Make it impossible to forget a conversion for the rustdoc ItemType enum

Author: GuillaumeGomez

src/librustdoc/formats/item_type.rs

@@ -8,6 +8,9 @@ use serde::{Deserialize, Deserializer, Serialize, Serializer, de};
 
 use crate::clean;
 
+macro_rules! item_type {
+    ($($variant:ident = $number:literal,)+) => {
+
 /// Item type. Corresponds to `clean::ItemEnum` variants.
 ///
 /// The search index uses item types encoded as smaller numbers which equal to
@@ -29,35 +32,7 @@ use crate::clean;
 #[derive(Copy, PartialEq, Eq, Hash, Clone, Debug, PartialOrd, Ord)]
 #[repr(u8)]
 pub(crate) enum ItemType {
-    Keyword = 0,
-    Primitive = 1,
-    Module = 2,
-    ExternCrate = 3,
-    Import = 4,
-    Struct = 5,
-    Enum = 6,
-    Function = 7,
-    TypeAlias = 8,
-    Static = 9,
-    Trait = 10,
-    Impl = 11,
-    TyMethod = 12,
-    Method = 13,
-    StructField = 14,
-    Variant = 15,
-    Macro = 16,
-    AssocType = 17,
-    Constant = 18,
-    AssocConst = 19,
-    Union = 20,
-    ForeignType = 21,
-    // OpaqueTy used to be here, but it was removed in #127276
-    ProcAttribute = 23,
-    ProcDerive = 24,
-    TraitAlias = 25,
-    // This number is reserved for use in JavaScript
-    // Generic = 26,
-    Attribute = 27,
+    $($variant = $number,)+
 }
 
 impl Serialize for ItemType {
@@ -82,32 +57,7 @@ impl<'de> Deserialize<'de> for ItemType {
             }
             fn visit_u64<E: de::Error>(self, v: u64) -> Result<ItemType, E> {
                 Ok(match v {
-                    0 => ItemType::Keyword,
-                    1 => ItemType::Primitive,
-                    2 => ItemType::Module,
-                    3 => ItemType::ExternCrate,
-                    4 => ItemType::Import,
-                    5 => ItemType::Struct,
-                    6 => ItemType::Enum,
-                    7 => ItemType::Function,
-                    8 => ItemType::TypeAlias,
-                    9 => ItemType::Static,
-                    10 => ItemType::Trait,
-                    11 => ItemType::Impl,
-                    12 => ItemType::TyMethod,
-                    13 => ItemType::Method,
-                    14 => ItemType::StructField,
-                    15 => ItemType::Variant,
-                    16 => ItemType::Macro,
-                    17 => ItemType::AssocType,
-                    18 => ItemType::Constant,
-                    19 => ItemType::AssocConst,
-                    20 => ItemType::Union,
-                    21 => ItemType::ForeignType,
-                    23 => ItemType::ProcAttribute,
-                    24 => ItemType::ProcDerive,
-                    25 => ItemType::TraitAlias,
-                    27 => ItemType::Attribute,
+                    $($number => ItemType::$variant,)+
                     _ => return Err(E::missing_field("unknown number for `ItemType` enum")),
                 })
             }
@@ -116,6 +66,41 @@ impl<'de> Deserialize<'de> for ItemType {
     }
 }
 
+    }
+}
+
+item_type! {
+    Keyword = 0,
+    Primitive = 1,
+    Module = 2,
+    ExternCrate = 3,
+    Import = 4,
+    Struct = 5,
+    Enum = 6,
+    Function = 7,
+    TypeAlias = 8,
+    Static = 9,
+    Trait = 10,
+    Impl = 11,
+    TyMethod = 12,
+    Method = 13,
+    StructField = 14,
+    Variant = 15,
+    Macro = 16,
+    AssocType = 17,
+    Constant = 18,
+    AssocConst = 19,
+    Union = 20,
+    ForeignType = 21,
+    // OpaqueTy used to be here, but it was removed in #127276
+    ProcAttribute = 23,
+    ProcDerive = 24,
+    TraitAlias = 25,
+    // This number is reserved for use in JavaScript
+    // Generic = 26,
+    Attribute = 27,
+}
+
 impl<'a> From<&'a clean::Item> for ItemType {
     fn from(item: &'a clean::Item) -> ItemType {
         let kind = match &item.kind {