feat: array unpacking

crates/erg_compiler/error/lower.rs

@@ -1089,6 +1089,36 @@ impl LowerError {
             caused_by,
         )
     }
+
+    pub fn set_homogeneity_error(
+        input: Input,
+        errno: usize,
+        loc: Location,
+        caused_by: String,
+    ) -> Self {
+        LowerError::syntax_error(
+            input,
+            errno,
+            loc,
+            caused_by,
+            switch_lang!(
+                "japanese" => "集合の要素は全て同じ型である必要があります",
+                "simplified_chinese" => "集合元素必须全部是相同类型",
+                "traditional_chinese" => "集合元素必須全部是相同類型",
+                "english" => "all elements of a set must be of the same type",
+            )
+            .to_owned(),
+            Some(
+                switch_lang!(
+                    "japanese" => "Int or Strなど明示的に型を指定してください",
+                    "simplified_chinese" => "明确指定类型，例如: Int or Str",
+                    "traditional_chinese" => "明確指定類型，例如: Int or Str",
+                    "english" => "please specify the type explicitly, e.g. Int or Str",
+                )
+                .to_owned(),
+            ),
+        )
+    }
 }
 
 impl LowerWarning {

crates/erg_compiler/lower.rs

@@ -633,27 +633,11 @@ impl<A: ASTBuildable> GenericASTLowerer<A> {
             let elem = self.lower_expr(elem.expr, expect_elem.as_ref())?;
             union = self.module.context.union(&union, elem.ref_t());
             if ERG_MODE && union.is_union_type() {
-                return Err(LowerErrors::from(LowerError::syntax_error(
+                return Err(LowerErrors::from(LowerError::set_homogeneity_error(
                     self.cfg.input.clone(),
                     line!() as usize,
                     elem.loc(),
-                    String::from(&self.module.context.name[..]),
-                    switch_lang!(
-                        "japanese" => "集合の要素は全て同じ型である必要があります",
-                        "simplified_chinese" => "集合元素必须全部是相同类型",
-                        "traditional_chinese" => "集合元素必須全部是相同類型",
-                        "english" => "all elements of a set must be of the same type",
-                    )
-                    .to_owned(),
-                    Some(
-                        switch_lang!(
-                            "japanese" => "Int or Strなど明示的に型を指定してください",
-                            "simplified_chinese" => "明确指定类型，例如: Int or Str",
-                            "traditional_chinese" => "明確指定類型，例如: Int or Str",
-                            "english" => "please specify the type explicitly, e.g. Int or Str",
-                        )
-                        .to_owned(),
-                    ),
+                    self.module.context.caused_by(),
                 )));
             }
             new_set.push(elem);

crates/erg_parser/ast.rs

@@ -335,7 +335,15 @@ impl NestedDisplay for Args {
     fn fmt_nest(&self, f: &mut std::fmt::Formatter<'_>, level: usize) -> std::fmt::Result {
         fmt_lines(self.pos_args.iter(), f, level)?;
         writeln!(f)?;
-        fmt_lines(self.kw_args.iter(), f, level)
+        if let Some(var) = &self.var_args {
+            writeln!(f, "*{var}")?;
+        }
+        fmt_lines(self.kw_args.iter(), f, level)?;
+        if let Some(var) = &self.kw_var_args {
+            writeln!(f)?;
+            write!(f, "**{var}")?;
+        }
+        Ok(())
     }
 }
 
@@ -4566,11 +4574,16 @@ impl VarSignature {
 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
 pub struct Vars {
     pub(crate) elems: Vec<VarSignature>,
+    pub(crate) starred: Option<Box<VarSignature>>,
 }
 
 impl NestedDisplay for Vars {
     fn fmt_nest(&self, f: &mut fmt::Formatter<'_>, _level: usize) -> fmt::Result {
-        write!(f, "{}", fmt_vec(&self.elems))
+        write!(f, "{}", fmt_vec(&self.elems))?;
+        if let Some(starred) = &self.starred {
+            write!(f, ", *{starred}")?;
+        }
+        Ok(())
     }
 }
 
@@ -4588,12 +4601,15 @@ impl Locational for Vars {
 }
 
 impl Vars {
-    pub const fn new(elems: Vec<VarSignature>) -> Self {
-        Self { elems }
+    pub fn new(elems: Vec<VarSignature>, starred: Option<VarSignature>) -> Self {
+        Self {
+            elems,
+            starred: starred.map(Box::new),
+        }
     }
 
-    pub const fn empty() -> Self {
-        Self::new(vec![])
+    pub fn empty() -> Self {
+        Self::new(vec![], None)
     }
 }
 

crates/erg_parser/convert.rs

@@ -101,7 +101,7 @@ impl Parser {
         match array {
             Array::Normal(arr) => {
                 let mut vars = Vars::empty();
-                for elem in arr.elems.into_iters().0 {
+                for elem in arr.elems.pos_args {
                     let pat = self
                         .convert_rhs_to_sig(elem.expr)
                         .map_err(|_| self.stack_dec(fn_name!()))?;
@@ -117,6 +117,22 @@ impl Parser {
                         }
                     }
                 }
+                if let Some(var) = arr.elems.var_args {
+                    let pat = self
+                        .convert_rhs_to_sig(var.expr)
+                        .map_err(|_| self.stack_dec(fn_name!()))?;
+                    match pat {
+                        Signature::Var(v) => {
+                            vars.starred = Some(Box::new(v));
+                        }
+                        Signature::Subr(subr) => {
+                            let err = ParseError::simple_syntax_error(line!() as usize, subr.loc());
+                            self.errs.push(err);
+                            debug_exit_info!(self);
+                            return Err(());
+                        }
+                    }
+                }
                 let pat = VarArrayPattern::new(arr.l_sqbr, vars, arr.r_sqbr);
                 debug_exit_info!(self);
                 Ok(pat)
@@ -215,7 +231,7 @@ impl Parser {
         let mut vars = Vars::empty();
         match tuple {
             Tuple::Normal(tup) => {
-                let (pos_args, _var_args, _kw_args, _kw_var, paren) = tup.elems.deconstruct();
+                let (pos_args, var_args, _kw_args, _kw_var, paren) = tup.elems.deconstruct();
                 for arg in pos_args {
                     let sig = self
                         .convert_rhs_to_sig(arg.expr)
@@ -233,6 +249,23 @@ impl Parser {
                         }
                     }
                 }
+                if let Some(var_args) = var_args {
+                    let sig = self
+                        .convert_rhs_to_sig(var_args.expr)
+                        .map_err(|_| self.stack_dec(fn_name!()))?;
+                    match sig {
+                        Signature::Var(var) => {
+                            vars.starred = Some(Box::new(var));
+                        }
+                        other => {
+                            let err =
+                                ParseError::simple_syntax_error(line!() as usize, other.loc());
+                            self.errs.push(err);
+                            debug_exit_info!(self);
+                            return Err(());
+                        }
+                    }
+                }
                 let tuple = VarTuplePattern::new(paren, vars);
                 debug_exit_info!(self);
                 Ok(tuple)

crates/erg_parser/desugar.rs

@@ -713,6 +713,10 @@ impl Desugarer {
                     for (n, elem) in tup.elems.iter().enumerate() {
                         self.desugar_nested_var_pattern(new, elem, &buf_name, BufIndex::Tuple(n));
                     }
+                    let elems_len = tup.elems.len();
+                    if let Some(var) = tup.elems.starred.as_ref() {
+                        self.desugar_rest_values(new, var, &buf_name, elems_len);
+                    }
                 }
                 VarPattern::Array(arr) => {
                     let (buf_name, buf_sig) = self.gen_buf_name_and_sig(v.loc(), v.t_spec);
@@ -722,6 +726,10 @@ impl Desugarer {
                     for (n, elem) in arr.elems.iter().enumerate() {
                         self.desugar_nested_var_pattern(new, elem, &buf_name, BufIndex::Array(n));
                     }
+                    let elems_len = arr.elems.len();
+                    if let Some(var) = arr.elems.starred.as_ref() {
+                        self.desugar_rest_values(new, var, &buf_name, elems_len);
+                    }
                 }
                 VarPattern::Record(rec) => {
                     let (buf_name, buf_sig) = self.gen_buf_name_and_sig(v.loc(), v.t_spec);
@@ -961,6 +969,36 @@ impl Desugarer {
         }
     }
 
+    /// `a, *b = aaa` -> `a = aaa[0]; b = aaa[1..MAX]`
+    fn desugar_rest_values(
+        &mut self,
+        new_module: &mut Vec<Expr>,
+        sig: &VarSignature,
+        buf_name: &str,
+        elems_len: usize,
+    ) {
+        let obj = Expr::local(
+            buf_name,
+            sig.ln_begin().unwrap_or(1),
+            sig.col_begin().unwrap_or(0),
+            sig.col_end().unwrap_or(0),
+        );
+        let op = Token::from_str(TokenKind::Assign, "=");
+        let id = DefId(get_hash(&(&obj, buf_name)));
+        let start = Expr::Literal(Literal::nat(elems_len, sig.ln_begin().unwrap_or(1)));
+        // FIXME: infinity
+        let max = 109521666047; // 102*1024*1024*1024-1 but why is this the limit?
+        let end = Expr::Literal(Literal::nat(max, sig.ln_begin().unwrap_or(1)));
+        let range = Token::new_with_loc(TokenKind::Closed, "..", sig.loc());
+        let acc = obj.subscr(
+            start.bin_op(range, end).into(),
+            Token::new_fake(TokenKind::RBrace, "]", 0, 0, 0),
+        );
+        let body = DefBody::new(op, Block::new(vec![Expr::Accessor(acc)]), id);
+        let starred = Def::new(Signature::Var(sig.clone()), body);
+        new_module.push(Expr::Def(starred));
+    }
+
     /// `{x; y}` -> `{x = x; y = y}`
     fn desugar_shortened_record(module: Module) -> Module {
         Self::desugar_all_chunks(module, Self::rec_desugar_shortened_record)

crates/erg_parser/parse.rs

@@ -893,6 +893,15 @@ impl Parser {
                 debug_exit_info!(self);
                 return Ok(ArrayInner::WithLength(elems.remove_pos(0), len));
             }
+            Some(PreStar) => {
+                self.lpop();
+                let rest = self
+                    .try_reduce_expr(false, false, false, false)
+                    .map_err(|_| self.stack_dec(fn_name!()))?;
+                elems.set_var_args(PosArg::new(rest));
+                debug_exit_info!(self);
+                return Ok(ArrayInner::Normal(elems));
+            }
             Some(Inclusion) => {
                 self.lpop();
                 let Expr::Accessor(Accessor::Ident(sym)) = elems.remove_pos(0).expr else {
@@ -981,6 +990,14 @@ impl Parser {
                         Some(RParen | RSqBr | RBrace | Dedent) => {
                             break;
                         }
+                        Some(PreStar) => {
+                            self.lpop();
+                            let rest = self
+                                .try_reduce_expr(false, false, false, false)
+                                .map_err(|_| self.stack_dec(fn_name!()))?;
+                            elems.set_var_args(PosArg::new(rest));
+                            break;
+                        }
                         _ => {}
                     }
                     elems.push_pos(
@@ -2485,6 +2502,7 @@ impl Parser {
                 debug_exit_info!(self);
                 Ok(call_or_acc)
             }
+            // REVIEW: correct?
             Some(t) if t.is(PreStar) || t.is(PreDblStar) => {
                 let kind = t.kind;
                 let _ = self.lpop();

tests/should_ok/star_expr.er

@@ -0,0 +1,3 @@
+[a, *b] = [1, 2, 3]
+assert a == 1
+assert b == [2, 3]

tests/test.rs

@@ -374,6 +374,11 @@ fn exec_slice() -> Result<(), ()> {
     expect_success("tests/should_ok/slice.er", 0)
 }
 
+#[test]
+fn exec_star_expr() -> Result<(), ()> {
+    expect_success("tests/should_ok/star_expr.er", 0)
+}
+
 #[test]
 fn exec_structural_example() -> Result<(), ()> {
     expect_success("examples/structural.er", 0)