Re: Throw compilation error(or warning) if duplicate keys are present in hash

There is no duplicate key at compile-time — the list is only created and assigned to the hash at run-time — so the answer to your literal question is "no".

However, it is possible to write an opcode checker that detects the posted code pattern at compile-time. (For example, module autovivification uses an opcode checker to not only examine opcodes, but to replace them.) This approach would probably be better to add a *run-time* warning.

A better approach to detecting the situation at compile-time would be to write a Perl::Critic rule to look for the code pattern you posted.

Comment on Re: Throw compilation error(or warning) if duplicate keys are present in hash

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Re^2: Throw compilation error(or warning) if duplicate keys are present in hash by I_love_perl (Novice) on Nov 24, 2011 at 09:18 UTC
Hi Ikegami, Thanks for your quick response. I've tried using Perl::Critic (http://perlcritic.com/), but it is not throwing up any warning with respect to the re-occurrence of the hash key. Correct me if I'm doing something wrong in using Perl::Critic	[reply]
Re^3: Throw compilation error(or warning) if duplicate keys are present in hash by ikegami (Patriarch) on Nov 25, 2011 at 03:54 UTC
I didn't say a rule already existed to check this. Quite the opposite, I assumed there wasn't one and told you you'd have to actually write the rule.	[reply]
Re^4: Throw compilation error(or warning) if duplicate keys are present in hash by petdance (Parson) on Nov 27, 2012 at 21:20 UTC
A policy for this now exists, but you'll need to install Perl::Critic::Pulp. See http://search.cpan.org/dist/Perl-Critic-Pulp/lib/Perl/Critic/Policy/ValuesAndExpressions/ProhibitDuplicateHashKeys.pm xoxo, Andy	[reply]