Re: c++/10864: [diagnostic] Unreadable error message for "no match for 'A < B' operator" if A,B are templates

[Gabriel Dos Reis <gdr@integrable-solutions.net>]

The following reply was made to PR c++/10864; it has been noted by GNATS.

From: Gabriel Dos Reis <gdr@integrable-solutions.net>
To: bangerth@dealii.org
Cc: gcc-gnats@gcc.gnu.org
Subject: Re: c++/10864: [diagnostic] Unreadable error message for "no match for 'A < B' operator" if A,B are templates
Date: 19 May 2003 23:08:18 +0200

 bangerth@dealii.org writes:
 
 | g/x> /home/bangerth/bin/gcc-3.4-pre/bin/c++ -c y.cc
 | y.cc: In member function `bool less<T>::foo() [with T =
 |    X<std::vector<std::string, std::allocator<std::string> >,
 |    std::vector<std::string, std::allocator<std::string> > >]':
 | y.cc:10:   instantiated from here
 | y.cc:5: error: no match for `X<std::vector<std::string,
 |    std::allocator<std::string> >, std::vector<std::string,
 |    std::allocator<std::string> > > < X<std::vector<std::string,
 |    std::allocator<std::string> >, std::vector<std::string,
 |    std::allocator<std::string> > >' operator
 | 
 | Now, that's pretty hard to read. What it says is:
 |   no match for `A < B' operator
 | but the "<" is totally lost in all these template args.
 | I also always thought that the message was somehow
 | truncated, since usually in C++ there must be something
 | after the "operator" :-)
 
 I fully agree.  I must confess that I have never been sympathetic to
 the way we handle messages saying "no match for bubble[tangle] operator".
 Sometime, they just look very strange to read. 
 
 | I think it would be nice if the message could be changed
 | to read like
 |   no match for operator< in expression `A < B'
 | That way it would be simpler to figure out which operator
 | exactly is missing.
 
 I think that is a very good suggestion.
 
 -- Gaby