Add regression test for #81899

src/test/ui/borrowck/issue-81899.rs

@@ -0,0 +1,13 @@
+// Regression test for #81899.
+// The `panic!()` below is important to trigger the fixed ICE.
+
+const _CONST: &[u8] = &f(&[], |_| {});
+
+const fn f<F>(_: &[u8], _: F) -> &[u8]
+where
+    F: FnMut(&u8),
+{
+    panic!() //~ ERROR: evaluation of constant value failed
+}
+
+fn main() {}

src/test/ui/borrowck/issue-81899.stderr

@@ -0,0 +1,17 @@
+error[E0080]: evaluation of constant value failed
+  --> $DIR/issue-81899.rs:10:5
+   |
+LL | const _CONST: &[u8] = &f(&[], |_| {});
+   |                        -------------- inside `_CONST` at $DIR/issue-81899.rs:4:24
+...
+LL |     panic!()
+   |     ^^^^^^^^
+   |     |
+   |     the evaluated program panicked at 'explicit panic', $DIR/issue-81899.rs:10:5
+   |     inside `f::<[closure@$DIR/issue-81899.rs:4:31: 4:37]>` at $SRC_DIR/std/src/panic.rs:LL:COL
+   |
+   = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0080`.