Rollup merge of #47892 - Badel2:const_type_id_of, r=oli-obk

Turn `type_id` into a constant intrinsic

https://github.com/rust-lang/rust/issues/27745

The method `get_type_id` in `Any` is intended to support reflection. It's currently unstable in favor of using an associated constant instead. This PR makes the `type_id` intrinsic a constant intrinsic, the same as `size_of` and `align_of`, allowing `TypeId::of` to be a `const fn`, which will allow using an associated constant in `Any`.

1 files changed, 4 insertions, 0 deletions

diff --git a/src/librustc_const_eval/eval.rs b/src/librustc_const_eval/eval.rs
index 1d2813e4f67..8e4ec93c14b 100644
--- a/src/librustc_const_eval/eval.rs
+++ b/src/librustc_const_eval/eval.rs
@@ -327,6 +327,10 @@ fn eval_const_expr_partial<'a, 'tcx>(cx: &ConstContext<'a, 'tcx>,
                     return Ok(mk_const(Integral(Usize(ConstUsize::new(align,
                         tcx.sess.target.usize_ty).unwrap()))));
                 }
+                "type_id" => {
+                    let type_id = tcx.type_id_hash(substs.type_at(0));
+                    return Ok(mk_const(Integral(U64(type_id))));
+                }
                 _ => signal!(e, TypeckError)
             }
           }