From e3a4baed0166f60ffea835532bc934050250b164 Mon Sep 17 00:00:00 2001
From: Asuna <SpriteOvO@gmail.com>
Date: Thu, 19 Feb 2026 02:02:40 +0000
Subject: [PATCH] Support if-let-guard in `matches!` and `assert_matches!`

---
 library/core/src/macros/mod.rs    | 31 +++++++++++++++++++++++++++++++
 library/coretests/tests/macros.rs | 10 ++++++++++
 2 files changed, 41 insertions(+)

diff --git a/library/core/src/macros/mod.rs b/library/core/src/macros/mod.rs
index d900b4a21b36d..00b5ac6978b5d 100644
--- a/library/core/src/macros/mod.rs
+++ b/library/core/src/macros/mod.rs
@@ -192,6 +192,30 @@ pub macro assert_matches {
             }
         }
     },
+    ($left:expr, $(|)? $( $pattern:pat_param )|+ $( if let $($let_guards: tt)+ )? $(,)?) => {
+        match $left {
+            $( $pattern )|+ $( if let $($let_guards)+ )? => {}
+            ref left_val => {
+                $crate::panicking::assert_matches_failed(
+                    left_val,
+                    $crate::stringify!($($pattern)|+ $(if let $($let_guards)+)?),
+                    $crate::option::Option::None
+                );
+            }
+        }
+    },
+    ($left:expr, $(|)? $( $pattern:pat_param )|+ $( if let $($let_guards: tt)+ )?, $($arg:tt)+) => {
+        match $left {
+            $( $pattern )|+ $( if let $($let_guards)+ )? => {}
+            ref left_val => {
+                $crate::panicking::assert_matches_failed(
+                    left_val,
+                    $crate::stringify!($($pattern)|+ $(if let $($let_guards)+)?),
+                    $crate::option::Option::Some($crate::format_args!($($arg)+))
+                );
+            }
+        }
+    },
 }
 
 /// Selects code at compile-time based on `cfg` predicates.
@@ -435,6 +459,13 @@ macro_rules! matches {
             _ => false
         }
     };
+    ($expression:expr, $pattern:pat $(if let $($let_guards:tt)+)? $(,)?) => {
+        #[allow(non_exhaustive_omitted_patterns)]
+        match $expression {
+            $pattern $(if let $($let_guards)+)? => true,
+            _ => false
+        }
+    };
 }
 
 /// Unwraps a result or propagates its error.
diff --git a/library/coretests/tests/macros.rs b/library/coretests/tests/macros.rs
index 50b5eb63e43a7..7fd3fc367ceda 100644
--- a/library/coretests/tests/macros.rs
+++ b/library/coretests/tests/macros.rs
@@ -44,6 +44,16 @@ fn matches_leading_pipe() {
     matches!(1, | 1 | 2 | 3);
 }
 
+#[test]
+fn matches_if_let_guard() {
+    use std::assert_matches;
+
+    assert!(
+        matches!(Some(Some(2_i32)), Some(inner) if let Some(value) = inner && value.pow(2) == 4)
+    );
+    assert_matches!(Some(Some(2_i32)), Some(inner) if let Some(value) = inner && value.pow(2) == 4);
+}
+
 #[test]
 fn cfg_select_basic() {
     cfg_select! {