iter 22b.2.1: add Constraint struct, Type::Forall.constraints

crates/ailang-codegen/src/lib.rs

@@ -1845,7 +1845,7 @@ impl<'a> Emitter<'a> {
                 ))
             })?;
         let (forall_vars, params, ret) = match &fdef.ty {
-            Type::Forall { vars, body } => match body.as_ref() {
+            Type::Forall { vars, constraints: _, body } => match body.as_ref() {
                 Type::Fn { params, ret, .. } => {
                     (vars.clone(), params.clone(), (**ret).clone())
                 }
@@ -2434,7 +2434,7 @@ impl<'a> Emitter<'a> {
                 let cty = self.synth_with_extras(callee, extras)?;
                 match cty {
                     Type::Fn { ret, .. } => Ok(*ret),
-                    Type::Forall { vars, body } => {
+                    Type::Forall { vars, constraints: _, body } => {
                         let arg_tys: Vec<Type> = args
                             .iter()
                             .map(|a| self.synth_with_extras(a, extras))

crates/ailang-codegen/src/subst.rs

@@ -191,8 +191,9 @@ pub(crate) fn qualify_local_types_codegen(
             param_modes: vec![],
             ret_mode: ParamMode::Implicit,
         },
-        Type::Forall { vars, body } => Type::Forall {
+        Type::Forall { vars, constraints, body } => Type::Forall {
             vars: vars.clone(),
+            constraints: constraints.clone(),
             body: Box::new(qualify_local_types_codegen(body, owner_module, owner_local_types)),
         },
         Type::Var { .. } => t.clone(),
@@ -216,7 +217,7 @@ pub(crate) fn apply_subst_to_type(t: &Type, subst: &BTreeMap<String, Type>) -> T
             param_modes: vec![],
             ret_mode: ParamMode::Implicit,
         },
-        Type::Forall { vars, body } => {
+        Type::Forall { vars, constraints, body } => {
             // Inner forall shadows: don't substitute re-bound names.
             let inner: BTreeMap<String, Type> = subst
                 .iter()
@@ -225,6 +226,7 @@ pub(crate) fn apply_subst_to_type(t: &Type, subst: &BTreeMap<String, Type>) -> T
                 .collect();
             Type::Forall {
                 vars: vars.clone(),
+                constraints: constraints.clone(),
                 body: Box::new(apply_subst_to_type(body, &inner)),
             }
         }

crates/ailang-codegen/src/synth.rs

@@ -83,6 +83,7 @@ pub(crate) fn builtin_ail_type(name: &str) -> Option<Type> {
         // constant i1 1) on those resolved types.
         "==" => Type::Forall {
             vars: vec!["a".into()],
+            constraints: vec![],
             body: Box::new(Type::Fn {
                 params: vec![
                     Type::Var { name: "a".into() },
@@ -105,6 +106,7 @@ pub(crate) fn builtin_ail_type(name: &str) -> Option<Type> {
         // (`forall a. a`). Mirrors the typechecker's `builtins::install`.
         "__unreachable__" => Type::Forall {
             vars: vec!["a".into()],
+            constraints: vec![],
             body: Box::new(Type::Var { name: "a".into() }),
         },
         _ => return None,