conlang: Add constructor expression for structs!

grammar:
- Add new rules `PathLike`, `Structor`, `Fielder`
- Replace Path with PathLike in Primary expressions

cl-ast:
- Add nodes for Structor and Fielder

cl-parser:
- Add branch to path-expression parsing
- Parse Structor bodies

interpret:
- Add TODO

compiler/cl-ast/src/ast.rs

@@ -350,6 +350,8 @@ pub enum ExprKind {
     Unary(Unary),
     /// An Array [Index] expression: a[10, 20, 30]
     Index(Index),
+    /// A [Struct creation](Structor) expression: [Path] `{` ([Fielder] `,`)* [Fielder]? `}`
+    Structor(Structor),
     /// A [path expression](Path): `::`? [PathPart] (`::` [PathPart])*
     Path(Path),
     /// A [Literal]: 0x42, 1e123, 2.4, "Hello"
@@ -466,6 +468,20 @@ pub struct Index {
     pub indices: Vec<Expr>,
 }
 
+/// A [Struct creation](Structor) expression: [Path] `{` ([Fielder] `,`)* [Fielder]? `}`
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Structor {
+    pub to: Path,
+    pub init: Vec<Fielder>,
+}
+
+/// A [Struct field initializer] expression: [Identifier] (`=` [Expr])?
+#[derive(Clone, Debug, PartialEq, Eq, Hash)]
+pub struct Fielder {
+    pub name: Identifier,
+    pub init: Option<Box<Expr>>,
+}
+
 /// An [Array] literal: `[` [`Expr`] (`,` [`Expr`])\* `]`
 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
 pub struct Array {

compiler/cl-ast/src/ast_impl.rs

@@ -424,6 +424,7 @@ mod display {
                 ExprKind::Binary(v) => v.fmt(f),
                 ExprKind::Unary(v) => v.fmt(f),
                 ExprKind::Index(v) => v.fmt(f),
+                ExprKind::Structor(v) => v.fmt(f),
                 ExprKind::Path(v) => v.fmt(f),
                 ExprKind::Literal(v) => v.fmt(f),
                 ExprKind::Array(v) => v.fmt(f),
@@ -540,6 +541,25 @@ mod display {
         }
     }
 
+    impl Display for Structor {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            let Self { to, init } = self;
+            write!(f, "{to}: ")?;
+            separate(init, ", ")(f.delimit(INLINE_BRACES))
+        }
+    }
+
+    impl Display for Fielder {
+        fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            let Self { name, init } = self;
+            write!(f, "{name}")?;
+            if let Some(init) = init {
+                write!(f, ": {init}")?;
+            }
+            Ok(())
+        }
+    }
+
     impl Display for Array {
         fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
             separate(&self.values, ", ")(f.delimit(INLINE_SQUARE))

compiler/cl-ast/src/ast_visitor/fold.rs

@@ -269,6 +269,22 @@ pub trait Fold {
             indices: indices.into_iter().map(|e| self.fold_expr(e)).collect(),
         }
     }
+
+    fn fold_structor(&mut self, s: Structor) -> Structor {
+        let Structor { to, init } = s;
+        Structor {
+            to: self.fold_path(to),
+            init: init.into_iter().map(|f| self.fold_fielder(f)).collect(),
+        }
+    }
+
+    fn fold_fielder(&mut self, f: Fielder) -> Fielder {
+        let Fielder { name, init } = f;
+        Fielder {
+            name: self.fold_identifier(name),
+            init: init.map(|e| Box::new(self.fold_expr(*e))),
+        }
+    }
     fn fold_array(&mut self, a: Array) -> Array {
         let Array { values } = a;
         Array { values: values.into_iter().map(|e| self.fold_expr(e)).collect() }
@@ -499,6 +515,7 @@ pub fn or_fold_expr_kind<F: Fold + ?Sized>(folder: &mut F, kind: ExprKind) -> Ex
         ExprKind::Binary(b) => ExprKind::Binary(folder.fold_binary(b)),
         ExprKind::Unary(u) => ExprKind::Unary(folder.fold_unary(u)),
         ExprKind::Index(i) => ExprKind::Index(folder.fold_index(i)),
+        ExprKind::Structor(s) => ExprKind::Structor(folder.fold_structor(s)),
         ExprKind::Path(p) => ExprKind::Path(folder.fold_path(p)),
         ExprKind::Literal(l) => ExprKind::Literal(folder.fold_literal(l)),
         ExprKind::Array(a) => ExprKind::Array(folder.fold_array(a)),

compiler/cl-ast/src/ast_visitor/visit.rs

@@ -228,6 +228,18 @@ pub trait Visit<'a>: Sized {
         self.visit_expr_kind(head);
         indices.iter().for_each(|e| self.visit_expr(e));
     }
+    fn visit_structor(&mut self, s: &'a Structor) {
+        let Structor { to, init } = s;
+        self.visit_path(to);
+        init.iter().for_each(|e| self.visit_fielder(e))
+    }
+    fn visit_fielder(&mut self, f: &'a Fielder) {
+        let Fielder { name, init } = f;
+        self.visit_identifier(name);
+        if let Some(init) = init {
+            self.visit_expr(init);
+        }
+    }
     fn visit_array(&mut self, a: &'a Array) {
         let Array { values } = a;
         values.iter().for_each(|e| self.visit_expr(e))
@@ -415,6 +427,7 @@ pub fn or_visit_expr_kind<'a, V: Visit<'a>>(visitor: &mut V, e: &'a ExprKind) {
         ExprKind::Binary(b) => visitor.visit_binary(b),
         ExprKind::Unary(u) => visitor.visit_unary(u),
         ExprKind::Index(i) => visitor.visit_index(i),
+        ExprKind::Structor(s) => visitor.visit_structor(s),
         ExprKind::Path(p) => visitor.visit_path(p),
         ExprKind::Literal(l) => visitor.visit_literal(l),
         ExprKind::Array(a) => visitor.visit_array(a),

compiler/cl-interpret/src/interpret.rs

@@ -126,17 +126,18 @@ impl Interpret for Expr {
 impl Interpret for ExprKind {
     fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
         match self {
+            ExprKind::Empty => Ok(ConValue::Empty),
             ExprKind::Assign(v) => v.interpret(env),
             ExprKind::Binary(v) => v.interpret(env),
             ExprKind::Unary(v) => v.interpret(env),
             ExprKind::Index(v) => v.interpret(env),
+            ExprKind::Structor(v) => v.interpret(env),
             ExprKind::Path(v) => v.interpret(env),
             ExprKind::Literal(v) => v.interpret(env),
             ExprKind::Array(v) => v.interpret(env),
             ExprKind::ArrayRep(v) => v.interpret(env),
             ExprKind::AddrOf(v) => v.interpret(env),
             ExprKind::Block(v) => v.interpret(env),
-            ExprKind::Empty => Ok(ConValue::Empty),
             ExprKind::Group(v) => v.interpret(env),
             ExprKind::Tuple(v) => v.interpret(env),
             ExprKind::Loop(v) => v.interpret(env),
@@ -322,6 +323,11 @@ impl Interpret for Index {
         Ok(head)
     }
 }
+impl Interpret for Structor {
+    fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
+        todo!("struct construction in {env}")
+    }
+}
 impl Interpret for Path {
     fn interpret(&self, env: &mut Environment) -> IResult<ConValue> {
         let Self { absolute: _, parts } = self;

compiler/cl-parser/src/error.rs

@@ -91,6 +91,8 @@ pub enum Parsing {
     Unary,
     UnaryKind,
     Index,
+    Structor,
+    Fielder,
     Call,
     Member,
     PathExpr,
@@ -190,6 +192,8 @@ impl Display for Parsing {
             Parsing::Unary => "a unary expression",
             Parsing::UnaryKind => "a unary operator",
             Parsing::Index => "an indexing expression",
+            Parsing::Structor => "a struct constructor expression",
+            Parsing::Fielder => "a struct field expression",
             Parsing::Call => "a call expression",
             Parsing::Member => "a member access expression",
             Parsing::PathExpr => "a path",

compiler/cl-parser/src/parser.rs

@@ -820,7 +820,7 @@ impl<'t> Parser<'t> {
         // Prefix expressions
         let mut head = match self.peek_kind(Parsing::Unary)? {
             literal_like!() => self.literal()?.into(),
-            path_like!() => self.path()?.into(),
+            path_like!() => self.exprkind_pathlike()?,
             TokenKind::Punct(Punct::Amp | Punct::AmpAmp) => self.addrof()?.into(),
             TokenKind::Punct(Punct::LCurly) => self.block()?.into(),
             TokenKind::Punct(Punct::LBrack) => self.exprkind_arraylike()?,
@@ -912,6 +912,38 @@ impl<'t> Parser<'t> {
         Ok(head)
     }
 
+    /// Parses an expression beginning with a [Path] (i.e. [Path] or [Structor])
+    pub fn exprkind_pathlike(&mut self) -> PResult<ExprKind> {
+        let head = self.path()?;
+        Ok(match self.match_op(Punct::Colon, Parsing::PathExpr) {
+            Ok(_) => ExprKind::Structor(self.structor_body(head)?),
+            Err(_) => ExprKind::Path(head),
+        })
+    }
+
+    /// [Structor]Body = `{` ([Fielder] `,`)* [Fielder]? `}`
+    pub fn structor_body(&mut self, to: Path) -> PResult<Structor> {
+        let init = delim(
+            sep(Self::fielder, Punct::Comma, CURLIES.1, Parsing::Structor),
+            CURLIES,
+            Parsing::Structor,
+        )(self)?;
+
+        Ok(Structor { to, init })
+    }
+
+    /// [Fielder] = [Identifier] (`:` [Expr])?
+    pub fn fielder(&mut self) -> PResult<Fielder> {
+        const PARSING: Parsing = Parsing::Fielder;
+        Ok(Fielder {
+            name: self.identifier()?,
+            init: match self.match_op(Punct::Colon, PARSING) {
+                Ok(_) => Some(Box::new(self.expr()?)),
+                Err(_) => None,
+            },
+        })
+    }
+
     /// [Array] = '[' ([Expr] ',')* [Expr]? ']'
     ///
     /// Array and ArrayRef are ambiguous until the second token,

compiler/cl-repl/examples/yaml.rs

@@ -391,6 +391,7 @@ pub mod yamlify {
                 ExprKind::Binary(k) => k.yaml(y),
                 ExprKind::Unary(k) => k.yaml(y),
                 ExprKind::Index(k) => k.yaml(y),
+                ExprKind::Structor(k) => k.yaml(y),
                 ExprKind::Path(k) => k.yaml(y),
                 ExprKind::Literal(k) => k.yaml(y),
                 ExprKind::Array(k) => k.yaml(y),
@@ -461,6 +462,18 @@ pub mod yamlify {
             y.key("Index").pair("head", head).list(indices);
         }
     }
+    impl Yamlify for Structor {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { to, init } = self;
+            y.key("Structor").pair("to", to).list(init);
+        }
+    }
+    impl Yamlify for Fielder {
+        fn yaml(&self, y: &mut Yamler) {
+            let Self { name: Identifier(name), init } = self;
+            y.key("Fielder").pair("name", name).pair("init", init);
+        }
+    }
     impl Yamlify for Array {
         fn yaml(&self, y: &mut Yamler) {
             let Self { values } = self;

grammar.ebnf

@@ -103,12 +103,15 @@ Call        = Index  ('(' Tuple? ')')* ;
 Index       = Primary ('[' Indices ']')* ;
 Indices     = (Expr ',')* Expr? ;
 
-Primary     = Literal | Path  | Array | ArrayRep | AddrOf 
-            | Block   | Group | Loop
-            | If      | While | For   | Break    | Return | Continue;
+Primary     = Literal | PathLike | Array | ArrayRep | AddrOf | Block  | Group
+            | Loop    | If       | While | For      | Break  | Return | Continue;
 
 Literal     = STRING | CHARACTER | FLOAT | INTEGER | Bool ;
 
+PathLike    = Path | Structor ;
+Structor    = Path ':' '{' (Fielder ',')* Fielder? '}' ;
+Fielder     = Identifier ('=' Expr)? ;
+
 Array       = '[' (Expr ',')* Expr? ']' ;
 ArrayRep    = '[' Expr ';' Expr ']' ;