feat(lint): add too_many_instance_attributes rule

crates/erg_linter/lint.rs

@@ -8,9 +8,11 @@ use erg_common::traits::{BlockKind, ExitStatus, Locational, New, Runnable, Strea
 use erg_compiler::artifact::{Buildable, ErrorArtifact};
 use erg_compiler::build_package::PackageBuilder;
 use erg_compiler::error::{CompileError, CompileErrors, CompileWarnings};
-use erg_compiler::hir::{Accessor, Def, Dict, Expr, List, Literal, Set, Signature, Tuple, HIR};
+use erg_compiler::hir::{
+    Accessor, ClassDef, Def, Dict, Expr, List, Literal, Set, Signature, Tuple, HIR,
+};
 use erg_compiler::module::SharedCompilerResource;
-use erg_compiler::ty::ValueObj;
+use erg_compiler::ty::{value::TypeObj, Type, ValueObj};
 
 use erg_parser::token::TokenKind;
 use erg_parser::ParserRunner;
@@ -155,6 +157,7 @@ impl Linter {
         for chunk in hir.module.iter() {
             self.lint_too_many_params(chunk);
             self.lint_bool_comparison(chunk);
+            self.lint_too_many_instance_attributes(chunk);
         }
         log!(info "Finished linting");
         self.warns.take()
@@ -216,6 +219,25 @@ impl Linter {
         }
     }
 
+    fn lint_too_many_instance_attributes(&mut self, expr: &Expr) {
+        const MAX_INSTANCE_ATTRIBUTES: usize = 36;
+        if let Expr::ClassDef(ClassDef { obj, .. }) = expr {
+            if let Some(TypeObj::Builtin {
+                t: Type::Record(record),
+                ..
+            }) = obj.base_or_sup()
+            {
+                if record.len() >= MAX_INSTANCE_ATTRIBUTES {
+                    self.warns.push(too_many_instance_attributes(
+                        self.input(),
+                        self.caused_by(),
+                        expr.loc(),
+                    ));
+                }
+            }
+        }
+    }
+
     /* ↓ Helper methods ↓ */
     fn check_recursively(&mut self, lint_fn: &impl Fn(&mut Linter, &Expr), expr: &Expr) {
         match expr {

crates/erg_linter/warn.rs

@@ -1,5 +1,6 @@
 use erg_common::error::{ErrorCore, ErrorKind, Location, SubMessage};
 use erg_common::io::Input;
+use erg_common::switch_lang;
 use erg_common::traits::NoTypeDisplay;
 use erg_compiler::error::CompileWarning;
 use erg_compiler::hir::Expr;
@@ -18,6 +19,38 @@ pub(crate) fn too_many_params(input: Input, caused_by: String, loc: Location) ->
     )
 }
 
+pub(crate) fn too_many_instance_attributes(
+    input: Input,
+    caused_by: String,
+    loc: Location,
+) -> CompileWarning {
+    let msg = switch_lang!(
+            "japanese" => "インスタンス属性が多すぎます",
+            "simplified_chinese" => "实例属性过多",
+            "traditional_chinese" => "實例屬性過多",
+            "english" => "too many instance attributes",
+    )
+    .to_string();
+    let hint = switch_lang!(
+            "japanese" => "サブクラスやデータクラスを活用してください",
+            "simplified_chinese" => "利用子类和数据类",
+            "traditional_chinese" => "利用子類和資料類",
+            "english" => "take advantage of subclasses and data classes",
+    )
+    .to_string();
+    CompileWarning::new(
+        ErrorCore::new(
+            vec![SubMessage::ambiguous_new(loc, vec![], Some(hint))],
+            msg,
+            0,
+            ErrorKind::AttributeWarning,
+            loc,
+        ),
+        input,
+        caused_by,
+    )
+}
+
 pub(crate) fn true_comparison(
     expr: &Expr,
     input: Input,