do not remove discriminant value if exists (rust-lang#3771) (rust-lang#3772)

Author: iam-afk

src/items.rs

@@ -557,24 +557,20 @@ impl<'a> FmtVisitor<'a> {
                 self.block_indent,
                 Some(one_line_width),
             )?,
-            ast::VariantData::Unit(..) => {
-                if let Some(ref expr) = field.node.disr_expr {
-                    let lhs = format!(
-                        "{:1$} =",
-                        rewrite_ident(&context, field.node.ident),
-                        pad_discrim_ident_to
-                    );
-                    rewrite_assign_rhs_with(
-                        &context,
-                        lhs,
-                        &*expr.value,
-                        shape,
-                        RhsTactics::AllowOverflow,
-                    )?
-                } else {
-                    rewrite_ident(&context, field.node.ident).to_owned()
-                }
-            }
+            ast::VariantData::Unit(..) => rewrite_ident(&context, field.node.ident).to_owned(),
+        };
+
+        let variant_body = if let Some(ref expr) = field.node.disr_expr {
+            let lhs = format!("{:1$} =", variant_body, pad_discrim_ident_to);
+            rewrite_assign_rhs_with(
+                &context,
+                lhs,
+                &*expr.value,
+                shape,
+                RhsTactics::AllowOverflow,
+            )?
+        } else {
+            variant_body
         };
 
         combine_strs_with_missing_comments(&context, &attrs_str, &variant_body, span, shape, false)

tests/source/enum.rs

@@ -202,3 +202,11 @@ enum PublishedFileVisibility {
     FriendsOnly = sys::ERemoteStoragePublishedFileVisibility_k_ERemoteStoragePublishedFileVisibilityFriendsOnly,
     Private = sys::ERemoteStoragePublishedFileVisibility_k_ERemoteStoragePublishedFileVisibilityPrivate,
 }
+
+// #3771
+//#![feature(arbitrary_enum_discriminant)]
+#[repr(u32)]
+pub enum E {
+    A { a: u32 } = 0x100,
+    B { field1: u32, field2: u8, field3: m::M } = 0x300 // comment
+}

tests/target/enum.rs

@@ -273,3 +273,17 @@ enum PublishedFileVisibility {
     Private =
         sys::ERemoteStoragePublishedFileVisibility_k_ERemoteStoragePublishedFileVisibilityPrivate,
 }
+
+// #3771
+//#![feature(arbitrary_enum_discriminant)]
+#[repr(u32)]
+pub enum E {
+    A {
+        a: u32,
+    } = 0x100,
+    B {
+        field1: u32,
+        field2: u8,
+        field3: m::M,
+    } = 0x300, // comment
+}