feat(macros): 🎸 support path to declare widget type

CHANGELOG.md

@@ -31,6 +31,23 @@ Please only add new entries below the [Unreleased](#unreleased---releasedate) he
 
 - **core**: Added support to query a `WriteRef` from a state, enabling users to modify the state after attaching it to a widget. (#601 @M-Adoo)
 - **core**: Introduced the `DeclareInto` trait for any type that implements `DeclareFrom`. (#604 @M-Adoo)
+- **macros**: Improved widget declaration to allow specifying widget types via path. (#606 @M-Adoo)
+  ```rust
+    // Previously, a widget type could only be specified using an identifier, requiring prior import of `Row`.
+    use ribir::prelude::*;
+    fn_widget! {
+      @Row {
+        ...
+      }
+    }
+
+    // Now, the widget type can be specified using a path, removing the need for a prior import.
+    fn_widget! {
+      @ribir::prelude::Row {
+        ...
+      }
+    }
+```
 
 ### Changed
 

docs/en/get_started/quick_start.md

@@ -259,6 +259,18 @@ fn main() {
   });
 }
 ```
+For expression widgets that are simple function calls, the `{}` can be omitted for brevity:
+
+```rust ignore
+fn_widget! {
+  // Instead of using braces:
+  let label = @ { Label::new("Increment") };
+  // You can directly write:
+  let label = @Label::new("Increment");
+  ...
+};
+```
+
 ## State -- make data watchable and shareable
 
 Although we have created a counter, it always shows `0` and does not respond to the button. In this section, you will learn how to make your counter work through state.

docs/zh/get_started/quick_start.md

@@ -259,6 +259,18 @@ fn main() {
 }
 ```
 
+对于简单的函数调用形式的表达式 widget ，可以省略 `{}` 以简化书写：
+
+```rust ignore
+fn_widget! {
+  // 使用大括号的写法：
+  let label = @ { Label::new("Increment") };
+  // 可以直接写为：
+  let label = @Label::new("Increment");
+  ...
+};
+```
+
 ## 状态——让数据变得可被侦和共享
 
 我们虽然创建了一个计数器，但它总是显示 `0`，也不响应按钮做任何事情。在这一节中，你将会了解到如何通过状态让你的计数器工作。

examples/todos/src/ui.rs

@@ -9,15 +9,13 @@ impl Compose for Todos {
         align_items: Align::Center,
         item_gap: 12.,
         @H1 { text: "Todo" }
-        @ {
-          input(None, move |text| {
-            $this.write().new_task(text.to_string());
-          })
-        }
+        @input(None, move |text| {
+          $this.write().new_task(text.to_string());
+        })
         @Tabs {
           @Tab {
-            @TabItem { @{ Label::new("ALL") } }
-            @TabPane { @{ task_lists(&this, |_| true) } }
+            @TabItem { @Label::new("ALL") }
+            @TabPane { @task_lists(&this, |_| true) }
           }
           @Tab {
             @TabItem { @{ Label::new("ACTIVE") } }

macros/src/symbol_process.rs

@@ -113,47 +113,40 @@ mod tokens_pre_process {
         {
           tokens.push(TokenTree::Ident(Ident::new(KW_RDL, at.span())));
           tokens.push(not_token(at.span()));
-
-          let body = match iter.next() {
-            // declare a new widget: `@ SizedBox { ... }`
-            Some(TokenTree::Ident(name)) => {
-              let next = iter.next();
-              let Some(TokenTree::Group(body)) = next else {
-                return rdl_syntax_err(
-                  at.span(),
-                  next.map(|n| n.span()).or_else(|| Some(name.span()))
-                )
-              };
-              let tokens = TokenStream::from_iter([TokenTree::Ident(name), TokenTree::Group(body)]);
-              Group::new(Delimiter::Brace, tokens)
-            }
+          let mut rdl_group = smallvec::SmallVec::<[TokenTree; 3]>::default();
+           match iter.next() {
             // declare a variable widget as parent,  `@ $var { ... }`
             Some(TokenTree::Punct(dollar)) if dollar.as_char() == '$' => {
               if let Some(TokenTree::Ident(var)) = iter.next() {
-                let next = iter.next();
-                let Some(TokenTree::Group(body))  =  next else {
-                  return rdl_syntax_err(
-                    at.span(),
-                    next.map(|n| n.span()).or_else(|| Some(var.span()))
-                  )
+                rdl_group.push(TokenTree::Punct(dollar));
+                rdl_group.push(TokenTree::Ident(var));
+                if let Some(g)  = iter.next()  {
+                 rdl_group.push(g);
                 };
-                let tokens = TokenStream::from_iter([
-                  TokenTree::Punct(dollar),
-                  TokenTree::Ident(var),
-                  TokenTree::Group(body),
-                ]);
-                Group::new(Delimiter::Brace, tokens)
               } else {
                 return dollar_err(dollar.span());
               }
             }
             // declare a expression widget  `@ { ... }`
-            Some(TokenTree::Group(g)) => g,
-            n => {
-              return rdl_syntax_err(at.span(), n.map(|n| n.span()));
-            }
+            Some(TokenTree::Group(g)) => rdl_group.push(TokenTree::Group(g)) ,
+            // declare a new widget: `@ SizedBox { ... }`
+            mut n => {
+              while let Some(t) = n.take() {
+                let is_group = matches!(t, TokenTree::Group(_));
+                rdl_group.push(t);
+                if is_group {
+                  break
+                }
+                n = iter.next();
+              };
+            },
           };
-          tokens.push(TokenTree::Group(body));
+          if let Some(TokenTree::Group(_)) = rdl_group.last()  {
+            let rdl_group = TokenStream::from_iter(rdl_group);
+            tokens.push(TokenTree::Group(Group::new(Delimiter::Brace, rdl_group)));
+          } else {
+            return rdl_syntax_err(at.span(), rdl_group.last().map(|n| n.span()));
+          }
         }
         Some(TokenTree::Punct(p)) if p.as_char() == '$' => {
           match iter.next() {