From db6db2aacc083381c6b268c12c42bde92816ab4c Mon Sep 17 00:00:00 2001
From: Chayim Refael Friedman <chayimfr@gmail.com>
Date: Mon, 21 Apr 2025 03:43:15 +0300
Subject: [PATCH] Allow wrapping `builtin#offset_of` fields argument in
 parentheses

This is necessary to correctly handle nested fields (`foo.bar`), see the comments in the code for explanation.
---
 crates/parser/src/grammar/expressions/atom.rs | 12 ++++++
 crates/parser/test_data/generated/runner.rs   |  4 ++
 .../parser/inline/ok/offset_of_parens.rast    | 42 +++++++++++++++++++
 .../parser/inline/ok/offset_of_parens.rs      |  3 ++
 4 files changed, 61 insertions(+)
 create mode 100644 crates/parser/test_data/parser/inline/ok/offset_of_parens.rast
 create mode 100644 crates/parser/test_data/parser/inline/ok/offset_of_parens.rs

diff --git a/crates/parser/src/grammar/expressions/atom.rs b/crates/parser/src/grammar/expressions/atom.rs
index 407320e1d0..c66afed91c 100644
--- a/crates/parser/src/grammar/expressions/atom.rs
+++ b/crates/parser/src/grammar/expressions/atom.rs
@@ -258,6 +258,15 @@ fn builtin_expr(p: &mut Parser<'_>) -> Option<CompletedMarker> {
         p.expect(T!['(']);
         type_(p);
         p.expect(T![,]);
+        // Due to our incomplete handling of macro groups, especially
+        // those with empty delimiters, we wrap `expr` fragments in
+        // parentheses sometimes. Since `offset_of` is a macro, and takes
+        // `expr`, the field names could be wrapped in parentheses.
+        let wrapped_in_parens = p.eat(T!['(']);
+        // test offset_of_parens
+        // fn foo() {
+        //     builtin#offset_of(Foo, (bar.baz.0));
+        // }
         while !p.at(EOF) && !p.at(T![')']) {
             name_ref_mod_path_or_index(p);
             if !p.at(T![')']) {
@@ -265,6 +274,9 @@ fn builtin_expr(p: &mut Parser<'_>) -> Option<CompletedMarker> {
             }
         }
         p.expect(T![')']);
+        if wrapped_in_parens {
+            p.expect(T![')']);
+        }
         Some(m.complete(p, OFFSET_OF_EXPR))
     } else if p.at_contextual_kw(T![format_args]) {
         p.bump_remap(T![format_args]);
diff --git a/crates/parser/test_data/generated/runner.rs b/crates/parser/test_data/generated/runner.rs
index 2ea29345ed..a8fe61e7af 100644
--- a/crates/parser/test_data/generated/runner.rs
+++ b/crates/parser/test_data/generated/runner.rs
@@ -416,6 +416,10 @@ mod ok {
         run_and_expect_no_errors("test_data/parser/inline/ok/nocontentexpr_after_item.rs");
     }
     #[test]
+    fn offset_of_parens() {
+        run_and_expect_no_errors("test_data/parser/inline/ok/offset_of_parens.rs");
+    }
+    #[test]
     fn or_pattern() { run_and_expect_no_errors("test_data/parser/inline/ok/or_pattern.rs"); }
     #[test]
     fn param_list() { run_and_expect_no_errors("test_data/parser/inline/ok/param_list.rs"); }
diff --git a/crates/parser/test_data/parser/inline/ok/offset_of_parens.rast b/crates/parser/test_data/parser/inline/ok/offset_of_parens.rast
new file mode 100644
index 0000000000..4e23455cfc
--- /dev/null
+++ b/crates/parser/test_data/parser/inline/ok/offset_of_parens.rast
@@ -0,0 +1,42 @@
+SOURCE_FILE
+  FN
+    FN_KW "fn"
+    WHITESPACE " "
+    NAME
+      IDENT "foo"
+    PARAM_LIST
+      L_PAREN "("
+      R_PAREN ")"
+    WHITESPACE " "
+    BLOCK_EXPR
+      STMT_LIST
+        L_CURLY "{"
+        WHITESPACE "\n    "
+        EXPR_STMT
+          OFFSET_OF_EXPR
+            BUILTIN_KW "builtin"
+            POUND "#"
+            OFFSET_OF_KW "offset_of"
+            L_PAREN "("
+            PATH_TYPE
+              PATH
+                PATH_SEGMENT
+                  NAME_REF
+                    IDENT "Foo"
+            COMMA ","
+            WHITESPACE " "
+            L_PAREN "("
+            NAME_REF
+              IDENT "bar"
+            DOT "."
+            NAME_REF
+              IDENT "baz"
+            DOT "."
+            NAME_REF
+              INT_NUMBER "0"
+            R_PAREN ")"
+            R_PAREN ")"
+          SEMICOLON ";"
+        WHITESPACE "\n"
+        R_CURLY "}"
+  WHITESPACE "\n"
diff --git a/crates/parser/test_data/parser/inline/ok/offset_of_parens.rs b/crates/parser/test_data/parser/inline/ok/offset_of_parens.rs
new file mode 100644
index 0000000000..a797d5c820
--- /dev/null
+++ b/crates/parser/test_data/parser/inline/ok/offset_of_parens.rs
@@ -0,0 +1,3 @@
+fn foo() {
+    builtin#offset_of(Foo, (bar.baz.0));
+}