From 93c6e6dd5ef26ca047ef2e3d4cea3f51d5ea4f89 Mon Sep 17 00:00:00 2001
From: Cam McHenry <camchenry@users.noreply.github.com>
Date: Wed, 28 Oct 2026 22:28:48 -0400
Subject: [PATCH] perf(linter/unicorn/no-useless-fallback-in-spread): narrow
 AST dispatch (#28361)
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Start from spread elements and retain the existing object-spread and
parentheses checks. Reduce fixture callbacks from 12,119 to 454.


---

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Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 .../src/generated/rule_runner_impls.rs        |  2 +-
 .../unicorn/no_useless_fallback_in_spread.rs  | 19 ++++++++++---------
 .../track_linter_timings/linter_timings.snap  |  2 +-
 3 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/crates/oxc_linter/src/generated/rule_runner_impls.rs b/crates/oxc_linter/src/generated/rule_runner_impls.rs
index 12437243b0..1fc38f6df0 100644
--- a/crates/oxc_linter/src/generated/rule_runner_impls.rs
+++ b/crates/oxc_linter/src/generated/rule_runner_impls.rs
@@ -3561,7 +3561,7 @@ impl RuleRunner
     for crate::rules::unicorn::no_useless_fallback_in_spread::NoUselessFallbackInSpread
 {
     const NODE_TYPES: Option<&AstTypesBitset> =
-        Some(&AstTypesBitset::from_types(&[AstType::LogicalExpression]));
+        Some(&AstTypesBitset::from_types(&[AstType::SpreadElement]));
     const RUN_FUNCTIONS: RuleRunFunctionsImplemented = RuleRunFunctionsImplemented::Run;
 }
 
diff --git a/crates/oxc_linter/src/rules/unicorn/no_useless_fallback_in_spread.rs b/crates/oxc_linter/src/rules/unicorn/no_useless_fallback_in_spread.rs
index a5b598b9bf..d498a4219e 100644
--- a/crates/oxc_linter/src/rules/unicorn/no_useless_fallback_in_spread.rs
+++ b/crates/oxc_linter/src/rules/unicorn/no_useless_fallback_in_spread.rs
@@ -47,7 +47,12 @@ declare_oxc_lint!(
 
 impl Rule for NoUselessFallbackInSpread {
     fn run<'a>(&self, node: &AstNode<'a>, ctx: &LintContext<'a>) {
-        let AstKind::LogicalExpression(logical_expression) = node.kind() else {
+        let AstKind::SpreadElement(spread_element) = node.kind() else {
+            return;
+        };
+        let Expression::LogicalExpression(logical_expression) =
+            spread_element.argument.without_parentheses()
+        else {
             return;
         };
 
@@ -69,14 +74,6 @@ impl Rule for NoUselessFallbackInSpread {
             return;
         };
 
-        let AstKind::SpreadElement(spread_element) = parent.kind() else {
-            return;
-        };
-
-        let Some(parent) = outermost_paren_parent(parent, ctx) else {
-            return;
-        };
-
         if !matches!(parent.kind(), AstKind::ObjectExpression(_)) {
             return;
         }
@@ -130,6 +127,8 @@ fn test() {
         "const object = call({}, ...(foo || {}))",
         r#"const object = {...(foo || {not: "empty"})}"#,
         "const object = {...(foo || {...{}})}",
+        "const object = {...((foo || {}) as object)}",
+        "const object = {...(foo || ({} as object))}",
     ];
 
     let fail = vec![
@@ -162,6 +161,8 @@ fn test() {
     ];
 
     let fix = vec![
+        ("const object = {...((foo || {}))}", "const object = {...foo}"),
+        ("const object = {...(foo || {}), ...(bar ?? {})}", "const object = {...foo, ...bar}"),
         (r"const object = {...(foo || {})}", r"const object = {...foo}"),
         (r"const object = {...(foo?.bar || {})}", r"const object = {...foo?.bar}"),
         (r"const object = {...(foo() || {})}", r"const object = {...foo()}"),
diff --git a/tasks/track_linter_timings/linter_timings.snap b/tasks/track_linter_timings/linter_timings.snap
index cde02ba698..8bf06f84c7 100644
--- a/tasks/track_linter_timings/linter_timings.snap
+++ b/tasks/track_linter_timings/linter_timings.snap
@@ -574,7 +574,7 @@ unicorn/no-unreadable-array-destructuring               |    276
 unicorn/no-unreadable-iife                              |  62606
 unicorn/no-useless-collection-argument                  |   1421
 unicorn/no-useless-error-capture-stack-trace            |  62606
-unicorn/no-useless-fallback-in-spread                   |  12119
+unicorn/no-useless-fallback-in-spread                   |    454
 unicorn/no-useless-iterator-to-array                    |  65257
 unicorn/no-useless-length-check                         |  12119
 unicorn/no-useless-promise-resolve-reject               |  62606