Make change_visibility assist work for tuple struct field visibility

Author: Jesse Bakker

crates/ra_assists/src/handlers/change_visibility.rs

@@ -47,8 +47,7 @@ fn add_vis(ctx: AssistCtx) -> Option<Assist> {
             return None;
         }
         (vis_offset(&parent), keyword.text_range())
-    } else {
-        let field_name: ast::Name = ctx.find_node_at_offset()?;
+    } else if let Some(field_name) = ctx.find_node_at_offset::<ast::Name>() {
         let field = field_name.syntax().ancestors().find_map(ast::RecordFieldDef::cast)?;
         if field.name()? != field_name {
             tested_by!(change_visibility_field_false_positive);
@@ -58,6 +57,13 @@ fn add_vis(ctx: AssistCtx) -> Option<Assist> {
             return None;
         }
         (vis_offset(field.syntax()), field_name.syntax().text_range())
+    } else if let Some(field) = ctx.find_node_at_offset::<ast::TupleFieldDef>() {
+        if field.visibility().is_some() {
+            return None;
+        }
+        (vis_offset(field.syntax()), field.syntax().text_range())
+    } else {
+        return None;
     };
 
     ctx.add_assist(AssistId("change_visibility"), "Change visibility to pub(crate)", |edit| {
@@ -129,7 +135,8 @@ mod tests {
             change_visibility,
             r"struct S { <|>field: u32 }",
             r"struct S { <|>pub(crate) field: u32 }",
-        )
+        );
+        check_assist(change_visibility, r"struct S ( <|>u32 )", r"struct S ( <|>pub(crate) u32 )");
     }
 
     #[test]