feat: Improve hover too long parameter list

crates/hir/src/display.rs

@@ -172,8 +172,13 @@ fn write_function<'db>(f: &mut HirFormatter<'_, 'db>, func_id: FunctionId) -> Re
 
     write_generic_params(GenericDefId::FunctionId(func_id), f)?;
 
+    let too_long_param = data.params.len() > 4;
     f.write_char('(')?;
 
+    if too_long_param {
+        f.write_str("\n    ")?;
+    }
+
     let mut first = true;
     let mut skip_self = 0;
     if let Some(self_param) = func.self_param(db) {
@@ -182,11 +187,12 @@ fn write_function<'db>(f: &mut HirFormatter<'_, 'db>, func_id: FunctionId) -> Re
         skip_self = 1;
     }
 
+    let comma = if too_long_param { ",\n    " } else { ", " };
     // FIXME: Use resolved `param.ty` once we no longer discard lifetimes
     let body = db.body(func_id.into());
     for (type_ref, param) in data.params.iter().zip(func.assoc_fn_params(db)).skip(skip_self) {
         if !first {
-            f.write_str(", ")?;
+            f.write_str(comma)?;
         } else {
             first = false;
         }
@@ -201,11 +207,14 @@ fn write_function<'db>(f: &mut HirFormatter<'_, 'db>, func_id: FunctionId) -> Re
 
     if data.is_varargs() {
         if !first {
-            f.write_str(", ")?;
+            f.write_str(comma)?;
         }
         f.write_str("...")?;
     }
 
+    if too_long_param {
+        f.write_char('\n')?;
+    }
     f.write_char(')')?;
 
     // `FunctionData::ret_type` will be `::core::future::Future<Output = ...>` for async fns.

crates/ide/src/hover/tests.rs

@@ -9719,6 +9719,99 @@ fn test_hover_function_with_pat_param() {
     );
 }
 
+#[test]
+fn test_hover_function_with_too_long_param() {
+    check(
+        r#"
+fn fn_$0(
+    attrs: impl IntoIterator<Item = ast::Attr>,
+    visibility: Option<ast::Visibility>,
+    fn_name: ast::Name,
+    type_params: Option<ast::GenericParamList>,
+    where_clause: Option<ast::WhereClause>,
+    params: ast::ParamList,
+    body: ast::BlockExpr,
+    ret_type: Option<ast::RetType>,
+    is_async: bool,
+    is_const: bool,
+    is_unsafe: bool,
+    is_gen: bool,
+) -> ast::Fn {}
+        "#,
+        expect![[r#"
+            *fn_*
+
+            ```rust
+            ra_test_fixture
+            ```
+
+            ```rust
+            fn fn_(
+                attrs: impl IntoIterator<Item = ast::Attr>,
+                visibility: Option<ast::Visibility>,
+                fn_name: ast::Name,
+                type_params: Option<ast::GenericParamList>,
+                where_clause: Option<ast::WhereClause>,
+                params: ast::ParamList,
+                body: ast::BlockExpr,
+                ret_type: Option<ast::RetType>,
+                is_async: bool,
+                is_const: bool,
+                is_unsafe: bool,
+                is_gen: bool
+            ) -> ast::Fn
+            ```
+        "#]],
+    );
+
+    check(
+        r#"
+fn fn_$0(
+    &self,
+    attrs: impl IntoIterator<Item = ast::Attr>,
+    visibility: Option<ast::Visibility>,
+    fn_name: ast::Name,
+    type_params: Option<ast::GenericParamList>,
+    where_clause: Option<ast::WhereClause>,
+    params: ast::ParamList,
+    body: ast::BlockExpr,
+    ret_type: Option<ast::RetType>,
+    is_async: bool,
+    is_const: bool,
+    is_unsafe: bool,
+    is_gen: bool,
+    ...
+) -> ast::Fn {}
+        "#,
+        expect![[r#"
+            *fn_*
+
+            ```rust
+            ra_test_fixture
+            ```
+
+            ```rust
+            fn fn_(
+                &self,
+                attrs: impl IntoIterator<Item = ast::Attr>,
+                visibility: Option<ast::Visibility>,
+                fn_name: ast::Name,
+                type_params: Option<ast::GenericParamList>,
+                where_clause: Option<ast::WhereClause>,
+                params: ast::ParamList,
+                body: ast::BlockExpr,
+                ret_type: Option<ast::RetType>,
+                is_async: bool,
+                is_const: bool,
+                is_unsafe: bool,
+                is_gen: bool,
+                ...
+            ) -> ast::Fn
+            ```
+        "#]],
+    );
+}
+
 #[test]
 fn hover_path_inside_block_scope() {
     check(