Rollup merge of #93086 - c410-f3r:let-guard, r=Mark-Simulacrum

Add tests to ensure that `let_chains` works with `if_let_guard`

The current machinery already makes such combination possible but lacks tests.

cc `@matthewjasper`

src/test/ui/rfc-2497-if-let-chains/irrefutable-lets.rs

@@ -1,6 +1,6 @@
 // check-pass
 
-#![feature(let_chains)]
+#![feature(if_let_guard, let_chains)]
 
 use std::ops::Range;
 
@@ -16,6 +16,16 @@ fn main() {
         && let None = local_start {
     }
 
+    match opt {
+        Some(ref first) if let second = first && let _third = second => {},
+        _ => {}
+    }
+    match opt {
+        Some(ref first) if let Range { start: local_start, end: _ } = first
+            && let None = local_start => {},
+        _ => {}
+    }
+
     while let first = &opt && let Some(ref second) = first && let None = second.start {
     }
     while let Some(ref first) = opt && let second = first && let _third = second {

src/test/ui/rfc-2497-if-let-chains/then-else-blocks.rs

@@ -1,6 +1,6 @@
 // run-pass
 
-#![feature(let_chains)]
+#![feature(if_let_guard, let_chains)]
 
 fn check_if_let(opt: Option<Option<Option<i32>>>, value: i32) -> bool {
     if let Some(first) = opt
@@ -15,6 +15,17 @@ fn check_if_let(opt: Option<Option<Option<i32>>>, value: i32) -> bool {
     }
 }
 
+fn check_let_guard(opt: Option<Option<Option<i32>>>, value: i32) -> bool {
+    match opt {
+        Some(first) if let Some(second) = first && let Some(third) = second && third == value => {
+            true
+        }
+        _ => {
+            false
+        }
+    }
+}
+
 fn check_while_let(opt: Option<Option<Option<i32>>>, value: i32) -> bool {
     while let Some(first) = opt
         && let Some(second) = first
@@ -30,6 +41,9 @@ fn main() {
     assert_eq!(check_if_let(Some(Some(Some(1))), 1), true);
     assert_eq!(check_if_let(Some(Some(Some(1))), 9), false);
 
+    assert_eq!(check_let_guard(Some(Some(Some(1))), 1), true);
+    assert_eq!(check_let_guard(Some(Some(Some(1))), 9), false);
+
     assert_eq!(check_while_let(Some(Some(Some(1))), 1), true);
     assert_eq!(check_while_let(Some(Some(Some(1))), 9), false);
 }