Add Mutability to chalk-ir

Author: nathanwhit

chalk-ir/src/fold/boring_impls.rs

@@ -248,6 +248,7 @@ copy_fold!(IntTy);
 copy_fold!(FloatTy);
 copy_fold!(Scalar);
 copy_fold!(ClausePriority);
+copy_fold!(Mutability);
 
 #[macro_export]
 macro_rules! id_fold {

chalk-ir/src/lib.rs

@@ -136,6 +136,12 @@ pub enum Scalar {
     Float(FloatTy),
 }
 
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum Mutability {
+    Mut,
+    Not,
+}
+
 #[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Fold, Visit)]
 pub enum TypeName<I: Interner> {
     /// a type like `Vec<T>`

chalk-ir/src/visit/boring_impls.rs

@@ -5,7 +5,7 @@
 //! The more interesting impls of `Visit` remain in the `visit` module.
 
 use crate::{
-    AssocTypeId, ClausePriority, DebruijnIndex, FloatTy, Goals, ImplId, IntTy, Interner,
+    AssocTypeId, ClausePriority, DebruijnIndex, FloatTy, Goals, ImplId, IntTy, Interner, Mutability,
     OpaqueTyId, Parameter, ParameterKind, PlaceholderIndex, ProgramClause, ProgramClauseData,
     ProgramClauses, QuantifiedWhereClauses, QuantifierKind, Scalar, StructId, Substitution,
     SuperVisit, TraitId, UintTy, UniverseIndex, Visit, VisitResult, Visitor,
@@ -211,6 +211,7 @@ const_visit!(Scalar);
 const_visit!(UintTy);
 const_visit!(IntTy);
 const_visit!(FloatTy);
+const_visit!(Mutability);
 
 #[macro_export]
 macro_rules! id_visit {