir::ImplBlock::from_source(db, src).unwrap();
+    let block = module.descendants().filter_map(ast::ImplBlock::cast).find_map(|impl_blk| {
+        let src = InFile { file_id: ctx.frange.file_id.into(), value: impl_blk.clone() };
+        let blk = hir::ImplBlock::from_source(db, src)?;
 
         let same_ty = blk.target_ty(db) == struct_ty;
         let not_trait_impl = blk.target_trait(db).is_none();
 
         if !(same_ty && not_trait_impl) {
-            return false;
+            None
+        } else {
+            Some(impl_blk)
         }
-
-        found_new_fn = has_new_fn(impl_blk);
-        true
     });
 
-    if found_new_fn {
-        None
-    } else {
-        Some(block)
+    if let Some(ref impl_blk) = block {
+        if has_new_fn(impl_blk) {
+            return None;
+        }
     }
+
+    Some(block)
 }
 
 fn has_new_fn(imp: &ast::ImplBlock) -> bool {
     if let Some(il) = imp.item_list() {
         for item in il.impl_items() {
             if let ast::ImplItem::FnDef(f) = item {
-                if f.name().unwrap().text().eq_ignore_ascii_case("new") {
-                    return true;
+                if let Some(name) = f.name() {
+                    if name.text().eq_ignore_ascii_case("new") {
+                        return true;
+                    }
                 }
             }
         }
diff --git a/crates/ra_assists/src/assists/early_return.rs b/crates/ra_assists/src/assists/early_return.rs
index 264412526..023917aca 100644
--- a/crates/ra_assists/src/assists/early_return.rs
+++ b/crates/ra_assists/src/assists/early_return.rs
@@ -83,8 +83,8 @@ pub(crate) fn convert_to_guarded_return(ctx: AssistCtx<impl HirDatabase>) -> Opt
     let parent_container = parent_block.syntax().parent()?.parent()?;
 
     let early_expression: ast::Expr = match parent_container.kind() {
-        WHILE_EXPR | LOOP_EXPR => make::expr_continue().into(),
-        FN_DEF => make::expr_return().into(),
+        WHILE_EXPR | LOOP_EXPR => make::expr_continue(),
+        FN_DEF => make::expr_return(),
         _ => return None,
     };
 
@@ -116,13 +116,13 @@ pub(crate) fn convert_to_guarded_return(ctx: AssistCtx<impl HirDatabase>) -> Opt
                             )
                             .into(),
                         ),
-                        make::expr_path(make::path_from_name_ref(make::name_ref("it"))).into(),
+                        make::expr_path(make::path_from_name_ref(make::name_ref("it"))),
                     );
 
                     let sad_arm = make::match_arm(
                         // FIXME: would be cool to use `None` or `Err(_)` if appropriate
                         once(make::placeholder_pat().into()),
-                        early_expression.into(),
+                        early_expression,
                     );
 
                     make::expr_match(cond_expr, make::match_arm_list(vec![happy_arm, sad_arm]))
@@ -130,7 +130,7 @@ pub(crate) fn convert_to_guarded_return(ctx: AssistCtx<impl HirDatabase>) -> Opt
 
                 let let_stmt = make::let_stmt(
                     make::bind_pat(make::name(&bound_ident.syntax().to_string())).into(),
-                    Some(match_expr.into()),
+                    Some(match_expr),
                 );
                 let let_stmt = if_indent_level.increase_indent(let_stmt);
                 replace(let_stmt.syntax(), &then_block, &parent_block, &if_expr)