Add ConstVid

Co-Authored-By: Gabriel Smith <[email protected]>

Author: varkor

src/librustc/ty/sty.rs

@@ -16,6 +16,7 @@ use crate::mir::interpret::{Scalar, Pointer};
 use smallvec::SmallVec;
 use std::iter;
 use std::cmp::Ordering;
+use std::marker::PhantomData;
 use rustc_target::spec::abi;
 use syntax::ast::{self, Ident};
 use syntax::symbol::{keywords, InternedString};
@@ -1249,6 +1250,12 @@ pub struct TyVid {
     pub index: u32,
 }
 
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
+pub struct ConstVid<'tcx> {
+    pub index: u32,
+    pub phantom: PhantomData<&'tcx ()>,
+}
+
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
 pub struct IntVid {
     pub index: u32,