Almost there

crates/ide/src/hover/render.rs

@@ -3,7 +3,7 @@ use std::fmt::Display;
 
 use either::Either;
 use hir::{
-    db::HirDatabase, AsAssocItem, AttributeTemplate, HasAttrs, HasSource, HirDisplay, Semantics, TypeInfo,
+    db::HirDatabase, AsAssocItem, AttributeTemplate, HasAttrs, HasSource, HirDisplay, Semantics, StructKind, TypeInfo,
 };
 use ide_db::{
     base_db::SourceDatabase,
@@ -348,12 +348,12 @@ 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_value_and_docs(db, it, |&it| {
-            let body = it.eval(db);
-            match body {
-                Ok(x) => Some(format!("{}", x)),
-                Err(_) => it.value(db).map(|x| format!("{}", x)),
-            }
+        Definition::Variant(it) => label_value_and_docs(db, it, |&it| match it.kind(db) {
+            StructKind::Unit => match it.eval(db) {
+                Ok(x) => Some(format!("{}", x.enum_value().unwrap_or(x))),
+                Err(_) => it.value(db).map(|x| format!("{:?}", x)),
+            },
+            _ => None,
         }),
         Definition::Const(it) => label_value_and_docs(db, it, |it| {
             let body = it.eval(db);

crates/ide/src/hover/tests.rs

@@ -3529,6 +3529,31 @@ impl<const LEN: usize> Foo<LEN$0> {}
 
 #[test]
 fn hover_const_eval_variant() {
+    check(
+        r#"
+#[repr(u8)]
+enum E {
+    A = 4,
+    /// This is a doc
+    B$0 = E::A as u8 + 1,
+}
+"#,
+        expect![[r#"
+            *B*
+
+            ```rust
+            test::E
+            ```
+
+            ```rust
+            B = 5
+            ```
+
+            ---
+
+            This is a doc
+        "#]],
+    );
     // show hex for <10
     check(
         r#"
@@ -3586,7 +3611,7 @@ enum E {
 enum E {
     A = 1,
     /// This is a doc
-    B$0 = E::A + 1,
+    B$0 = E::A as u8 + 1,
 }
 "#,
         expect![[r#"
@@ -3602,6 +3627,32 @@ enum E {
 
             ---
 
+            This is a doc
+        "#]],
+    );
+    // unspecified variant should increment by one
+    check(
+        r#"
+#[repr(u8)]
+enum E {
+    A = 4,
+    /// This is a doc
+    B$0,
+}
+"#,
+        expect![[r#"
+            *B*
+
+            ```rust
+            test::E
+            ```
+
+            ```rust
+            B = 5
+            ```
+
+            ---
+
             This is a doc
         "#]],
     );