diff --git a/vlib/v/markused/markused.v b/vlib/v/markused/markused.v
index 7fd1ef3c2d2e96..265bcc51869cd7 100644
--- a/vlib/v/markused/markused.v
+++ b/vlib/v/markused/markused.v
@@ -123,6 +123,7 @@ pub fn mark_used(mut table ast.Table, mut pref_ pref.Preferences, ast_files []&a
 		if table.used_features.range_index || pref_.is_shared {
 			core_fns << string_idx_str + '.substr_with_check'
 			core_fns << string_idx_str + '.substr_ni'
+			core_fns << string_idx_str + '.substr'
 			core_fns << array_idx_str + '.slice_ni'
 			core_fns << array_idx_str + '.get_with_check' // used for `x := a[i] or {}`
 			core_fns << array_idx_str + '.clone_static_to_depth'
@@ -187,6 +188,7 @@ pub fn mark_used(mut table ast.Table, mut pref_ pref.Preferences, ast_files []&a
 		}
 		if table.used_features.as_cast {
 			core_fns << '__as_cast'
+			core_fns << 'new_array_from_c_array'
 		}
 		if table.used_features.anon_fn {
 			core_fns << 'memdup_uncollectable'
@@ -526,13 +528,6 @@ pub fn mark_used(mut table ast.Table, mut pref_ pref.Preferences, ast_files []&a
 		}
 	}
 
-	if table.used_features.range_index {
-		walker.fn_by_name(string_idx_str + '.substr')
-	}
-	if walker.as_cast_type_names.len > 0 {
-		walker.fn_by_name('new_array_from_c_array')
-	}
-
 	table.used_features.used_fns = walker.used_fns.move()
 	table.used_features.used_consts = walker.used_consts.move()
 	table.used_features.used_globals = walker.used_globals.move()
diff --git a/vlib/v/markused/walker.v b/vlib/v/markused/walker.v
index 09d6644113299c..3cbe99bb552128 100644
--- a/vlib/v/markused/walker.v
+++ b/vlib/v/markused/walker.v
@@ -22,8 +22,6 @@ mut:
 	all_fns     map[string]ast.FnDecl
 	all_consts  map[string]ast.ConstField
 	all_globals map[string]ast.GlobalField
-	//
-	as_cast_type_names map[string]string
 }
 
 pub fn Walker.new(params Walker) &Walker {
@@ -513,7 +511,6 @@ fn (mut w Walker) expr(node_ ast.Expr) {
 		///
 		ast.AsCast {
 			w.expr(node.expr)
-			w.as_cast(node)
 		}
 		ast.AtExpr {}
 		ast.BoolLiteral {}
@@ -733,37 +730,3 @@ pub fn (mut w Walker) or_block(node ast.OrExpr) {
 		w.stmts(node.stmts)
 	}
 }
-
-pub fn (mut w Walker) as_cast(node ast.AsCast) {
-	if node.typ == 0 {
-		return
-	}
-	if node.typ.has_flag(.generic) {
-		w.as_cast_type_names['some_generic_type'] = 'some_generic_name'
-		return
-	}
-	if node.expr_type == 0 {
-		return
-	}
-	if node.expr_type.has_flag(.generic) {
-		w.as_cast_type_names['some_generic_type'] = 'some_generic_name'
-		return
-	}
-	mut expr_type_sym := w.table.sym(node.expr_type)
-	if mut expr_type_sym.info is ast.SumType {
-		w.fill_as_cast_type_names(expr_type_sym.info.variants)
-	} else if mut expr_type_sym.info is ast.Interface && node.expr_type != node.typ {
-		w.fill_as_cast_type_names(expr_type_sym.info.types)
-	}
-}
-
-fn (mut w Walker) fill_as_cast_type_names(types []ast.Type) {
-	for variant in types {
-		idx := u32(variant).str()
-		if idx in w.as_cast_type_names {
-			continue
-		}
-		variant_sym := w.table.sym(variant)
-		w.as_cast_type_names[idx] = variant_sym.name
-	}
-}