5 files changed, 119 insertions, 0 deletions

diff --git a/crates/completion/Cargo.toml b/crates/completion/Cargo.toml
index 3015ec9e0..799b4a3d5 100644
--- a/crates/completion/Cargo.toml
+++ b/crates/completion/Cargo.toml
@@ -13,6 +13,7 @@ doctest = false
 itertools = "0.9.0"
 log = "0.4.8"
 rustc-hash = "1.1.0"
+either = "1.6.1"
 
 assists = { path = "../assists", version = "0.0.0" }
 stdx = { path = "../stdx", version = "0.0.0" }
@@ -21,6 +22,7 @@ text_edit = { path = "../text_edit", version = "0.0.0" }
 base_db = { path = "../base_db", version = "0.0.0" }
 ide_db = { path = "../ide_db", version = "0.0.0" }
 profile = { path = "../profile", version = "0.0.0" }
+assists = { path = "../assists", version = "0.0.0" }
 test_utils = { path = "../test_utils", version = "0.0.0" }
 
 # completions crate should depend only on the top-level `hir` package. if you need
diff --git a/crates/completion/src/completions.rs b/crates/completion/src/completions.rs
index 75dbb1a23..99db5f998 100644
--- a/crates/completion/src/completions.rs
+++ b/crates/completion/src/completions.rs
@@ -13,6 +13,7 @@ pub(crate) mod postfix;
 pub(crate) mod macro_in_item_position;
 pub(crate) mod trait_impl;
 pub(crate) mod mod_;
+pub(crate) mod complete_magic;
 
 use hir::{ModPath, ScopeDef, Type};
 
diff --git a/crates/completion/src/completions/complete_magic.rs b/crates/completion/src/completions/complete_magic.rs
new file mode 100644
index 000000000..857a0b620
--- /dev/null
+++ b/crates/completion/src/completions/complete_magic.rs
@@ -0,0 +1,114 @@
+//! TODO kb move this into the complete_unqualified_path when starts to work properly
+
+use assists::utils::{insert_use, mod_path_to_ast, ImportScope, MergeBehaviour};
+use hir::Query;
+use itertools::Itertools;
+use syntax::AstNode;
+use text_edit::TextEdit;
+
+use crate::{context::CompletionContext, item::CompletionKind, CompletionItem, CompletionItemKind};
+
+use super::Completions;
+
+pub(crate) fn complete_magic(acc: &mut Completions, ctx: &CompletionContext) -> Option<()> {
+    if !(ctx.is_trivial_path || ctx.is_pat_binding_or_const) {
+        return None;
+    }
+    let current_module = ctx.scope.module()?;
+    let anchor = ctx.name_ref_syntax.as_ref()?;
+    let import_scope = ImportScope::find_insert_use_container(anchor.syntax(), &ctx.sema)?;
+    // TODO kb now this is the whole file, which is not disjoint with any other change in the same file, fix it
+    // otherwise it's impossible to correctly add the use statement and also change the completed text into something more meaningful
+    let import_syntax = import_scope.as_syntax_node();
+
+    // TODO kb consider heuristics, such as "don't show `hash_map` import if `HashMap` is the import for completion"
+    // TODO kb module functions are not completed, consider `std::io::stdin` one
+    let potential_import_name = ctx.token.to_string();
+
+    let possible_imports = ctx
+        .krate?
+        // TODO kb use imports_locator instead?
+        .query_external_importables(ctx.db, Query::new(&potential_import_name).limit(40))
+        .unique()
+        .filter_map(|import_candidate| match import_candidate {
+            either::Either::Left(module_def) => current_module.find_use_path(ctx.db, module_def),
+            either::Either::Right(macro_def) => current_module.find_use_path(ctx.db, macro_def),
+        })
+        .filter_map(|mod_path| {
+            let correct_qualifier = mod_path.segments.last()?.to_string();
+            let rewriter =
+                insert_use(&import_scope, mod_path_to_ast(&mod_path), Some(MergeBehaviour::Full));
+            let rewritten_node = rewriter.rewrite(import_syntax);
+            let insert_use_edit =
+                TextEdit::replace(import_syntax.text_range(), rewritten_node.to_string());
+            let mut completion_edit =
+                TextEdit::replace(anchor.syntax().text_range(), correct_qualifier);
+            completion_edit.union(insert_use_edit).expect("TODO kb");
+
+            let completion_item: CompletionItem = CompletionItem::new(
+                CompletionKind::Magic,
+                ctx.source_range(),
+                mod_path.to_string(),
+            )
+            .kind(CompletionItemKind::Struct)
+            .text_edit(completion_edit)
+            .into();
+            Some(completion_item)
+        });
+    acc.add_all(possible_imports);
+
+    Some(())
+}
+
+#[cfg(test)]
+mod tests {
+    use expect_test::{expect, Expect};
+
+    use crate::{
+        item::CompletionKind,
+        test_utils::{check_edit, completion_list},
+    };
+
+    fn check(ra_fixture: &str, expect: Expect) {
+        let actual = completion_list(ra_fixture, CompletionKind::Magic);
+        expect.assert_eq(&actual)
+    }
+
+    #[test]
+    fn case_insensitive_magic_completion_works() {
+        check(
+            r#"
+//- /lib.rs crate:dep
+pub struct TestStruct;
+
+//- /main.rs crate:main deps:dep
+fn main() {
+    teru<|>
+}
+"#,
+            expect![[r#"
+                st dep::TestStruct
+            "#]],
+        );
+
+        check_edit(
+            "dep::TestStruct",
+            r#"
+//- /lib.rs crate:dep
+pub struct TestStruct;
+
+//- /main.rs crate:main deps:dep
+fn main() {
+    teru<|>
+}
+"#,
+            r#"
+use dep::TestStruct;
+
+fn main() {
+    TestStruct
+}
+"#,
+        );
+    }
+}
diff --git a/crates/completion/src/item.rs b/crates/completion/src/item.rs
index 6d1d085f4..f23913935 100644
--- a/crates/completion/src/item.rs
+++ b/crates/completion/src/item.rs
@@ -31,6 +31,7 @@ pub struct CompletionItem {
     ///
     /// Typically, replaces `source_range` with new identifier.
     text_edit: TextEdit,
+
     insert_text_format: InsertTextFormat,
 
     /// What item (struct, function, etc) are we completing.
diff --git a/crates/completion/src/lib.rs b/crates/completion/src/lib.rs
index cb6e0554e..e920fa6b5 100644
--- a/crates/completion/src/lib.rs
+++ b/crates/completion/src/lib.rs
@@ -118,6 +118,7 @@ pub fn completions(
     completions::macro_in_item_position::complete_macro_in_item_position(&mut acc, &ctx);
     completions::trait_impl::complete_trait_impl(&mut acc, &ctx);
     completions::mod_::complete_mod(&mut acc, &ctx);
+    completions::complete_magic::complete_magic(&mut acc, &ctx);
 
     Some(acc)
 }