diff --git a/crates/erg_common/config.rs b/crates/erg_common/config.rs
index 8fa97f4f..229aaa44 100644
--- a/crates/erg_common/config.rs
+++ b/crates/erg_common/config.rs
@@ -180,6 +180,8 @@ pub struct ErgConfig {
     pub effect_check: bool,
     pub ownership_check: bool,
     pub use_pylyzer: bool,
+    pub no_infer_fn_type: bool,
+    pub fast_error_report: bool,
 }
 
 impl Default for ErgConfig {
@@ -208,6 +210,8 @@ impl Default for ErgConfig {
             effect_check: true,
             ownership_check: true,
             use_pylyzer: false,
+            no_infer_fn_type: false,
+            fast_error_report: false,
         }
     }
 }
diff --git a/crates/erg_compiler/context/inquire.rs b/crates/erg_compiler/context/inquire.rs
index 9796801e..bc2cc4eb 100644
--- a/crates/erg_compiler/context/inquire.rs
+++ b/crates/erg_compiler/context/inquire.rs
@@ -2913,6 +2913,9 @@ impl Context {
     }
 
     pub(crate) fn get_similar_name(&self, name: &str) -> Option<&str> {
+        if self.cfg.fast_error_report {
+            return None;
+        }
         levenshtein::get_similar_name(
             self.dir().into_iter().map(|(vn, _)| &vn.inspect()[..]),
             name,
@@ -2924,6 +2927,9 @@ impl Context {
     }
 
     pub(crate) fn get_similar_name_and_info(&self, name: &str) -> Option<(&VarInfo, &str)> {
+        if self.cfg.fast_error_report {
+            return None;
+        }
         levenshtein::get_similar_name_and_some(
             self.dir()
                 .into_iter()
@@ -2948,6 +2954,9 @@ impl Context {
     }
 
     pub(crate) fn get_similar_attr<'a>(&'a self, self_t: &'a Type, name: &str) -> Option<&'a str> {
+        if self.cfg.fast_error_report {
+            return None;
+        }
         for ctx in self.get_nominal_super_type_ctxs(self_t)? {
             if let Some(name) = ctx.get_similar_name(name) {
                 return Some(name);
@@ -2973,6 +2982,9 @@ impl Context {
         self_t: &'a Type,
         name: &str,
     ) -> Option<(&'a VarInfo, &'a str)> {
+        if self.cfg.fast_error_report {
+            return None;
+        }
         for ctx in self.get_nominal_super_type_ctxs(self_t)? {
             if let Some((vi, name)) = ctx.get_similar_name_and_info(name) {
                 return Some((vi, name));
diff --git a/crates/erg_compiler/context/instantiate_spec.rs b/crates/erg_compiler/context/instantiate_spec.rs
index 22e0f297..cc750581 100644
--- a/crates/erg_compiler/context/instantiate_spec.rs
+++ b/crates/erg_compiler/context/instantiate_spec.rs
@@ -256,6 +256,8 @@ impl Context {
         let mut tmp_tv_cache = TyVarCache::new(self.level, self);
         let spec_t = if let Some(t_spec) = t_spec {
             self.instantiate_typespec_full(t_spec, None, &mut tmp_tv_cache, mode, false)?
+        } else if self.cfg.no_infer_fn_type {
+            Type::Failure
         } else {
             free_var(self.level, Constraint::new_type_of(Type))
         };
@@ -405,6 +407,8 @@ impl Context {
                     ty
                 }
             }
+        } else if self.cfg.no_infer_fn_type {
+            Type::Failure
         } else {
             // preregisterならouter scopeで型宣言(see inference.md)
             let level = if mode.is_preregister() {
@@ -451,6 +455,9 @@ impl Context {
     ) -> Failable<Type> {
         let mut errs = TyCheckErrors::empty();
         let gen_free_t = || {
+            if self.cfg.no_infer_fn_type {
+                return Type::Failure;
+            }
             let level = if mode.is_preregister() {
                 self.level
             } else {