[PATCH] C++0x right angle brackets

["Doug Gregor" <doug dot gregor at gmail dot com>]

This patch implements the "right angle brackets" feature of C++0x,
which is part of the current C++0x working draft (and has been for a
while). Essentially, it allows users to write, e.g.,

 vector<vector<int>> v;

and it will parse the ">>" token as two separate ">" tokens, ending
the two, nested template argument lists. Essentially, C++0x uses the
same rule for ">>" tokens when there is an active "<" (for a template
argument list or a new-style case) as it does for ">" tokens, breaking
apart ">>" into ">" and ">".

This new behavior is only available when we're in C++0x mode, which is
particularly important because it breaks some existing programs. For
example, the following is legal C++98 but ill-formed C++0x:

 template<int> struct X { };
 X<100 >> 2> x; // ">>" is a right-shift operator in C++98, two ">"
tokens in C++0x

This patch, of course, maintains the C++98 behavior in the default
C++98 mode and uses the C++0x behavior in C++0x mode. When the C++0x
compatibility warnings (-Wc++0x-compat) are turned on, this patch will
warn about cases where the behavior will change and suggest that the
user put parentheses around the expression.

C++ front end and testsuite patches attached.

Tested i386-apple-darwin8.8.1, no regressions.

Okay for mainline?

 Cheers,
 Doug

2007-02-13  Douglas Gregor  <doug.gregor@gmail.com>

	* parser.c (struct cp_parser): Update comment for
	greater_than_is_operator_p.
	(cp_parser_primary_expression): In C++0x mode, a cast operator can
	be terminated with a `>>' token when !GREATER_THAN_IS_OPERATOR_P.
	(TOKEN_PRECEDENCE): In C++0x mode, `>>' is treated like `>' when
	!GREATER_THAN_IS_OPERATOR_P.
	(cp_parser_binary_expression): When -Wc++0x-compat, warn about
	`>>' operators that will become two `>' tokens in C++0x.
	(cp_parser_parameter_declaration): Treate `>>' like `>' in C++0x
	mode, allowing it to terminate default arguments.
	(cp_parser_enclosed_template_argument_list): In C++0x mode, treat
	`>>' like two consecutive `>' tokens.
	(cp_parser_skip_to_end_of_template_parameter_list): Ditto.
	(cp_parser_next_token_ends_template_argument_p): In C++0x, `>>'
	ends a template argument.

2007-02-13  Douglas Gregor  <doug.gregor@gmail.com>

	* g++.dg/cpp0x/bracket1.C: New.
	* g++.dg/cpp0x/bracket2.C: New.
	* g++.dg/cpp0x/bracket3.C: New.

Attachment: rangle-cp.patch
Description: Binary data

Attachment: rangle-testsuite.patch
Description: Binary data