Implemented basic enum const eval

crates/ide/src/hover/render.rs

@@ -2,7 +2,9 @@
 use std::fmt::Display;
 
 use either::Either;
-use hir::{AsAssocItem, AttributeTemplate, HasAttrs, HasSource, HirDisplay, Semantics, TypeInfo};
+use hir::{
+    db::HirDatabase, AsAssocItem, AttributeTemplate, HasAttrs, HasSource, HirDisplay, Semantics, TypeInfo,
+};
 use ide_db::{
     base_db::SourceDatabase,
     defs::Definition,
@@ -346,7 +348,14 @@ pub(super) fn definition(
         Definition::Module(it) => label_and_docs(db, it),
         Definition::Function(it) => label_and_docs(db, it),
         Definition::Adt(it) => label_and_docs(db, it),
-        Definition::Variant(it) => label_and_docs(db, it),
+        Definition::Variant(it) => label_value_and_docs(db, it, |&it| {
+            let hir_db: &dyn HirDatabase = db;
+            let body = hir_db.const_eval_variant(it.into());
+            match body {
+                Ok(x) => Some(format!("{}", x)),
+                Err(_) => it.value(db).map(|s| format!("{}", s)),
+            }
+        }),
         Definition::Const(it) => label_value_and_docs(db, it, |it| {
             let body = it.eval(db);
             match body {

crates/ide/src/hover/tests.rs

@@ -3527,6 +3527,86 @@ impl<const LEN: usize> Foo<LEN$0> {}
     );
 }
 
+#[test]
+fn hover_const_eval_variant() {
+    // show hex for <10
+    check(
+        r#"
+#[repr(u8)]
+enum E {
+    /// This is a doc
+    A$0 = 1 << 3,
+}
+"#,
+        expect![[r#"
+            *A*
+
+            ```rust
+            test::E
+            ```
+
+            ```rust
+            A = 8
+            ```
+
+            ---
+
+            This is a doc
+        "#]],
+    );
+    // show hex for >10
+    check(
+        r#"
+#[repr(u8)]
+enum E {
+    /// This is a doc
+    A$0 = (1 << 3) + (1 << 2),
+}
+"#,
+        expect![[r#"
+            *A*
+
+            ```rust
+            test::E
+            ```
+
+            ```rust
+            A = 12 (0xC)
+            ```
+
+            ---
+
+            This is a doc
+        "#]],
+    );
+    // enums in const eval
+    check(
+        r#"
+#[repr(u8)]
+enum E {
+    A = 1,
+    /// This is a doc
+    B$0 = E::A + 1,
+}
+"#,
+        expect![[r#"
+            *B*
+
+            ```rust
+            test::E
+            ```
+
+            ```rust
+            B = 2
+            ```
+
+            ---
+
+            This is a doc
+        "#]],
+    );
+}
+
 #[test]
 fn hover_const_eval() {
     // show hex for <10
@@ -3820,6 +3900,35 @@ fn foo() {
 
             ---
 
+            This is a doc
+        "#]],
+    );
+    check(
+        r#"
+enum E {
+    /// This is a doc
+    A = 3,
+}
+fn foo(e: E) {
+    match e {
+        E::A$0 => (),
+        _ => ()
+    }
+}
+"#,
+        expect![[r#"
+            *A*
+
+            ```rust
+            test::E
+            ```
+
+            ```rust
+            A = 3
+            ```
+
+            ---
+
             This is a doc
         "#]],
     );