Remove the uninitialized instance variable verbose mode warning

This speeds up all instance variable access, even when not in
verbose mode.  Uninitialized instance variable warnings were
rarely helpful, and resulted in slower code if you wanted to
avoid warnings when run in verbose mode.

Implements [Feature #17055]

7 files changed, 12 insertions, 24 deletions

diff --git a/NEWS.md b/NEWS.md
index f310c74188..945675b765 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -582,6 +582,8 @@ end
   message and backtrace are printed in order from the innermost.
   [[Feature #8661]]
 
+* Accessing an uninitialized instance variable no longer emits a
+  warning in verbose mode. [[Feature #17055]]
 
 [Bug #4352]:      https://bugs.ruby-lang.org/issues/4352
 [Bug #6087]:      https://bugs.ruby-lang.org/issues/6087
@@ -629,6 +631,7 @@ end
 [Feature #16815]: https://bugs.ruby-lang.org/issues/16815
 [Feature #16828]: https://bugs.ruby-lang.org/issues/16828
 [Misc #16961]:    https://bugs.ruby-lang.org/issues/16961
+[Feature #17055]: https://bugs.ruby-lang.org/issues/17055
 [Feature #17104]: https://bugs.ruby-lang.org/issues/17104
 [Feature #17122]: https://bugs.ruby-lang.org/issues/17122
 [Feature #17134]: https://bugs.ruby-lang.org/issues/17134
diff --git a/test/-ext-/symbol/test_inadvertent_creation.rb b/test/-ext-/symbol/test_inadvertent_creation.rb
index b0508e9a07..995e01ee15 100644
--- a/test/-ext-/symbol/test_inadvertent_creation.rb
+++ b/test/-ext-/symbol/test_inadvertent_creation.rb
@@ -485,10 +485,8 @@ module Test_Symbol
 
     def test_iv_get
       obj = Object.new
-      assert_warning(/not initialized/) do
-        assert_no_immortal_symbol_created("rb_iv_get") do |name|
-          Bug::Symbol.iv_get(obj, name)
-        end
+      assert_no_immortal_symbol_created("rb_iv_get") do |name|
+        Bug::Symbol.iv_get(obj, name)
       end
     end
   end
diff --git a/test/ruby/test_exception.rb b/test/ruby/test_exception.rb
index 536a02925c..087bcda5ac 100644
--- a/test/ruby/test_exception.rb
+++ b/test/ruby/test_exception.rb
@@ -955,8 +955,8 @@ $stderr = $stdout; raise "\x82\xa0"') do |outs, errs, status|
   end
 
   def test_warning_warn
-    warning = capture_warning_warn {@a}
-    assert_match(/instance variable @a not initialized/, warning[0])
+    warning = capture_warning_warn {$asdfasdsda_test_warning_warn}
+    assert_match(/global variable `\$asdfasdsda_test_warning_warn' not initialized/, warning[0])
 
     assert_equal(["a\nz\n"], capture_warning_warn {warn "a\n", "z"})
     assert_equal([],         capture_warning_warn {warn})
@@ -1040,7 +1040,7 @@ $stderr = $stdout; raise "\x82\xa0"') do |outs, errs, status|
   end
 
   def test_warning_warn_super
-    assert_in_out_err(%[-W0], "#{<<~"{#"}\n#{<<~'};'}", [], /instance variable @a not initialized/)
+    assert_in_out_err(%[-W0], "#{<<~"{#"}\n#{<<~'};'}", [], /global variable `\$asdfiasdofa_test_warning_warn_super' not initialized/)
     {#
       module Warning
         def warn(message)
@@ -1049,7 +1049,7 @@ $stderr = $stdout; raise "\x82\xa0"') do |outs, errs, status|
       end
 
       $VERBOSE = true
-      @a
+      $asdfiasdofa_test_warning_warn_super
     };
   end
 
diff --git a/test/ruby/test_jit.rb b/test/ruby/test_jit.rb
index bec6d30dfc..3a38b1a998 100644
--- a/test/ruby/test_jit.rb
+++ b/test/ruby/test_jit.rb
@@ -829,11 +829,9 @@ class TestJIT < Test::Unit::TestCase
         end
       end
 
-      verbose, $VERBOSE = $VERBOSE, false # suppress "instance variable @b not initialized"
       print(Foo.new.bar)
       print(Foo.new.bar)
       print(Foo.new.bar)
-      $VERBOSE = verbose
     end;
   end
 
diff --git a/test/ruby/test_module.rb b/test/ruby/test_module.rb
index d63f31a56f..b676145ba7 100644
--- a/test/ruby/test_module.rb
+++ b/test/ruby/test_module.rb
@@ -2401,7 +2401,7 @@ class TestModule < Test::Unit::TestCase
 
   def test_uninitialized_instance_variable
     a = AttrTest.new
-    assert_warning(/instance variable @ivar not initialized/) do
+    assert_warning('') do
       assert_nil(a.ivar)
     end
     a.instance_variable_set(:@ivar, 42)
@@ -2410,7 +2410,7 @@ class TestModule < Test::Unit::TestCase
     end
 
     name = "@\u{5909 6570}"
-    assert_warning(/instance variable #{name} not initialized/) do
+    assert_warning('') do
       assert_nil(a.instance_eval(name))
     end
   end
diff --git a/variable.c b/variable.c
index 9f9813319e..81c0a7da2f 100644
--- a/variable.c
+++ b/variable.c
@@ -1217,14 +1217,8 @@ rb_ivar_lookup(VALUE obj, ID id, VALUE undef)
 VALUE
 rb_ivar_get(VALUE obj, ID id)
 {
-    VALUE iv = rb_ivar_lookup(obj, id, Qundef);
+    VALUE iv = rb_ivar_lookup(obj, id, Qnil);
     RB_DEBUG_COUNTER_INC(ivar_get_base);
-
-    if (iv == Qundef) {
-	if (RTEST(ruby_verbose))
-	    rb_warning("instance variable %"PRIsVALUE" not initialized", QUOTE_ID(id));
-	iv = Qnil;
-    }
     return iv;
 }
 
@@ -3526,8 +3520,6 @@ rb_iv_get(VALUE obj, const char *name)
     ID id = rb_check_id_cstr(name, strlen(name), rb_usascii_encoding());
 
     if (!id) {
-        if (RTEST(ruby_verbose))
-            rb_warning("instance variable %s not initialized", name);
         return Qnil;
     }
     return rb_ivar_get(obj, id);
diff --git a/vm_insnhelper.c b/vm_insnhelper.c
index e6282ca668..9205273199 100644
--- a/vm_insnhelper.c
+++ b/vm_insnhelper.c
@@ -1179,9 +1179,6 @@ vm_getivar(VALUE obj, ID id, const rb_iseq_t *iseq, IVC ic, const struct rb_call
             return val;
         }
         else {
-            if (!is_attr && RTEST(ruby_verbose)) {
-                rb_warning("instance variable %"PRIsVALUE" not initialized", QUOTE_ID(id));
-            }
             return Qnil;
         }
     }