function unification...

nac3core/src/typecheck/test_typedef.rs

@@ -8,14 +8,12 @@ mod test {
     struct TestEnvironment {
         pub unifier: Unifier,
         type_mapping: HashMap<String, Type>,
-        var_max_id: u32,
     }
 
     impl TestEnvironment {
         fn new() -> TestEnvironment {
-            let unifier = Unifier::new();
+            let mut unifier = Unifier::new();
             let mut type_mapping = HashMap::new();
-            let mut var_max_id = 0;
 
             type_mapping.insert(
                 "int".into(),
@@ -41,38 +39,30 @@ mod test {
                     params: HashMap::new(),
                 }),
             );
-            let v0 = unifier.add_ty(TypeEnum::TVar { id: 0 });
+            let (v0, id) = unifier.get_fresh_var();
-            var_max_id += 1;
             type_mapping.insert(
                 "Foo".into(),
                 unifier.add_ty(TypeEnum::TObj {
                     obj_id: 3,
                     fields: [("a".into(), v0)].iter().cloned().collect(),
-                    params: [(0u32, v0)].iter().cloned().collect(),
+                    params: [(id, v0)].iter().cloned().collect(),
                 }),
             );
 
             TestEnvironment {
                 unifier,
                 type_mapping,
-                var_max_id,
             }
         }
 
-        fn get_fresh_var(&mut self) -> Type {
+        fn parse(&mut self, typ: &str, mapping: &Mapping<String>) -> Type {
-            let id = self.var_max_id + 1;
-            self.var_max_id += 1;
-            self.unifier.add_ty(TypeEnum::TVar { id })
-        }
-
-        fn parse(&self, typ: &str, mapping: &Mapping<String>) -> Type {
             let result = self.internal_parse(typ, mapping);
             assert!(result.1.is_empty());
             result.0
         }
 
         fn internal_parse<'a, 'b>(
-            &'a self,
+            &'a mut self,
             typ: &'b str,
             mapping: &Mapping<String>,
         ) -> (Type, &'b str) {
@@ -189,8 +179,8 @@ mod test {
             let mut env = TestEnvironment::new();
             let mut mapping = HashMap::new();
             for i in 1..=variable_count {
-                let v = env.get_fresh_var();
+                let v = env.unifier.get_fresh_var();
-                mapping.insert(format!("v{}", i), v);
+                mapping.insert(format!("v{}", i), v.0);
             }
             // unification may have side effect when we do type resolution, so freeze the types
             // before doing unification.
@@ -259,8 +249,8 @@ mod test {
         let mut env = TestEnvironment::new();
         let mut mapping = HashMap::new();
         for i in 1..=variable_count {
-            let v = env.get_fresh_var();
+            let v = env.unifier.get_fresh_var();
-            mapping.insert(format!("v{}", i), v);
+            mapping.insert(format!("v{}", i), v.0);
         }
         // unification may have side effect when we do type resolution, so freeze the types
         // before doing unification.

nac3core/src/typecheck/typedef.rs

@@ -48,7 +48,7 @@ impl Deref for TypeCell {
 }
 
 pub type Mapping<K, V = Type> = HashMap<K, V>;
-pub type VarMap = Mapping<u32>;
+type VarMap = Mapping<u32>;
 
 #[derive(Clone)]
 pub struct Call {
@@ -65,6 +65,13 @@ pub struct FuncArg {
     is_optional: bool,
 }
 
+#[derive(Clone)]
+pub struct FunSignature {
+    args: Vec<FuncArg>,
+    ret: Type,
+    params: VarMap,
+}
+
 // We use a lot of `Rc`/`RefCell`s here as we want to simplify our code.
 // We may not really need so much `Rc`s, but we would have to do complicated
 // stuffs otherwise.
@@ -96,11 +103,7 @@ pub enum TypeEnum {
     TCall {
         calls: Vec<Rc<Call>>,
     },
-    TFunc {
+    TFunc(FunSignature),
-        args: Vec<FuncArg>,
-        ret: Type,
-        params: VarMap,
-    },
 }
 
 // Order:
@@ -199,40 +202,41 @@ pub struct ObjDef {
 }
 
 pub struct Unifier {
-    unification_table: RefCell<InPlaceUnificationTable<Type>>,
+    unification_table: InPlaceUnificationTable<Type>,
     obj_def_table: Vec<ObjDef>,
+    var_id: u32,
 }
 
 impl Unifier {
     pub fn new() -> Unifier {
         Unifier {
-            unification_table: RefCell::new(InPlaceUnificationTable::new()),
+            unification_table: InPlaceUnificationTable::new(),
             obj_def_table: Vec::new(),
+            var_id: 0,
         }
     }
 
     /// Register a type to the unifier.
     /// Returns a key in the unification_table.
-    pub fn add_ty(&self, a: TypeEnum) -> Type {
+    pub fn add_ty(&mut self, a: TypeEnum) -> Type {
-        self.unification_table
+        self.unification_table.new_key(TypeCell(Rc::new(a.into())))
-            .borrow_mut()
-            .new_key(TypeCell(Rc::new(a.into())))
     }
 
     /// Get the TypeEnum of a type.
-    pub fn get_ty(&self, a: Type) -> Rc<RefCell<TypeEnum>> {
+    pub fn get_ty(&mut self, a: Type) -> Rc<RefCell<TypeEnum>> {
-        let mut table = self.unification_table.borrow_mut();
+        self.unification_table.probe_value(a).0
-        table.probe_value(a).0
     }
 
     /// Unify two types, i.e. a = b.
-    pub fn unify(&self, mut a: Type, mut b: Type) -> Result<(), String> {
+    pub fn unify(&mut self, mut a: Type, mut b: Type) -> Result<(), String> {
         let (mut ty_a_cell, mut ty_b_cell) = {
-            let mut table = self.unification_table.borrow_mut();
+            if self.unification_table.unioned(a, b) {
-            if table.unioned(a, b) {
                 return Ok(());
             }
-            (table.probe_value(a), table.probe_value(b))
+            (
+                self.unification_table.probe_value(a),
+                self.unification_table.probe_value(b),
+            )
         };
 
         let (ty_a, ty_b) = {
@@ -353,7 +357,6 @@ impl Unifier {
                     TypeEnum::TVirtual { ty } => {
                         // not sure if this is correct...
                         self.unify(a, *ty)?;
-                        self.set_a_to_b(a, b);
                     }
                     _ => {
                         return self.incompatible_types(&*ty_a, &*ty_b);
@@ -390,14 +393,105 @@ impl Unifier {
                     return self.incompatible_types(&*ty_a, &*ty_b);
                 }
             }
-            _ => unimplemented!(),
+            TypeEnum::TCall { calls: c1 } => match &*ty_b {
+                TypeEnum::TCall { .. } => {
+                    drop(ty_b);
+                    if let TypeEnum::TCall { calls: c2 } = &mut *ty_b_cell.as_ref().borrow_mut() {
+                        c2.extend(c1.iter().cloned());
+                    } else {
+                        unreachable!()
+                    }
+                    self.set_a_to_b(a, b);
+                }
+                TypeEnum::TFunc(signature) => {
+                    let required: Vec<String> = signature
+                        .args
+                        .iter()
+                        .filter(|v| !v.is_optional)
+                        .map(|v| v.name.clone())
+                        .rev()
+                        .collect();
+                    for c in c1 {
+                        let Call {
+                            posargs,
+                            kwargs,
+                            ret,
+                            fun,
+                        } = c.as_ref();
+                        let instantiated = self.instantiate_fun(b, signature);
+                        let signature;
+                        let r = self.get_ty(instantiated);
+                        let r = r.as_ref().borrow();
+                        if let TypeEnum::TFunc(s) = &*r {
+                            signature = s;
+                        } else {
+                            unreachable!();
+                        }
+                        let mut required = required.clone();
+                        let mut all_names: Vec<_> = signature
+                            .args
+                            .iter()
+                            .map(|v| (v.name.clone(), v.ty))
+                            .rev()
+                            .collect();
+                        for (i, t) in posargs.iter().enumerate() {
+                            if signature.args.len() <= i {
+                                return Err(format!("Too many arguments."));
+                            }
+                            if !required.is_empty() {
+                                required.pop();
+                            }
+                            self.unify(all_names.pop().unwrap().1, *t)?;
+                        }
+                        for (k, t) in kwargs.iter() {
+                            if let Some(i) = required.iter().position(|v| v == k) {
+                                required.remove(i);
+                            }
+                            if let Some(i) = all_names.iter().position(|v| &v.0 == k) {
+                                self.unify(all_names.remove(i).1, *t)?;
+                            } else {
+                                return Err(format!("Unknown keyword argument {}", k));
+                            }
+                        }
+                        self.unify(*ret, signature.ret)?;
+                        *fun.borrow_mut() = Some(instantiated);
+                    }
+                    self.set_a_to_b(a, b);
+                }
+                _ => {
+                    return self.incompatible_types(&*ty_a, &*ty_b);
+                }
+            },
+            TypeEnum::TFunc(sign1) => {
+                if let TypeEnum::TFunc(sign2) = &*ty_b {
+                    if !sign1.params.is_empty() || !sign2.params.is_empty() {
+                        return Err(format!("Polymorphic function pointer is prohibited."));
+                    }
+                    if sign1.args.len() != sign2.args.len() {
+                        return Err(format!("Functions differ in number of parameters."));
+                    }
+                    for (x, y) in sign1.args.iter().zip(sign2.args.iter()) {
+                        if x.name != y.name {
+                            return Err(format!("Functions differ in parameter names."));
+                        }
+                        if x.is_optional != y.is_optional {
+                            return Err(format!("Functions differ in optional parameters."));
+                        }
+                        self.unify(x.ty, y.ty)?;
+                    }
+                    self.unify(sign1.ret, sign2.ret)?;
+                    self.set_a_to_b(a, b);
+                } else {
+                    return self.incompatible_types(&*ty_a, &*ty_b);
+                }
+            }
         }
         Ok(())
     }
 
-    fn set_a_to_b(&self, a: Type, b: Type) {
+    fn set_a_to_b(&mut self, a: Type, b: Type) {
         // unify a and b together, and set the value to b's value.
-        let mut table = self.unification_table.borrow_mut();
+        let table = &mut self.unification_table;
         let ty_b = table.probe_value(b);
         table.union(a, b);
         table.union_value(a, ty_b);
@@ -411,11 +505,11 @@ impl Unifier {
         ))
     }
 
-    fn occur_check(&self, a: Type, b: Type) -> Result<(), String> {
+    fn occur_check(&mut self, a: Type, b: Type) -> Result<(), String> {
-        if self.unification_table.borrow_mut().unioned(a, b) {
+        if self.unification_table.unioned(a, b) {
             return Err("Recursive type is prohibited.".to_owned());
         }
-        let ty = self.unification_table.borrow_mut().probe_value(b);
+        let ty = self.unification_table.probe_value(b);
         let ty = ty.borrow();
 
         match &*ty {
@@ -454,7 +548,7 @@ impl Unifier {
                     self.occur_check(a, *t)?;
                 }
             }
-            TypeEnum::TFunc { args, ret, params } => {
+            TypeEnum::TFunc(FunSignature { args, ret, params }) => {
                 for t in args
                     .iter()
                     .map(|v| &v.ty)
@@ -472,8 +566,8 @@ impl Unifier {
     /// If this returns Some(T), T would be the substituted type.
     /// If this returns None, the result type would be the original type
     /// (no substitution has to be done).
-    pub fn subst(&self, a: Type, mapping: &VarMap) -> Option<Type> {
+    pub fn subst(&mut self, a: Type, mapping: &VarMap) -> Option<Type> {
-        let ty_cell = self.unification_table.borrow_mut().probe_value(a);
+        let ty_cell = self.unification_table.probe_value(a);
         let ty = ty_cell.borrow();
         // this function would only be called when we instantiate functions.
         // function type signature should ONLY contain concrete types and type
@@ -512,10 +606,10 @@ impl Unifier {
                 // parameter list, we don't need to substitute the fields.
                 // This is also used to prevent infinite substitution...
                 let need_subst = params.values().any(|v| {
-                    let ty_cell = self.unification_table.borrow_mut().probe_value(*v);
+                    let ty_cell = self.unification_table.probe_value(*v);
                     let ty = ty_cell.borrow();
                     if let TypeEnum::TVar { id } = &*ty {
-                        mapping.contains_key(id)
+                        mapping.contains_key(&id)
                     } else {
                         false
                     }
@@ -537,7 +631,7 @@ impl Unifier {
                     None
                 }
             }
-            TypeEnum::TFunc { args, ret, params } => {
+            TypeEnum::TFunc(FunSignature { args, ret, params }) => {
                 let new_params = self.subst_map(params, mapping);
                 let new_ret = self.subst(*ret, mapping);
                 let mut new_args = None;
@@ -557,7 +651,7 @@ impl Unifier {
                     let params = new_params.unwrap_or_else(|| params.clone());
                     let ret = new_ret.unwrap_or_else(|| *ret);
                     let args = new_args.unwrap_or_else(|| args.clone());
-                    Some(self.add_ty(TypeEnum::TFunc { params, ret, args }))
+                    Some(self.add_ty(TypeEnum::TFunc(FunSignature { params, ret, args })))
                 } else {
                     None
                 }
@@ -566,7 +660,7 @@ impl Unifier {
         }
     }
 
-    fn subst_map<K>(&self, map: &Mapping<K>, mapping: &VarMap) -> Option<Mapping<K>>
+    fn subst_map<K>(&mut self, map: &Mapping<K>, mapping: &VarMap) -> Option<Mapping<K>>
     where
         K: std::hash::Hash + std::cmp::Eq + std::clone::Clone,
     {
@@ -582,13 +676,43 @@ impl Unifier {
         map2
     }
 
+    /// Instantiate a function if it hasn't been instntiated.
+    /// Returns Some(T) where T is the instantiated type.
+    /// Returns None if the function is already instantiated.
+    fn instantiate_fun(&mut self, ty: Type, fun: &FunSignature) -> Type {
+        let mut instantiated = false;
+        for (k, v) in fun.params.iter() {
+            if let TypeEnum::TVar { id } =
+                &*self.unification_table.probe_value(*v).as_ref().borrow()
+            {
+                if k != id {
+                    instantiated = true;
+                    break;
+                }
+            } else {
+                instantiated = true;
+                break;
+            }
+        }
+        if instantiated {
+            ty
+        } else {
+            let mapping = fun
+                .params
+                .iter()
+                .map(|(k, _)| (*k, self.get_fresh_var().0))
+                .collect();
+            self.subst(ty, &mapping).unwrap_or(ty)
+        }
+    }
+
     /// Check whether two types are equal.
-    pub fn eq(&self, a: Type, b: Type) -> bool {
+    pub fn eq(&mut self, a: Type, b: Type) -> bool {
         if a == b {
             return true;
         }
         let (ty_a, ty_b) = {
-            let mut table = self.unification_table.borrow_mut();
+            let table = &mut self.unification_table;
             if table.unioned(a, b) {
                 return true;
             }
@@ -629,7 +753,7 @@ impl Unifier {
         }
     }
 
-    fn map_eq<K>(&self, map1: &Mapping<K>, map2: &Mapping<K>) -> bool
+    fn map_eq<K>(&mut self, map1: &Mapping<K>, map2: &Mapping<K>) -> bool
     where
         K: std::hash::Hash + std::cmp::Eq + std::clone::Clone,
     {
@@ -643,4 +767,11 @@ impl Unifier {
         }
         true
     }
+
+    /// Get a fresh type variable.
+    pub fn get_fresh_var(&mut self) -> (Type, u32) {
+        let id = self.var_id + 1;
+        self.var_id += 1;
+        (self.add_ty(TypeEnum::TVar { id }), id)
+    }
 }