conlang: add lang items, remove Empty, and shuffle typeck

compiler/cl-ast/src/ast.rs

@@ -224,7 +224,6 @@ pub struct Ty {
 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
 pub enum TyKind {
     Never,
-    Empty,
     Infer,
     Path(Path),
     Array(TyArray),

compiler/cl-ast/src/ast_impl/display.rs

@@ -165,7 +165,6 @@ impl Display for Function {
         let Self { name, gens, sign: sign @ TyFn { args, rety }, bind, body } = self;
         let types = match args.kind {
             TyKind::Tuple(TyTuple { ref types }) => types.as_slice(),
-            TyKind::Empty => Default::default(),
             _ => {
                 write!(f, "Invalid function signature: {sign}")?;
                 Default::default()
@@ -191,7 +190,9 @@ impl Display for Function {
                 write!(f, "{arg}: {ty}")?;
             }
         }
-        if TyKind::Empty != rety.kind {
+        if let TyKind::Tuple(TyTuple { types }) = &rety.kind
+            && !types.as_slice().is_empty()
+        {
             write!(f, " -> {rety}")?
         }
 
@@ -295,7 +296,6 @@ impl Display for TyKind {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
             TyKind::Never => "!".fmt(f),
-            TyKind::Empty => "()".fmt(f),
             TyKind::Infer => "_".fmt(f),
             TyKind::Path(v) => v.fmt(f),
             TyKind::Array(v) => v.fmt(f),
@@ -349,8 +349,10 @@ impl Display for TyFn {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         let Self { args, rety } = self;
         write!(f, "fn {args}")?;
-        if TyKind::Empty != rety.kind {
-            write!(f, " -> {rety}")?;
+        if let TyKind::Tuple(TyTuple { types }) = &rety.kind
+            && !types.as_slice().is_empty()
+        {
+            write!(f, " -> {rety}")?
         }
         Ok(())
     }

compiler/cl-ast/src/ast_impl/weight_of.rs

@@ -192,7 +192,7 @@ impl WeightOf for Ty {
 impl WeightOf for TyKind {
     fn weight_of(&self) -> usize {
         match self {
-            TyKind::Never | TyKind::Empty | TyKind::Infer => size_of_val(self),
+            TyKind::Never | TyKind::Infer => size_of_val(self),
             TyKind::Path(v) => v.weight_of(),
             TyKind::Array(v) => v.weight_of(),
             TyKind::Slice(v) => v.weight_of(),

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

@@ -531,7 +531,6 @@ pub fn or_fold_use_tree<F: Fold + ?Sized>(folder: &mut F, tree: UseTree) -> UseT
 pub fn or_fold_ty_kind<F: Fold + ?Sized>(folder: &mut F, kind: TyKind) -> TyKind {
     match kind {
         TyKind::Never => TyKind::Never,
-        TyKind::Empty => TyKind::Empty,
         TyKind::Infer => TyKind::Infer,
         TyKind::Path(p) => TyKind::Path(folder.fold_path(p)),
         TyKind::Array(a) => TyKind::Array(folder.fold_ty_array(a)),

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

@@ -369,7 +369,6 @@ impl Walk for TyKind {
     fn children<'a, V: Visit<'a>>(&'a self, v: &mut V) {
         match self {
             TyKind::Never => {}
-            TyKind::Empty => {}
             TyKind::Infer => {}
             TyKind::Path(value) => value.visit_in(v),
             TyKind::Array(value) => value.visit_in(v),