From: nobu@...
Date: 2017-12-12T10:04:58+00:00
Subject: [ruby-core:84201] [Ruby trunk Feature#11256] anonymous block	forwarding

Issue #11256 has been updated by nobu (Nobuyoshi Nakada).


Current patch.

```diff
diff --git a/parse.y b/parse.y
index 1026d5c896..2a98016002 100644
--- a/parse.y
+++ b/parse.y
@@ -347,6 +347,8 @@ static int parser_yyerror(struct parser_params*, const char*);
 
 #define lambda_beginning_p() (lpar_beg && lpar_beg == paren_nest)
 
+#define ANON_BLOCK_ID '&'
+
 static enum yytokentype yylex(YYSTYPE*, YYLTYPE*, struct parser_params*);
 
 #ifndef RIPPER
@@ -2560,6 +2562,18 @@ block_arg	: tAMPER arg_value
 			$$ = $2;
 		    %*/
 		    }
+		| tAMPER
+		    {
+		    /*%%%*/
+			if (!local_id(ANON_BLOCK_ID)) {
+			    compile_error(PARSER_ARG "no anonymous block parameter");
+			}
+			$$ = NEW_BLOCK_PASS(new_lvar(ANON_BLOCK_ID, &@1));
+			$$->nd_loc = @$;
+		    /*%
+			$$ = Qnil;
+		    %*/
+		    }
 		;
 
 opt_block_arg	: ',' block_arg
@@ -4913,6 +4927,15 @@ f_block_arg	: blkarg_mark tIDENTIFIER
 			$$ = dispatch1(blockarg, $2);
 		    %*/
 		    }
+		| blkarg_mark
+		    {
+		    /*%%%*/
+			$$ = ANON_BLOCK_ID;
+			arg_var($$);
+		    /*%
+			$$ = dispatch1(blockarg, Qnil);
+		    %*/
+		    }
 		;
 
 opt_f_block_arg	: ',' f_block_arg
```

----------------------------------------
Feature #11256: anonymous block forwarding
https://bugs.ruby-lang.org/issues/11256#change-68318

* Author: bughit (bug hit)
* Status: Assigned
* Priority: Normal
* Assignee: matz (Yukihiro Matsumoto)
* Target version: 
----------------------------------------
since capturing a block into a proc is slow: foo(&block)
and creating chains of blocks is kind of ugly and ultimately also inefficient: foo{yield}
why not allow block forwarding without capturing: foo(&) foo(1, 2, &)



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