Correctly complete items with leading underscore

Author: fmease

crates/ide/src/completion/complete_unqualified_path.rs

@@ -267,6 +267,26 @@ fn quux() { <|> }
         );
     }
 
+    /// Regression test for issue #6091.
+    #[test]
+    fn correctly_completes_module_items_prefixed_with_underscore() {
+        check_edit(
+            "_alpha",
+            r#"
+fn main() {
+    _<|>
+}
+fn _alpha() {}
+"#,
+            r#"
+fn main() {
+    _alpha()$0
+}
+fn _alpha() {}
+"#,
+        )
+    }
+
     #[test]
     fn completes_extern_prelude() {
         check(

crates/ide/src/completion/completion_context.rs

@@ -221,10 +221,11 @@ impl<'a> CompletionContext<'a> {
         Some(ctx)
     }
 
-    // The range of the identifier that is being completed.
+    /// The range of the identifier that is being completed.
     pub(crate) fn source_range(&self) -> TextRange {
         // check kind of macro-expanded token, but use range of original token
-        if self.token.kind() == IDENT || self.token.kind().is_keyword() {
+        let kind = self.token.kind();
+        if kind == IDENT || kind == UNDERSCORE || kind.is_keyword() {
             mark::hit!(completes_if_prefix_is_keyword);
             self.original_token.text_range()
         } else {