From 761346a9604ca2c79777d1d67fb5dcc3c30dbf69 Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Thu, 4 Jul 2019 16:54:34 +0900
Subject: [PATCH] Show the previous definition location,

when reopened class/module redefinition mismatched the previous
definition.  [Feature #11460]
---
 test/ruby/test_class.rb  | 10 ++++++----
 test/ruby/test_module.rb | 10 ++++++----
 vm_insnhelper.c          | 28 ++++++++++++++++++++++++----
 3 files changed, 36 insertions(+), 12 deletions(-)

diff --git a/test/ruby/test_class.rb b/test/ruby/test_class.rb
index f07a1cdc40..6960ab5971 100644
--- a/test/ruby/test_class.rb
+++ b/test/ruby/test_class.rb
@@ -591,15 +591,17 @@ class TestClass < Test::Unit::TestCase
 
   def test_redefinition_mismatch
     m = Module.new
-    m.module_eval "A = 1"
-    assert_raise_with_message(TypeError, /is not a class/) {
+    m.module_eval "A = 1", __FILE__, line = __LINE__
+    e = assert_raise_with_message(TypeError, /is not a class/) {
       m.module_eval "class A; end"
     }
+    assert_include(e.message, "#{__FILE__}:#{line}: previous definition")
     n = "M\u{1f5ff}"
-    m.module_eval "#{n} = 42"
-    assert_raise_with_message(TypeError, "#{n} is not a class") {
+    m.module_eval "#{n} = 42", __FILE__, line = __LINE__
+    e = assert_raise_with_message(TypeError, /#{n} is not a class/) {
       m.module_eval "class #{n}; end"
     }
+    assert_include(e.message, "#{__FILE__}:#{line}: previous definition")
 
     assert_separately([], "#{<<~"begin;"}\n#{<<~"end;"}")
     begin;
diff --git a/test/ruby/test_module.rb b/test/ruby/test_module.rb
index d56e63e4be..7bb2261ffb 100644
--- a/test/ruby/test_module.rb
+++ b/test/ruby/test_module.rb
@@ -2383,15 +2383,17 @@ class TestModule < Test::Unit::TestCase
 
   def test_redefinition_mismatch
     m = Module.new
-    m.module_eval "A = 1"
-    assert_raise_with_message(TypeError, /is not a module/) {
+    m.module_eval "A = 1", __FILE__, line = __LINE__
+    e = assert_raise_with_message(TypeError, /is not a module/) {
       m.module_eval "module A; end"
     }
+    assert_include(e.message, "#{__FILE__}:#{line}: previous definition")
     n = "M\u{1f5ff}"
-    m.module_eval "#{n} = 42"
-    assert_raise_with_message(TypeError, "#{n} is not a module") {
+    m.module_eval "#{n} = 42", __FILE__, line = __LINE__
+    e = assert_raise_with_message(TypeError, /#{n} is not a module/) {
       m.module_eval "module #{n}; end"
     }
+    assert_include(e.message, "#{__FILE__}:#{line}: previous definition")
 
     assert_separately([], <<-"end;")
       Etc = (class C\u{1f5ff}; self; end).new
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index e80a036e06..925d465669 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -3389,7 +3389,7 @@ static VALUE
 vm_check_if_class(ID id, rb_num_t flags, VALUE super, VALUE klass)
 {
     if (!RB_TYPE_P(klass, T_CLASS)) {
-	rb_raise(rb_eTypeError, "%"PRIsVALUE" is not a class", rb_id2str(id));
+        return 0;
     }
     else if (VM_DEFINECLASS_HAS_SUPERCLASS_P(flags)) {
 	VALUE tmp = rb_class_real(RCLASS_SUPER(klass));
@@ -3412,7 +3412,7 @@ static VALUE
 vm_check_if_module(ID id, VALUE mod)
 {
     if (!RB_TYPE_P(mod, T_MODULE)) {
-	rb_raise(rb_eTypeError, "%"PRIsVALUE" is not a module", rb_id2str(id));
+        return 0;
     }
     else {
 	return mod;
@@ -3442,6 +3442,22 @@ vm_declare_module(ID id, VALUE cbase)
     return mod;
 }
 
+NORETURN(static void unmatched_redefinition(const char *type, VALUE cbase, ID id, VALUE old));
+static void
+unmatched_redefinition(const char *type, VALUE cbase, ID id, VALUE old)
+{
+    VALUE name = rb_id2str(id);
+    VALUE message = rb_sprintf("%"PRIsVALUE" is not a %s",
+                               name, type);
+    VALUE location = rb_const_source_location_at(cbase, id);
+    if (!NIL_P(location)) {
+        rb_str_catf(message, "\n%"PRIsVALUE":%"PRIsVALUE":"
+                    " previous definition of %"PRIsVALUE" was here",
+                    rb_ary_entry(location, 0), rb_ary_entry(location, 1), name);
+    }
+    rb_exc_raise(rb_exc_new_str(rb_eTypeError, message));
+}
+
 static VALUE
 vm_define_class(ID id, rb_num_t flags, VALUE cbase, VALUE super)
 {
@@ -3458,7 +3474,9 @@ vm_define_class(ID id, rb_num_t flags, VALUE cbase, VALUE super)
     /* find klass */
     rb_autoload_load(cbase, id);
     if ((klass = vm_const_get_under(id, flags, cbase)) != 0) {
-	return vm_check_if_class(id, flags, super, klass);
+        if (!vm_check_if_class(id, flags, super, klass))
+            unmatched_redefinition("class", cbase, id, klass);
+        return klass;
     }
     else {
 	return vm_declare_class(id, flags, cbase, super);
@@ -3472,7 +3490,9 @@ vm_define_module(ID id, rb_num_t flags, VALUE cbase)
 
     vm_check_if_namespace(cbase);
     if ((mod = vm_const_get_under(id, flags, cbase)) != 0) {
-	return vm_check_if_module(id, mod);
+        if (!vm_check_if_module(id, mod))
+            unmatched_redefinition("module", cbase, id, mod);
+        return mod;
     }
     else {
 	return vm_declare_module(id, cbase);