chore: add ast::VarPattern::Phi

crates/erg_common/triple.rs

@@ -77,6 +77,14 @@ impl<T, E> Triple<T, E> {
         }
     }
 
+    pub fn or_else_triple(self, f: impl FnOnce() -> Triple<T, E>) -> Triple<T, E> {
+        match self {
+            Triple::None => f(),
+            Triple::Ok(ok) => Triple::Ok(ok),
+            Triple::Err(err) => Triple::Err(err),
+        }
+    }
+
     pub fn unwrap_or(self, default: T) -> T {
         match self {
             Triple::None => default,

crates/erg_compiler/context/compare.rs

@@ -445,6 +445,23 @@ impl Context {
                     && var_params_judge
                     && default_check() // contravariant
             }
+            // {Int} <: Obj -> Int
+            (Subr(_) | Quantified(_), Refinement(refine))
+                if rhs.singleton_value().is_some() && self.subtype_of(&refine.t, &ClassType) =>
+            {
+                let Ok(typ) = self.convert_tp_into_type(rhs.singleton_value().unwrap().clone())
+                else {
+                    return false;
+                };
+                let Some(ctx) = self.get_nominal_type_ctx(&typ) else {
+                    return false;
+                };
+                if let Some((_, __call__)) = ctx.get_class_attr("__call__") {
+                    self.supertype_of(lhs, &__call__.t)
+                } else {
+                    false
+                }
+            }
             // ?T(<: Int) :> ?U(:> Nat)
             // ?T(<: Int) :> ?U(:> Int)
             // ?T(<: Nat) !:> ?U(:> Int) (if the upper bound of LHS is smaller than the lower bound of RHS, LHS cannot not be a supertype)

crates/erg_compiler/context/initialize/procs.rs

@@ -60,7 +60,7 @@ impl Context {
         )
         .quantify();
         let t_proc_ret = if PYTHON_MODE { Obj } else { NoneType };
-        let t_for = nd_proc(
+        let t_for = proc(
             vec![
                 kw("iterable", poly("Iterable", vec![ty_tp(T.clone())])),
                 kw(
@@ -69,6 +69,8 @@ impl Context {
                 ),
             ],
             None,
+            vec![kw("else!", nd_proc(vec![], None, t_proc_ret.clone()))],
+            None,
             NoneType,
         )
         .quantify();
@@ -90,12 +92,14 @@ impl Context {
             // not Bool! type because `cond` may be the result of evaluation of a mutable object's method returns Bool.
             nd_proc(vec![], None, Bool)
         };
-        let t_while = nd_proc(
+        let t_while = proc(
             vec![
                 kw("cond!", t_cond),
-                kw("proc!", nd_proc(vec![], None, t_proc_ret)),
+                kw("proc!", nd_proc(vec![], None, t_proc_ret.clone())),
             ],
             None,
+            vec![kw("else!", nd_proc(vec![], None, t_proc_ret.clone()))],
+            None,
             NoneType,
         );
         let P = mono_q("P", subtypeof(mono("PathLike")));

crates/erg_compiler/context/inquire.rs

@@ -750,6 +750,27 @@ impl Context {
         Triple::None
     }
 
+    pub(crate) fn rec_get_param_or_decl_info(&self, name: &str) -> Option<VarInfo> {
+        if let Some(vi) = self
+            .params
+            .iter()
+            .find(|(var_name, _)| var_name.as_ref().is_some_and(|n| n.inspect() == name))
+            .map(|(_, vi)| vi)
+            .or_else(|| self.decls.get(name))
+        {
+            return Some(vi.clone());
+        }
+        for method_ctx in self.methods_list.iter() {
+            if let Some(vi) = method_ctx.rec_get_param_or_decl_info(name) {
+                return Some(vi);
+            }
+        }
+        if let Some(parent) = self.get_outer_scope().or_else(|| self.get_builtins()) {
+            return parent.rec_get_param_or_decl_info(name);
+        }
+        None
+    }
+
     pub(crate) fn get_attr_info(
         &self,
         obj: &hir::Expr,

crates/erg_compiler/context/register.rs

@@ -130,7 +130,7 @@ impl Context {
         let mut errs = TyCheckErrors::empty();
         let muty = Mutability::from(&sig.inspect().unwrap_or(UBAR)[..]);
         let ident = match &sig.pat {
-            ast::VarPattern::Ident(ident) => ident,
+            ast::VarPattern::Ident(ident) | ast::VarPattern::Phi(ident) => ident,
             ast::VarPattern::Discard(_) | ast::VarPattern::Glob(_) => {
                 return Ok(());
             }
@@ -287,7 +287,7 @@ impl Context {
             None
         };
         let ident = match &sig.pat {
-            ast::VarPattern::Ident(ident) => ident,
+            ast::VarPattern::Ident(ident) | ast::VarPattern::Phi(ident) => ident,
             ast::VarPattern::Discard(_) => {
                 return Ok(VarInfo {
                     t: body_t.clone(),

crates/erg_compiler/context/unify.rs

@@ -1874,6 +1874,8 @@ impl<'c, 'l, 'u, L: Locational> Unifier<'c, 'l, 'u, L> {
                 }
                 self.sub_unify_pred(&sub.pred, &supe.pred)?;
             }
+            // {Int} <: Obj -> Int
+            (Refinement(_), Subr(_) | Quantified(_)) if maybe_sub.singleton_value().is_some() => {}
             // {I: Int | I >= 1} <: Nat == {I: Int | I >= 0}
             (Refinement(_), sup) => {
                 let sup = sup.clone().into_refinement();

crates/erg_compiler/lower.rs

@@ -2253,6 +2253,11 @@ impl<A: ASTBuildable> GenericASTLowerer<A> {
             errors.extend(errs);
         }
         let outer = self.module.context.outer.as_ref().unwrap();
+        let existing_vi = sig
+            .ident()
+            .and_then(|ident| outer.get_current_scope_var(&ident.name))
+            .cloned();
+        let existing_t = existing_vi.as_ref().map(|vi| vi.t.clone());
         let expect_body_t = sig
             .t_spec
             .as_ref()
@@ -2269,14 +2274,14 @@ impl<A: ASTBuildable> GenericASTLowerer<A> {
             })
             .or_else(|| {
                 sig.ident()
-                    .and_then(|ident| outer.get_current_scope_var(&ident.name))
+                    .and_then(|ident| outer.rec_get_param_or_decl_info(ident.inspect()))
                     .map(|vi| vi.t.clone())
             });
         match self.lower_block(body.block, expect_body.or(expect_body_t.as_ref())) {
             Ok(block) => {
                 let found_body_t = block.ref_t();
                 let ident = match &sig.pat {
-                    ast::VarPattern::Ident(ident) => ident.clone(),
+                    ast::VarPattern::Ident(ident) | ast::VarPattern::Phi(ident) => ident.clone(),
                     ast::VarPattern::Discard(token) => {
                         ast::Identifier::private_from_token(token.clone())
                     }
@@ -2291,6 +2296,7 @@ impl<A: ASTBuildable> GenericASTLowerer<A> {
                             .map_err(|errs| (None, errors.concat(errs)));
                     }
                 };
+                let mut no_reassign = false;
                 if let Some(expect_body_t) = expect_body_t {
                     // TODO: expect_body_t is smaller for constants
                     // TODO: 定数の場合、expect_body_tのほうが小さくなってしまう
@@ -2302,20 +2308,35 @@ impl<A: ASTBuildable> GenericASTLowerer<A> {
                             found_body_t,
                         ) {
                             errors.push(e);
+                            no_reassign = true;
                         }
                     }
                 }
-                let vi = match self.module.context.outer.as_mut().unwrap().assign_var_sig(
-                    &sig,
-                    found_body_t,
-                    body.id,
-                    block.last(),
-                    None,
-                ) {
-                    Ok(vi) => vi,
-                    Err(errs) => {
-                        errors.extend(errs);
-                        VarInfo::ILLEGAL
+                let found_body_t = if sig.is_phi() {
+                    self.module
+                        .context
+                        .union(existing_t.as_ref().unwrap_or(&Type::Never), found_body_t)
+                } else {
+                    found_body_t.clone()
+                };
+                let vi = if no_reassign {
+                    VarInfo {
+                        t: found_body_t,
+                        ..existing_vi.unwrap_or_default()
+                    }
+                } else {
+                    match self.module.context.outer.as_mut().unwrap().assign_var_sig(
+                        &sig,
+                        &found_body_t,
+                        body.id,
+                        block.last(),
+                        None,
+                    ) {
+                        Ok(vi) => vi,
+                        Err(errs) => {
+                            errors.extend(errs);
+                            VarInfo::ILLEGAL
+                        }
                     }
                 };
                 let ident = hir::Identifier::new(ident, None, vi);
@@ -2351,7 +2372,7 @@ impl<A: ASTBuildable> GenericASTLowerer<A> {
                 errors.extend(errs);
                 let found_body_t = block.ref_t();
                 let ident = match &sig.pat {
-                    ast::VarPattern::Ident(ident) => ident.clone(),
+                    ast::VarPattern::Ident(ident) | ast::VarPattern::Phi(ident) => ident.clone(),
                     ast::VarPattern::Discard(token) => {
                         ast::Identifier::private_from_token(token.clone())
                     }
@@ -2366,9 +2387,16 @@ impl<A: ASTBuildable> GenericASTLowerer<A> {
                             .map_err(|errs| (None, errors.concat(errs)));
                     }
                 };
+                let found_body_t = if sig.is_phi() {
+                    self.module
+                        .context
+                        .union(existing_t.as_ref().unwrap_or(&Type::Never), found_body_t)
+                } else {
+                    found_body_t.clone()
+                };
                 if let Err(errs) = self.module.context.outer.as_mut().unwrap().assign_var_sig(
                     &sig,
-                    found_body_t,
+                    &found_body_t,
                     ast::DefId(0),
                     None,
                     None,

crates/erg_parser/ast.rs

@@ -4723,6 +4723,10 @@ pub enum VarPattern {
     Discard(Token),
     Glob(Token),
     Ident(Identifier),
+    /// Used when a different value is assigned in a branch other than `Ident`.
+    /// (e.g. the else variable when a variable is defined with Python if-else)
+    /// Not used in Erg mode at this time
+    Phi(Identifier),
     /// e.g. `[x, y, z]` of `[x, y, z] = [1, 2, 3]`
     List(VarListPattern),
     /// e.g. `(x, y, z)` of `(x, y, z) = (1, 2, 3)`
@@ -4739,6 +4743,7 @@ impl NestedDisplay for VarPattern {
             Self::Discard(_) => write!(f, "_"),
             Self::Glob(_) => write!(f, "*"),
             Self::Ident(ident) => write!(f, "{ident}"),
+            Self::Phi(ident) => write!(f, "(phi){ident}"),
             Self::List(l) => write!(f, "{l}"),
             Self::Tuple(t) => write!(f, "{t}"),
             Self::Record(r) => write!(f, "{r}"),
@@ -4748,9 +4753,9 @@ impl NestedDisplay for VarPattern {
 }
 
 impl_display_from_nested!(VarPattern);
-impl_locational_for_enum!(VarPattern; Discard, Glob, Ident, List, Tuple, Record, DataPack);
-impl_into_py_for_enum!(VarPattern; Discard, Glob, Ident, List, Tuple, Record, DataPack);
-impl_from_py_for_enum!(VarPattern; Discard(Token), Glob(Token), Ident(Identifier), List(VarListPattern), Tuple(VarTuplePattern), Record(VarRecordPattern), DataPack(VarDataPackPattern));
+impl_locational_for_enum!(VarPattern; Discard, Glob, Ident, Phi, List, Tuple, Record, DataPack);
+impl_into_py_for_enum!(VarPattern; Discard, Glob, Ident, Phi, List, Tuple, Record, DataPack);
+impl_from_py_for_enum!(VarPattern; Discard(Token), Glob(Token), Ident(Identifier), Phi(Identifier), List(VarListPattern), Tuple(VarTuplePattern), Record(VarRecordPattern), DataPack(VarDataPackPattern));
 
 impl VarPattern {
     pub const fn inspect(&self) -> Option<&Str> {
@@ -4900,10 +4905,14 @@ impl VarSignature {
 
     pub fn ident(&self) -> Option<&Identifier> {
         match &self.pat {
-            VarPattern::Ident(ident) => Some(ident),
+            VarPattern::Ident(ident) | VarPattern::Phi(ident) => Some(ident),
             _ => None,
         }
     }
+
+    pub fn is_phi(&self) -> bool {
+        matches!(self.pat, VarPattern::Phi(_))
+    }
 }
 
 #[pyclass]

crates/erg_parser/desugar.rs

@@ -763,7 +763,10 @@ impl Desugarer {
                         self.desugar_nested_var_pattern(new, rhs, &buf_name, BufIndex::Record(lhs));
                     }
                 }
-                VarPattern::Ident(_) | VarPattern::Discard(_) | VarPattern::Glob(_) => {
+                VarPattern::Ident(_)
+                | VarPattern::Phi(_)
+                | VarPattern::Discard(_)
+                | VarPattern::Glob(_) => {
                     if let VarPattern::Ident(ident) = v.pat {
                         v.pat = VarPattern::Ident(Self::desugar_ident(ident));
                     }
@@ -966,7 +969,10 @@ impl Desugarer {
                     );
                 }
             }
-            VarPattern::Ident(_) | VarPattern::Discard(_) | VarPattern::Glob(_) => {
+            VarPattern::Ident(_)
+            | VarPattern::Phi(_)
+            | VarPattern::Discard(_)
+            | VarPattern::Glob(_) => {
                 let def = Def::new(Signature::Var(sig.clone()), body);
                 new_module.push(Expr::Def(def));
             }