refactor: Rewrite Graphviz label group

lib/src/ast/statement.rs

@@ -57,7 +57,10 @@ impl Statement {
     ) -> Self {
         Self {
             kind: StmtKind::Expr(expr),
-            info: StmtInfo::default(),
+            info: StmtInfo {
+                start_pos: start,
+                end_pos: end,
+            },
         }
     }
 

lib/src/ast/visitor.rs

@@ -316,8 +316,8 @@ pub trait AstVisitor<'ast>: Sized {
     }
 
     #[inline]
-    fn visit_expr_statement(&mut self, stmt: &'ast Statement, expr: &'ast ExprStatement) {
-        walk_expr_statement(self, stmt, expr)
+    fn visit_expr_statement(&mut self, info: &'ast StmtInfo, expr: &'ast ExprStatement) {
+        walk_expr_statement(self, info, expr)
     }
 
     #[inline]
@@ -374,7 +374,7 @@ fn walk_expression<'a, V: AstVisitor<'a>>(vis: &mut V, expr: &'a Expression) {
 #[inline]
 fn walk_statement<'a, V: AstVisitor<'a>>(vis: &mut V, stmt: &'a Statement) {
     match stmt.kind {
-        StmtKind::Expr(ref expr) => vis.visit_expr_statement(stmt, expr),
+        StmtKind::Expr(ref expr) => vis.visit_expr_statement(&stmt.info, expr),
         StmtKind::If(ref ifst) => vis.visit_if_statement(&stmt.info, ifst),
         StmtKind::Stmts(ref v) => vis.visit_statement_list(v),
     }
@@ -390,17 +390,13 @@ fn walk_statement_list<'a, V: AstVisitor<'a>>(vis: &mut V, stmts: &'a Vec<Statem
 #[inline]
 fn walk_expr_statement<'a, V: AstVisitor<'a>>(
     vis: &mut V,
-    stmt: &'a Statement,
+    _: &'a StmtInfo,
     expr: &'a ExprStatement,
 ) {
     vis.visit_expression(expr.expr())
 }
 
-fn walk_if_statement<'a, V: AstVisitor<'a>>(
-    vis: &mut V,
-    info: &'a StmtInfo,
-    ifst: &'a IfStatement,
-) {
+fn walk_if_statement<'a, V: AstVisitor<'a>>(vis: &mut V, _: &'a StmtInfo, ifst: &'a IfStatement) {
     vis.visit_expression(ifst.condition());
     if let Some(ctrl) = ifst.then_controlled() {
         vis.visit_statement(ctrl);