3 files changed, 37 insertions, 6 deletions

diff --git a/crates/ra_assists/src/assists/introduce_variable.rs b/crates/ra_assists/src/assists/introduce_variable.rs
index 43378c4b0..8245dc99f 100644
--- a/crates/ra_assists/src/assists/introduce_variable.rs
+++ b/crates/ra_assists/src/assists/introduce_variable.rs
@@ -1,5 +1,3 @@
-//! FIXME: write short doc here
-
 use format_buf::format;
 use hir::db::HirDatabase;
 use ra_syntax::{
@@ -14,6 +12,22 @@ use test_utils::tested_by;
 
 use crate::{Assist, AssistCtx, AssistId};
 
+// Assist: introduce_variable
+//
+// Extracts subexpression into a variable.
+//
+// ```
+// fn main() {
+//     <|>(1 + 2)<|> * 4;
+// }
+// ```
+// ->
+// ```
+// fn main() {
+//     let var_name = (1 + 2);
+//     var_name * 4;
+// }
+// ```
 pub(crate) fn introduce_variable(mut ctx: AssistCtx<impl HirDatabase>) -> Option<Assist> {
     if ctx.frange.range.is_empty() {
         return None;
diff --git a/crates/ra_assists/src/doc_tests.rs b/crates/ra_assists/src/doc_tests.rs
index 872bbdf17..0ccf9d730 100644
--- a/crates/ra_assists/src/doc_tests.rs
+++ b/crates/ra_assists/src/doc_tests.rs
@@ -7,13 +7,12 @@ mod generated;
 
 use hir::mock::MockDatabase;
 use ra_db::FileRange;
-use ra_syntax::TextRange;
-use test_utils::{assert_eq_text, extract_offset};
+use test_utils::{assert_eq_text, extract_range_or_offset};
 
 fn check(assist_id: &str, before: &str, after: &str) {
-    let (before_cursor_pos, before) = extract_offset(before);
+    let (selection, before) = extract_range_or_offset(before);
     let (db, _source_root, file_id) = MockDatabase::with_single_file(&before);
-    let frange = FileRange { file_id, range: TextRange::offset_len(before_cursor_pos, 0.into()) };
+    let frange = FileRange { file_id, range: selection.into() };
 
     let (_assist_id, action) = crate::assists(&db, frange)
         .into_iter()
diff --git a/crates/ra_assists/src/doc_tests/generated.rs b/crates/ra_assists/src/doc_tests/generated.rs
index d390db33c..493bd94d0 100644
--- a/crates/ra_assists/src/doc_tests/generated.rs
+++ b/crates/ra_assists/src/doc_tests/generated.rs
@@ -255,3 +255,21 @@ fn main() {
 "#####,
     )
 }
+
+#[test]
+fn doctest_introduce_variable() {
+    check(
+        "introduce_variable",
+        r#####"
+fn main() {
+    <|>(1 + 2)<|> * 4;
+}
+"#####,
+        r#####"
+fn main() {
+    let var_name = (1 + 2);
+    var_name * 4;
+}
+"#####,
+    )
+}