Support #[derive_const(Trait)]

crates/hir-def/src/macro_expansion_tests/builtin_derive_macro.rs

@@ -278,6 +278,44 @@ impl < > core::cmp::Eq for Command< > where {}"#]],
     );
 }
 
+#[test]
+fn test_partial_eq_expand_with_derive_const() {
+    // FIXME: actually expand with const
+    check(
+        r#"
+//- minicore: derive, eq
+#[derive_const(PartialEq, Eq)]
+enum Command {
+    Move { x: i32, y: i32 },
+    Do(&'static str),
+    Jump,
+}
+"#,
+        expect![[r#"
+#[derive_const(PartialEq, Eq)]
+enum Command {
+    Move { x: i32, y: i32 },
+    Do(&'static str),
+    Jump,
+}
+
+impl < > core::cmp::PartialEq for Command< > where {
+    fn eq(&self , other: &Self ) -> bool {
+        match (self , other) {
+            (Command::Move {
+                x: x_self, y: y_self,
+            }
+            , Command::Move {
+                x: x_other, y: y_other,
+            }
+            )=>x_self.eq(x_other) && y_self.eq(y_other), (Command::Do(f0_self, ), Command::Do(f0_other, ))=>f0_self.eq(f0_other), (Command::Jump, Command::Jump)=>true , _unused=>false
+        }
+    }
+}
+impl < > core::cmp::Eq for Command< > where {}"#]],
+    );
+}
+
 #[test]
 fn test_partial_ord_expand() {
     check(

crates/hir-expand/src/builtin_attr_macro.rs

@@ -35,7 +35,7 @@ macro_rules! register_builtin {
 
 impl BuiltinAttrExpander {
     pub fn is_derive(self) -> bool {
-        matches!(self, BuiltinAttrExpander::Derive)
+        matches!(self, BuiltinAttrExpander::Derive | BuiltinAttrExpander::DeriveConst)
     }
     pub fn is_test(self) -> bool {
         matches!(self, BuiltinAttrExpander::Test)
@@ -50,6 +50,8 @@ register_builtin! {
     (cfg_accessible, CfgAccessible) => dummy_attr_expand,
     (cfg_eval, CfgEval) => dummy_attr_expand,
     (derive, Derive) => derive_attr_expand,
+    // derive const is equivalent to derive for our proposes.
+    (derive_const, DeriveConst) => derive_attr_expand,
     (global_allocator, GlobalAllocator) => dummy_attr_expand,
     (test, Test) => dummy_attr_expand,
     (test_case, TestCase) => dummy_attr_expand

crates/hir-expand/src/name.rs

@@ -365,6 +365,7 @@ pub mod known {
         cfg_eval,
         crate_type,
         derive,
+        derive_const,
         global_allocator,
         no_core,
         no_std,

crates/ide-completion/src/tests/attribute.rs

@@ -300,6 +300,7 @@ struct Foo;
             at deprecated
             at derive           macro derive
             at derive(…)
+            at derive_const     macro derive_const
             at doc = "…"
             at doc(alias = "…")
             at doc(hidden)

crates/test-utils/src/minicore.rs

@@ -1311,6 +1311,11 @@ mod macros {
         pub macro derive($item:item) {
             /* compiler built-in */
         }
+
+        #[rustc_builtin_macro]
+        pub macro derive_const($item:item) {
+            /* compiler built-in */
+        }
     }
     // endregion:derive
 
@@ -1385,7 +1390,7 @@ pub mod prelude {
             convert::{From, Into},                   // :from
             default::Default,                        // :default
             iter::{IntoIterator, Iterator},          // :iterator
-            macros::builtin::derive,            // :derive
+            macros::builtin::{derive, derive_const}, // :derive
             marker::Copy,                            // :copy
             marker::Send,                            // :send
             marker::Sized,                           // :sized