Eliminate todo!s

compiler/erg_compiler/context/eval.rs

@@ -1,7 +1,6 @@
 use std::mem;
 
 use erg_common::dict::Dict;
-use erg_common::enum_unwrap;
 use erg_common::error::Location;
 #[allow(unused)]
 use erg_common::log;
@@ -10,6 +9,7 @@ use erg_common::shared::Shared;
 use erg_common::traits::{Locational, Stream};
 use erg_common::vis::Field;
 use erg_common::{dict, fn_name, option_enum_unwrap, set};
+use erg_common::{enum_unwrap, fmt_vec};
 use erg_common::{RcArray, Str};
 use OpKind::*;
 
@@ -34,6 +34,17 @@ use crate::error::{EvalError, EvalErrors, EvalResult, SingleEvalResult};
 use super::instantiate::TyVarCache;
 use super::Variance;
 
+macro_rules! feature_error {
+    ($ctx: expr, $loc: expr, $name: expr) => {
+        $crate::feature_error!(EvalErrors, EvalError, $ctx, $loc, $name)
+    };
+}
+macro_rules! unreachable_error {
+    ($ctx: expr) => {
+        $crate::unreachable_error!(EvalErrors, EvalError, $ctx)
+    };
+}
+
 #[inline]
 pub fn type_from_token_kind(kind: TokenKind) -> Type {
     use TokenKind::*;
@@ -139,7 +150,9 @@ impl Context {
                 let obj = self.eval_const_expr(&attr.obj)?;
                 Ok(self.eval_attr(obj, &attr.ident)?)
             }
-            _ => todo!(),
+            other => {
+                feature_error!(self, other.loc(), &format!("eval {other}")).map_err(Into::into)
+            }
         }
     }
 
@@ -260,7 +273,9 @@ impl Context {
 
     fn call(&self, subr: ConstSubr, args: ValueArgs, loc: Location) -> EvalResult<ValueObj> {
         match subr {
-            ConstSubr::User(_user) => todo!(),
+            ConstSubr::User(_user) => {
+                feature_error!(self, loc, "calling user-defined subroutines").map_err(Into::into)
+            }
             ConstSubr::Builtin(builtin) => builtin.call(args, self).map_err(|mut e| {
                 if e.0.loc.is_unknown() {
                     e.0.loc = loc;
@@ -387,7 +402,7 @@ impl Context {
     fn eval_const_record(&self, record: &Record) -> EvalResult<ValueObj> {
         match record {
             Record::Normal(rec) => self.eval_const_normal_record(rec),
-            Record::Mixed(_rec) => unreachable!(), // should be desugared
+            Record::Mixed(_rec) => unreachable_error!(self), // should be desugared
         }
     }
 
@@ -408,9 +423,13 @@ impl Context {
             let ident = match &attr.sig {
                 Signature::Var(var) => match &var.pat {
                     VarPattern::Ident(ident) => Field::new(ident.vis(), ident.inspect().clone()),
-                    _ => todo!(),
+                    other => {
+                        return feature_error!(self, other.loc(), &format!("record field: {other}"))
+                    }
                 },
-                _ => todo!(),
+                other => {
+                    return feature_error!(self, other.loc(), &format!("record field: {other}"))
+                }
             };
             attrs.push((ident, elem));
         }
@@ -720,7 +739,8 @@ impl Context {
             (lhs @ TyParam::FreeVar(_), rhs) => Ok(TyParam::bin(op, lhs, rhs)),
             (lhs, rhs @ TyParam::FreeVar(_)) => Ok(TyParam::bin(op, lhs, rhs)),
             (e @ TyParam::Erased(_), _) | (_, e @ TyParam::Erased(_)) => Ok(e),
-            (l, r) => todo!("{l:?} {op} {r:?}"),
+            (l, r) => feature_error!(self, Location::Unknown, &format!("{l:?} {op} {r:?}"))
+                .map_err(Into::into),
         }
     }
 
@@ -742,7 +762,7 @@ impl Context {
                 line!(),
             ))),
             Mutate => Ok(ValueObj::Mut(Shared::new(val))),
-            other => unreachable!("{other}"),
+            _other => unreachable_error!(self),
         }
     }
 
@@ -759,15 +779,19 @@ impl Context {
                     let tp = TyParam::FreeVar(fv);
                     Ok(tp)
                 } else {
-                    todo!("{op} {fv}")
+                    feature_error!(self, Location::Unknown, &format!("{op} {fv}"))
                 }
             }
-            other => todo!("{op} {other}"),
+            other => feature_error!(self, Location::Unknown, &format!("{op} {other}")),
         }
     }
 
-    fn eval_app(&self, _name: Str, _args: Vec<TyParam>) -> EvalResult<TyParam> {
-        todo!()
+    fn eval_app(&self, name: Str, args: Vec<TyParam>) -> EvalResult<TyParam> {
+        feature_error!(
+            self,
+            Location::Unknown,
+            &format!("{name}({})", fmt_vec(&args))
+        )
     }
 
     /// 量化変数などはそのまま返す
@@ -810,12 +834,7 @@ impl Context {
                 Ok(TyParam::Dict(new_dic))
             }
             TyParam::Type(_) | TyParam::Erased(_) | TyParam::Value(_) => Ok(p.clone()),
-            _other => Err(EvalErrors::from(EvalError::feature_error(
-                self.cfg.input.clone(),
-                Location::Unknown,
-                "???",
-                self.caused_by(),
-            ))),
+            _other => feature_error!(self, Location::Unknown, "???"),
         }
     }
 
@@ -897,12 +916,7 @@ impl Context {
                 Ok(not(l, r))
             }
             other if other.is_monomorphic() => Ok(other),
-            _other => Err(EvalErrors::from(EvalError::feature_error(
-                self.cfg.input.clone(),
-                t_loc,
-                "???",
-                self.caused_by(),
-            ))),
+            _other => feature_error!(self, t_loc, "???"),
         }
     }
 
@@ -1252,7 +1266,7 @@ impl Context {
                     let t = enum_unwrap!(t, ValueObj::Type); // TODO: error handling
                     return Ok(t.into_typ());
                 } else {
-                    todo!()
+                    return feature_error!(self, t_loc, "??");
                 }
             }
             for (_class, methods) in ty_ctx.methods_list.iter() {
@@ -1267,7 +1281,7 @@ impl Context {
                         let t = enum_unwrap!(t, ValueObj::Type); // TODO: error handling
                         return Ok(t.into_typ());
                     } else {
-                        todo!()
+                        return feature_error!(self, t_loc, "??");
                     }
                 }
             }
@@ -1332,7 +1346,7 @@ impl Context {
                 if let Some(t) = fv.get_type() {
                     Ok(t)
                 } else {
-                    todo!() // Type
+                    feature_error!(self, Location::Unknown, "??")
                 }
             }
             TyParam::Type(typ) => Ok(self.meta_type(&typ)),
@@ -1361,13 +1375,21 @@ impl Context {
             dict @ TyParam::Dict(_) => Ok(dict_t(dict)),
             TyParam::UnaryOp { op, val } => match op {
                 OpKind::Mutate => Ok(self.get_tp_t(&val)?.mutate()),
-                _ => todo!(),
+                _ => feature_error!(self, Location::Unknown, "??"),
             },
             TyParam::BinOp { op, lhs, rhs } => {
                 let op_name = op_to_name(op);
-                todo!("get type: {op_name}({lhs}, {rhs})")
+                feature_error!(
+                    self,
+                    Location::Unknown,
+                    &format!("get type: {op_name}({lhs}, {rhs})")
+                )
             }
-            other => todo!("{other}"),
+            other => feature_error!(
+                self,
+                Location::Unknown,
+                &format!("getting the type of {other}")
+            ),
         }
     }
 
@@ -1380,7 +1402,7 @@ impl Context {
                 if let Some(t) = fv.get_type() {
                     Ok(t)
                 } else {
-                    todo!()
+                    feature_error!(self, Location::Unknown, "??")
                 }
             }
             TyParam::Type(_) => Ok(Type::Type),
@@ -1395,7 +1417,11 @@ impl Context {
                         ))
                     })
             }
-            other => todo!("{other}"),
+            other => feature_error!(
+                self,
+                Location::Unknown,
+                &format!("getting the class of {other}")
+            ),
         }
     }
 

compiler/erg_compiler/context/initialize/const_func.rs

@@ -3,8 +3,9 @@ use std::mem;
 use erg_common::enum_unwrap;
 
 use crate::context::Context;
+use crate::feature_error;
 use crate::ty::constructors::{and, mono};
-use crate::ty::value::{EvalValueResult, GenTypeObj, TypeObj, ValueObj};
+use crate::ty::value::{EvalValueError, EvalValueResult, GenTypeObj, TypeObj, ValueObj};
 use crate::ty::ValueArgs;
 use erg_common::error::{ErrorCore, ErrorKind, Location, SubMessage};
 use erg_common::style::{Color, StyledStr, StyledString, THEME};
@@ -110,7 +111,12 @@ pub fn inheritable_func(mut args: ValueArgs, _ctx: &Context) -> EvalValueResult<
             }
             Ok(ValueObj::Type(TypeObj::Generated(gen)))
         }
-        _ => todo!(),
+        other => feature_error!(
+            EvalValueError,
+            _ctx,
+            Location::Unknown,
+            &format!("Inheritable {other}")
+        ),
     }
 }
 
@@ -126,7 +132,7 @@ pub fn trait_func(mut args: ValueArgs, ctx: &Context) -> EvalValueResult<ValueOb
         )
     })?;
     let Some(require) = require.as_type() else {
-        let require = StyledString::new(&format!("{}", require), Some(ERR), None);
+        let require = StyledString::new(&format!("{require}"), Some(ERR), None);
         return Err(ErrorCore::new(
             vec![SubMessage::only_loc(Location::Unknown)],
             format!(

compiler/erg_compiler/context/inquire.rs

@@ -29,9 +29,9 @@ use crate::error::{
     binop_to_dname, readable_name, unaryop_to_dname, SingleTyCheckResult, TyCheckError,
     TyCheckErrors, TyCheckResult,
 };
-use crate::hir;
 use crate::varinfo::{Mutability, VarInfo, VarKind};
 use crate::AccessKind;
+use crate::{feature_error, hir};
 use RegistrationMode::*;
 use Visibility::*;
 
@@ -940,8 +940,8 @@ impl Context {
                 self.substitute_call(obj, attr_name, &fv.crack(), pos_args, kw_args)
             }
             Type::FreeVar(fv) => {
-                if let Some(_attr_name) = attr_name {
-                    todo!()
+                if let Some(attr_name) = attr_name {
+                    feature_error!(TyCheckErrors, TyCheckError, self, attr_name.loc(), "")
                 } else {
                     let is_procedural = obj
                         .show_acc()

compiler/erg_compiler/context/instantiate.rs

@@ -19,12 +19,14 @@ use erg_parser::ast;
 use erg_parser::token::TokenKind;
 use erg_parser::Parser;
 
+use crate::feature_error;
 use crate::ty::constructors::*;
 use crate::ty::free::CanbeFree;
 use crate::ty::free::{Constraint, HasLevel};
 use crate::ty::typaram::{IntervalOp, TyParam, TyParamOrdering};
 use crate::ty::value::ValueObj;
 use crate::ty::{HasType, ParamTy, Predicate, SubrKind, Type};
+use crate::type_feature_error;
 use TyParamOrdering::*;
 use Type::*;
 
@@ -393,7 +395,7 @@ impl Context {
                     )))
                 }
             }
-            other => todo!("{other}"),
+            other => type_feature_error!(self, other.loc(), &format!("instantiating {other}")),
         }
     }
 
@@ -579,7 +581,7 @@ impl Context {
                     self.get_similar_name(name.inspect()),
                 )))
             }
-            _ => todo!(),
+            other => type_feature_error!(self, other.loc(), &format!("instantiating {other}")),
         }
     }
 
@@ -592,7 +594,7 @@ impl Context {
         match self.instantiate_const_expr(expr, erased_idx, tmp_tv_cache)? {
             TyParam::Type(t) => Ok(*t),
             TyParam::Value(ValueObj::Type(t)) => Ok(t.into_typ()),
-            other => todo!("{other}"),
+            other => type_feature_error!(self, expr.loc(), &format!("{other}")),
         }
     }
 
@@ -621,13 +623,13 @@ impl Context {
 
     pub(crate) fn instantiate_typespec(
         &self,
-        spec: &TypeSpec,
+        t_spec: &TypeSpec,
         opt_decl_t: Option<&ParamTy>,
         tmp_tv_cache: &mut TyVarCache,
         mode: RegistrationMode,
         not_found_is_qvar: bool,
     ) -> TyCheckResult<Type> {
-        match spec {
+        match t_spec {
             TypeSpec::Infer(_) => Ok(free_var(self.level, Constraint::new_type_of(Type))),
             TypeSpec::PreDeclTy(predecl) => Ok(self.instantiate_predecl_t(
                 predecl,
@@ -830,7 +832,7 @@ impl Context {
                 ))
             }
             TypeSpec::TypeApp { spec, args } => {
-                todo!("{spec}{args}")
+                type_feature_error!(self, t_spec.loc(), &format!("instantiating {spec}{args}"))
             }
         }
     }
@@ -850,7 +852,9 @@ impl Context {
                         TokenKind::SubtypeOf => Constraint::new_subtype_of(
                             self.instantiate_typespec(&spec.t_spec, None, tv_cache, mode, true)?,
                         ),
-                        TokenKind::SupertypeOf => todo!(),
+                        TokenKind::SupertypeOf => {
+                            return type_feature_error!(self, spec.loc(), "supertype of");
+                        }
                         TokenKind::Colon => Constraint::new_type_of(self.instantiate_typespec(
                             &spec.t_spec,
                             None,
@@ -862,10 +866,14 @@ impl Context {
                     };
                 let tv = named_free_var(lhs.inspect().clone(), self.level, constr);
                 tv_cache.push_or_init_tyvar(lhs.inspect(), &tv);
+                Ok(())
             }
-            TypeBoundSpec::WithDefault { .. } => todo!(),
+            TypeBoundSpec::WithDefault { .. } => type_feature_error!(
+                self,
+                bound.loc(),
+                "type boundary specification with default"
+            ),
         }
-        Ok(())
     }
 
     pub(crate) fn instantiate_ty_bounds(
@@ -983,7 +991,7 @@ impl Context {
             | TyParam::Mono(_)
             | TyParam::FreeVar(_)
             | TyParam::Erased(_)) => Ok(p),
-            other => todo!("{other}"),
+            other => type_feature_error!(self, loc, &format!("instantiating {other}")),
         }
     }
 
@@ -1134,7 +1142,7 @@ impl Context {
                 Ok(not(l, r))
             }
             other if other.is_monomorphic() => Ok(other),
-            other => todo!("{other}"),
+            other => type_feature_error!(self, loc, &format!("instantiating {other}")),
         }
     }
 

compiler/erg_compiler/context/tyvar.rs

@@ -18,7 +18,7 @@ use crate::ty::{HasType, Predicate, Type};
 // use crate::context::eval::SubstContext;
 use crate::context::{Context, Variance};
 use crate::error::{SingleTyCheckResult, TyCheckError, TyCheckErrors, TyCheckResult};
-use crate::hir;
+use crate::{feature_error, hir, type_feature_error};
 
 use Predicate as Pred;
 use Type::*;
@@ -674,7 +674,12 @@ impl Context {
                     self.resolve_expr_t(&mut arr.len)?;
                     Ok(())
                 }
-                _ => todo!(),
+                other => feature_error!(
+                    TyCheckError,
+                    self,
+                    other.loc(),
+                    "resolve types of array comprehension"
+                ),
             },
             hir::Expr::Tuple(tuple) => match tuple {
                 hir::Tuple::Normal(tup) => {
@@ -711,7 +716,12 @@ impl Context {
                     }
                     Ok(())
                 }
-                other => todo!("{other}"),
+                other => feature_error!(
+                    TyCheckError,
+                    self,
+                    other.loc(),
+                    "resolve types of dict comprehension"
+                ),
             },
             hir::Expr::Record(record) => {
                 for attr in record.attrs.iter_mut() {
@@ -1367,10 +1377,12 @@ impl Context {
                 }
                 Ok(())
             }
-            (Type::FreeVar(lfv), _) if lfv.is_linked() =>
-                self.sub_unify(&lfv.crack(), maybe_sup, loc, param_name),
-            (_, Type::FreeVar(rfv)) if rfv.is_linked() =>
-                self.sub_unify(maybe_sub, &rfv.crack(), loc, param_name),
+            (Type::FreeVar(lfv), _) if lfv.is_linked() => {
+                self.sub_unify(&lfv.crack(), maybe_sup, loc, param_name)
+            }
+            (_, Type::FreeVar(rfv)) if rfv.is_linked() => {
+                self.sub_unify(maybe_sub, &rfv.crack(), loc, param_name)
+            }
             (_, Type::FreeVar(rfv)) if rfv.is_unbound() => {
                 // NOTE: cannot `borrow_mut` because of cycle reference
                 let rfv_ref = unsafe { rfv.as_ptr().as_mut().unwrap() };
@@ -1477,15 +1489,24 @@ impl Context {
             }
             (Type::Subr(lsub), Type::Subr(rsub)) => {
                 for lpt in lsub.default_params.iter() {
-                    if let Some(rpt) = rsub.default_params.iter().find(|rpt| rpt.name() == lpt.name()) {
+                    if let Some(rpt) = rsub
+                        .default_params
+                        .iter()
+                        .find(|rpt| rpt.name() == lpt.name())
+                    {
                         // contravariant
                         self.sub_unify(rpt.typ(), lpt.typ(), loc, param_name)?;
-                    } else { todo!() }
+                    } else {
+                        todo!()
+                    }
                 }
-                lsub.non_default_params.iter().zip(rsub.non_default_params.iter()).try_for_each(|(l, r)| {
-                    // contravariant
-                    self.sub_unify(r.typ(), l.typ(), loc, param_name)
-                })?;
+                lsub.non_default_params
+                    .iter()
+                    .zip(rsub.non_default_params.iter())
+                    .try_for_each(|(l, r)| {
+                        // contravariant
+                        self.sub_unify(r.typ(), l.typ(), loc, param_name)
+                    })?;
                 // covariant
                 self.sub_unify(&lsub.return_t, &rsub.return_t, loc, param_name)?;
                 Ok(())
@@ -1493,17 +1514,32 @@ impl Context {
             (Type::Quantified(lsub), Type::Subr(rsub)) => {
                 let Type::Subr(lsub) = lsub.as_ref() else { unreachable!() };
                 for lpt in lsub.default_params.iter() {
-                    if let Some(rpt) = rsub.default_params.iter().find(|rpt| rpt.name() == lpt.name()) {
-                        if lpt.typ().is_generalized() { continue; }
+                    if let Some(rpt) = rsub
+                        .default_params
+                        .iter()
+                        .find(|rpt| rpt.name() == lpt.name())
+                    {
+                        if lpt.typ().is_generalized() {
+                            continue;
+                        }
                         // contravariant
                         self.sub_unify(rpt.typ(), lpt.typ(), loc, param_name)?;
-                    } else { todo!() }
+                    } else {
+                        todo!()
+                    }
                 }
-                lsub.non_default_params.iter().zip(rsub.non_default_params.iter()).try_for_each(|(l, r)| {
-                    if l.typ().is_generalized() { Ok(()) }
-                    // contravariant
-                    else { self.sub_unify(r.typ(), l.typ(), loc, param_name) }
-                })?;
+                lsub.non_default_params
+                    .iter()
+                    .zip(rsub.non_default_params.iter())
+                    .try_for_each(|(l, r)| {
+                        if l.typ().is_generalized() {
+                            Ok(())
+                        }
+                        // contravariant
+                        else {
+                            self.sub_unify(r.typ(), l.typ(), loc, param_name)
+                        }
+                    })?;
                 // covariant
                 if !lsub.return_t.is_generalized() {
                     self.sub_unify(&lsub.return_t, &rsub.return_t, loc, param_name)?;
@@ -1513,17 +1549,31 @@ impl Context {
             (Type::Subr(lsub), Type::Quantified(rsub)) => {
                 let Type::Subr(rsub) = rsub.as_ref() else { unreachable!() };
                 for lpt in lsub.default_params.iter() {
-                    if let Some(rpt) = rsub.default_params.iter().find(|rpt| rpt.name() == lpt.name()) {
+                    if let Some(rpt) = rsub
+                        .default_params
+                        .iter()
+                        .find(|rpt| rpt.name() == lpt.name())
+                    {
                         // contravariant
-                        if rpt.typ().is_generalized() { continue; }
+                        if rpt.typ().is_generalized() {
+                            continue;
+                        }
                         self.sub_unify(rpt.typ(), lpt.typ(), loc, param_name)?;
-                    } else { todo!() }
+                    } else {
+                        todo!()
+                    }
                 }
-                lsub.non_default_params.iter().zip(rsub.non_default_params.iter()).try_for_each(|(l, r)| {
-                    // contravariant
-                    if r.typ().is_generalized() { Ok(()) }
-                    else { self.sub_unify(r.typ(), l.typ(), loc, param_name) }
-                })?;
+                lsub.non_default_params
+                    .iter()
+                    .zip(rsub.non_default_params.iter())
+                    .try_for_each(|(l, r)| {
+                        // contravariant
+                        if r.typ().is_generalized() {
+                            Ok(())
+                        } else {
+                            self.sub_unify(r.typ(), l.typ(), loc, param_name)
+                        }
+                    })?;
                 // covariant
                 if !rsub.return_t.is_generalized() {
                     self.sub_unify(&lsub.return_t, &rsub.return_t, loc, param_name)?;
@@ -1547,9 +1597,14 @@ impl Context {
                         self.substitute_typarams(sub_def_t, maybe_sub);
                         for sup_trait in sub_ctx.super_traits.iter() {
                             if self.supertype_of(maybe_sup, sup_trait) {
-                                for (l_maybe_sub, r_maybe_sup) in sup_trait.typarams().iter().zip(rps.iter()) {
+                                for (l_maybe_sub, r_maybe_sup) in
+                                    sup_trait.typarams().iter().zip(rps.iter())
+                                {
                                     self.sub_unify_tp(l_maybe_sub, r_maybe_sup, None, loc, false)
-                                        .map_err(|e| { self.undo_substitute_typarams(sub_def_t); e })?;
+                                        .map_err(|e| {
+                                            self.undo_substitute_typarams(sub_def_t);
+                                            e
+                                        })?;
                                 }
                                 self.undo_substitute_typarams(sub_def_t);
                                 return Ok(());
@@ -1582,21 +1637,15 @@ impl Context {
                 self.sub_unify(maybe_sub, r, loc, param_name)
             }
             // (X and Y) <: Z is valid when X <: Z or Y <: Z
-            (Type::And(l, r), _) => {
-                self.sub_unify(l, maybe_sup, loc, param_name)
-                    .or_else(|_e| self.sub_unify(r, maybe_sup, loc, param_name))
-            }
+            (Type::And(l, r), _) => self
+                .sub_unify(l, maybe_sup, loc, param_name)
+                .or_else(|_e| self.sub_unify(r, maybe_sup, loc, param_name)),
             // X <: (Y or Z) is valid when X <: Y or X <: Z
-            (_, Type::Or(l, r)) => {
-                self.sub_unify(maybe_sub, l, loc, param_name)
-                    .or_else(|_e| self.sub_unify(maybe_sub, r, loc, param_name))
-            }
-            (_, Type::Ref(t)) => {
-                self.sub_unify(maybe_sub, t, loc, param_name)
-            }
-            (_, Type::RefMut{ before, .. }) => {
-                self.sub_unify(maybe_sub, before, loc, param_name)
-            }
+            (_, Type::Or(l, r)) => self
+                .sub_unify(maybe_sub, l, loc, param_name)
+                .or_else(|_e| self.sub_unify(maybe_sub, r, loc, param_name)),
+            (_, Type::Ref(t)) => self.sub_unify(maybe_sub, t, loc, param_name),
+            (_, Type::RefMut { before, .. }) => self.sub_unify(maybe_sub, before, loc, param_name),
             (Type::Proj { .. }, _) => todo!(),
             (_, Type::Proj { .. }) => todo!(),
             // TODO: Judgment for any number of preds
@@ -1616,16 +1665,22 @@ impl Context {
                     return Ok(());
                 }
                 todo!("{sub}, {sup}")
-            },
+            }
             // {I: Int | I >= 1} <: Nat == {I: Int | I >= 0}
             (Type::Refinement(_), sup) => {
                 let sup = sup.clone().into_refinement();
                 self.sub_unify(maybe_sub, &Type::Refinement(sup), loc, param_name)
-            },
+            }
             (Type::Subr(_) | Type::Record(_), Type) => Ok(()),
             // REVIEW: correct?
-            (Type::Poly{ name, .. }, Type) if &name[..] == "Array" || &name[..] == "Tuple" => Ok(()),
-            _ => todo!("{maybe_sub} can be a subtype of {maybe_sup}, but failed to semi-unify (or existential types are not supported)"),
+            (Type::Poly { name, .. }, Type) if &name[..] == "Array" || &name[..] == "Tuple" => {
+                Ok(())
+            }
+            _ => type_feature_error!(
+                self,
+                loc,
+                &format!("{maybe_sub} can be a subtype of {maybe_sup}, but failed to semi-unify")
+            ),
         }
     }
 }

compiler/erg_compiler/error.rs

@@ -20,6 +20,51 @@ use crate::context::Context;
 use crate::hir::{Expr, Identifier, Signature};
 use crate::ty::{HasType, Predicate, Type};
 
+/// `unreachable!(self: Context)`
+#[macro_export]
+macro_rules! unreachable_error {
+    ($Strcs: ident, $Strc: ident, $ctx: expr) => {
+        Err($Strcs::from($Strc::unreachable(
+            $ctx.cfg.input.clone(),
+            fn_name!(),
+            line!(),
+        )))
+    };
+    ($Strc: ident, $ctx: expr) => {
+        Err($Strc::unreachable(
+            $ctx.cfg.input.clone(),
+            fn_name!(),
+            line!(),
+        ))
+    };
+}
+/// `feature_error!($Strc: struct, ctx: Context, loc: Location, name: &str)`
+#[macro_export]
+macro_rules! feature_error {
+    ($Strcs: ident, $Strc: ident, $ctx: expr, $loc: expr, $name: expr) => {
+        Err($Strcs::from($Strc::feature_error(
+            $ctx.cfg.input.clone(),
+            $loc,
+            $name,
+            $ctx.caused_by(),
+        )))
+    };
+    ($Strc: ident, $ctx: expr, $loc: expr, $name: expr) => {
+        Err($Strc::feature_error(
+            $ctx.cfg.input.clone(),
+            $loc,
+            $name,
+            $ctx.caused_by(),
+        ))
+    };
+}
+#[macro_export]
+macro_rules! type_feature_error {
+    ($ctx: expr, $loc: expr, $name: expr) => {
+        feature_error!(TyCheckErrors, TyCheckError, $ctx, $loc, $name)
+    };
+}
+
 pub fn ordinal_num(n: usize) -> String {
     match n.to_string().chars().last().unwrap() {
         '1' => format!("{n}st"),

compiler/erg_compiler/lower.rs

@@ -40,28 +40,9 @@ use crate::mod_cache::SharedModuleCache;
 use crate::reorder::Reorderer;
 use crate::varinfo::{VarInfo, VarKind};
 use crate::AccessKind;
+use crate::{feature_error, unreachable_error};
 use Visibility::*;
 
-macro_rules! unreachable_error {
-    ($self: ident) => {
-        Err(LowerErrors::from(LowerError::unreachable(
-            $self.cfg.input.clone(),
-            fn_name!(),
-            line!(),
-        )))
-    };
-}
-macro_rules! todo_error {
-    ($self: ident, $loc: expr, $name: expr) => {
-        Err(LowerErrors::from(LowerError::feature_error(
-            $self.cfg.input.clone(),
-            $loc,
-            $name,
-            $self.ctx.caused_by(),
-        )))
-    };
-}
-
 /// Checks & infers types of an AST, and convert (lower) it into a HIR
 #[derive(Debug)]
 pub struct ASTLowerer {
@@ -337,7 +318,13 @@ impl ASTLowerer {
             ast::Array::WithLength(arr) => {
                 Ok(hir::Array::WithLength(self.lower_array_with_length(arr)?))
             }
-            other => todo_error!(self, other.loc(), "array comprehension"),
+            other => feature_error!(
+                LowerErrors,
+                LowerError,
+                self.ctx,
+                other.loc(),
+                "array comprehension"
+            ),
         }
     }
 
@@ -622,7 +609,13 @@ impl ASTLowerer {
         log!(info "enter {}({dict})", fn_name!());
         match dict {
             ast::Dict::Normal(set) => Ok(hir::Dict::Normal(self.lower_normal_dict(set)?)),
-            other => todo_error!(self, other.loc(), "dict comprehension"),
+            other => feature_error!(
+                LowerErrors,
+                LowerError,
+                self.ctx,
+                other.loc(),
+                "dict comprehension"
+            ),
             // ast::Dict::WithLength(set) => Ok(hir::Dict::WithLength(self.lower_dict_with_length(set)?)),
         }
     }
@@ -726,9 +719,15 @@ impl ASTLowerer {
                 let acc = hir::Accessor::Attr(hir::Attribute::new(obj, ident));
                 Ok(acc)
             }
-            ast::Accessor::TypeApp(t_app) => todo_error!(self, t_app.loc(), "type application"),
+            ast::Accessor::TypeApp(t_app) => feature_error!(
+                LowerErrors,
+                LowerError,
+                self.ctx,
+                t_app.loc(),
+                "type application"
+            ),
             // TupleAttr, Subscr are desugared
-            _ => unreachable!(),
+            _ => unreachable_error!(LowerErrors, LowerError, self.ctx),
         }
     }
 
@@ -1193,7 +1192,7 @@ impl ASTLowerer {
                 let body = hir::DefBody::new(body.op, block, body.id);
                 Ok(hir::Def::new(hir::Signature::Subr(sig), body))
             }
-            _ => unreachable_error!(self),
+            _ => unreachable_error!(LowerErrors, LowerError, self),
         }
     }
 
@@ -1217,7 +1216,7 @@ impl ASTLowerer {
                             )?,
                             tasc.t_spec.loc(),
                         ),
-                        _ => return unreachable_error!(self),
+                        _ => return unreachable_error!(LowerErrors, LowerError, self),
                     };
                     (
                         self.ctx.instantiate_typespec(
@@ -1339,7 +1338,7 @@ impl ASTLowerer {
         ) {
             (dunder_new_vi.t.clone(), new_vi.kind == VarKind::Auto)
         } else {
-            return unreachable_error!(self);
+            return unreachable_error!(LowerErrors, LowerError, self);
         };
         let require_or_sup = self.get_require_or_sup_or_base(hir_def.body.block.remove(0));
         Ok(hir::ClassDef::new(
@@ -1591,12 +1590,12 @@ impl ASTLowerer {
                                 }
                             }
                             other => {
-                                return todo_error!(
-                                    self,
+                                return feature_error!(
+                                    LowerError,
+                                    self.ctx,
                                     Location::Unknown,
                                     &format!("Impl {other}")
-                                )
-                                .map_err(|mut e| e.remove(0));
+                                );
                             }
                         },
                         TypeObj::Builtin(_typ) => {

compiler/erg_compiler/ty/value.rs

@@ -8,8 +8,9 @@ use std::mem;
 use std::ops::Neg;
 use std::rc::Rc;
 
+use erg_common::config::Input;
 use erg_common::dict::Dict;
-use erg_common::error::ErrorCore;
+use erg_common::error::{ErrorCore, ErrorKind, Location};
 use erg_common::fresh::fresh_varname;
 use erg_common::python_util::PythonVersion;
 use erg_common::serialize::*;
@@ -44,6 +45,18 @@ impl From<EvalValueError> for ErrorCore {
     }
 }
 
+impl EvalValueError {
+    pub fn feature_error(_input: Input, loc: Location, name: &str, caused_by: String) -> Self {
+        Self::from(ErrorCore::new(
+            vec![],
+            format!("{name} is not supported yet: {caused_by}"),
+            0,
+            ErrorKind::FeatureError,
+            loc,
+        ))
+    }
+}
+
 pub type EvalValueResult<T> = Result<T, EvalValueError>;
 
 #[derive(Clone, Debug, PartialEq, Eq, Hash)]