From 9b52bacc62c3db13ea18fa5ea4d9b9a92b5fcb86 Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Thu, 21 Nov 2019 02:14:20 +0900
Subject: Refined inspection of argument forwarding

---
 proc.c                   | 51 ++++++++++++++++++++++++++++++++++++------------
 test/ruby/test_method.rb |  6 ++++--
 2 files changed, 43 insertions(+), 14 deletions(-)

diff --git a/proc.c b/proc.c
index 9859116baf..e0ce44297c 100644
--- a/proc.c
+++ b/proc.c
@@ -2838,6 +2838,7 @@ method_inspect(VALUE method)
         const VALUE keyrest = ID2SYM(rb_intern("keyrest"));
         const VALUE block = ID2SYM(rb_intern("block"));
         const VALUE nokey = ID2SYM(rb_intern("nokey"));
+        int forwarding = 0;
 
         rb_str_buf_cat2(str, "(");
 
@@ -2850,30 +2851,56 @@ method_inspect(VALUE method)
                 // FIXME: can it be reduced to switch/case?
                 if (kind == req || kind == opt) {
                     name = rb_str_new2("_");
-                } else if (kind == rest || kind == keyrest) {
+                }
+                else if (kind == rest || kind == keyrest) {
                     name = rb_str_new2("");
-                } else if (kind == block) {
+                }
+                else if (kind == block) {
                     name = rb_str_new2("block");
-                } else if (kind == nokey) {
+                }
+                else if (kind == nokey) {
                     name = rb_str_new2("nil");
                 }
             }
 
             if (kind == req) {
                 rb_str_catf(str, "%"PRIsVALUE, name);
-            } else if (kind == opt) {
+            }
+            else if (kind == opt) {
                 rb_str_catf(str, "%"PRIsVALUE"=...", name);
-            } else if (kind == keyreq) {
+            }
+            else if (kind == keyreq) {
                 rb_str_catf(str, "%"PRIsVALUE":", name);
-            } else if (kind == key) {
+            }
+            else if (kind == key) {
                 rb_str_catf(str, "%"PRIsVALUE": ...", name);
-            } else if (kind == rest) {
-                rb_str_catf(str, "*%"PRIsVALUE, name);
-            } else if (kind == keyrest) {
+            }
+            else if (kind == rest) {
+                if (name == ID2SYM('*')) {
+                    forwarding = 1;
+                    rb_str_cat_cstr(str, "...");
+                }
+                else {
+                    rb_str_catf(str, "*%"PRIsVALUE, name);
+                }
+            }
+            else if (kind == keyrest) {
                 rb_str_catf(str, "**%"PRIsVALUE, name);
-            } else if (kind == block) {
-                rb_str_catf(str, "&%"PRIsVALUE, name);
-            } else if (kind == nokey) {
+            }
+            else if (kind == block) {
+                if (name == ID2SYM('&')) {
+                    if (forwarding) {
+                        rb_str_set_len(str, RSTRING_LEN(str) - 2);
+                    }
+                    else {
+                        rb_str_cat_cstr(str, "...");
+                    }
+                }
+                else {
+                    rb_str_catf(str, "&%"PRIsVALUE, name);
+                }
+            }
+            else if (kind == nokey) {
                 rb_str_buf_cat2(str, "**nil");
             }
 
diff --git a/test/ruby/test_method.rb b/test/ruby/test_method.rb
index 38bcaba622..edd1da368c 100644
--- a/test/ruby/test_method.rb
+++ b/test/ruby/test_method.rb
@@ -555,6 +555,7 @@ class TestMethod < Test::Unit::TestCase
     assert_equal([[:req, :a], [:opt, :b], [:rest, :c], [:req, :d], [:keyrest, :o]], method(:mk7).parameters)
     assert_equal([[:req, :a], [:opt, :b], [:rest, :c], [:req, :d], [:keyreq, :e], [:key, :f], [:keyrest, :o]], method(:mk8).parameters)
     assert_equal([[:nokey]], method(:mnk).parameters)
+    # pending
     assert_equal([[:rest, :*], [:block, :&]], method(:mf).parameters)
   end
 
@@ -580,6 +581,7 @@ class TestMethod < Test::Unit::TestCase
     assert_equal([[:req, :a], [:opt, :b], [:rest, :c], [:req, :d], [:keyrest, :o]], self.class.instance_method(:mk7).parameters)
     assert_equal([[:req, :a], [:opt, :b], [:rest, :c], [:req, :d], [:keyreq, :e], [:key, :f], [:keyrest, :o]], self.class.instance_method(:mk8).parameters)
     assert_equal([[:nokey]], self.class.instance_method(:mnk).parameters)
+    # pending
     assert_equal([[:rest, :*], [:block, :&]], self.class.instance_method(:mf).parameters)
   end
 
@@ -657,7 +659,7 @@ class TestMethod < Test::Unit::TestCase
     assert_include(method(:mk7).inspect, "(a, b=..., *c, d, **o)")
     assert_include(method(:mk8).inspect, "(a, b=..., *c, d, e:, f: ..., **o)")
     assert_include(method(:mnk).inspect, "(**nil)")
-    assert_include(method(:mf).inspect, "(**, &&)")
+    assert_include(method(:mf).inspect, "(...)")
   end
 
   def test_unbound_method_parameters_inspect
@@ -682,7 +684,7 @@ class TestMethod < Test::Unit::TestCase
     assert_include(self.class.instance_method(:mk7).inspect, "(a, b=..., *c, d, **o)")
     assert_include(self.class.instance_method(:mk8).inspect, "(a, b=..., *c, d, e:, f: ..., **o)")
     assert_include(self.class.instance_method(:mnk).inspect, "(**nil)")
-    assert_include(self.class.instance_method(:mf).inspect, "(**, &&)")
+    assert_include(self.class.instance_method(:mf).inspect, "(...)")
   end
 
   def test_public_method_with_zsuper_method
-- 
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