Support const generics in derive

Co-Authored-By: Gabriel Smith <yodaldevoid@users.noreply.github.com>

2 files changed, 15 insertions, 1 deletions

diff --git a/src/libsyntax_ext/deriving/generic/mod.rs b/src/libsyntax_ext/deriving/generic/mod.rs
index e6fe125da9f..4678c752045 100644
--- a/src/libsyntax_ext/deriving/generic/mod.rs
+++ b/src/libsyntax_ext/deriving/generic/mod.rs
@@ -560,6 +560,7 @@ impl<'a> TraitDef<'a> {
 
                 cx.typaram(self.span, param.ident, vec![], bounds, None)
             }
+            GenericParamKind::Const { .. } => param.clone(),
         }));
 
         // and similarly for where clauses
@@ -657,6 +658,9 @@ impl<'a> TraitDef<'a> {
             GenericParamKind::Type { .. } => {
                 GenericArg::Type(cx.ty_ident(self.span, param.ident))
             }
+            GenericParamKind::Const { .. } => {
+                GenericArg::Const(cx.const_ident(self.span, param.ident))
+            }
         }).collect();
 
         // Create the type of `self`.
diff --git a/src/libsyntax_ext/deriving/generic/ty.rs b/src/libsyntax_ext/deriving/generic/ty.rs
index ea6e07922b2..100ec0057ee 100644
--- a/src/libsyntax_ext/deriving/generic/ty.rs
+++ b/src/libsyntax_ext/deriving/generic/ty.rs
@@ -94,7 +94,7 @@ impl<'a> Path<'a> {
     }
 }
 
-/// A type. Supports pointers, Self, and literals
+/// A type. Supports pointers, Self, and literals.
 #[derive(Clone)]
 pub enum Ty<'a> {
     Self_,
@@ -107,6 +107,13 @@ pub enum Ty<'a> {
     Tuple(Vec<Ty<'a>>),
 }
 
+/// A const expression. Supports literals and blocks.
+#[derive(Clone, Eq, PartialEq)]
+pub enum Const {
+    Literal,
+    Block,
+}
+
 pub fn borrowed_ptrty<'r>() -> PtrTy<'r> {
     Borrowed(None, ast::Mutability::Immutable)
 }
@@ -180,6 +187,9 @@ impl<'a> Ty<'a> {
                     GenericParamKind::Type { .. } => {
                         GenericArg::Type(cx.ty_ident(span, param.ident))
                     }
+                    GenericParamKind::Const { .. } => {
+                        GenericArg::Const(cx.const_ident(span, param.ident))
+                    }
                 }).collect();
 
                 cx.path_all(span, false, vec![self_ty], params, vec![])