Not linting irrefutable_let_patterns on let chains

Author: Natural-selection1

compiler/rustc_mir_build/src/thir/pattern/check_match.rs

@@ -569,6 +569,11 @@ impl<'p, 'tcx> MatchVisitor<'p, 'tcx> {
     ) {
         assert!(self.let_source != LetSource::None);
 
+        // for let chains, don't emit IRREFUTABLE_LET_PATTERNS
+        if chain_refutabilities.len() > 1 {
+            return;
+        }
+
         if chain_refutabilities.iter().all(|r| matches!(*r, Some((_, Irrefutable)))) {
             // The entire chain is made up of irrefutable `let` statements
             report_irrefutable_let_patterns(

tests/ui/binding/irrefutable-in-let-chains.rs

@@ -0,0 +1,34 @@
+//@ run-pass
+//@ edition:2024
+
+#![allow(unused)]
+
+enum Outer {
+    Middle(Middle),
+}
+enum Middle {
+    Inner(Inner),
+    Other(bool),
+}
+struct Inner {
+    id: u32,
+}
+
+fn test_1(outer: Outer) {
+    if let Outer::Middle(middle) = outer
+        && let Middle::Inner(internal) = middle
+        && let Inner { id } = internal
+    {
+        println!("{id}");
+    }
+}
+
+fn test_2() -> usize { 42 }
+
+fn main() {
+    if let mx = test_2() && mx < usize::MAX {
+        println!("{mx}");
+    } else if let x = test_2() && x > 0 {
+        println!("{x}");
+    }
+}