Rollup merge of #135985 - Zalathar:whats-upvar, r=lqd

Rename test to `unresolvable-upvar-issue-87987.rs` and add some notes

Extracted from #135756. I had to figure out what this test was trying to test, so I might as well write it down for future reference.

src/tools/tidy/src/issues.txt

@@ -409,7 +409,6 @@ ui/closure_context/issue-26046-fn-once.rs
 ui/closure_context/issue-42065.rs
 ui/closures/2229_closure_analysis/issue-118144.rs
 ui/closures/2229_closure_analysis/issue-87378.rs
-ui/closures/2229_closure_analysis/issue-87987.rs
 ui/closures/2229_closure_analysis/issue-88118-2.rs
 ui/closures/2229_closure_analysis/issue-88476.rs
 ui/closures/2229_closure_analysis/issue-89606.rs

tests/ui/closures/2229_closure_analysis/unresolvable-upvar-issue-87987.rs

@@ -0,0 +1,46 @@
+//! When a closure syntactically captures a place, but doesn't actually capture
+//! it, make sure MIR building doesn't ICE when handling that place.
+//!
+//! Under the Rust 2021 disjoint capture rules, this sort of non-capture can
+//! occur when a place is only inspected by infallible non-binding patterns.
+
+// FIXME(#135985): On its own, this test should probably just be check-pass.
+// But there are few/no other tests that use non-binding array patterns and
+// invoke the later parts of the compiler, so building/running has some value.
+
+//@ run-pass
+//@ edition:2021
+
+#[expect(dead_code)]
+struct Props {
+    field_1: u32,
+    field_2: u32,
+}
+
+fn main() {
+    // Test 1
+    let props_2 = Props { field_1: 1, field_2: 1 };
+
+    let _ = || {
+        let _: Props = props_2;
+    };
+
+    // Test 2
+    let mut arr = [1, 3, 4, 5];
+
+    let mref = &mut arr;
+
+    // These array patterns don't need to inspect the array, so the array
+    // isn't captured.
+    let _c = || match arr {
+        [_, _, _, _] => println!("C"),
+    };
+    let _d = || match arr {
+        [_, .., _] => println!("D"),
+    };
+    let _e = || match arr {
+        [_, ..] => println!("E"),
+    };
+
+    println!("{:#?}", mref);
+}