From 0113bd28a4709cbbe35589fb8e278b1502aa229f Mon Sep 17 00:00:00 2001
From: Nat Mote <nat@natmote.net>
Date: Wed, 10 Aug 2022 07:25:46 -0700
Subject: [PATCH 1/2] Test for unused extra alias

Tests the issue described in #1834
---
 .../test_grammars/aliased_rules/corpus.txt     |  3 ++-
 .../test_grammars/aliased_rules/grammar.js     | 18 +++++++++++++++---
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/test/fixtures/test_grammars/aliased_rules/corpus.txt b/test/fixtures/test_grammars/aliased_rules/corpus.txt
index 8789179d..f843dec8 100644
--- a/test/fixtures/test_grammars/aliased_rules/corpus.txt
+++ b/test/fixtures/test_grammars/aliased_rules/corpus.txt
@@ -2,11 +2,12 @@
 Method calls
 ======================================
 
-a.b(c(d.e));
+*a.b(c(d.e));
 
 ---
 
 (statement
+  (star_aliased)
   (call_expression
     (member_expression
       (variable_name)
diff --git a/test/fixtures/test_grammars/aliased_rules/grammar.js b/test/fixtures/test_grammars/aliased_rules/grammar.js
index c3cb15cb..a615a90d 100644
--- a/test/fixtures/test_grammars/aliased_rules/grammar.js
+++ b/test/fixtures/test_grammars/aliased_rules/grammar.js
@@ -1,7 +1,10 @@
 module.exports = grammar({
     name: 'aliased_rules',
 
-    extras: $ => [/\s/],
+    extras: $ => [
+      /\s/,
+      $.star,
+    ],
 
     rules: {
         statement: $ => seq($._expression, ';'),
@@ -25,6 +28,15 @@ module.exports = grammar({
             alias($.identifier, $.property_name)
         )),
 
-        identifier: $ => /[a-z]+/
+        identifier: $ => /[a-z]+/,
+
+        // Tests for https://github.com/tree-sitter/tree-sitter/issues/1834
+        //
+        // Even though the alias is unused, that issue causes all instances of
+        // the extra that appear in the tree to be renamed to `star_aliased`.
+        //
+        // Instead, this alias should have no effect because it is unused.
+        star: $ => '*',
+        unused: $ => alias($.star, $.star_aliased),
     }
-});
\ No newline at end of file
+});

From 4e3179fbc0fbe65f83780bf4a93f1106545a6df2 Mon Sep 17 00:00:00 2001
From: Nat Mote <nat@natmote.net>
Date: Tue, 9 Aug 2022 17:18:56 -0700
Subject: [PATCH 2/2] Avoid extracting default alias for extras

Fixes #1834
---
 .../prepare_grammar/extract_default_aliases.rs       | 12 ++++++++++++
 test/fixtures/test_grammars/aliased_rules/corpus.txt |  2 +-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/cli/src/generate/prepare_grammar/extract_default_aliases.rs b/cli/src/generate/prepare_grammar/extract_default_aliases.rs
index 13edb090..d39bf8dd 100644
--- a/cli/src/generate/prepare_grammar/extract_default_aliases.rs
+++ b/cli/src/generate/prepare_grammar/extract_default_aliases.rs
@@ -62,6 +62,18 @@ pub(super) fn extract_default_aliases(
         }
     }
 
+    for symbol in syntax_grammar.extra_symbols.iter() {
+        let mut status = match symbol.kind {
+            SymbolType::External => &mut external_status_list[symbol.index],
+            SymbolType::NonTerminal => &mut non_terminal_status_list[symbol.index],
+            SymbolType::Terminal => &mut terminal_status_list[symbol.index],
+            SymbolType::End | SymbolType::EndOfNonTerminalExtra => {
+                panic!("Unexpected end token")
+            }
+        };
+        status.appears_unaliased = true;
+    }
+
     let symbols_with_statuses = (terminal_status_list
         .iter_mut()
         .enumerate()
diff --git a/test/fixtures/test_grammars/aliased_rules/corpus.txt b/test/fixtures/test_grammars/aliased_rules/corpus.txt
index f843dec8..32093729 100644
--- a/test/fixtures/test_grammars/aliased_rules/corpus.txt
+++ b/test/fixtures/test_grammars/aliased_rules/corpus.txt
@@ -7,7 +7,7 @@ Method calls
 ---
 
 (statement
-  (star_aliased)
+  (star)
   (call_expression
     (member_expression
       (variable_name)