hir: show const value in hover

crates/hir/src/display.rs

@@ -401,7 +401,8 @@ fn write_where_clause(def: GenericDefId, f: &mut HirFormatter) -> Result<(), Hir
 
 impl HirDisplay for Const {
     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
-        write_visibility(self.module(f.db).id, self.visibility(f.db), f)?;
+        let module_id = self.module(f.db).id;
+        write_visibility(module_id, self.visibility(f.db), f)?;
         let data = f.db.const_data(self.id);
         write!(f, "const ")?;
         match &data.name {
@@ -409,6 +410,15 @@ impl HirDisplay for Const {
             None => write!(f, "_: ")?,
         }
         data.type_ref.hir_fmt(f)?;
+        let ast_id_map = f.db.ast_id_map(data.file_id);
+        let ast_node = ast_id_map.get(data.ast_id);
+        if let Some(syntax_node) = f.db.parse_or_expand(data.file_id) {
+            let ast_node = ast_node.to_node(&syntax_node);
+            if let Some(body) = ast_node.body() {
+                write!(f, " = {}", body)?;
+            }
+        }
+
         Ok(())
     }
 }

crates/hir_def/src/data.rs

@@ -2,7 +2,7 @@
 
 use std::sync::Arc;
 
-use hir_expand::{name::Name, InFile};
+use hir_expand::{ast_id_map::FileAstId, name::Name, HirFileId, InFile};
 use syntax::ast;
 
 use crate::{
@@ -255,6 +255,8 @@ pub struct ConstData {
     pub name: Option<Name>,
     pub type_ref: Interned<TypeRef>,
     pub visibility: RawVisibility,
+    pub ast_id: FileAstId<ast::Const>,
+    pub file_id: HirFileId,
 }
 
 impl ConstData {
@@ -267,6 +269,8 @@ impl ConstData {
             name: konst.name.clone(),
             type_ref: konst.type_ref.clone(),
             visibility: item_tree[konst.visibility].clone(),
+            ast_id: konst.ast_id.clone(),
+            file_id: loc.id.file_id(),
         })
     }
 }

crates/ide/src/hover/tests.rs

@@ -510,7 +510,7 @@ fn hover_const_static() {
             ```
 
             ```rust
-                const foo: u32
+            const foo: u32 = 123
             ```
         "#]],
     );
@@ -795,7 +795,7 @@ fn main() {
             ```
 
             ```rust
-                const C: u32
+            const C: u32 = 1
             ```
         "#]],
     )
@@ -3183,7 +3183,7 @@ fn foo() {
             ```
 
             ```rust
-                const FOO: usize
+            const FOO: usize = 3
             ```
 
             ---