feat/schema: add ast and test

schema/azschema.bnf

@@ -16,25 +16,30 @@ name: _name_initial {_name_char};
 !whitespace: ' ' | '\t' | '\n' | '\r';
 !comment: ';' {.} '\n';
 
-<<>>
+<<
+import (
+    "azalea/schema/ast"
+    "azalea/schema/token"
+)
+>>
 Schema: ExprList;
 ExprList
-    : Expr
-    | ExprList Expr
+    : Expr <<ast.NewExprList($0)>>
+    | ExprList Expr <<ast.AppendExpr($0, $1)>>
     ;
 ValList
-    : Val
-    | ValList Val
+    : Val <<ast.NewValList($0)>>
+    | ValList Val <<ast.AppendVal($0, $1)>>
     ;
 Val
-    : string
-    | number
-    | name
-    | Expr
+    : string <<ast.NewStringVal($T0)>>
+    | number <<ast.NewNumberVal($T0)>>
+    | name <<ast.NewNameVal($T0)>>
+    | Expr <<ast.NewExprVal($0)>>
     ;
 Expr
-    : "(" name Val Val ")"
-    | "(" name Val ")"
-    | "(" name ")"
-    | "(" "." ValList ")"
+    : "(" name Val Val ")" <<ast.NewExpr($T1, $2, $3)>>
+    | "(" name Val ")" <<ast.NewExpr($T1, $2, nil)>>
+    | "(" name ")" <<ast.NewExpr($T1, nil, nil)>>
+    | "(" "." ValList ")" <<ast.ListExpr($2)>>
     ;