From c8703a17ceedae4a72f83c962a4d098731a85dda Mon Sep 17 00:00:00 2001
From: Nobuyoshi Nakada <nobu@ruby-lang.org>
Date: Mon, 18 May 2020 10:09:28 +0900
Subject: [PATCH] [Feature #16254] Allow `__builtin.func` style

---
 compile.c                 | 25 ++++++++++++++++++-------
 tool/mk_builtin_loader.rb | 23 ++++++++++++++++++++---
 2 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/compile.c b/compile.c
index 6316985b3d..13df6a0062 100644
--- a/compile.c
+++ b/compile.c
@@ -7039,18 +7039,30 @@ iseq_builtin_function_lookup(const rb_iseq_t *iseq, const char *name)
 }
 
 static const char *
-iseq_builtin_function_name(ID mid)
+iseq_builtin_function_name(const enum node_type type, const NODE *recv, ID mid)
 {
     const char *name = rb_id2name(mid);
     static const char prefix[] = "__builtin_";
     const size_t prefix_len = sizeof(prefix) - 1;
 
-    if (UNLIKELY(strncmp(prefix, name, prefix_len) == 0)) {
-        return &name[prefix_len];
+    if (type == NODE_CALL) {
+        if (recv) {
+            switch (nd_type(recv)) {
+              case NODE_VCALL:
+                if (recv->nd_mid == rb_intern("__builtin")) {
+                    return name;
+                }
+                break;
+              default: break;
+            }
+        }
     }
-    else {
-        return NULL;
+    else if (type == NODE_VCALL || type == NODE_FCALL) {
+        if (UNLIKELY(strncmp(prefix, name, prefix_len) == 0)) {
+            return &name[prefix_len];
+        }
     }
+    return NULL;
 }
 
 static int
@@ -7204,8 +7216,7 @@ compile_call(rb_iseq_t *iseq, LINK_ANCHOR *const ret, const NODE *const node, co
     NODE *args_node = node->nd_args;
 
     if (UNLIKELY(iseq_has_builtin_function_table(iseq)) &&
-        (type == NODE_VCALL || type == NODE_FCALL) &&
-        (builtin_func = iseq_builtin_function_name(mid)) != NULL) {
+        (builtin_func = iseq_builtin_function_name(type, node->nd_recv, mid)) != NULL) {
 
         if (parent_block != NULL) {
             COMPILE_ERROR(iseq, line, "should not call builtins here.");
diff --git a/tool/mk_builtin_loader.rb b/tool/mk_builtin_loader.rb
index 505a256ba8..ae6c3b3812 100644
--- a/tool/mk_builtin_loader.rb
+++ b/tool/mk_builtin_loader.rb
@@ -72,7 +72,7 @@ end
 
 def collect_builtin base, tree, name, bs, inlines, params = nil
   while tree
-    call = sep = mid = args = nil
+    call = recv = sep = mid = args = nil
     case tree.first
     when :def
       params = collect_params(tree[2])
@@ -93,6 +93,8 @@ def collect_builtin base, tree, name, bs, inlines, params = nil
     when :method_add_arg
       _, mid, (_, (_, args)) = tree
       case mid.first
+      when :call
+        _, recv, sep, mid = mid
       when :fcall
         _, mid = mid
       else
@@ -102,12 +104,27 @@ def collect_builtin base, tree, name, bs, inlines, params = nil
       _, mid = tree
     when :command               # FCALL
       _, mid, (_, args) = tree
+    when :call, :command_call   # CALL
+      _, recv, sep, mid, (_, args) = tree
     end
     if mid
       raise "unknown sexp: #{mid.inspect}" unless mid.first == :@ident
       _, mid, (lineno,) = mid
-      if /\A__builtin_(.+)/ =~ mid
-        cfunc_name = func_name = $1
+      if recv
+        func_name = nil
+        case recv.first
+        when :vcall
+          _, recv = recv
+          if recv.first == :@ident and recv[1] == "__builtin"
+            func_name = mid.to_s
+          end
+        end
+        collect_builtin(base, recv, name, bs, inlines) unless func_name
+      else
+        func_name = mid[/\A__builtin_(.+)/, 1]
+      end
+      if func_name
+        cfunc_name = func_name
         args.pop unless (args ||= []).last
         argc = args.size