function unification...
This commit is contained in:
parent
f4121b570d
commit
d67407716c
@ -8,14 +8,12 @@ mod test {
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struct TestEnvironment {
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pub unifier: Unifier,
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type_mapping: HashMap<String, Type>,
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var_max_id: u32,
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}
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impl TestEnvironment {
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fn new() -> TestEnvironment {
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let unifier = Unifier::new();
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let mut unifier = Unifier::new();
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let mut type_mapping = HashMap::new();
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let mut var_max_id = 0;
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type_mapping.insert(
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"int".into(),
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@ -41,38 +39,30 @@ mod test {
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params: HashMap::new(),
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}),
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);
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let v0 = unifier.add_ty(TypeEnum::TVar { id: 0 });
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var_max_id += 1;
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let (v0, id) = unifier.get_fresh_var();
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type_mapping.insert(
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"Foo".into(),
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unifier.add_ty(TypeEnum::TObj {
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obj_id: 3,
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fields: [("a".into(), v0)].iter().cloned().collect(),
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params: [(0u32, v0)].iter().cloned().collect(),
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params: [(id, v0)].iter().cloned().collect(),
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}),
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);
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TestEnvironment {
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unifier,
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type_mapping,
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var_max_id,
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}
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}
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fn get_fresh_var(&mut self) -> Type {
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let id = self.var_max_id + 1;
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self.var_max_id += 1;
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self.unifier.add_ty(TypeEnum::TVar { id })
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}
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fn parse(&self, typ: &str, mapping: &Mapping<String>) -> Type {
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fn parse(&mut self, typ: &str, mapping: &Mapping<String>) -> Type {
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let result = self.internal_parse(typ, mapping);
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assert!(result.1.is_empty());
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result.0
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}
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fn internal_parse<'a, 'b>(
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&'a self,
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&'a mut self,
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typ: &'b str,
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mapping: &Mapping<String>,
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) -> (Type, &'b str) {
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@ -189,8 +179,8 @@ mod test {
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let mut env = TestEnvironment::new();
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let mut mapping = HashMap::new();
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for i in 1..=variable_count {
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let v = env.get_fresh_var();
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mapping.insert(format!("v{}", i), v);
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let v = env.unifier.get_fresh_var();
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mapping.insert(format!("v{}", i), v.0);
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}
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// unification may have side effect when we do type resolution, so freeze the types
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// before doing unification.
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@ -259,8 +249,8 @@ mod test {
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let mut env = TestEnvironment::new();
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let mut mapping = HashMap::new();
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for i in 1..=variable_count {
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let v = env.get_fresh_var();
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mapping.insert(format!("v{}", i), v);
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let v = env.unifier.get_fresh_var();
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mapping.insert(format!("v{}", i), v.0);
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}
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// unification may have side effect when we do type resolution, so freeze the types
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// before doing unification.
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@ -48,7 +48,7 @@ impl Deref for TypeCell {
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}
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pub type Mapping<K, V = Type> = HashMap<K, V>;
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pub type VarMap = Mapping<u32>;
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type VarMap = Mapping<u32>;
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#[derive(Clone)]
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pub struct Call {
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@ -65,6 +65,13 @@ pub struct FuncArg {
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is_optional: bool,
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}
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#[derive(Clone)]
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pub struct FunSignature {
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args: Vec<FuncArg>,
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ret: Type,
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params: VarMap,
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}
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// We use a lot of `Rc`/`RefCell`s here as we want to simplify our code.
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// We may not really need so much `Rc`s, but we would have to do complicated
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// stuffs otherwise.
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@ -96,11 +103,7 @@ pub enum TypeEnum {
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TCall {
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calls: Vec<Rc<Call>>,
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},
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TFunc {
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args: Vec<FuncArg>,
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ret: Type,
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params: VarMap,
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},
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TFunc(FunSignature),
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}
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// Order:
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@ -199,40 +202,41 @@ pub struct ObjDef {
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}
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pub struct Unifier {
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unification_table: RefCell<InPlaceUnificationTable<Type>>,
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unification_table: InPlaceUnificationTable<Type>,
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obj_def_table: Vec<ObjDef>,
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var_id: u32,
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}
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impl Unifier {
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pub fn new() -> Unifier {
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Unifier {
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unification_table: RefCell::new(InPlaceUnificationTable::new()),
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unification_table: InPlaceUnificationTable::new(),
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obj_def_table: Vec::new(),
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var_id: 0,
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}
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}
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/// Register a type to the unifier.
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/// Returns a key in the unification_table.
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pub fn add_ty(&self, a: TypeEnum) -> Type {
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self.unification_table
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.borrow_mut()
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.new_key(TypeCell(Rc::new(a.into())))
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pub fn add_ty(&mut self, a: TypeEnum) -> Type {
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self.unification_table.new_key(TypeCell(Rc::new(a.into())))
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}
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/// Get the TypeEnum of a type.
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pub fn get_ty(&self, a: Type) -> Rc<RefCell<TypeEnum>> {
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let mut table = self.unification_table.borrow_mut();
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table.probe_value(a).0
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pub fn get_ty(&mut self, a: Type) -> Rc<RefCell<TypeEnum>> {
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self.unification_table.probe_value(a).0
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}
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/// Unify two types, i.e. a = b.
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pub fn unify(&self, mut a: Type, mut b: Type) -> Result<(), String> {
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pub fn unify(&mut self, mut a: Type, mut b: Type) -> Result<(), String> {
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let (mut ty_a_cell, mut ty_b_cell) = {
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let mut table = self.unification_table.borrow_mut();
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if table.unioned(a, b) {
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if self.unification_table.unioned(a, b) {
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return Ok(());
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}
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(table.probe_value(a), table.probe_value(b))
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(
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self.unification_table.probe_value(a),
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self.unification_table.probe_value(b),
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)
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};
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let (ty_a, ty_b) = {
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@ -353,7 +357,6 @@ impl Unifier {
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TypeEnum::TVirtual { ty } => {
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// not sure if this is correct...
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self.unify(a, *ty)?;
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self.set_a_to_b(a, b);
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}
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_ => {
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return self.incompatible_types(&*ty_a, &*ty_b);
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@ -390,14 +393,105 @@ impl Unifier {
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return self.incompatible_types(&*ty_a, &*ty_b);
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}
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}
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_ => unimplemented!(),
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TypeEnum::TCall { calls: c1 } => match &*ty_b {
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TypeEnum::TCall { .. } => {
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drop(ty_b);
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if let TypeEnum::TCall { calls: c2 } = &mut *ty_b_cell.as_ref().borrow_mut() {
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c2.extend(c1.iter().cloned());
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} else {
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unreachable!()
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}
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self.set_a_to_b(a, b);
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}
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TypeEnum::TFunc(signature) => {
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let required: Vec<String> = signature
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.args
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.iter()
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.filter(|v| !v.is_optional)
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.map(|v| v.name.clone())
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.rev()
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.collect();
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for c in c1 {
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let Call {
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posargs,
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kwargs,
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ret,
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fun,
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} = c.as_ref();
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let instantiated = self.instantiate_fun(b, signature);
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let signature;
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let r = self.get_ty(instantiated);
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let r = r.as_ref().borrow();
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if let TypeEnum::TFunc(s) = &*r {
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signature = s;
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} else {
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unreachable!();
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}
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let mut required = required.clone();
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let mut all_names: Vec<_> = signature
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.args
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.iter()
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.map(|v| (v.name.clone(), v.ty))
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.rev()
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.collect();
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for (i, t) in posargs.iter().enumerate() {
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if signature.args.len() <= i {
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return Err(format!("Too many arguments."));
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}
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if !required.is_empty() {
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required.pop();
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}
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self.unify(all_names.pop().unwrap().1, *t)?;
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}
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for (k, t) in kwargs.iter() {
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if let Some(i) = required.iter().position(|v| v == k) {
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required.remove(i);
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}
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if let Some(i) = all_names.iter().position(|v| &v.0 == k) {
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self.unify(all_names.remove(i).1, *t)?;
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} else {
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return Err(format!("Unknown keyword argument {}", k));
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}
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}
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self.unify(*ret, signature.ret)?;
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*fun.borrow_mut() = Some(instantiated);
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}
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self.set_a_to_b(a, b);
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}
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_ => {
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return self.incompatible_types(&*ty_a, &*ty_b);
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}
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},
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TypeEnum::TFunc(sign1) => {
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if let TypeEnum::TFunc(sign2) = &*ty_b {
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if !sign1.params.is_empty() || !sign2.params.is_empty() {
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return Err(format!("Polymorphic function pointer is prohibited."));
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}
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if sign1.args.len() != sign2.args.len() {
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return Err(format!("Functions differ in number of parameters."));
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}
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for (x, y) in sign1.args.iter().zip(sign2.args.iter()) {
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if x.name != y.name {
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return Err(format!("Functions differ in parameter names."));
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}
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if x.is_optional != y.is_optional {
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return Err(format!("Functions differ in optional parameters."));
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}
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self.unify(x.ty, y.ty)?;
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}
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self.unify(sign1.ret, sign2.ret)?;
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self.set_a_to_b(a, b);
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} else {
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return self.incompatible_types(&*ty_a, &*ty_b);
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}
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}
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}
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Ok(())
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}
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fn set_a_to_b(&self, a: Type, b: Type) {
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fn set_a_to_b(&mut self, a: Type, b: Type) {
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// unify a and b together, and set the value to b's value.
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let mut table = self.unification_table.borrow_mut();
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let table = &mut self.unification_table;
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let ty_b = table.probe_value(b);
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table.union(a, b);
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table.union_value(a, ty_b);
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@ -411,11 +505,11 @@ impl Unifier {
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))
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}
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fn occur_check(&self, a: Type, b: Type) -> Result<(), String> {
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if self.unification_table.borrow_mut().unioned(a, b) {
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fn occur_check(&mut self, a: Type, b: Type) -> Result<(), String> {
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if self.unification_table.unioned(a, b) {
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return Err("Recursive type is prohibited.".to_owned());
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}
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let ty = self.unification_table.borrow_mut().probe_value(b);
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let ty = self.unification_table.probe_value(b);
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let ty = ty.borrow();
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match &*ty {
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@ -454,7 +548,7 @@ impl Unifier {
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self.occur_check(a, *t)?;
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}
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}
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TypeEnum::TFunc { args, ret, params } => {
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TypeEnum::TFunc(FunSignature { args, ret, params }) => {
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for t in args
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.iter()
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.map(|v| &v.ty)
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@ -472,8 +566,8 @@ impl Unifier {
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/// If this returns Some(T), T would be the substituted type.
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/// If this returns None, the result type would be the original type
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/// (no substitution has to be done).
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pub fn subst(&self, a: Type, mapping: &VarMap) -> Option<Type> {
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let ty_cell = self.unification_table.borrow_mut().probe_value(a);
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pub fn subst(&mut self, a: Type, mapping: &VarMap) -> Option<Type> {
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let ty_cell = self.unification_table.probe_value(a);
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let ty = ty_cell.borrow();
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// this function would only be called when we instantiate functions.
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// function type signature should ONLY contain concrete types and type
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@ -512,10 +606,10 @@ impl Unifier {
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// parameter list, we don't need to substitute the fields.
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// This is also used to prevent infinite substitution...
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let need_subst = params.values().any(|v| {
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let ty_cell = self.unification_table.borrow_mut().probe_value(*v);
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let ty_cell = self.unification_table.probe_value(*v);
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let ty = ty_cell.borrow();
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if let TypeEnum::TVar { id } = &*ty {
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mapping.contains_key(id)
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mapping.contains_key(&id)
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} else {
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false
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}
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@ -537,7 +631,7 @@ impl Unifier {
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None
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}
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}
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TypeEnum::TFunc { args, ret, params } => {
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TypeEnum::TFunc(FunSignature { args, ret, params }) => {
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let new_params = self.subst_map(params, mapping);
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let new_ret = self.subst(*ret, mapping);
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let mut new_args = None;
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@ -557,7 +651,7 @@ impl Unifier {
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let params = new_params.unwrap_or_else(|| params.clone());
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let ret = new_ret.unwrap_or_else(|| *ret);
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let args = new_args.unwrap_or_else(|| args.clone());
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Some(self.add_ty(TypeEnum::TFunc { params, ret, args }))
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Some(self.add_ty(TypeEnum::TFunc(FunSignature { params, ret, args })))
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} else {
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None
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}
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@ -566,7 +660,7 @@ impl Unifier {
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}
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}
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fn subst_map<K>(&self, map: &Mapping<K>, mapping: &VarMap) -> Option<Mapping<K>>
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fn subst_map<K>(&mut self, map: &Mapping<K>, mapping: &VarMap) -> Option<Mapping<K>>
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where
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K: std::hash::Hash + std::cmp::Eq + std::clone::Clone,
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{
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@ -582,13 +676,43 @@ impl Unifier {
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map2
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}
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/// Instantiate a function if it hasn't been instntiated.
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/// Returns Some(T) where T is the instantiated type.
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/// Returns None if the function is already instantiated.
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fn instantiate_fun(&mut self, ty: Type, fun: &FunSignature) -> Type {
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let mut instantiated = false;
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for (k, v) in fun.params.iter() {
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if let TypeEnum::TVar { id } =
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&*self.unification_table.probe_value(*v).as_ref().borrow()
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{
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if k != id {
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instantiated = true;
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break;
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}
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} else {
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instantiated = true;
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break;
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}
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}
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if instantiated {
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ty
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} else {
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let mapping = fun
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.params
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.iter()
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.map(|(k, _)| (*k, self.get_fresh_var().0))
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.collect();
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self.subst(ty, &mapping).unwrap_or(ty)
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}
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}
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/// Check whether two types are equal.
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pub fn eq(&self, a: Type, b: Type) -> bool {
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pub fn eq(&mut self, a: Type, b: Type) -> bool {
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if a == b {
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return true;
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}
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let (ty_a, ty_b) = {
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let mut table = self.unification_table.borrow_mut();
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let table = &mut self.unification_table;
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if table.unioned(a, b) {
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return true;
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}
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@ -629,7 +753,7 @@ impl Unifier {
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}
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}
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fn map_eq<K>(&self, map1: &Mapping<K>, map2: &Mapping<K>) -> bool
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fn map_eq<K>(&mut self, map1: &Mapping<K>, map2: &Mapping<K>) -> bool
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where
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K: std::hash::Hash + std::cmp::Eq + std::clone::Clone,
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{
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@ -643,4 +767,11 @@ impl Unifier {
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}
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true
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}
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/// Get a fresh type variable.
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pub fn get_fresh_var(&mut self) -> (Type, u32) {
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let id = self.var_id + 1;
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self.var_id += 1;
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(self.add_ty(TypeEnum::TVar { id }), id)
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}
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}
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