implement __functor

fix-builtins/src/lib.rs

@@ -244,6 +244,8 @@ pub enum PrimOpPhase {
 
     // TODO: split into separate enums
     CallPattern,
+    CallFunctor1,
+    CallFunctor2,
 
     Illegal,
 }

fix-vm/src/dispatch_tailcall.rs

@@ -271,7 +271,7 @@ table! {
     JumpIfTrue            => op_jump_if_true,
     Jump                  => op_jump,
 
-    CoerceToString                 => op_coerce_to_string,
+    CoerceToString        => op_coerce_to_string,
 
     ConcatStrings         => op_concat_strings,
     ResolvePath           => op_resolve_path,

fix-vm/src/instructions/calls.rs

@@ -85,8 +85,30 @@ impl<'gc> crate::Vm<'gc> {
                 new_app.args[position] = arg;
                 self.push(Value::new_gc(Gc::new(mc, new_app)))
             }
+        } else if let Some(attrs) = func.as_gc::<AttrSet>()
+            && let Some(functor) = attrs.lookup(self.functor_sym)
+        {
+            // f arg  =>  (f.__functor f) arg
+            //
+            // Stage the work for `CallFunctor1` so retries during force are
+            // safe: the stack invariant `[..., orig_arg, self, functor]`
+            // holds every time control re-enters phase 1.
+            self.call_depth -= 1;
+            self.call_stack.push(CallFrame {
+                pc: resume_pc,
+                thunk: None,
+                env: self.env,
+            });
+            self.push(arg);
+            self.push(func.relax());
+            self.push(functor);
+            reader.set_pc(PrimOpPhase::CallFunctor1.ip() as usize);
+            return Step::Continue(());
         } else {
-            todo!("call other types: {func:?}")
+            return self.finish_err(Error::eval_error(format!(
+                "attempt to call something which is not a function but {}",
+                func.ty()
+            )));
         }
         Step::Continue(())
     }

fix-vm/src/lib.rs

@@ -223,6 +223,8 @@ pub struct Vm<'gc> {
 
     #[collect(require_static)]
     result: Option<Result<fix_common::Value>>,
+
+    functor_sym: StringId,
 }
 
 enum OperandData {
@@ -340,6 +342,8 @@ impl<'gc> Vm<'gc> {
             force_mode,
 
             result: None,
+
+            functor_sym: ctx.intern_string("__functor"),
         }
     }
 

fix-vm/src/primops/control.rs

@@ -4,11 +4,12 @@ use gc_arena::{Gc, Mutation, RefLock};
 use smallvec::SmallVec;
 
 use crate::value::*;
-use crate::{BytecodeReader, Step, Vm, VmRuntimeCtx, VmRuntimeCtxExt};
+use crate::{BytecodeReader, NixNum, Step, Vm, VmRuntimeCtx, VmRuntimeCtxExt};
 
 impl<'gc> Vm<'gc> {
     pub(crate) fn primop_seq(
         &mut self,
+        ctx: &mut impl VmRuntimeCtx,
         reader: &mut BytecodeReader<'_>,
         mc: &Mutation<'gc>,
     ) -> Step {
@@ -36,6 +37,7 @@ impl<'gc> Vm<'gc> {
 
     pub(crate) fn primop_deep_seq_force_top(
         &mut self,
+        ctx: &mut impl VmRuntimeCtx,
         reader: &mut BytecodeReader<'_>,
         mc: &Mutation<'gc>,
     ) -> Step {
@@ -84,6 +86,7 @@ impl<'gc> Vm<'gc> {
 
     pub(crate) fn primop_deep_seq_push(
         &mut self,
+        ctx: &mut impl VmRuntimeCtx,
         reader: &mut BytecodeReader<'_>,
         mc: &Mutation<'gc>,
     ) -> Step {
@@ -271,6 +274,43 @@ impl<'gc> Vm<'gc> {
         }
     }
 
+    pub(crate) fn primop_call_functor_1(
+        &mut self,
+        reader: &mut BytecodeReader<'_>,
+        mc: &Mutation<'gc>,
+    ) -> Step {
+        // Stack invariant on every (re-)entry: [..., orig_arg, self, functor]
+        // where `functor` is TOS. Retries during force land back here safely.
+        let functor = self.force_and_retry::<StrictValue>(reader, mc)?;
+        // Stack now: [..., orig_arg, self]
+        let self_val = self.pop();
+        self.push(functor.relax());
+        // Stack: [..., orig_arg, functor]
+        // Call 1: functor(self). Resume into CallFunctor2 once it returns.
+        self.call(
+            reader,
+            mc,
+            self_val,
+            PrimOpPhase::CallFunctor2.ip() as usize,
+        )
+    }
+
+    pub(crate) fn primop_call_functor_2(
+        &mut self,
+        reader: &mut BytecodeReader<'_>,
+        mc: &Mutation<'gc>,
+    ) -> Step {
+        // Stack on entry: [..., orig_arg, intermediate]
+        // call_stack top: synthetic frame with caller's resume_pc.
+        let intermediate = self.pop();
+        let orig_arg = self.pop();
+        let saved = self.call_stack.pop().expect("functor outer frame missing");
+        self.env = saved.env;
+        self.push(intermediate);
+        // Call 2: intermediate(orig_arg). Resume to caller.
+        self.call(reader, mc, orig_arg, saved.pc)
+    }
+
     pub(crate) fn primop_call_pattern(
         &mut self,
         ctx: &mut impl VmRuntimeCtx,

fix-vm/src/primops/list.rs

@@ -3,7 +3,7 @@ use gc_arena::Mutation;
 
 use crate::bytecode_reader::BytecodeReader;
 use crate::value::*;
-use crate::{Step, Vm};
+use crate::{Step, Vm, VmRuntimeCtx};
 
 impl<'gc> Vm<'gc> {
     pub(crate) fn primop_filter_force_list(
@@ -44,6 +44,7 @@ impl<'gc> Vm<'gc> {
 
     pub(crate) fn primop_filter_check(
         &mut self,
+        ctx: &mut impl VmRuntimeCtx,
         reader: &mut BytecodeReader<'_>,
         mc: &Mutation<'gc>,
     ) -> Step {

fix-vm/src/primops/mod.rs

@@ -32,14 +32,14 @@ impl<'gc> Vm<'gc> {
         match phase {
             Abort => self.primop_abort(ctx, reader, mc),
 
-            DeepSeq => self.primop_deep_seq_force_top(reader, mc),
+            DeepSeq => self.primop_deep_seq_force_top(ctx, reader, mc),
-            DeepSeqPush => self.primop_deep_seq_push(reader, mc),
+            DeepSeqPush => self.primop_deep_seq_push(ctx, reader, mc),
             DeepSeqLoop => self.primop_deep_seq_loop(reader, mc),
-            Seq => self.primop_seq(reader, mc),
+            Seq => self.primop_seq(ctx, reader, mc),
 
             FilterForceList => self.primop_filter_force_list(reader, mc),
             FilterCallPred => self.primop_filter_call_pred(reader, mc),
-            FilterCheck => self.primop_filter_check(reader, mc),
+            FilterCheck => self.primop_filter_check(ctx, reader, mc),
 
             ForceResultShallow => self.primop_force_result_shallow(ctx, reader, mc),
             ForceResultShallowPush => self.primop_force_result_shallow_push(ctx, reader, mc),
@@ -47,6 +47,8 @@ impl<'gc> Vm<'gc> {
             ForceResultDeepFinish => self.primop_force_result_deep_finish(ctx, reader, mc),
 
             CallPattern => self.primop_call_pattern(ctx, reader, mc),
+            CallFunctor1 => self.primop_call_functor_1(reader, mc),
+            CallFunctor2 => self.primop_call_functor_2(reader, mc),
 
             phase => todo!("primop phase {phase:?}"),
         }