1 files changed, 35 insertions, 10 deletions

diff --git a/class.c b/class.c
index f181f33690..98b2a1d92e 100644
--- a/class.c
+++ b/class.c
@@ -894,12 +894,21 @@ add_refined_method_entry_i(ID key, VALUE value, void *data)
 
 static void ensure_origin(VALUE klass);
 
+static enum rb_id_table_iterator_result
+clear_module_cache_i(ID id, VALUE val, void *data)
+{
+    VALUE klass = (VALUE)data;
+    rb_clear_method_cache(klass, id);
+    return ID_TABLE_CONTINUE;
+}
+
 static int
 include_modules_at(const VALUE klass, VALUE c, VALUE module, int search_super)
 {
     VALUE p, iclass;
     int method_changed = 0, constant_changed = 0;
     struct rb_id_table *const klass_m_tbl = RCLASS_M_TBL(RCLASS_ORIGIN(klass));
+    VALUE original_klass = klass;
 
     if (FL_TEST(module, RCLASS_REFINED_BY_ANY)) {
         ensure_origin(module);
@@ -912,7 +921,7 @@ include_modules_at(const VALUE klass, VALUE c, VALUE module, int search_super)
 	if (klass_m_tbl && klass_m_tbl == RCLASS_M_TBL(module))
 	    return -1;
 	/* ignore if the module included already in superclasses */
-	for (p = RCLASS_SUPER(klass); p; p = RCLASS_SUPER(p)) {
+        for (p = RCLASS_SUPER(klass); p; p = RCLASS_SUPER(p)) {
 	    int type = BUILTIN_TYPE(p);
 	    if (type == T_ICLASS) {
 		if (RCLASS_M_TBL(p) == RCLASS_M_TBL(module)) {
@@ -924,37 +933,53 @@ include_modules_at(const VALUE klass, VALUE c, VALUE module, int search_super)
 	    }
 	    else if (type == T_CLASS) {
 		if (!search_super) break;
-		superclass_seen = TRUE;
+                superclass_seen = TRUE;
 	    }
 	}
-	iclass = rb_include_class_new(module, RCLASS_SUPER(c));
+
+        VALUE super_class = RCLASS_SUPER(c);
+
+        // invalidate inline method cache
+        tbl = RMODULE_M_TBL(module);
+        if (tbl && rb_id_table_size(tbl)) {
+            if (search_super) { // include
+                if (super_class && !RB_TYPE_P(super_class, T_MODULE)) {
+                    rb_id_table_foreach(tbl, clear_module_cache_i, (void *)super_class);
+                }
+            }
+            else { // prepend
+                if (!RB_TYPE_P(original_klass, T_MODULE)) {
+                    rb_id_table_foreach(tbl, clear_module_cache_i, (void *)original_klass);
+                }
+            }
+            method_changed = 1;
+        }
+
+        // setup T_ICLASS for the include/prepend module
+	iclass = rb_include_class_new(module, super_class);
 	c = RCLASS_SET_SUPER(c, iclass);
         RCLASS_SET_INCLUDER(iclass, klass);
 
 	{
 	    VALUE m = module;
-	    if (BUILTIN_TYPE(m) == T_ICLASS) m = RBASIC(m)->klass;
-	    rb_module_add_to_subclasses_list(m, iclass);
+            if (BUILTIN_TYPE(m) == T_ICLASS) m = RBASIC(m)->klass;
+            rb_module_add_to_subclasses_list(m, iclass);
 	}
 
 	if (FL_TEST(klass, RMODULE_IS_REFINEMENT)) {
 	    VALUE refined_class =
 		rb_refinement_module_get_refined_class(klass);
 
-	    rb_id_table_foreach(RMODULE_M_TBL(module), add_refined_method_entry_i, (void *)refined_class);
+            rb_id_table_foreach(RMODULE_M_TBL(module), add_refined_method_entry_i, (void *)refined_class);
 	    FL_SET(c, RMODULE_INCLUDED_INTO_REFINEMENT);
 	}
 
-	tbl = RMODULE_M_TBL(module);
-	if (tbl && rb_id_table_size(tbl)) method_changed = 1;
-
 	tbl = RMODULE_CONST_TBL(module);
 	if (tbl && rb_id_table_size(tbl)) constant_changed = 1;
       skip:
 	module = RCLASS_SUPER(module);
     }
 
-    if (method_changed) rb_clear_method_cache_by_class(klass);
     if (constant_changed) rb_clear_constant_cache();
 
     return method_changed;