dict splatterns first draft

src/compiler.rs

@@ -55,6 +55,8 @@ pub enum Op {
     ConcatDict,
     LoadDictValue,
     MatchDict,
+    MatchSplattedDict,
+    DropDictEntry,
     PushBox,
     GetKey,
     PanicNoWhen,
@@ -179,6 +181,8 @@ impl std::fmt::Display for Op {
             ConcatDict => "concat_dict",
             LoadDictValue => "load_dict_value",
             MatchDict => "match_dict",
+            MatchSplattedDict => "match_splatted_dict",
+            DropDictEntry => "drop_dict_entry",
             PushBox => "push_box",
             GetKey => "get_key",
             PanicNoWhen => "panic_no_when",
@@ -269,9 +273,9 @@ impl Chunk {
                 *i += 1;
             }
             PushBinding | MatchTuple | MatchSplattedTuple | LoadSplattedTuple | MatchList
-            | MatchSplattedList | LoadSplattedList | MatchDict | LoadDictValue | PushTuple
-            | PushBox | MatchDepth | PopN | StoreAt | Call | SetUpvalue | GetUpvalue | Partial
-            | MatchString | PushStringMatches => {
+            | MatchSplattedList | LoadSplattedList | MatchDict | MatchSplattedDict
+            | DropDictEntry | LoadDictValue | PushTuple | PushBox | MatchDepth | PopN | StoreAt
+            | Call | SetUpvalue | GetUpvalue | Partial | MatchString | PushStringMatches => {
                 let next = self.bytecode[*i + 1];
                 println!("{i:04}: {:16} {next:03}", op.to_string());
                 *i += 1;
@@ -853,13 +857,28 @@ impl<'a> Compiler<'a> {
                 // then, match against all the values
                 // then push the dict itself as last value
                 // and then emit an opcode and constant/keyword to OMIT that key from the dict
+                let mut is_splatted = false;
+                if let Some((Splattern(_), _)) = pairs.last() {
+                    is_splatted = true;
+                    self.emit_op(Op::MatchSplattedDict);
+                } else {
                     self.emit_op(Op::MatchDict);
+                }
                 self.emit_byte(pairs.len());
                 let before_load_dict_idx = self.stub_jump(Op::JumpIfNoMatch);
 
                 let mut jump_idxes = vec![];
-                let dict_stack_pos = self.stack_depth - 1;
-                for pair in pairs {
+                let dict_stack_pos = self.stack_depth - self.match_depth - 1;
+                let mut splattern = None;
+                let mut pairs_len = pairs.len();
+                if is_splatted {
+                    splattern = pairs.last();
+                    pairs_len -= 1;
+                }
+
+                let mut match_depth = self.match_depth;
+                self.match_depth = 0;
+                for pair in pairs.iter().take(pairs_len) {
                     let (PairPattern(key, pattern), _) = pair else {
                         unreachable!()
                     };
@@ -869,6 +888,28 @@ impl<'a> Compiler<'a> {
                     self.visit(pattern);
                     jump_idxes.push(self.stub_jump(Op::JumpIfNoMatch));
                 }
+
+                if is_splatted {
+                    // pull the dict out of the stack
+                    // drop every value in the pattern
+                    self.emit_op(Op::PushBinding);
+                    self.emit_byte(dict_stack_pos);
+
+                    for pair in pairs.iter().take(pairs_len) {
+                        let (PairPattern(key, _), _) = pair else {
+                            unreachable!()
+                        };
+                        self.emit_constant(Value::Keyword(key));
+                        self.emit_op(Op::DropDictEntry);
+                    }
+
+                    if let Some(splatt) = splattern {
+                        self.visit(splatt);
+                    }
+                }
+
+                self.match_depth = match_depth + pairs.len();
+
                 let jump_idx = self.stub_jump(Op::Jump);
 
                 for idx in jump_idxes {

src/main.rs

@@ -75,8 +75,8 @@ pub fn run(src: &'static str) {
 pub fn main() {
     env::set_var("RUST_BACKTRACE", "1");
     let src = "
-let (...y) = (1, 2, 3, 4, 5)    
-y
+let (#{a, ...}, d, (e)) = (#{:a 1, :b 2}, :foo, (:bar))
+(a, d, e)
 ";
     run(src);
 }

src/vm.rs

@@ -594,6 +594,27 @@ impl Vm {
                     };
                     self.ip += 2;
                 }
+                MatchSplattedDict => {
+                    let idx = self.stack.len() - self.match_depth as usize - 1;
+                    let patt_len = self.chunk().bytecode[self.ip + 1];
+                    let scrutinee = self.stack[idx].clone();
+                    match scrutinee {
+                        Value::Dict(members) => self.matches = members.len() >= patt_len as usize,
+                        _ => self.matches = false,
+                    }
+                    self.ip += 2;
+                }
+                DropDictEntry => {
+                    let Value::Keyword(key_to_drop) = self.pop() else {
+                        unreachable!()
+                    };
+                    let Value::Dict(mut dict) = self.pop() else {
+                        unreachable!()
+                    };
+                    dict.remove(key_to_drop);
+                    self.push(Value::Dict(dict));
+                    self.ip += 1;
+                }
                 PushBox => {
                     let val = self.pop();
                     self.push(Value::Box(Rc::new(RefCell::new(val))));