2 files changed, 20 insertions, 532 deletions

diff --git a/crates/ra_assists/src/handlers/auto_import.rs b/crates/ra_assists/src/handlers/auto_import.rs
index edf0cf6d0..46fbdb525 100644
--- a/crates/ra_assists/src/handlers/auto_import.rs
+++ b/crates/ra_assists/src/handlers/auto_import.rs
@@ -1,6 +1,7 @@
 use crate::{
     assist_ctx::{Assist, AssistCtx},
-    insert_use_statement, AssistId,
+    utils::insert_use_statement,
+    AssistId,
 };
 use hir::{
     AsAssocItem, AssocItemContainer, ModPath, Module, ModuleDef, PathResolution, Semantics, Trait,
diff --git a/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs b/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs
index eac452413..44f3f5e7f 100644
--- a/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs
+++ b/crates/ra_assists/src/handlers/replace_qualified_name_with_use.rs
@@ -1,42 +1,12 @@
-use hir::{self, ModPath};
-use ra_syntax::{
-    ast::{self, NameOwner},
-    AstNode, Direction, SmolStr,
-    SyntaxKind::{PATH, PATH_SEGMENT},
-    SyntaxNode, TextRange, T,
-};
-use ra_text_edit::TextEditBuilder;
+use hir;
+use ra_syntax::{ast, AstNode, SmolStr, TextRange};
 
 use crate::{
     assist_ctx::{Assist, AssistCtx},
+    utils::insert_use_statement,
     AssistId,
 };
 
-/// Creates and inserts a use statement for the given path to import.
-/// The use statement is inserted in the scope most appropriate to the
-/// the cursor position given, additionally merged with the existing use imports.
-pub fn insert_use_statement(
-    // Ideally the position of the cursor, used to
-    position: &SyntaxNode,
-    // The statement to use as anchor (last resort)
-    anchor: &SyntaxNode,
-    path_to_import: &ModPath,
-    edit: &mut TextEditBuilder,
-) {
-    let target = path_to_import.to_string().split("::").map(SmolStr::new).collect::<Vec<_>>();
-    let container = position.ancestors().find_map(|n| {
-        if let Some(module) = ast::Module::cast(n.clone()) {
-            return module.item_list().map(|it| it.syntax().clone());
-        }
-        ast::SourceFile::cast(n).map(|it| it.syntax().clone())
-    });
-
-    if let Some(container) = container {
-        let action = best_action_for_target(container, anchor.clone(), &target);
-        make_assist(&action, &target, edit);
-    }
-}
-
 // Assist: replace_qualified_name_with_use
 //
 // Adds a use statement for a given fully-qualified name.
@@ -76,507 +46,24 @@ pub(crate) fn replace_qualified_name_with_use(ctx: AssistCtx) -> Option<Assist>
         AssistId("replace_qualified_name_with_use"),
         "Replace qualified path with use",
         |edit| {
-            replace_with_use(&position, &path, &segments, edit.text_edit_builder());
-        },
-    )
-}
-
-fn collect_path_segments_raw(
-    segments: &mut Vec<ast::PathSegment>,
-    mut path: ast::Path,
-) -> Option<usize> {
-    let oldlen = segments.len();
-    loop {
-        let mut children = path.syntax().children_with_tokens();
-        let (first, second, third) = (
-            children.next().map(|n| (n.clone(), n.kind())),
-            children.next().map(|n| (n.clone(), n.kind())),
-            children.next().map(|n| (n.clone(), n.kind())),
-        );
-        match (first, second, third) {
-            (Some((subpath, PATH)), Some((_, T![::])), Some((segment, PATH_SEGMENT))) => {
-                path = ast::Path::cast(subpath.as_node()?.clone())?;
-                segments.push(ast::PathSegment::cast(segment.as_node()?.clone())?);
-            }
-            (Some((segment, PATH_SEGMENT)), _, _) => {
-                segments.push(ast::PathSegment::cast(segment.as_node()?.clone())?);
-                break;
-            }
-            (_, _, _) => return None,
-        }
-    }
-    // We need to reverse only the new added segments
-    let only_new_segments = segments.split_at_mut(oldlen).1;
-    only_new_segments.reverse();
-    Some(segments.len() - oldlen)
-}
-
-fn fmt_segments_raw(segments: &[SmolStr], buf: &mut String) {
-    let mut iter = segments.iter();
-    if let Some(s) = iter.next() {
-        buf.push_str(s);
-    }
-    for s in iter {
-        buf.push_str("::");
-        buf.push_str(s);
-    }
-}
-
-/// Returns the number of common segments.
-fn compare_path_segments(left: &[SmolStr], right: &[ast::PathSegment]) -> usize {
-    left.iter().zip(right).take_while(|(l, r)| compare_path_segment(l, r)).count()
-}
-
-fn compare_path_segment(a: &SmolStr, b: &ast::PathSegment) -> bool {
-    if let Some(kb) = b.kind() {
-        match kb {
-            ast::PathSegmentKind::Name(nameref_b) => a == nameref_b.text(),
-            ast::PathSegmentKind::SelfKw => a == "self",
-            ast::PathSegmentKind::SuperKw => a == "super",
-            ast::PathSegmentKind::CrateKw => a == "crate",
-            ast::PathSegmentKind::Type { .. } => false, // not allowed in imports
-        }
-    } else {
-        false
-    }
-}
-
-fn compare_path_segment_with_name(a: &SmolStr, b: &ast::Name) -> bool {
-    a == b.text()
-}
-
-#[derive(Clone, Debug)]
-enum ImportAction {
-    Nothing,
-    // Add a brand new use statement.
-    AddNewUse {
-        anchor: Option<SyntaxNode>, // anchor node
-        add_after_anchor: bool,
-    },
-
-    // To split an existing use statement creating a nested import.
-    AddNestedImport {
-        // how may segments matched with the target path
-        common_segments: usize,
-        path_to_split: ast::Path,
-        // the first segment of path_to_split we want to add into the new nested list
-        first_segment_to_split: Option<ast::PathSegment>,
-        // Wether to add 'self' in addition to the target path
-        add_self: bool,
-    },
-    // To add the target path to an existing nested import tree list.
-    AddInTreeList {
-        common_segments: usize,
-        // The UseTreeList where to add the target path
-        tree_list: ast::UseTreeList,
-        add_self: bool,
-    },
-}
-
-impl ImportAction {
-    fn add_new_use(anchor: Option<SyntaxNode>, add_after_anchor: bool) -> Self {
-        ImportAction::AddNewUse { anchor, add_after_anchor }
-    }
-
-    fn add_nested_import(
-        common_segments: usize,
-        path_to_split: ast::Path,
-        first_segment_to_split: Option<ast::PathSegment>,
-        add_self: bool,
-    ) -> Self {
-        ImportAction::AddNestedImport {
-            common_segments,
-            path_to_split,
-            first_segment_to_split,
-            add_self,
-        }
-    }
-
-    fn add_in_tree_list(
-        common_segments: usize,
-        tree_list: ast::UseTreeList,
-        add_self: bool,
-    ) -> Self {
-        ImportAction::AddInTreeList { common_segments, tree_list, add_self }
-    }
-
-    fn better(left: ImportAction, right: ImportAction) -> ImportAction {
-        if left.is_better(&right) {
-            left
-        } else {
-            right
-        }
-    }
-
-    fn is_better(&self, other: &ImportAction) -> bool {
-        match (self, other) {
-            (ImportAction::Nothing, _) => true,
-            (ImportAction::AddInTreeList { .. }, ImportAction::Nothing) => false,
-            (
-                ImportAction::AddNestedImport { common_segments: n, .. },
-                ImportAction::AddInTreeList { common_segments: m, .. },
-            )
-            | (
-                ImportAction::AddInTreeList { common_segments: n, .. },
-                ImportAction::AddNestedImport { common_segments: m, .. },
-            )
-            | (
-                ImportAction::AddInTreeList { common_segments: n, .. },
-                ImportAction::AddInTreeList { common_segments: m, .. },
-            )
-            | (
-                ImportAction::AddNestedImport { common_segments: n, .. },
-                ImportAction::AddNestedImport { common_segments: m, .. },
-            ) => n > m,
-            (ImportAction::AddInTreeList { .. }, _) => true,
-            (ImportAction::AddNestedImport { .. }, ImportAction::Nothing) => false,
-            (ImportAction::AddNestedImport { .. }, _) => true,
-            (ImportAction::AddNewUse { .. }, _) => false,
-        }
-    }
-}
-
-// Find out the best ImportAction to import target path against current_use_tree.
-// If current_use_tree has a nested import the function gets called recursively on every UseTree inside a UseTreeList.
-fn walk_use_tree_for_best_action(
-    current_path_segments: &mut Vec<ast::PathSegment>, // buffer containing path segments
-    current_parent_use_tree_list: Option<ast::UseTreeList>, // will be Some value if we are in a nested import
-    current_use_tree: ast::UseTree, // the use tree we are currently examinating
-    target: &[SmolStr],             // the path we want to import
-) -> ImportAction {
-    // We save the number of segments in the buffer so we can restore the correct segments
-    // before returning. Recursive call will add segments so we need to delete them.
-    let prev_len = current_path_segments.len();
-
-    let tree_list = current_use_tree.use_tree_list();
-    let alias = current_use_tree.alias();
-
-    let path = match current_use_tree.path() {
-        Some(path) => path,
-        None => {
-            // If the use item don't have a path, it means it's broken (syntax error)
-            return ImportAction::add_new_use(
-                current_use_tree
-                    .syntax()
-                    .ancestors()
-                    .find_map(ast::UseItem::cast)
-                    .map(|it| it.syntax().clone()),
-                true,
-            );
-        }
-    };
-
-    // This can happen only if current_use_tree is a direct child of a UseItem
-    if let Some(name) = alias.and_then(|it| it.name()) {
-        if compare_path_segment_with_name(&target[0], &name) {
-            return ImportAction::Nothing;
-        }
-    }
-
-    collect_path_segments_raw(current_path_segments, path.clone());
-
-    // We compare only the new segments added in the line just above.
-    // The first prev_len segments were already compared in 'parent' recursive calls.
-    let left = target.split_at(prev_len).1;
-    let right = current_path_segments.split_at(prev_len).1;
-    let common = compare_path_segments(left, &right);
-    let mut action = match common {
-        0 => ImportAction::add_new_use(
-            // e.g: target is std::fmt and we can have
-            // use foo::bar
-            // We add a brand new use statement
-            current_use_tree
-                .syntax()
-                .ancestors()
-                .find_map(ast::UseItem::cast)
-                .map(|it| it.syntax().clone()),
-            true,
-        ),
-        common if common == left.len() && left.len() == right.len() => {
-            // e.g: target is std::fmt and we can have
-            // 1- use std::fmt;
-            // 2- use std::fmt::{ ... }
-            if let Some(list) = tree_list {
-                // In case 2 we need to add self to the nested list
-                // unless it's already there
-                let has_self = list.use_trees().map(|it| it.path()).any(|p| {
-                    p.and_then(|it| it.segment())
-                        .and_then(|it| it.kind())
-                        .filter(|k| *k == ast::PathSegmentKind::SelfKw)
-                        .is_some()
-                });
-
-                if has_self {
-                    ImportAction::Nothing
-                } else {
-                    ImportAction::add_in_tree_list(current_path_segments.len(), list, true)
-                }
-            } else {
-                // Case 1
-                ImportAction::Nothing
-            }
-        }
-        common if common != left.len() && left.len() == right.len() => {
-            // e.g: target is std::fmt and we have
-            // use std::io;
-            // We need to split.
-            let segments_to_split = current_path_segments.split_at(prev_len + common).1;
-            ImportAction::add_nested_import(
-                prev_len + common,
-                path,
-                Some(segments_to_split[0].clone()),
-                false,
-            )
-        }
-        common if common == right.len() && left.len() > right.len() => {
-            // e.g: target is std::fmt and we can have
-            // 1- use std;
-            // 2- use std::{ ... };
-
-            // fallback action
-            let mut better_action = ImportAction::add_new_use(
-                current_use_tree
-                    .syntax()
-                    .ancestors()
-                    .find_map(ast::UseItem::cast)
-                    .map(|it| it.syntax().clone()),
-                true,
+            let path_to_import = hir_path.mod_path().clone();
+            insert_use_statement(
+                &position,
+                &path.syntax(),
+                &path_to_import,
+                edit.text_edit_builder(),
             );
-            if let Some(list) = tree_list {
-                // Case 2, check recursively if the path is already imported in the nested list
-                for u in list.use_trees() {
-                    let child_action = walk_use_tree_for_best_action(
-                        current_path_segments,
-                        Some(list.clone()),
-                        u,
-                        target,
-                    );
-                    if child_action.is_better(&better_action) {
-                        better_action = child_action;
-                        if let ImportAction::Nothing = better_action {
-                            return better_action;
-                        }
-                    }
-                }
-            } else {
-                // Case 1, split adding self
-                better_action = ImportAction::add_nested_import(prev_len + common, path, None, true)
-            }
-            better_action
-        }
-        common if common == left.len() && left.len() < right.len() => {
-            // e.g: target is std::fmt and we can have
-            // use std::fmt::Debug;
-            let segments_to_split = current_path_segments.split_at(prev_len + common).1;
-            ImportAction::add_nested_import(
-                prev_len + common,
-                path,
-                Some(segments_to_split[0].clone()),
-                true,
-            )
-        }
-        common if common < left.len() && common < right.len() => {
-            // e.g: target is std::fmt::nested::Debug
-            // use std::fmt::Display
-            let segments_to_split = current_path_segments.split_at(prev_len + common).1;
-            ImportAction::add_nested_import(
-                prev_len + common,
-                path,
-                Some(segments_to_split[0].clone()),
-                false,
-            )
-        }
-        _ => unreachable!(),
-    };
-
-    // If we are inside a UseTreeList adding a use statement become adding to the existing
-    // tree list.
-    action = match (current_parent_use_tree_list, action.clone()) {
-        (Some(use_tree_list), ImportAction::AddNewUse { .. }) => {
-            ImportAction::add_in_tree_list(prev_len, use_tree_list, false)
-        }
-        (_, _) => action,
-    };
-
-    // We remove the segments added
-    current_path_segments.truncate(prev_len);
-    action
-}
-
-fn best_action_for_target(
-    container: SyntaxNode,
-    anchor: SyntaxNode,
-    target: &[SmolStr],
-) -> ImportAction {
-    let mut storage = Vec::with_capacity(16); // this should be the only allocation
-    let best_action = container
-        .children()
-        .filter_map(ast::UseItem::cast)
-        .filter_map(|it| it.use_tree())
-        .map(|u| walk_use_tree_for_best_action(&mut storage, None, u, target))
-        .fold(None, |best, a| match best {
-            Some(best) => Some(ImportAction::better(best, a)),
-            None => Some(a),
-        });
-
-    match best_action {
-        Some(action) => action,
-        None => {
-            // We have no action and no UseItem was found in container so we find
-            // another item and we use it as anchor.
-            // If there are no items above, we choose the target path itself as anchor.
-            // todo: we should include even whitespace blocks as anchor candidates
-            let anchor = container
-                .children()
-                .find(|n| n.text_range().start() < anchor.text_range().start())
-                .or_else(|| Some(anchor));
-
-            let add_after_anchor = anchor
-                .clone()
-                .and_then(ast::Attr::cast)
-                .map(|attr| attr.kind() == ast::AttrKind::Inner)
-                .unwrap_or(false);
-            ImportAction::add_new_use(anchor, add_after_anchor)
-        }
-    }
-}
-
-fn make_assist(action: &ImportAction, target: &[SmolStr], edit: &mut TextEditBuilder) {
-    match action {
-        ImportAction::AddNewUse { anchor, add_after_anchor } => {
-            make_assist_add_new_use(anchor, *add_after_anchor, target, edit)
-        }
-        ImportAction::AddInTreeList { common_segments, tree_list, add_self } => {
-            // We know that the fist n segments already exists in the use statement we want
-            // to modify, so we want to add only the last target.len() - n segments.
-            let segments_to_add = target.split_at(*common_segments).1;
-            make_assist_add_in_tree_list(tree_list, segments_to_add, *add_self, edit)
-        }
-        ImportAction::AddNestedImport {
-            common_segments,
-            path_to_split,
-            first_segment_to_split,
-            add_self,
-        } => {
-            let segments_to_add = target.split_at(*common_segments).1;
-            make_assist_add_nested_import(
-                path_to_split,
-                first_segment_to_split,
-                segments_to_add,
-                *add_self,
-                edit,
-            )
-        }
-        _ => {}
-    }
-}
 
-fn make_assist_add_new_use(
-    anchor: &Option<SyntaxNode>,
-    after: bool,
-    target: &[SmolStr],
-    edit: &mut TextEditBuilder,
-) {
-    if let Some(anchor) = anchor {
-        let indent = ra_fmt::leading_indent(anchor);
-        let mut buf = String::new();
-        if after {
-            buf.push_str("\n");
-            if let Some(spaces) = &indent {
-                buf.push_str(spaces);
-            }
-        }
-        buf.push_str("use ");
-        fmt_segments_raw(target, &mut buf);
-        buf.push_str(";");
-        if !after {
-            buf.push_str("\n\n");
-            if let Some(spaces) = &indent {
-                buf.push_str(&spaces);
+            if let Some(last) = path.segment() {
+                // Here we are assuming the assist will provide a correct use statement
+                // so we can delete the path qualifier
+                edit.delete(TextRange::from_to(
+                    path.syntax().text_range().start(),
+                    last.syntax().text_range().start(),
+                ));
             }
-        }
-        let position = if after { anchor.text_range().end() } else { anchor.text_range().start() };
-        edit.insert(position, buf);
-    }
-}
-
-fn make_assist_add_in_tree_list(
-    tree_list: &ast::UseTreeList,
-    target: &[SmolStr],
-    add_self: bool,
-    edit: &mut TextEditBuilder,
-) {
-    let last = tree_list.use_trees().last();
-    if let Some(last) = last {
-        let mut buf = String::new();
-        let comma = last.syntax().siblings(Direction::Next).find(|n| n.kind() == T![,]);
-        let offset = if let Some(comma) = comma {
-            comma.text_range().end()
-        } else {
-            buf.push_str(",");
-            last.syntax().text_range().end()
-        };
-        if add_self {
-            buf.push_str(" self")
-        } else {
-            buf.push_str(" ");
-        }
-        fmt_segments_raw(target, &mut buf);
-        edit.insert(offset, buf);
-    } else {
-    }
-}
-
-fn make_assist_add_nested_import(
-    path: &ast::Path,
-    first_segment_to_split: &Option<ast::PathSegment>,
-    target: &[SmolStr],
-    add_self: bool,
-    edit: &mut TextEditBuilder,
-) {
-    let use_tree = path.syntax().ancestors().find_map(ast::UseTree::cast);
-    if let Some(use_tree) = use_tree {
-        let (start, add_colon_colon) = if let Some(first_segment_to_split) = first_segment_to_split
-        {
-            (first_segment_to_split.syntax().text_range().start(), false)
-        } else {
-            (use_tree.syntax().text_range().end(), true)
-        };
-        let end = use_tree.syntax().text_range().end();
-
-        let mut buf = String::new();
-        if add_colon_colon {
-            buf.push_str("::");
-        }
-        buf.push_str("{");
-        if add_self {
-            buf.push_str("self, ");
-        }
-        fmt_segments_raw(target, &mut buf);
-        if !target.is_empty() {
-            buf.push_str(", ");
-        }
-        edit.insert(start, buf);
-        edit.insert(end, "}".to_string());
-    }
-}
-
-fn replace_with_use(
-    container: &SyntaxNode,
-    path: &ast::Path,
-    target: &[SmolStr],
-    edit: &mut TextEditBuilder,
-) {
-    let action = best_action_for_target(container.clone(), path.syntax().clone(), target);
-    make_assist(&action, target, edit);
-    if let Some(last) = path.segment() {
-        // Here we are assuming the assist will provide a correct use statement
-        // so we can delete the path qualifier
-        edit.delete(TextRange::from_to(
-            path.syntax().text_range().start(),
-            last.syntax().text_range().start(),
-        ));
-    }
+        },
+    )
 }
 
 fn collect_hir_path_segments(path: &hir::Path) -> Option<Vec<SmolStr>> {