Rollup merge of #100359 - b-naber:valtrees-pretty-print-ice, r=lcnr

Special-case references to leafs in valtree pretty-printing

Fixes https://github.com/rust-lang/rust/issues/100313

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -1513,6 +1513,10 @@ pub trait PrettyPrinter<'tcx>:
                 }
                 return Ok(self);
             }
+            (ty::ValTree::Leaf(leaf), ty::Ref(_, inner_ty, _)) => {
+                p!(write("&"));
+                return self.pretty_print_const_scalar_int(leaf, *inner_ty, print_ty);
+            }
             (ty::ValTree::Leaf(leaf), _) => {
                 return self.pretty_print_const_scalar_int(leaf, ty, print_ty);
             }

src/test/ui/const-generics/issues/issue-100313.rs

@@ -0,0 +1,21 @@
+#![allow(incomplete_features)]
+#![feature(const_mut_refs)]
+#![feature(adt_const_params)]
+
+struct T<const B: &'static bool>;
+
+impl <const B: &'static bool> T<B> {
+    const fn set_false(&self) {
+        unsafe {
+            *(B as *const bool as *mut bool) = false;
+            //~^ ERROR evaluation of constant value failed [E0080]
+        }
+    }
+}
+
+const _: () = {
+    let x = T::<{&true}>;
+    x.set_false();
+};
+
+fn main() {}

src/test/ui/const-generics/issues/issue-100313.stderr

@@ -0,0 +1,15 @@
+error[E0080]: evaluation of constant value failed
+  --> $DIR/issue-100313.rs:10:13
+   |
+LL |             *(B as *const bool as *mut bool) = false;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |             |
+   |             writing to alloc7 which is read-only
+   |             inside `T::<&true>::set_false` at $DIR/issue-100313.rs:10:13
+...
+LL |     x.set_false();
+   |     ------------- inside `_` at $DIR/issue-100313.rs:18:5
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0080`.