Add generic arg infer

compiler/rustc_hir/src/intravisit.rs

@@ -436,13 +436,22 @@ pub trait Visitor<'v>: Sized {
     fn visit_label(&mut self, label: &'v Label) {
         walk_label(self, label)
     }
+    fn visit_infer(&mut self, inf: &'v InferArg) {
+        self.visit_id(inf.hir_id);
+    }
     fn visit_generic_arg(&mut self, generic_arg: &'v GenericArg<'v>) {
         match generic_arg {
             GenericArg::Lifetime(lt) => self.visit_lifetime(lt),
             GenericArg::Type(ty) => self.visit_ty(ty),
             GenericArg::Const(ct) => self.visit_anon_const(&ct.value),
+            GenericArg::Infer(inf) => self.visit_infer(inf),
         }
     }
+    /*
+    fn tcx(&self) -> Option<&TyCtxt<'tcx>> {
+        None
+    }
+    */
     fn visit_lifetime(&mut self, lifetime: &'v Lifetime) {
         walk_lifetime(self, lifetime)
     }
@@ -746,6 +755,10 @@ pub fn walk_ty<'v, V: Visitor<'v>>(visitor: &mut V, typ: &'v Ty<'v>) {
     }
 }
 
+pub fn walk_inf<'v, V: Visitor<'v>>(visitor: &mut V, inf: &'v InferArg) {
+    visitor.visit_id(inf.hir_id);
+}
+
 pub fn walk_qpath<'v, V: Visitor<'v>>(
     visitor: &mut V,
     qpath: &'v QPath<'v>,