parser/
stmt.rs

1use crate::try_parse;
2use dynamic::{Dynamic, Type};
3
4use super::{Expr, Parser, Pattern, Span, expr::ExprKind, pattern::PatternKind};
5use anyhow::{Result, anyhow};
6use smol_str::SmolStr;
7
8/// 把 pattern 引入的所有变量绑定生成出来,追加到 `out`。
9/// `access` 是该 pattern 整体对应的访问表达式(如 `__m_scrut` 或 `__m_scrut.field`)。
10fn collect_bindings(pat: &Pattern, access: &Expr, out: &mut Vec<Stmt>, span: Span) {
11    use crate::expr::BinaryOp;
12    let mk_let_ident = |name: SmolStr, value: Expr, span: Span| {
13        let p = Pattern::new(PatternKind::Ident { name, ty: Type::Any }, span);
14        let value_stmt = Stmt::new(StmtKind::Expr(value, true), span);
15        Stmt::new(StmtKind::Let { pat: p, value: Box::new(value_stmt) }, span)
16    };
17    let mk_bin = |left: Expr, op: BinaryOp, right: Expr, span: Span| Expr::new(ExprKind::Binary { left: Box::new(left), op, right: Box::new(right) }, span);
18    let mk_idx_int = |obj: Expr, i: i32, span: Span| mk_bin(obj, BinaryOp::Idx, Expr::new(ExprKind::Value(Dynamic::I32(i)), span), span);
19    let mk_field = |obj: Expr, name: SmolStr, span: Span| mk_bin(obj, BinaryOp::Idx, Expr::new(ExprKind::Value(Dynamic::String(name)), span), span);
20
21    match &pat.kind {
22        PatternKind::Ident { name, .. } => {
23            out.push(mk_let_ident(name.clone(), access.clone(), span));
24        }
25        PatternKind::Tuple(items) => {
26            for (i, p) in items.iter().enumerate() {
27                let elem = mk_idx_int(access.clone(), i as i32, span);
28                collect_bindings(p, &elem, out, span);
29            }
30        }
31        PatternKind::List { elems, has_rest } => {
32            let prefix = if *has_rest { elems.len() - 1 } else { elems.len() };
33            for (i, p) in elems.iter().take(prefix).enumerate() {
34                let elem = mk_idx_int(access.clone(), i as i32, span);
35                collect_bindings(p, &elem, out, span);
36            }
37            if *has_rest {
38                if let PatternKind::Ident { name, .. } = &elems.last().unwrap().kind {
39                    // 切片: access[prefix..];用 `ExprKind::Range` 而不是 `Binary{RangeOpen}`,
40                    // 与 parser 产物一致,这样下游 type infer / 优化都走同一条路径。
41                    let from = Expr::new(ExprKind::Value((prefix as u32).into()), span);
42                    let range = Expr::new(ExprKind::Range { start: Box::new(from), stop: Box::new(Expr::new(ExprKind::Value(Dynamic::Null), span)), inclusive: false }, span);
43                    let slice = Expr::new(ExprKind::Binary { left: Box::new(access.clone()), op: BinaryOp::Idx, right: Box::new(range) }, span);
44                    out.push(mk_let_ident(name.clone(), slice, span));
45                }
46            }
47        }
48        PatternKind::Struct { fields, .. } => {
49            for (fname, sub) in fields {
50                let field_access = mk_field(access.clone(), fname.clone(), span);
51                match sub {
52                    None => {
53                        // 简写 `field` —— 绑定同名变量
54                        out.push(mk_let_ident(fname.clone(), field_access, span));
55                    }
56                    Some(sub_pat) => {
57                        collect_bindings(sub_pat, &field_access, out, span);
58                    }
59                }
60            }
61        }
62        // 其它(Wildcard / Literal / Var / Member / Idx)在 match 上下文中不产生绑定
63        _ => {}
64    }
65}
66
67#[derive(Debug, Clone)]
68pub struct Stmt {
69    pub kind: StmtKind,
70    pub span: Span,
71}
72
73#[derive(Debug, Clone)]
74pub enum StmtKind {
75    Let { pat: Pattern, value: Box<Stmt> },
76    Expr(Expr, bool),
77    Block(Vec<Stmt>),
78    Break,
79    Continue,
80    Return(Option<Expr>),
81    While { cond: Expr, body: Box<Stmt> },
82    Loop(Box<Stmt>),
83    For { pat: Pattern, range: Expr, body: Box<Stmt> },
84    Fn { name: SmolStr, generic_params: Vec<Type>, args: Vec<(SmolStr, Type)>, body: Box<Stmt>, is_pub: bool },
85    Struct { name: SmolStr, def: Type, is_pub: bool },
86    Impl { target: Type, body: Box<Stmt> },
87    If { cond: Expr, then_body: Box<Stmt>, else_body: Option<Box<Stmt>> },
88    Static { name: SmolStr, ty: Type, value: Option<Expr>, is_pub: bool },
89    Const { name: SmolStr, ty: Type, value: Expr, is_pub: bool },
90}
91
92impl Stmt {
93    pub fn new(kind: StmtKind, span: Span) -> Self {
94        Self { kind, span }
95    }
96
97    pub fn expr(&self) -> Option<Expr> {
98        if let StmtKind::Expr(expr, _) = &self.kind { Some(expr.clone()) } else { None }
99    }
100
101    pub fn is_return(&self) -> bool {
102        matches!(self.kind, StmtKind::Return(_))
103    }
104
105    pub fn last_return(&mut self) -> bool {
106        match &mut self.kind {
107            StmtKind::Block(stmts) => stmts.last_mut().map(|stmt| stmt.last_return()).unwrap_or(false),
108            StmtKind::If { then_body, else_body, .. } => {
109                let then_returns = then_body.last_return();
110                let else_returns = else_body.as_mut().map(|body| body.last_return()).unwrap_or(false);
111                then_returns && else_returns
112            }
113            StmtKind::Expr(e, close) => {
114                if !*close {
115                    let span = e.span;
116                    *self = Self::new(StmtKind::Return(Some(std::mem::take(e))), span);
117                    true
118                } else {
119                    false
120                }
121            }
122            StmtKind::Return(_) => true,
123            _ => false,
124        }
125    }
126
127    pub fn get_type(&self) -> Option<Type> {
128        match &self.kind {
129            StmtKind::Expr(expr, _) => Some(expr.get_type()),
130            StmtKind::Block(stmts) => stmts.last().and_then(|stmt| stmt.get_type()),
131            StmtKind::If { then_body, .. } => then_body.get_type(),
132            _ => None,
133        }
134    }
135
136    fn get_assign(idx: u32, expr: Expr) -> Self {
137        let span = expr.span;
138        Self::new(StmtKind::Expr(Expr::new(ExprKind::Binary { left: Box::new(Expr::new(ExprKind::Var(idx), span)), op: crate::BinaryOp::Assign, right: Box::new(expr) }, span), true), span)
139    }
140
141    fn get_idx_assign(pat: Expr, idx: usize, expr: Expr) -> Self {
142        let span = pat.span.merge(expr.span);
143        let right = Expr::new(ExprKind::Binary { left: Box::new(expr), op: crate::BinaryOp::Idx, right: Box::new(Expr::new(ExprKind::Value((idx as u32).into()), span)) }, span);
144        Self::new(StmtKind::Expr(Expr::new(ExprKind::Binary { left: Box::new(pat), op: crate::BinaryOp::Assign, right: Box::new(right) }, span), true), span)
145    }
146
147    /// 与 `get_idx_assign` 类似,但把右侧索引读取包成 `Typed { value, ty }`。
148    /// 解构生成的 `arr[i]` / `arr.pop()` 默认返回 `Any`(指向 Dynamic 的指针),
149    /// 不加类型标注的话元素槽会被声明成 Any,后续读取拿到的是裸指针而不是值。
150    /// 这里按模式里推导出的元素类型 `ty` 包一层 `Typed`,让 JIT 走 Any→ty 的转换。
151    fn get_idx_assign_typed(pat: Expr, idx: usize, expr: Expr, ty: Type) -> Self {
152        let span = pat.span.merge(expr.span);
153        let idx_expr = Expr::new(ExprKind::Binary { left: Box::new(expr), op: crate::BinaryOp::Idx, right: Box::new(Expr::new(ExprKind::Value((idx as u32).into()), span)) }, span);
154        let right = Expr::new(ExprKind::Typed { value: Box::new(idx_expr), ty }, span);
155        Self::new(StmtKind::Expr(Expr::new(ExprKind::Binary { left: Box::new(pat), op: crate::BinaryOp::Assign, right: Box::new(right) }, span), true), span)
156    }
157
158    fn get_assign_expr(pat: Expr, expr: Expr) -> Self {
159        let span = pat.span.merge(expr.span);
160        Self::new(StmtKind::Expr(Expr::new(ExprKind::Binary { left: Box::new(pat), op: crate::BinaryOp::Assign, right: Box::new(expr) }, span), true), span)
161    }
162
163    fn get_pop_assign(pat: Expr, expr: Expr) -> Self {
164        let span = pat.span.merge(expr.span);
165        let pop_name = Expr::new(ExprKind::Value(Dynamic::from("pop")), span);
166        let pop_method = Expr::new(ExprKind::Binary { left: Box::new(expr), op: crate::BinaryOp::Idx, right: Box::new(pop_name) }, span);
167        let pop_call = Expr::new(ExprKind::Call { obj: Box::new(pop_method), params: Vec::new() }, span);
168        Self::get_assign_expr(pat, pop_call)
169    }
170
171    /// 与 `get_pop_assign` 类似,但把 `expr.pop()` 的结果包成 `Typed { value, ty }`,
172    /// 避免解构元素槽被声明成 Any(裸指针)。见 `get_idx_assign_typed` 的说明。
173    fn get_pop_assign_typed(pat: Expr, expr: Expr, ty: Type) -> Self {
174        let span = pat.span.merge(expr.span);
175        let pop_name = Expr::new(ExprKind::Value(Dynamic::from("pop")), span);
176        let pop_method = Expr::new(ExprKind::Binary { left: Box::new(expr), op: crate::BinaryOp::Idx, right: Box::new(pop_name) }, span);
177        let pop_call = Expr::new(ExprKind::Call { obj: Box::new(pop_method), params: Vec::new() }, span);
178        let right = Expr::new(ExprKind::Typed { value: Box::new(pop_call), ty }, span);
179        Self::get_assign_expr(pat, right)
180    }
181
182    fn var_expr_with_ty(pat: &Pattern) -> Option<(Expr, Type)> {
183        if let PatternKind::Var { idx, ty } = &pat.kind
184            && !ty.is_any()
185        {
186            Some((Expr::new(ExprKind::Var(*idx), pat.span), ty.clone()))
187        } else {
188            None
189        }
190    }
191
192    pub fn bind_pattern(&mut self, pat: Pattern) -> Result<()> {
193        if let Some(expr) = self.expr() {
194            let stmt = match pat.kind {
195                PatternKind::Var { idx, ty } => {
196                    if expr.get_type() != ty {
197                        Self::get_assign(idx, Expr::new(ExprKind::Typed { value: Box::new(expr), ty }, pat.span))
198                    } else {
199                        Self::get_assign(idx, expr)
200                    }
201                }
202                PatternKind::Tuple(list) => {
203                    // `let (x, y) = expr` 消费 expr:按 rev 顺序逐个 `expr.pop()`,
204                    // pop 后 expr 不可再用。这里只是把 pop 结果按子模式的元素类型
205                    // 包成 `Typed`,避免元素槽退化为 Any(裸指针)—— 这是原 value bug
206                    // 的修复,pop 消费语义不变。
207                    let mut stmts = Vec::new();
208                    for p in list.into_iter().rev() {
209                        match Self::var_expr_with_ty(&p) {
210                            Some((p, ty)) => stmts.push(Self::get_pop_assign_typed(p, expr.clone(), ty)),
211                            None => match p.expr() {
212                                Ok(p) => stmts.push(Self::get_pop_assign(p, expr.clone())),
213                                Err(e) => return Err(e),
214                            },
215                        }
216                    }
217                    Self::new(StmtKind::Block(stmts), self.span)
218                }
219                PatternKind::List { elems, has_rest } => {
220                    let mut stmts = Vec::new();
221                    let prefix_count = if has_rest { elems.len() - 1 } else { elems.len() };
222                    if has_rest {
223                        for (idx, p) in elems.iter().take(prefix_count).enumerate() {
224                            match Self::var_expr_with_ty(p) {
225                                Some((p, ty)) => stmts.push(Self::get_idx_assign_typed(p, idx, expr.clone(), ty)),
226                                None => match p.expr() {
227                                    Ok(p) => stmts.push(Self::get_idx_assign(p, idx, expr.clone())),
228                                    Err(e) => return Err(e),
229                                },
230                            }
231                        }
232                    } else {
233                        // 同 Tuple:无 rest 的 `let [x, y] = expr` 也消费 expr,走 pop。
234                        for p in elems.iter().rev() {
235                            match Self::var_expr_with_ty(p) {
236                                Some((p, ty)) => stmts.push(Self::get_pop_assign_typed(p, expr.clone(), ty)),
237                                None => match p.expr() {
238                                    Ok(p) => stmts.push(Self::get_pop_assign(p, expr.clone())),
239                                    Err(e) => return Err(e),
240                                },
241                            }
242                        }
243                    }
244                    if has_rest {
245                        // 最后一个元素是 `..rest`,把它绑定为 expr[prefix_count..] 的切片。
246                        let rest_pat = elems.last().unwrap();
247                        let rest_expr = match &rest_pat.kind {
248                            PatternKind::Ident { name, .. } => Expr::new(ExprKind::Ident(name.clone()), rest_pat.span),
249                            PatternKind::Var { idx, .. } => Expr::new(ExprKind::Var(*idx), rest_pat.span),
250                            _ => return Err(anyhow!("..rest 后的模式必须是标识符")),
251                        };
252                        let from = Expr::new(ExprKind::Value((prefix_count as u32).into()), rest_pat.span);
253                        // 用 `ExprKind::Range` 与 parser 产物对齐,确保下游 type infer 走切片分支。
254                        let range = Expr::new(ExprKind::Range { start: Box::new(from), stop: Box::new(Expr::new(ExprKind::Value(Dynamic::Null), rest_pat.span)), inclusive: false }, rest_pat.span);
255                        let slice_idx = Expr::new(ExprKind::Binary { left: Box::new(expr.clone()), op: crate::BinaryOp::Idx, right: Box::new(range) }, rest_pat.span);
256                        stmts.push(Self::get_assign_expr(rest_expr, slice_idx));
257                    }
258                    Self::new(StmtKind::Block(stmts), self.span)
259                }
260                p => return Err(anyhow!("不支持的模式绑定: {:?}", p)),
261            };
262            let _ = std::mem::replace(self, stmt);
263        } else {
264            match &mut self.kind {
265                StmtKind::Block(stmts) => {
266                    if let Some(stmt) = stmts.last_mut() {
267                        stmt.bind_pattern(pat)?;
268                    }
269                }
270                StmtKind::If { then_body, else_body, .. } => {
271                    then_body.bind_pattern(pat.clone())?;
272                    if let Some(e) = else_body {
273                        e.bind_pattern(pat)?;
274                    }
275                }
276                _ => {}
277            }
278        }
279        Ok(())
280    }
281}
282
283use std::fmt;
284impl fmt::Display for Stmt {
285    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
286        match &self.kind {
287            StmtKind::Let { pat, value } => writeln!(f, "let {:?} = {}", pat, value)?,
288            StmtKind::Block(stmts) => stmts.iter().for_each(|s| {
289                let _ = write!(f, "{}", s);
290            }),
291            StmtKind::Expr(expr, close) => writeln!(f, "{:?}[{}]", expr, close)?,
292            StmtKind::Break => writeln!(f, "break")?,
293            StmtKind::Continue => writeln!(f, "continue")?,
294            StmtKind::Return(r) => writeln!(f, "return {:?}", r)?,
295            StmtKind::While { cond, body } => write!(f, "while {:?}\n{}", cond, body)?,
296            StmtKind::Loop(body) => write!(f, "loop\n{}", body)?,
297            StmtKind::For { pat, range, body } => writeln!(f, "for {:?} in {:?} \n{}", pat, range, body)?,
298            StmtKind::If { cond, then_body, else_body } => {
299                write!(f, "if {:?}\nthen-> {}\n", cond, then_body)?;
300                if let Some(e) = else_body {
301                    writeln!(f, "{}", e)?;
302                }
303            }
304            StmtKind::Fn { name, generic_params, args, body, is_pub } => {
305                let generic_suffix = if generic_params.is_empty() { String::new() } else { format!("<{:?}>", generic_params) };
306                if *is_pub {
307                    write!(f, "pub fn {:?}{} {:?}\n", name, generic_suffix, args)?
308                } else {
309                    write!(f, "fn {:?}{} {:?}\n", name, generic_suffix, args)?
310                }
311                write!(f, "{}", body)?;
312            }
313            _ => write!(f, "(todo display: {:?})", self.kind)?,
314        }
315        fmt::Result::Ok(())
316    }
317}
318
319impl Parser {
320    pub fn ident_typed(&mut self) -> Result<(SmolStr, Type)> {
321        let name = self.ident()?;
322        self.whitespace()?;
323        if self.take(b':').is_ok() { Ok((name, self.get_type()?)) } else { Ok((name, Type::Any)) }
324    }
325
326    pub fn ident_generic(&mut self) -> Result<(SmolStr, Vec<Type>)> {
327        self.whitespace()?;
328        let name = self.ident()?;
329        self.whitespace()?;
330        let params = if self.get()? == b'<' {
331            self.pos += 1;
332            crate::parse_list!(self, Vec::new(), b'>', b',', self.get_type_param()?)
333        } else {
334            Vec::new()
335        };
336        Ok((name, params))
337    }
338
339    pub fn block(&mut self) -> Result<Stmt> {
340        self.check_fatal()?;
341        self.whitespace()?;
342        let start = self.current_pos();
343        if self.get()? == b'{' {
344            self.pos += 1;
345            self.enter_depth()?;
346            self.push_decl_scope();
347            let result = (|| -> Result<Stmt> {
348                let body = crate::parse_list!(self, Vec::new(), b'}', 0, self.stmt(false)?);
349                Ok(Stmt::new(StmtKind::Block(body), self.span_from(start)))
350            })();
351            self.pop_decl_scope();
352            self.exit_depth();
353            result
354        } else {
355            Err(anyhow!("not code block"))
356        }
357    }
358
359    pub fn if_block(&mut self) -> Result<Stmt> {
360        let start = self.spans.last().copied().unwrap_or_else(|| self.current_pos());
361        let cond = self.get_expr_without_struct_literal()?;
362        let then_body = Box::new(self.block()?);
363        self.whitespace()?;
364        let else_body = if self.keyword("else").is_ok() {
365            self.whitespace()?;
366            let body = if self.keyword("if").is_ok() { self.if_block()? } else { self.block()? };
367            Some(Box::new(body))
368        } else {
369            None
370        };
371        Ok(Stmt::new(StmtKind::If { cond, then_body, else_body }, Span::new(start, self.current_pos())))
372    }
373
374    /// 解析 `match scrut { pat ("|" pat)* ("if" guard)? => body ","? ... }`,
375    /// desugar 成 `Block + Let + If 链 + 临时变量`,返回顶层 `Block`(再由
376    /// 调用方用 `ExprKind::Stmt` 包成表达式)。
377    pub fn match_block(&mut self, start: usize) -> Result<Stmt> {
378        use crate::expr::{BinaryOp, ExprKind, UnaryOp};
379        use crate::pattern::{Pattern, PatternKind};
380
381        // ---- 一、解析阶段 ----
382        let scrut = self.get_expr_without_struct_literal()?;
383        self.whitespace()?;
384        self.take(b'{').map_err(|_| anyhow!("match 缺少 `{{`"))?;
385
386        // 每个 arm 是 (pats: Vec<Pattern>, guard: Option<Expr>, body: Expr)
387        let mut arms: Vec<(Vec<Pattern>, Option<Expr>, Expr)> = Vec::new();
388        loop {
389            self.whitespace()?;
390            if self.take(b'}').is_ok() {
391                break;
392            }
393            self.push_decl_scope();
394            let arm_res: Result<(Vec<Pattern>, Option<Expr>, Expr)> = (|| {
395                // 一组 pattern(用 `|` 分隔,or-pattern)
396                let mut pats = vec![self.pattern()?];
397                self.whitespace()?;
398                while matches!(self.get(), Ok(b'|')) && !matches!(self.ahead(), Ok(b'|')) {
399                    self.pos += 1;
400                    self.whitespace()?;
401                    pats.push(self.pattern()?);
402                    self.whitespace()?;
403                }
404                // 声明 pattern 引入的变量(对每个 alt 都声明,允许重名 → 由
405                // declare_symbol_in_current_scope 容错;这里我们只用第一个 alt 的 binding)
406                for pat in &pats[..1] {
407                    self.declare_pattern_symbols(pat)?;
408                }
409                // 校验 or-pattern:第二及之后必须是 Literal(MVP 限制)
410                if pats.len() > 1 {
411                    for p in &pats[1..] {
412                        if !matches!(p.kind, PatternKind::Literal(_) | PatternKind::Wildcard) {
413                            return Err(anyhow!("or-pattern 中除第一个外只支持字面量 / 通配模式 (MVP 限制)"));
414                        }
415                    }
416                }
417                // 可选 guard
418                self.whitespace()?;
419                let guard = if self.keyword("if").is_ok() {
420                    self.whitespace()?;
421                    Some(self.get_expr_no_assign()?)
422                } else {
423                    None
424                };
425                // `=>`
426                self.whitespace()?;
427                self.just("=>").map_err(|_| anyhow!("match arm 缺少 `=>`"))?;
428                self.whitespace()?;
429                // 体
430                let body_start = self.current_pos();
431                let body = if self.get()? == b'{' {
432                    let block_stmt = self.block()?;
433                    Expr::new(ExprKind::Stmt(Box::new(block_stmt)), Span::new(body_start, self.current_pos()))
434                } else {
435                    // body 也用 no_assign 防止 `=> body, ...` 中 `,` 后或下一 arm
436                    // 的 `=>` 被错误吞入(同时仍允许 +-*/ 等正常二元)。
437                    self.get_expr_no_assign()?
438                };
439                // 容忍尾随逗号
440                self.whitespace()?;
441                let _ = self.take(b',');
442                Ok((pats, guard, body))
443            })();
444            self.pop_decl_scope();
445            arms.push(arm_res?);
446        }
447        let span = Span::new(start, self.current_pos());
448
449        // ---- 二、声明 match 顶层临时变量 ----
450        // 为避免嵌套 match 重名,加 counter 后缀(简单递增,parser 本地状态)
451        let suffix = self.match_counter;
452        self.match_counter += 1;
453        let scrut_name: SmolStr = format!("__m_scrut_{}", suffix).into();
454        let done_name: SmolStr = format!("__m_done_{}", suffix).into();
455        let out_name: SmolStr = format!("__m_out_{}", suffix).into();
456        self.declare_symbol_in_current_scope(&scrut_name)?;
457        self.declare_symbol_in_current_scope(&done_name)?;
458        self.declare_symbol_in_current_scope(&out_name)?;
459
460        // ---- 三、构建顶层 Block ----
461        let mk_ident = |name: &SmolStr, span: Span| Expr::new(ExprKind::Ident(name.clone()), span);
462        let mk_value = |v: Dynamic, span: Span| Expr::new(ExprKind::Value(v), span);
463        let mk_binary = |left: Expr, op: BinaryOp, right: Expr, span: Span| Expr::new(ExprKind::Binary { left: Box::new(left), op, right: Box::new(right) }, span);
464        let mk_let = |name: SmolStr, value: Expr, span: Span| {
465            let pat = Pattern::new(PatternKind::Ident { name, ty: Type::Any }, span);
466            let value_stmt = Stmt::new(StmtKind::Expr(value, true), span);
467            Stmt::new(StmtKind::Let { pat, value: Box::new(value_stmt) }, span)
468        };
469        let mk_assign_stmt = |name: &SmolStr, value: Expr, span: Span| {
470            let assign = mk_binary(mk_ident(name, span), BinaryOp::Assign, value, span);
471            Stmt::new(StmtKind::Expr(assign, true), span)
472        };
473        let mk_any = |value: Expr, span: Span| Expr::new(ExprKind::Typed { value: Box::new(value), ty: Type::Any }, span);
474
475        let mut stmts = Vec::new();
476        // let __m_scrut = SCRUT;
477        stmts.push(mk_let(scrut_name.clone(), scrut, span));
478        // let __m_done = false;
479        stmts.push(mk_let(done_name.clone(), mk_value(Dynamic::Bool(false), span), span));
480        // let __m_out = null;
481        stmts.push(mk_let(out_name.clone(), mk_value(Dynamic::Null, span), span));
482
483        // 每个 arm 一个 if(顺序构造)
484        for (pats, guard, body) in arms {
485            let arm_span = body.span;
486            let scrut_ident = mk_ident(&scrut_name, arm_span);
487            // test = pat[0].test || pat[1].test || ...
488            let mut test_chain = pats[0].match_test(&scrut_ident);
489            for p in &pats[1..] {
490                let t = p.match_test(&scrut_ident);
491                test_chain = mk_binary(test_chain, BinaryOp::Or, t, arm_span);
492            }
493            // !__m_done && (test_chain)
494            let not_done = Expr::new(ExprKind::Unary { op: UnaryOp::Not, value: Box::new(mk_ident(&done_name, arm_span)) }, arm_span);
495            let outer_cond = mk_binary(not_done, BinaryOp::And, test_chain, arm_span);
496
497            // arm body block:bind + guard + assign + done
498            let mut body_stmts = Vec::new();
499            collect_bindings(&pats[0], &mk_ident(&scrut_name, arm_span), &mut body_stmts, arm_span);
500            // 内层 body:__m_out = BODY; __m_done = true;
501            let inner_stmts = vec![mk_assign_stmt(&out_name, mk_any(body, arm_span), arm_span), mk_assign_stmt(&done_name, mk_value(Dynamic::Bool(true), arm_span), arm_span)];
502            let inner_block = Stmt::new(StmtKind::Block(inner_stmts), arm_span);
503            // 如果有 guard,再裹一层 if;否则直接展开
504            if let Some(g) = guard {
505                body_stmts.push(Stmt::new(StmtKind::If { cond: g, then_body: Box::new(inner_block), else_body: None }, arm_span));
506            } else {
507                body_stmts.push(inner_block);
508            }
509            let then_body = Stmt::new(StmtKind::Block(body_stmts), arm_span);
510            stmts.push(Stmt::new(StmtKind::If { cond: outer_cond, then_body: Box::new(then_body), else_body: None }, arm_span));
511        }
512        // 末尾求值:__m_out
513        stmts.push(Stmt::new(StmtKind::Expr(mk_any(mk_ident(&out_name, span), span), false), span));
514
515        Ok(Stmt::new(StmtKind::Block(stmts), span))
516    }
517
518    pub fn stmt(&mut self, is_pub: bool) -> Result<Stmt> {
519        self.check_fatal()?;
520        self.whitespace()?;
521        self.spans.push(self.pos);
522        let start = self.current_pos();
523        // 函数体内不允许 fn / struct / impl / const / static 顶层声明。
524        // 编译器对这些位置直接 panic，这里前置到 parser，让错误落到用户可见的地方。
525        if self.fn_body_depth > 0 {
526            for kw in &["fn", "struct", "impl", "const", "static"] {
527                if self.keyword(kw).is_ok() {
528                    return Err(anyhow!("函数体内不能定义 {}；请移到顶层或改用闭包", kw));
529                }
530            }
531        }
532        // impl body 允许 fn(方法)和 pub fn,但拒绝嵌套 struct / impl / const / static。
533        if self.impl_body_depth > 0 {
534            for kw in &["struct", "impl", "const", "static"] {
535                if self.keyword(kw).is_ok() {
536                    return Err(anyhow!("impl 体内不能定义 {}；请移到顶层", kw));
537                }
538            }
539        }
540        let stmt = if self.keyword("let").is_ok() {
541            let pat = self.pattern()?;
542            self.declare_pattern_symbols(&pat)?;
543            self.until(b'=')?;
544            self.whitespace()?;
545            let value = if self.get()? == b'{' {
546                if self.looks_like_dict() {
547                    self.get_expr()?
548                } else {
549                    // 块作为表达式:{ stmts; expr } 的值是最后一条语句的值。
550                    let span = self.current_pos();
551                    let block_stmt = self.block()?;
552                    Expr::new(ExprKind::Stmt(Box::new(block_stmt)), Span::new(span, self.current_pos()))
553                }
554            } else {
555                self.get_expr()?
556            };
557            self.whitespace()?;
558            let close = self.take(b';').is_ok();
559            let stmt = Stmt::new(StmtKind::Expr(value, close), Span::new(start, self.current_pos()));
560            Stmt::new(StmtKind::Let { pat, value: Box::new(stmt) }, Span::new(start, self.current_pos()))
561        } else if self.keyword("break").is_ok() {
562            self.until(b';')?;
563            Stmt::new(StmtKind::Break, Span::new(start, self.current_pos()))
564        } else if self.keyword("continue").is_ok() {
565            self.until(b';')?;
566            Stmt::new(StmtKind::Continue, Span::new(start, self.current_pos()))
567        } else if self.keyword("return").is_ok() {
568            self.whitespace()?;
569            let expr = if matches!(self.get(), Ok(b';' | b'}')) { None } else { Some(self.get_expr()?) };
570            self.whitespace()?;
571            if self.take(b';').is_err() && !matches!(self.get(), Ok(b'}')) {
572                self.until(b';')?;
573            }
574            Stmt::new(StmtKind::Return(expr), Span::new(start, self.current_pos()))
575        } else if self.keyword("if").is_ok() {
576            self.if_block()?
577        } else if self.keyword("loop").is_ok() {
578            Stmt::new(StmtKind::Loop(Box::new(self.block()?)), Span::new(start, self.current_pos()))
579        } else if self.keyword("while").is_ok() {
580            self.whitespace()?;
581            let cond = self.get_expr()?;
582            let body = Box::new(self.block()?);
583            Stmt::new(StmtKind::While { cond, body }, Span::new(start, self.current_pos()))
584        } else if self.keyword("for").is_ok() {
585            self.whitespace()?;
586            let pat = self.pattern()?;
587            self.whitespace()?;
588            self.keyword("in")?;
589            self.whitespace()?;
590            let range = self.get_expr()?;
591            self.push_decl_scope();
592            let result: Result<Stmt> = (|| {
593                self.declare_pattern_symbols(&pat)?;
594                let body = Box::new(self.block()?);
595                Ok(Stmt::new(StmtKind::For { pat, range, body }, Span::new(start, self.current_pos())))
596            })();
597            self.pop_decl_scope();
598            result?
599        } else if self.keyword("fn").is_ok() {
600            self.whitespace()?;
601            let (name, generic_params) = self.ident_generic()?;
602            self.declare_function_name(&name)?;
603            self.until(b'(')?;
604            let args = crate::parse_list!(self, Vec::new(), b')', b',', self.ident_typed()?);
605            let body = Box::new(self.function_body(&args)?);
606            Stmt::new(StmtKind::Fn { name, generic_params, args, body, is_pub }, Span::new(start, self.current_pos()))
607        } else if self.keyword("struct").is_ok() {
608            let (name, params) = self.ident_generic()?;
609            self.declare_symbol(&name)?;
610            if self.until(b'{').is_ok() {
611                let fields = crate::parse_list!(self, Vec::new(), b'}', b',', self.ident_typed()?);
612                if let Some(f) = fields.iter().find(|f| f.1.is_any()) {
613                    return Err(anyhow!("字段 {} 的类型未知", f.0));
614                }
615                Stmt::new(StmtKind::Struct { name, def: Type::Struct { params, fields }, is_pub }, Span::new(start, self.current_pos()))
616            } else {
617                self.until(b';')?;
618                Stmt::new(StmtKind::Struct { name, def: Type::Struct { params, fields: Vec::new() }, is_pub }, Span::new(start, self.current_pos()))
619            }
620        } else if self.keyword("const").is_ok() {
621            self.whitespace()?;
622            let (name, ty) = self.ident_typed()?;
623            self.declare_symbol(&name)?;
624            self.until(b'=')?;
625            let value = self.get_expr()?;
626            self.until(b';')?;
627            Stmt::new(StmtKind::Const { name, ty, value, is_pub }, Span::new(start, self.current_pos()))
628        } else if self.keyword("static").is_ok() {
629            self.whitespace()?;
630            let (name, ty) = self.ident_typed()?;
631            self.declare_symbol(&name)?;
632            self.whitespace()?;
633            if self.take(b'=').is_ok() {
634                let expr = self.get_expr()?;
635                self.until(b';')?;
636                Stmt::new(StmtKind::Static { name, ty, value: Some(expr), is_pub }, Span::new(start, self.current_pos()))
637            } else {
638                self.until(b';')?;
639                Stmt::new(StmtKind::Static { name, ty, value: None, is_pub }, Span::new(start, self.current_pos()))
640            }
641        } else if self.keyword("impl").is_ok() {
642            self.whitespace()?;
643            let target = self.get_type()?;
644            Stmt::new(StmtKind::Impl { target, body: Box::new(self.impl_body()?) }, Span::new(start, self.current_pos()))
645        } else if self.keyword("pub").is_ok() {
646            self.stmt(true)?
647        } else {
648            let expr = if self.get()? == b'{' {
649                if self.looks_like_empty_dict() {
650                    self.dict()?
651                } else if let Ok(block) = try_parse!(self, self.block()) {
652                    let _ = self.spans.pop();
653                    return Ok(block);
654                } else if let Ok(dict) = try_parse!(self, self.dict()) {
655                    dict
656                } else {
657                    let block = self.block()?;
658                    let _ = self.spans.pop();
659                    return Ok(block);
660                }
661            } else {
662                self.get_expr()?
663            };
664            self.whitespace()?;
665            if self.is_eof() {
666                Stmt::new(StmtKind::Expr(expr, false), Span::new(start, self.current_pos()))
667            } else if self.get()? == b';' {
668                self.pos += 1;
669                Stmt::new(StmtKind::Expr(expr, true), Span::new(start, self.current_pos()))
670            } else if self.get()? == b'}' {
671                Stmt::new(StmtKind::Expr(expr, false), Span::new(start, self.current_pos()))
672            } else {
673                return Err(anyhow!("未结束的表达式"));
674            }
675        };
676        let _ = self.spans.pop();
677        Ok(stmt)
678    }
679}
parser/stmt.rs

parser/
stmt.rs
