Merge #6458

6458: Qualify trait impl created by add_custom_impl assist r=matklad a=Veykril

When we find at least one trait with the same name as the derive accessible from the current module we now generate a qualified path to that trait in the generated impl.
If we don't find any we just do what was done before and emit the trait name in the generated impl.

Co-authored-by: Lukas Wirth <[email protected]>

Author: bors[bot]

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,
 };
 
@@ -30,78 +33,151 @@ 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};
 
     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(