feat: add hover display for trait assoc items

crates/hir-ty/src/display.rs

@@ -62,7 +62,7 @@ pub struct HirFormatter<'a> {
     fmt: &'a mut dyn HirWrite,
     buf: String,
     curr_size: usize,
-    pub(crate) max_size: Option<usize>,
+    pub max_size: Option<usize>,
     omit_verbose_types: bool,
     closure_style: ClosureStyle,
     display_target: DisplayTarget,

crates/hir/src/display.rs

@@ -17,10 +17,10 @@ use hir_ty::{
 };
 
 use crate::{
-    Adt, AsAssocItem, AssocItemContainer, Const, ConstParam, Enum, ExternCrateDecl, Field,
-    Function, GenericParam, HasCrate, HasVisibility, LifetimeParam, Macro, Module, SelfParam,
-    Static, Struct, Trait, TraitAlias, TupleField, TyBuilder, Type, TypeAlias, TypeOrConstParam,
-    TypeParam, Union, Variant,
+    Adt, AsAssocItem, AssocItem, AssocItemContainer, Const, ConstParam, Enum, ExternCrateDecl,
+    Field, Function, GenericParam, HasCrate, HasVisibility, LifetimeParam, Macro, Module,
+    SelfParam, Static, Struct, Trait, TraitAlias, TupleField, TyBuilder, Type, TypeAlias,
+    TypeOrConstParam, TypeParam, Union, Variant,
 };
 
 impl HirDisplay for Function {
@@ -595,6 +595,36 @@ impl HirDisplay for Trait {
         let def_id = GenericDefId::TraitId(self.id);
         write_generic_params(def_id, f)?;
         write_where_clause(def_id, f)?;
+
+        let assoc_items = self.items(f.db);
+        let assoc_items_size = assoc_items.len();
+        let max_display_size = f.max_size.unwrap_or(assoc_items_size);
+        if assoc_items.is_empty() {
+            f.write_str(" {}")?;
+        } else {
+            f.write_str(" {\n")?;
+            for (index, item) in assoc_items.iter().enumerate() {
+                f.write_str("    ")?;
+                match item {
+                    AssocItem::Function(func) => {
+                        func.hir_fmt(f)?;
+                    }
+                    AssocItem::Const(cst) => {
+                        cst.hir_fmt(f)?;
+                    }
+                    AssocItem::TypeAlias(type_alias) => {
+                        type_alias.hir_fmt(f)?;
+                    }
+                };
+                f.write_str(",\n")?;
+                if index + 1 == max_display_size && index + 1 != assoc_items_size {
+                    f.write_str("    ...\n")?;
+                    break;
+                }
+            }
+            f.write_str("}")?;
+        }
+
         Ok(())
     }
 }

crates/ide-db/src/defs.rs

@@ -24,6 +24,12 @@ use crate::documentation::{Documentation, HasDocs};
 use crate::famous_defs::FamousDefs;
 use crate::RootDatabase;
 
+#[derive(Default)]
+pub struct HoverDisplayConfig {
+    pub trait_item_display_num: Option<usize>,
+    // todo: add config for struct & enum
+}
+
 // FIXME: a more precise name would probably be `Symbol`?
 #[derive(Debug, PartialEq, Eq, Copy, Clone, Hash)]
 pub enum Definition {
@@ -213,7 +219,7 @@ impl Definition {
         })
     }
 
-    pub fn label(&self, db: &RootDatabase) -> String {
+    pub fn label(&self, db: &RootDatabase, hover_display_config: HoverDisplayConfig) -> String {
         match *self {
             Definition::Macro(it) => it.display(db).to_string(),
             Definition::Field(it) => it.display(db).to_string(),
@@ -224,7 +230,9 @@ impl Definition {
             Definition::Variant(it) => it.display(db).to_string(),
             Definition::Const(it) => it.display(db).to_string(),
             Definition::Static(it) => it.display(db).to_string(),
-            Definition::Trait(it) => it.display(db).to_string(),
+            Definition::Trait(it) => {
+                it.display_truncated(db, hover_display_config.trait_item_display_num).to_string()
+            }
             Definition::TraitAlias(it) => it.display(db).to_string(),
             Definition::TypeAlias(it) => it.display(db).to_string(),
             Definition::BuiltinType(it) => it.name().display(db).to_string(),

crates/ide/src/hover.rs

@@ -32,6 +32,7 @@ pub struct HoverConfig {
     pub documentation: bool,
     pub keywords: bool,
     pub format: HoverDocFormat,
+    pub trait_item_display_num: Option<usize>,
 }
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]

crates/ide/src/hover/render.rs

@@ -8,7 +8,7 @@ use hir::{
 };
 use ide_db::{
     base_db::SourceDatabase,
-    defs::Definition,
+    defs::{Definition, HoverDisplayConfig},
     documentation::HasDocs,
     famous_defs::FamousDefs,
     generated::lints::{CLIPPY_LINTS, DEFAULT_LINTS, FEATURES},
@@ -406,7 +406,8 @@ pub(super) fn definition(
     config: &HoverConfig,
 ) -> Markup {
     let mod_path = definition_mod_path(db, &def);
-    let label = def.label(db);
+    let hover_config = HoverDisplayConfig { trait_item_display_num: config.trait_item_display_num };
+    let label = def.label(db, hover_config);
     let docs = def.docs(db, famous_defs);
     let value = (|| match def {
         Definition::Variant(it) => {