refactor SyntaxKind::Pattern (#831)

5 files changed, 95 insertions, 86 deletions

diff --git a/src/eval/mod.rs b/src/eval/mod.rs
index 68d8148f..b8220112 100644
--- a/src/eval/mod.rs
+++ b/src/eval/mod.rs
@@ -1179,16 +1179,16 @@ impl Eval for ast::Closure {
 impl ast::Pattern {
     // Destruct the given value into the pattern.
     pub fn define(&self, vm: &mut Vm, value: Value) -> SourceResult<Value> {
-        match self.kind() {
-            ast::PatternKind::Ident(ident) => {
-                vm.define(ident, value);
+        match self {
+            ast::Pattern::Ident(ident) => {
+                vm.define(ident.clone(), value);
                 Ok(Value::None)
             }
-            ast::PatternKind::Destructure(pattern) => {
+            ast::Pattern::Destructuring(destruct) => {
                 match value {
                     Value::Array(value) => {
                         let mut i = 0;
-                        for p in &pattern {
+                        for p in destruct.bindings() {
                             match p {
                                 ast::DestructuringKind::Ident(ident) => {
                                     let Ok(v) = value.at(i) else {
@@ -1198,7 +1198,7 @@ impl ast::Pattern {
                                     i += 1;
                                 }
                                 ast::DestructuringKind::Sink(ident) => {
-                                    (1 + value.len() as usize).checked_sub(pattern.len()).and_then(|sink_size| {
+                                    (1 + value.len() as usize).checked_sub(destruct.bindings().count()).and_then(|sink_size| {
                                         let Ok(sink) = value.slice(i, Some(i + sink_size as i64)) else {
                                             return None;
                                         };
@@ -1224,10 +1224,10 @@ impl ast::Pattern {
                     Value::Dict(value) => {
                         let mut sink = None;
                         let mut used = HashSet::new();
-                        for p in &pattern {
+                        for p in destruct.bindings() {
                             match p {
                                 ast::DestructuringKind::Ident(ident) => {
-                                    let Ok(v) = value.at(ident) else {
+                                    let Ok(v) = value.at(&ident) else {
                                         bail!(ident.span(), "destructuring key not found in dictionary");
                                     };
                                     vm.define(ident.clone(), v.clone());
@@ -1237,7 +1237,7 @@ impl ast::Pattern {
                                     sink = ident.clone()
                                 }
                                 ast::DestructuringKind::Named(key, ident) => {
-                                    let Ok(v) = value.at(key) else {
+                                    let Ok(v) = value.at(&key) else {
                                         bail!(ident.span(), "destructuring key not found in dictionary");
                                     };
                                     vm.define(ident.clone(), v.clone());
@@ -1451,8 +1451,8 @@ impl Eval for ast::ForLoop {
         let iter = self.iter().eval(vm)?;
         let pattern = self.pattern();
 
-        match (pattern.kind(), iter.clone()) {
-            (ast::PatternKind::Ident(_), Value::Str(string)) => {
+        match (&pattern, iter.clone()) {
+            (ast::Pattern::Ident(_), Value::Str(string)) => {
                 // Iterate over graphemes of string.
                 iter!(for pattern in string.as_str().graphemes(true));
             }
@@ -1464,7 +1464,7 @@ impl Eval for ast::ForLoop {
                 // Iterate over values of array.
                 iter!(for pattern in array);
             }
-            (ast::PatternKind::Ident(_), _) => {
+            (ast::Pattern::Ident(_), _) => {
                 bail!(self.iter().span(), "cannot loop over {}", iter.type_name());
             }
             (_, _) => {
diff --git a/src/ide/highlight.rs b/src/ide/highlight.rs
index 9180aaee..259d34c3 100644
--- a/src/ide/highlight.rs
+++ b/src/ide/highlight.rs
@@ -239,14 +239,13 @@ pub fn highlight(node: &LinkedNode) -> Option<Tag> {
         SyntaxKind::Conditional => None,
         SyntaxKind::WhileLoop => None,
         SyntaxKind::ForLoop => None,
-        SyntaxKind::ForPattern => None,
         SyntaxKind::ModuleImport => None,
         SyntaxKind::ImportItems => None,
         SyntaxKind::ModuleInclude => None,
         SyntaxKind::LoopBreak => None,
         SyntaxKind::LoopContinue => None,
         SyntaxKind::FuncReturn => None,
-        SyntaxKind::Pattern => None,
+        SyntaxKind::Destructuring => None,
 
         SyntaxKind::LineComment => Some(Tag::Comment),
         SyntaxKind::BlockComment => Some(Tag::Comment),
diff --git a/src/syntax/ast.rs b/src/syntax/ast.rs
index e492297a..3c01bdff 100644
--- a/src/syntax/ast.rs
+++ b/src/syntax/ast.rs
@@ -1533,10 +1533,7 @@ impl Closure {
     ///
     /// This only exists if you use the function syntax sugar: `let f(x) = y`.
     pub fn name(&self) -> Option<Ident> {
-        match self.0.cast_first_match::<Pattern>()?.kind() {
-            PatternKind::Ident(ident) => Some(ident),
-            _ => Option::None,
-        }
+        self.0.children().next()?.cast()
     }
 
     /// The parameter bindings.
@@ -1594,16 +1591,7 @@ impl AstNode for Param {
 
 node! {
     /// A destructuring pattern: `x` or `(x, _, ..y)`.
-    Pattern
-}
-
-/// The kind of a pattern.
-#[derive(Debug, Clone, Hash)]
-pub enum PatternKind {
-    /// A single identifier: `x`.
-    Ident(Ident),
-    /// A destructuring pattern: `(x, _, ..y)`.
-    Destructure(Vec<DestructuringKind>),
+    Destructuring
 }
 
 /// The kind of an element in a destructuring pattern.
@@ -1617,64 +1605,82 @@ pub enum DestructuringKind {
     Named(Ident, Ident),
 }
 
-impl Pattern {
-    /// The kind of the pattern.
-    pub fn kind(&self) -> PatternKind {
-        if self
-            .0
-            .children()
-            .map(SyntaxNode::kind)
-            .skip_while(|&kind| kind == SyntaxKind::LeftParen)
-            .take_while(|&kind| kind != SyntaxKind::RightParen)
-            .eq([SyntaxKind::Ident])
-        {
-            return PatternKind::Ident(self.0.cast_first_match().unwrap_or_default());
-        }
-
-        let mut bindings = Vec::new();
-        for child in self.0.children() {
-            match child.kind() {
-                SyntaxKind::Ident => {
-                    bindings
-                        .push(DestructuringKind::Ident(child.cast().unwrap_or_default()));
-                }
-                SyntaxKind::Spread => {
-                    bindings.push(DestructuringKind::Sink(child.cast_first_match()));
-                }
-                SyntaxKind::Named => {
-                    let mut filtered = child.children().filter_map(SyntaxNode::cast);
-                    let key = filtered.next().unwrap_or_default();
-                    let ident = filtered.next().unwrap_or_default();
-                    bindings.push(DestructuringKind::Named(key, ident));
-                }
-                _ => (),
+impl Destructuring {
+    /// The bindings of the destructuring.
+    pub fn bindings(&self) -> impl Iterator<Item = DestructuringKind> + '_ {
+        self.0.children().filter_map(|child| match child.kind() {
+            SyntaxKind::Ident => {
+                Some(DestructuringKind::Ident(child.cast().unwrap_or_default()))
+            }
+            SyntaxKind::Spread => Some(DestructuringKind::Sink(child.cast_first_match())),
+            SyntaxKind::Named => {
+                let mut filtered = child.children().filter_map(SyntaxNode::cast);
+                let key = filtered.next().unwrap_or_default();
+                let ident = filtered.next().unwrap_or_default();
+                Some(DestructuringKind::Named(key, ident))
             }
+            _ => Option::None,
+        })
+    }
+
+    // Returns a list of all identifiers in the pattern.
+    pub fn idents(&self) -> impl Iterator<Item = Ident> + '_ {
+        self.bindings().into_iter().filter_map(|binding| match binding {
+            DestructuringKind::Ident(ident) => Some(ident),
+            DestructuringKind::Sink(ident) => ident,
+            DestructuringKind::Named(_, ident) => Some(ident),
+        })
+    }
+}
+
+/// The kind of a pattern.
+#[derive(Debug, Clone, Hash)]
+pub enum Pattern {
+    /// A single identifier: `x`.
+    Ident(Ident),
+    /// A destructuring pattern: `(x, _, ..y)`.
+    Destructuring(Destructuring),
+}
+
+impl AstNode for Pattern {
+    fn from_untyped(node: &SyntaxNode) -> Option<Self> {
+        match node.kind() {
+            SyntaxKind::Ident => node.cast().map(Self::Ident),
+            SyntaxKind::Destructuring => node.cast().map(Self::Destructuring),
+            _ => Option::None,
         }
+    }
 
-        PatternKind::Destructure(bindings)
+    fn as_untyped(&self) -> &SyntaxNode {
+        match self {
+            Self::Ident(v) => v.as_untyped(),
+            Self::Destructuring(v) => v.as_untyped(),
+        }
     }
+}
 
+impl Pattern {
     // Returns a list of all identifiers in the pattern.
     pub fn idents(&self) -> Vec<Ident> {
-        match self.kind() {
-            PatternKind::Ident(ident) => vec![ident],
-            PatternKind::Destructure(bindings) => bindings
-                .into_iter()
-                .filter_map(|binding| match binding {
-                    DestructuringKind::Ident(ident) => Some(ident),
-                    DestructuringKind::Sink(ident) => ident,
-                    DestructuringKind::Named(_, ident) => Some(ident),
-                })
-                .collect(),
+        match self {
+            Pattern::Ident(ident) => vec![ident.clone()],
+            Pattern::Destructuring(destruct) => destruct.idents().collect(),
         }
     }
 }
 
+impl Default for Pattern {
+    fn default() -> Self {
+        Self::Ident(Ident::default())
+    }
+}
+
 node! {
     /// A let binding: `let x = 1`.
     LetBinding
 }
 
+#[derive(Debug)]
 pub enum LetBindingKind {
     /// A normal binding: `let x = 1`.
     Normal(Pattern),
@@ -1713,7 +1719,12 @@ impl LetBinding {
     /// The expression the binding is initialized with.
     pub fn init(&self) -> Option<Expr> {
         match self.kind() {
-            LetBindingKind::Normal(_) => self.0.cast_last_match(),
+            LetBindingKind::Normal(Pattern::Ident(_)) => {
+                self.0.children().filter_map(SyntaxNode::cast).nth(1)
+            }
+            LetBindingKind::Normal(Pattern::Destructuring(_)) => {
+                self.0.cast_first_match()
+            }
             LetBindingKind::Closure(_) => self.0.cast_first_match(),
         }
     }
@@ -1821,7 +1832,11 @@ impl ForLoop {
 
     /// The expression to iterate over.
     pub fn iter(&self) -> Expr {
-        self.0.cast_first_match().unwrap_or_default()
+        self.0
+            .children()
+            .skip_while(|&c| c.kind() != SyntaxKind::In)
+            .find_map(SyntaxNode::cast)
+            .unwrap_or_default()
     }
 
     /// The expression to evaluate for each iteration.
diff --git a/src/syntax/kind.rs b/src/syntax/kind.rs
index fcde2bb4..d35901b0 100644
--- a/src/syntax/kind.rs
+++ b/src/syntax/kind.rs
@@ -230,8 +230,6 @@ pub enum SyntaxKind {
     WhileLoop,
     /// A for loop: `for x in y { z }`.
     ForLoop,
-    /// A for loop's destructuring pattern: `x` or `x, y`.
-    ForPattern,
     /// A module import: `import a, b, c from "utils.typ"`.
     ModuleImport,
     /// Items to import from a module: `a, b, c`.
@@ -244,8 +242,8 @@ pub enum SyntaxKind {
     LoopContinue,
     /// A return from a function: `return`, `return x + 1`.
     FuncReturn,
-    /// A destructuring pattern: `x`, `(x, _, ..y)`.
-    Pattern,
+    /// A destructuring pattern: `(x, _, ..y)`.
+    Destructuring,
 
     /// A line comment: `// ...`.
     LineComment,
@@ -425,14 +423,13 @@ impl SyntaxKind {
             Self::Conditional => "`if` expression",
             Self::WhileLoop => "while-loop expression",
             Self::ForLoop => "for-loop expression",
-            Self::ForPattern => "for-loop destructuring pattern",
             Self::ModuleImport => "`import` expression",
             Self::ImportItems => "import items",
             Self::ModuleInclude => "`include` expression",
             Self::LoopBreak => "`break` expression",
             Self::LoopContinue => "`continue` expression",
             Self::FuncReturn => "`return` expression",
-            Self::Pattern => "destructuring pattern",
+            Self::Destructuring => "destructuring pattern",
             Self::LineComment => "line comment",
             Self::BlockComment => "block comment",
             Self::Error => "syntax error",
diff --git a/src/syntax/parser.rs b/src/syntax/parser.rs
index 7c05eebc..e6807404 100644
--- a/src/syntax/parser.rs
+++ b/src/syntax/parser.rs
@@ -839,7 +839,7 @@ fn args(p: &mut Parser) {
 }
 
 enum PatternKind {
-    Normal,
+    Ident,
     Destructuring,
 }
 
@@ -849,18 +849,16 @@ fn pattern(p: &mut Parser) -> PatternKind {
     if p.at(SyntaxKind::LeftParen) {
         let kind = collection(p, false);
         validate_destruct_pattern(p, m);
-        p.wrap(m, SyntaxKind::Pattern);
 
         if kind == SyntaxKind::Parenthesized {
-            PatternKind::Normal
+            PatternKind::Ident
         } else {
+            p.wrap(m, SyntaxKind::Destructuring);
             PatternKind::Destructuring
         }
     } else {
-        if p.expect(SyntaxKind::Ident) {
-            p.wrap(m, SyntaxKind::Pattern);
-        }
-        PatternKind::Normal
+        p.expect(SyntaxKind::Ident);
+        PatternKind::Ident
     }
 }
 
@@ -872,7 +870,7 @@ fn let_binding(p: &mut Parser) {
     let mut closure = false;
     let mut destructuring = false;
     match pattern(p) {
-        PatternKind::Normal => {
+        PatternKind::Ident => {
             closure = p.directly_at(SyntaxKind::LeftParen);
             if closure {
                 let m3 = p.marker();