golint-comment.pl

#!/usr/bin/env perl
use strict;
use warnings;

sub comment_for {
    my $line = shift;
    if ($line =~ /^ (type|func|var) \s+ (\(.*?\))? \s* ([A-Z]\w+) /x) {
        my ($kind, $is_method, $name) = ($1, $2, $3);
        if ($is_method && grep { $name ne $_ } qw(String Error)) {
            # skip
            return;
        } else {
            return "// $name is\n";
        }
    }
    if ($line =~ /^var\s+\(\n/) {
        return "// constants\n";
    }
    return;
}

my @out;
while (<>) {
    my $comment = comment_for $_;
    if (!$comment) {
        push @out, $_;
        next;
    }

    pop @out if $out[-1] =~ m{^//};
    push @out, $comment, $_;
}

print for @out;