1 files changed, 79 insertions, 0 deletions

diff --git a/crates/assists/src/handlers/split_import.rs b/crates/assists/src/handlers/split_import.rs
new file mode 100644
index 000000000..15e67eaa1
--- /dev/null
+++ b/crates/assists/src/handlers/split_import.rs
@@ -0,0 +1,79 @@
+use std::iter::successors;
+
+use syntax::{ast, AstNode, T};
+
+use crate::{AssistContext, AssistId, AssistKind, Assists};
+
+// Assist: split_import
+//
+// Wraps the tail of import into braces.
+//
+// ```
+// use std::<|>collections::HashMap;
+// ```
+// ->
+// ```
+// use std::{collections::HashMap};
+// ```
+pub(crate) fn split_import(acc: &mut Assists, ctx: &AssistContext) -> Option<()> {
+    let colon_colon = ctx.find_token_at_offset(T![::])?;
+    let path = ast::Path::cast(colon_colon.parent())?.qualifier()?;
+    let top_path = successors(Some(path.clone()), |it| it.parent_path()).last()?;
+
+    let use_tree = top_path.syntax().ancestors().find_map(ast::UseTree::cast)?;
+
+    let new_tree = use_tree.split_prefix(&path);
+    if new_tree == use_tree {
+        return None;
+    }
+
+    let target = colon_colon.text_range();
+    acc.add(AssistId("split_import", AssistKind::RefactorRewrite), "Split import", target, |edit| {
+        edit.replace_ast(use_tree, new_tree);
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{check_assist, check_assist_not_applicable, check_assist_target};
+
+    use super::*;
+
+    #[test]
+    fn test_split_import() {
+        check_assist(
+            split_import,
+            "use crate::<|>db::RootDatabase;",
+            "use crate::{db::RootDatabase};",
+        )
+    }
+
+    #[test]
+    fn split_import_works_with_trees() {
+        check_assist(
+            split_import,
+            "use crate:<|>:db::{RootDatabase, FileSymbol}",
+            "use crate::{db::{RootDatabase, FileSymbol}}",
+        )
+    }
+
+    #[test]
+    fn split_import_target() {
+        check_assist_target(split_import, "use crate::<|>db::{RootDatabase, FileSymbol}", "::");
+    }
+
+    #[test]
+    fn issue4044() {
+        check_assist_not_applicable(split_import, "use crate::<|>:::self;")
+    }
+
+    #[test]
+    fn test_empty_use() {
+        check_assist_not_applicable(
+            split_import,
+            r"
+use std::<|>
+fn main() {}",
+        );
+    }
+}