Handle TypeInstantiation suffix in is_expression_simple

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Luau: Fixed panic when formatting explicit type instantiation (`f<<T>>()`) inside a nested function call argument (e.g. as a callback) ([#1088](https://github.com/JohnnyMorganz/StyLua/issues/1088))
+
 ## [2.4.0] - 2026-03-07
 
 ### Added

src/formatters/trivia_util.rs

@@ -156,6 +156,8 @@ fn is_expression_simple(expression: &Expression) -> bool {
                     },
                     other => unreachable!("unknown node: {:?}", other),
                 },
+                #[cfg(feature = "luau")]
+                Suffix::TypeInstantiation(_) => true,
                 other => unreachable!("unknown node: {:?}", other),
             })
         }

tests/inputs-luau/type-instantiation-in-callback.lua

@@ -0,0 +1,4 @@
+-- Test for issue #1088: turbofish/TypeInstantiation inside nested function call
+Charm.computed(function()
+    return createPluginSettingsStore<<AuthStore>>("PresenceAuthStore", defaultValue, validate)
+end)

tests/snapshots/tests__luau@type-instantiation-in-callback.lua.snap

@@ -0,0 +1,11 @@
+---
+source: tests/tests.rs
+assertion_line: 36
+expression: "format(&contents, LuaVersion::Luau)"
+input_file: tests/inputs-luau/type-instantiation-in-callback.lua
+---
+-- Test for issue #1088: turbofish/TypeInstantiation inside nested function call
+Charm.computed(function()
+	return createPluginSettingsStore<<AuthStore>>("PresenceAuthStore", defaultValue, validate)
+end)
+