1 files changed, 114 insertions, 38 deletions

diff --git a/crates/assists/src/handlers/add_custom_impl.rs b/crates/assists/src/handlers/add_custom_impl.rs
index 8757fa33f..669dd9b21 100644
--- a/crates/assists/src/handlers/add_custom_impl.rs
+++ b/crates/assists/src/handlers/add_custom_impl.rs
@@ -1,13 +1,16 @@
+use ide_db::imports_locator;
 use itertools::Itertools;
 use syntax::{
-    ast::{self, AstNode},
+    ast::{self, make, AstNode},
     Direction, SmolStr,
     SyntaxKind::{IDENT, WHITESPACE},
     TextRange, TextSize,
 };
 
 use crate::{
-    assist_context::{AssistContext, Assists},
+    assist_config::SnippetCap,
+    assist_context::{AssistBuilder, AssistContext, Assists},
+    utils::mod_path_to_ast,
     AssistId, AssistKind,
 };
 
@@ -30,72 +33,116 @@ use crate::{
 // ```
 pub(crate) fn add_custom_impl(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
     let attr = ctx.find_node_at_offset::<ast::Attr>()?;
-    let input = attr.token_tree()?;
 
     let attr_name = attr
         .syntax()
         .descendants_with_tokens()
         .filter(|t| t.kind() == IDENT)
-        .find_map(|i| i.into_token())
-        .filter(|t| *t.text() == "derive")?
+        .find_map(syntax::NodeOrToken::into_token)
+        .filter(|t| t.text() == "derive")?
         .text()
         .clone();
 
     let trait_token =
         ctx.token_at_offset().find(|t| t.kind() == IDENT && *t.text() != attr_name)?;
+    let trait_path = make::path_unqualified(make::path_segment(make::name_ref(trait_token.text())));
 
     let annotated = attr.syntax().siblings(Direction::Next).find_map(ast::Name::cast)?;
     let annotated_name = annotated.syntax().text().to_string();
-    let start_offset = annotated.syntax().parent()?.text_range().end();
+    let insert_pos = annotated.syntax().parent()?.text_range().end();
+
+    let current_module = ctx.sema.scope(annotated.syntax()).module()?;
+    let current_crate = current_module.krate();
+
+    let found_traits = imports_locator::find_imports(&ctx.sema, current_crate, trait_token.text())
+        .into_iter()
+        .filter_map(|candidate: either::Either<hir::ModuleDef, hir::MacroDef>| match candidate {
+            either::Either::Left(hir::ModuleDef::Trait(trait_)) => Some(trait_),
+            _ => None,
+        })
+        .flat_map(|trait_| {
+            current_module
+                .find_use_path(ctx.sema.db, hir::ModuleDef::Trait(trait_))
+                .as_ref()
+                .map(mod_path_to_ast)
+                .zip(Some(trait_))
+        });
 
-    let label =
-        format!("Add custom impl `{}` for `{}`", trait_token.text().as_str(), annotated_name);
+    let mut no_traits_found = true;
+    for (trait_path, _trait) in found_traits.inspect(|_| no_traits_found = false) {
+        add_assist(acc, ctx.config.snippet_cap, &attr, &trait_path, &annotated_name, insert_pos)?;
+    }
+    if no_traits_found {
+        add_assist(acc, ctx.config.snippet_cap, &attr, &trait_path, &annotated_name, insert_pos)?;
+    }
+    Some(())
+}
 
+fn add_assist(
+    acc: &mut Assists,
+    snippet_cap: Option<SnippetCap>,
+    attr: &ast::Attr,
+    trait_path: &ast::Path,
+    annotated_name: &str,
+    insert_pos: TextSize,
+) -> Option<()> {
     let target = attr.syntax().text_range();
-    acc.add(AssistId("add_custom_impl", AssistKind::Refactor), label, target, |builder| {
-        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.is_empty();
-
-        if has_more_derives {
-            let new_attr_input = format!("({})", new_attr_input.iter().format(", "));
-            builder.replace(input.syntax().text_range(), new_attr_input);
-        } else {
-            let attr_range = attr.syntax().text_range();
-            builder.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_else(|| TextRange::new(TextSize::from(0), TextSize::from(0)));
-            builder.delete(line_break_range);
-        }
+    let input = attr.token_tree()?;
+    let label = format!("Add custom impl `{}` for `{}`", trait_path, annotated_name);
+    let trait_name = trait_path.segment().and_then(|seg| seg.name_ref())?;
 
-        match ctx.config.snippet_cap {
+    acc.add(AssistId("add_custom_impl", AssistKind::Refactor), label, target, |builder| {
+        update_attribute(builder, &input, &trait_name, &attr);
+        match snippet_cap {
             Some(cap) => {
                 builder.insert_snippet(
                     cap,
-                    start_offset,
-                    format!("\n\nimpl {} for {} {{\n    $0\n}}", trait_token, annotated_name),
+                    insert_pos,
+                    format!("\n\nimpl {} for {} {{\n    $0\n}}", trait_path, annotated_name),
                 );
             }
             None => {
                 builder.insert(
-                    start_offset,
-                    format!("\n\nimpl {} for {} {{\n\n}}", trait_token, annotated_name),
+                    insert_pos,
+                    format!("\n\nimpl {} for {} {{\n\n}}", trait_path, annotated_name),
                 );
             }
         }
     })
 }
 
+fn update_attribute(
+    builder: &mut AssistBuilder,
+    input: &ast::TokenTree,
+    trait_name: &ast::NameRef,
+    attr: &ast::Attr,
+) {
+    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_name.text())
+        .collect::<Vec<SmolStr>>();
+    let has_more_derives = !new_attr_input.is_empty();
+
+    if has_more_derives {
+        let new_attr_input = format!("({})", new_attr_input.iter().format(", "));
+        builder.replace(input.syntax().text_range(), new_attr_input);
+    } else {
+        let attr_range = attr.syntax().text_range();
+        builder.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_else(|| TextRange::new(TextSize::from(0), TextSize::from(0)));
+        builder.delete(line_break_range);
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use crate::tests::{check_assist, check_assist_not_applicable};
@@ -103,6 +150,35 @@ mod tests {
     use super::*;
 
     #[test]
+    fn add_custom_impl_qualified() {
+        check_assist(
+            add_custom_impl,
+            "
+mod fmt {
+    pub trait Debug {}
+}
+
+#[derive(Debu<|>g)]
+struct Foo {
+    bar: String,
+}
+",
+            "
+mod fmt {
+    pub trait Debug {}
+}
+
+struct Foo {
+    bar: String,
+}
+
+impl fmt::Debug for Foo {
+    $0
+}
+",
+        )
+    }
+    #[test]
     fn add_custom_impl_for_unique_input() {
         check_assist(
             add_custom_impl,