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authorBjörn Gustavsson <[email protected]>2016-08-15 15:34:06 +0200
committerBjörn Gustavsson <[email protected]>2016-09-02 14:24:36 +0200
commit0baa07cdf2754748bbc2d969bf83f08c0976fb78 (patch)
treeb5d649dbe4778d8488ae09a99e68435adc216342 /lib/stdlib/test/qlc_SUITE.erl
parent8a04dd4dd2d479efe488b0bed118e10559835fb6 (diff)
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Fix overridden BIFs
The filters in a list comprehension can be guard expressions or an ordinary expressions. If a guard expression is used as a filter, an exception will basically mean the same as 'false': t() -> L = [{some_tag,42},an_atom], [X || X <- L, element(1, X) =:= some_tag] %% Returns [{some_tag,42}] On the other hand, if an ordinary expression is used as a filter, there will be an exception: my_element(N, T) -> element(N, T). t() -> L = [{some_tag,42},an_atom], [X || X <- L, my_element(1, X) =:= some_tag] %% Causes a 'badarg' exception when element(1, an_atom) is evaluated It has been allowed for several releases to override a BIF with a local function. Thus, if we define a function called element/2, it will be called instead of the BIF element/2 within the module. We must use the "erlang:" prefix to call the BIF. Therefore, the following code is expected to work the same way as in our second example above: -compile({no_auto_import,[element/2]}). element(N, T) -> erlang:element(N, T). t() -> L = [{some_tag,42},an_atom], [X || X <- L, element(1, X) =:= some_tag]. %% Causes a 'badarg' exception when element(1, an_atom) is evaluated But the compiler refuses to compile the code with the following diagnostic: call to local/imported function element/2 is illegal in guard
Diffstat (limited to 'lib/stdlib/test/qlc_SUITE.erl')
-rw-r--r--lib/stdlib/test/qlc_SUITE.erl21
1 files changed, 19 insertions, 2 deletions
diff --git a/lib/stdlib/test/qlc_SUITE.erl b/lib/stdlib/test/qlc_SUITE.erl
index 2bd940020c..8c7d5a5fcf 100644
--- a/lib/stdlib/test/qlc_SUITE.erl
+++ b/lib/stdlib/test/qlc_SUITE.erl
@@ -58,7 +58,7 @@
-export([
badarg/1, nested_qlc/1, unused_var/1, lc/1, fun_clauses/1,
filter_var/1, single/1, exported_var/1, generator_vars/1,
- nomatch/1, errors/1, pattern/1,
+ nomatch/1, errors/1, pattern/1, overridden_bif/1,
eval/1, cursor/1, fold/1, eval_unique/1, eval_cache/1, append/1,
evaluator/1, string_to_handle/1, table/1, process_dies/1,
@@ -126,7 +126,7 @@ groups() ->
[{parse_transform, [],
[badarg, nested_qlc, unused_var, lc, fun_clauses,
filter_var, single, exported_var, generator_vars,
- nomatch, errors, pattern]},
+ nomatch, errors, pattern, overridden_bif]},
{evaluation, [],
[eval, cursor, fold, eval_unique, eval_cache, append,
evaluator, string_to_handle, table, process_dies, sort,
@@ -468,6 +468,23 @@ pattern(Config) when is_list(Config) ->
-record(k, {t,v}).\n">>, Ts),
ok.
+%% Override a guard BIF with an imported or local function.
+overridden_bif(Config) ->
+ Ts = [
+ <<"[2] = qlc:e(qlc:q([P || P <- [1,2,3], port(P)])),
+ [10] = qlc:e(qlc:q([P || P <- [0,9,10,11,12],
+ (is_reference(P) andalso P > 5)])),
+ Empty = gb_sets:empty(), Single = gb_sets:singleton(42),
+ GbSets = [Empty,Single],
+ [Single] = qlc:e(qlc:q([S || S <- GbSets, size(S) =/= 0]))
+ ">>
+ ],
+ run(Config, "-import(gb_sets, [size/1]).
+ -compile({no_auto_import, [size/1, is_reference/1]}).
+ port(N) -> N rem 2 =:= 0.
+ is_reference(N) -> N rem 10 =:= 0.\n", Ts),
+ ok.
+
%% eval/2
eval(Config) when is_list(Config) ->