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| author | Michał Muskała <[email protected]> | 2018-04-27 12:40:07 +0200 |
|---|---|---|
| committer | Michał Muskała <[email protected]> | 2018-04-29 17:03:43 +0200 |
| commit | 5d0874a8f9fd617308d9024783db1e4e24268184 (patch) | |
| tree | ac61f2f0f8d7f7483af9e17df44b49aeb049e695 /lib/hipe | |
| parent | d423a7af502227afcdcf7d2a1efecded85ea95fb (diff) | |
| download | otp-5d0874a8f9fd617308d9024783db1e4e24268184.tar.gz otp-5d0874a8f9fd617308d9024783db1e4e24268184.tar.bz2 otp-5d0874a8f9fd617308d9024783db1e4e24268184.zip | |
Introduce is_map_key/2 guard BIF
This complements the `map_get/2` guard BIF introduced in #1784.
Rationale.
`map_get/2` allows accessing map fields in guards, but it might be
problematic in more complex guard expressions, for example:
foo(X) when map_get(a, X) =:= 1 or is_list(X) -> ...
The `is_list/1` part of the guard could never succeed since the
`map_get/2` guard would fail the whole guard expression. In this
situation, this could be solved by using `;` instead of `or` to separate
the guards, but it is not possible in every case.
To solve this situation, this PR proposes a `is_map_key/2` guard that
allows to check if a map has key inside a guard before trying to access
that key. When combined with `is_map/1` this allows to construct a
purely boolean guard expression testing a value of a key in a map.
Implementation.
Given the use case motivating the introduction of this function, the PR
contains compiler optimisations that produce optimial code for the
following guard expression:
foo(X) when is_map(X) and is_map_key(a, X) and map_get(a, X) =:= 1 -> ok;
foo(_) -> error.
Given all three tests share the failure label, the `is_map_key/2` and
`is_map/2` tests are optimised away.
As with `map_get/2` the `is_map_key/2` BIF is allowed in match specs.
Diffstat (limited to 'lib/hipe')
| -rw-r--r-- | lib/hipe/cerl/erl_bif_types.erl | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/lib/hipe/cerl/erl_bif_types.erl b/lib/hipe/cerl/erl_bif_types.erl index fe6ab0659c..48ce641ab9 100644 --- a/lib/hipe/cerl/erl_bif_types.erl +++ b/lib/hipe/cerl/erl_bif_types.erl @@ -665,6 +665,8 @@ type(erlang, is_map, 1, Xs, Opaques) -> check_guard(X, fun (Y) -> t_is_map(Y, Opaques) end, t_map(), Opaques) end, strict(erlang, is_map, 1, Xs, Fun, Opaques); +type(erlang, is_map_key, 2, Xs, Opaques) -> + type(maps, is_key, 2, Xs, Opaques); type(erlang, is_number, 1, Xs, Opaques) -> Fun = fun (X) -> check_guard(X, fun (Y) -> t_is_number(Y, Opaques) end, @@ -2374,6 +2376,8 @@ arg_types(erlang, is_list, 1) -> [t_any()]; arg_types(erlang, is_map, 1) -> [t_any()]; +arg_types(erlang, is_map_key, 2) -> + [t_any(), t_map()]; arg_types(erlang, is_number, 1) -> [t_any()]; arg_types(erlang, is_pid, 1) -> @@ -2396,7 +2400,7 @@ arg_types(erlang, map_size, 1) -> [t_map()]; %% Guard bif, needs to be here. arg_types(erlang, map_get, 2) -> - [t_map(), t_any()]; + [t_any(), t_map()]; arg_types(erlang, make_fun, 3) -> [t_atom(), t_atom(), t_arity()]; arg_types(erlang, make_tuple, 2) -> |