Initialize Aster project with basic structure, including Cargo configuration, lexer, parser, interpreter, and AST definitions. Add a sample script and README documentation. Implement basic error handling and environment management for variable storage.

src/ast/expr.rs

@@ -0,0 +1,84 @@
+use crate::ast::stmt::Stmt;
+
+#[derive(Debug, Clone)]
+pub enum Expr {
+    /// 字面量：number / string / bool / nil
+    Literal(Literal),
+
+    /// 变量引用
+    Variable(String),
+
+    /// 赋值表达式：a = b
+    Assign {
+        name: String,
+        value: Box<Expr>,
+    },
+
+    /// 一元运算：!expr / -expr
+    Unary {
+        op: UnaryOp,
+        right: Box<Expr>,
+    },
+
+    /// 二元运算：a + b
+    Binary {
+        left: Box<Expr>,
+        op: BinaryOp,
+        right: Box<Expr>,
+    },
+
+    /// 逻辑运算：&& ||
+    Logical {
+        left: Box<Expr>,
+        op: LogicalOp,
+        right: Box<Expr>,
+    },
+
+    /// 函数调用
+    Call {
+        callee: Box<Expr>,
+        arguments: Vec<Expr>,
+    },
+
+    /// 匿名函数（为闭包预留）
+    Lambda {
+        params: Vec<String>,
+        body: Vec<Stmt>,
+    },
+}
+
+#[derive(Debug, Clone)]
+pub enum Literal {
+    Number(f64),
+    String(String),
+    Bool(bool),
+    Nil,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum UnaryOp {
+    Negate, // -
+    Not,    // !
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum BinaryOp {
+    Add,
+    Sub,
+    Mul,
+    Div,
+
+    Greater,
+    GreaterEqual,
+    Less,
+    LessEqual,
+
+    Equal,
+    NotEqual,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum LogicalOp {
+    And,
+    Or,
+}

src/ast/mod.rs

@@ -0,0 +1,5 @@
+pub mod expr;
+pub mod stmt;
+
+pub use expr::*;
+pub use stmt::*;

src/ast/stmt.rs

@@ -0,0 +1,39 @@
+use crate::ast::expr::Expr;
+
+#[derive(Debug, Clone)]
+pub enum Stmt {
+    /// let x = expr;
+    Let {
+        name: String,
+        initializer: Expr,
+    },
+
+    /// 表达式语句：expr;
+    ExprStmt(Expr),
+
+    /// 代码块：{ ... }
+    Block(Vec<Stmt>),
+
+    /// if 语句
+    If {
+        condition: Expr,
+        then_branch: Box<Stmt>,
+        else_branch: Option<Box<Stmt>>,
+    },
+
+    /// while 循环
+    While {
+        condition: Expr,
+        body: Box<Stmt>,
+    },
+
+    /// 函数声明
+    Function {
+        name: String,
+        params: Vec<String>,
+        body: Vec<Stmt>,
+    },
+
+    /// return expr?;
+    Return(Option<Expr>),
+}