From e7b8d32e166815f2e7edebf32aa178915d191b8c Mon Sep 17 00:00:00 2001
From: Yusuke Endoh <mame@ruby-lang.org>
Date: Fri, 16 Dec 2022 07:31:27 +0900
Subject: [PATCH] Stop using receiver#inspect for "undefined method" errors

```
42.time    #=> undefined method `time' for object Integer (NoMethodError)

class Foo
  privatee #=> undefined local variable or method 'privatee' for class Foo (NoMethodError)
end

s = ""
def s.foo = nil
s.bar      #=> undefined method `bar' for extended object String (NoMethodError)
```

[Feature #18285]
---
 error.c   | 71 ++++++++++++++++++++++++++++++++++++++++---------------
 vm_eval.c | 10 ++++----
 2 files changed, 57 insertions(+), 24 deletions(-)

diff --git a/error.c b/error.c
index 8aa081c198..affee7d828 100644
--- a/error.c
+++ b/error.c
@@ -2066,43 +2066,76 @@ name_err_mesg_to_str(VALUE obj)
     if (NIL_P(mesg)) return Qnil;
     else {
         struct RString s_str, d_str;
-        VALUE c, s, d = 0, args[4];
-        int state = 0, singleton = 0;
+        VALUE c, s, d = 0, args[4], c2;
+        int state = 0;
         rb_encoding *usascii = rb_usascii_encoding();
 
 #define FAKE_CSTR(v, str) rb_setup_fake_str((v), (str), rb_strlen_lit(str), usascii)
+        c = s = FAKE_CSTR(&s_str, "");
         obj = ptr[NAME_ERR_MESG__RECV];
         switch (obj) {
           case Qnil:
-            d = FAKE_CSTR(&d_str, "nil");
+            c = d = FAKE_CSTR(&d_str, "nil");
             break;
           case Qtrue:
-            d = FAKE_CSTR(&d_str, "true");
+            c = d = FAKE_CSTR(&d_str, "true");
             break;
           case Qfalse:
-            d = FAKE_CSTR(&d_str, "false");
+            c = d = FAKE_CSTR(&d_str, "false");
             break;
           default:
-            d = rb_protect(name_err_mesg_receiver_name, obj, &state);
-            if (state || NIL_OR_UNDEF_P(d))
-                d = rb_protect(rb_inspect, obj, &state);
+            if (strstr(RSTRING_PTR(mesg), "%2$s")) {
+                d = rb_protect(name_err_mesg_receiver_name, obj, &state);
+                if (state || NIL_OR_UNDEF_P(d))
+                    d = rb_protect(rb_inspect, obj, &state);
+                if (state) {
+                    rb_set_errinfo(Qnil);
+                }
+                d = rb_check_string_type(d);
+                if (NIL_P(d)) {
+                    d = rb_any_to_s(obj);
+                }
+            }
+
+            if (!RB_SPECIAL_CONST_P(obj)) {
+                switch (RB_BUILTIN_TYPE(obj)) {
+                    case T_MODULE:
+                        s = FAKE_CSTR(&s_str, "module ");
+                        c = obj;
+                        break;
+                    case T_CLASS:
+                        s = FAKE_CSTR(&s_str, "class ");
+                        c = obj;
+                        break;
+                    default:
+                        goto object;
+                }
+            }
+            else {
+                VALUE klass;
+object:
+                klass = CLASS_OF(obj);
+                if (RB_TYPE_P(klass, T_CLASS) && FL_TEST(klass, FL_SINGLETON)) {
+                    s = FAKE_CSTR(&s_str, "extended object ");
+                }
+                else {
+                    s = FAKE_CSTR(&s_str, "object ");
+                }
+                c = rb_class_real(klass);
+            }
+            c2 = rb_protect(name_err_mesg_receiver_name, c, &state);
+            if (state || NIL_OR_UNDEF_P(c2))
+                c2 = rb_protect(rb_inspect, c, &state);
             if (state) {
                 rb_set_errinfo(Qnil);
             }
-            d = rb_check_string_type(d);
-            if (NIL_P(d)) {
-                d = rb_any_to_s(obj);
+            c2 = rb_check_string_type(c2);
+            if (NIL_P(c2)) {
+                c2 = rb_any_to_s(c);
             }
-            singleton = (RSTRING_LEN(d) > 0 && RSTRING_PTR(d)[0] == '#');
+            c = c2;
             break;
         }
-        if (!singleton) {
-            s = FAKE_CSTR(&s_str, ":");
-            c = rb_class_name(CLASS_OF(obj));
-        }
-        else {
-            c = s = FAKE_CSTR(&s_str, "");
-        }
         args[0] = rb_obj_as_string(ptr[NAME_ERR_MESG__NAME]);
         args[1] = d;
         args[2] = s;
diff --git a/vm_eval.c b/vm_eval.c
index 1caa76000b..f91d7d75cd 100644
--- a/vm_eval.c
+++ b/vm_eval.c
@@ -933,7 +933,7 @@ rb_make_no_method_exception(VALUE exc, VALUE format, VALUE obj,
     VALUE name = argv[0];
 
     if (!format) {
-        format = rb_fstring_lit("undefined method `%s' for %s%s%s");
+        format = rb_fstring_lit("undefined method `%1$s' for %3$s%4$s");
     }
     if (exc == rb_eNoMethodError) {
         VALUE args = rb_ary_new4(argc - 1, argv + 1);
@@ -965,17 +965,17 @@ raise_method_missing(rb_execution_context_t *ec, int argc, const VALUE *argv, VA
     stack_check(ec);
 
     if (last_call_status & MISSING_PRIVATE) {
-        format = rb_fstring_lit("private method `%s' called for %s%s%s");
+        format = rb_fstring_lit("private method `%1$s' called for %3$s%4$s");
     }
     else if (last_call_status & MISSING_PROTECTED) {
-        format = rb_fstring_lit("protected method `%s' called for %s%s%s");
+        format = rb_fstring_lit("protected method `%1$s' called for %3$s%4$s");
     }
     else if (last_call_status & MISSING_VCALL) {
-        format = rb_fstring_lit("undefined local variable or method `%s' for %s%s%s");
+        format = rb_fstring_lit("undefined local variable or method `%1$s' for %3$s%4$s");
         exc = rb_eNameError;
     }
     else if (last_call_status & MISSING_SUPER) {
-        format = rb_fstring_lit("super: no superclass method `%s' for %s%s%s");
+        format = rb_fstring_lit("super: no superclass method `%1$s' for %3$s%4$s");
     }
 
     {