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feat(library/coercion): improve error message when coercion has no viable source

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Daniel Selsam 2015-08-13 21:24:33 -07:00 committed by Leonardo de Moura
parent 5bef45b1fd
commit 7223293a93
1 changed files with 3 additions and 1 deletions
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4
src/library/coercion.cpp
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@ -366,7 +366,9 @@ environment add_coercion(environment const & env, io_state const &, name const &
t = binding_body(t);
}
if (Cs.empty())
throw exception(sstream() << "invalid coercion, '" << f << "' cannot be used as a coercion");
throw exception(sstream() << "invalid coercion, '" << f << "' cannot be used as a coercion "
<< "because there is no acceptable source type; coercions must be of the form\n"
<< "coe : Pi (x_1 : A_1) ... (x_n : A_n) (y: C x_1 ... x_n), <target>");
unsigned i = Cs.size();
while (i > 0) {
--i;