diff --git a/src/expr.rs b/src/expr.rs
index 7380dc4850ec..46e7e500f227 100644
--- a/src/expr.rs
+++ b/src/expr.rs
@@ -2578,10 +2578,10 @@ fn rewrite_assignment(
 
 // The left hand side must contain everything up to, and including, the
 // assignment operator.
-pub fn rewrite_assign_rhs<S: Into<String>>(
+pub fn rewrite_assign_rhs<S: Into<String>, R: Rewrite>(
     context: &RewriteContext,
     lhs: S,
-    ex: &ast::Expr,
+    ex: &R,
     shape: Shape,
 ) -> Option<String> {
     let lhs = lhs.into();
@@ -2596,9 +2596,9 @@ pub fn rewrite_assign_rhs<S: Into<String>>(
     Some(lhs + &rhs)
 }
 
-fn choose_rhs(
+fn choose_rhs<R: Rewrite>(
     context: &RewriteContext,
-    expr: &ast::Expr,
+    expr: &R,
     shape: Shape,
     orig_rhs: Option<String>,
 ) -> Option<String> {
diff --git a/src/items.rs b/src/items.rs
index fa697157ea32..e0bf02abe65a 100644
--- a/src/items.rs
+++ b/src/items.rs
@@ -111,7 +111,7 @@ impl Rewrite for ast::Local {
             // 1 = trailing semicolon;
             let nested_shape = shape.sub_width(1)?;
 
-            result = rewrite_assign_rhs(context, result, ex, nested_shape)?;
+            result = rewrite_assign_rhs(context, result, &**ex, nested_shape)?;
         }
 
         result.push(';');
@@ -550,7 +550,7 @@ impl<'a> FmtVisitor<'a> {
             ast::VariantData::Unit(..) => if let Some(ref expr) = field.node.disr_expr {
                 let lhs = format!("{} =", field.node.name);
                 // 1 = ','
-                rewrite_assign_rhs(&context, lhs, expr, shape.sub_width(1)?)?
+                rewrite_assign_rhs(&context, lhs, &**expr, shape.sub_width(1)?)?
             } else {
                 field.node.name.to_string()
             },
@@ -1593,7 +1593,7 @@ fn rewrite_static(
         rewrite_assign_rhs(
             context,
             lhs,
-            expr,
+            &**expr,
             Shape::legacy(remaining_width, offset.block_only()),
         ).and_then(|res| {
             recover_comment_removed(res, static_parts.span, context)