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authorAnthony Ramine <[email protected]>2014-03-25 03:00:15 +0100
committerBjörn Gustavsson <[email protected]>2014-03-25 04:34:24 +0100
commit7a72ebab6811bea482ae0ad9fc25c7f4820226fe (patch)
treeb086da6562d03ba74e7fb872b46210ab8b12b8cf /lib/compiler
parentc2b4eab25c907f453a394d382c04cd04e6c06b49 (diff)
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Correctly handle non-matching patterns against literal values
The pass sys_core_fold did not correctly handle non-matching patterns in code such as: 0 = case <<>> of <<>> -> 0; a -> 1 end. Function case_opt_lit/3 is rewritten in two passes to first remove any non-matching clause and only then potentially remove the related patterns in each clause. Reported-by: Ulf Norell
Diffstat (limited to 'lib/compiler')
-rw-r--r--lib/compiler/src/sys_core_fold.erl43
-rw-r--r--lib/compiler/test/core_fold_SUITE.erl14
2 files changed, 38 insertions, 19 deletions
diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl
index 52d6dfe184..b7422318b2 100644
--- a/lib/compiler/src/sys_core_fold.erl
+++ b/lib/compiler/src/sys_core_fold.erl
@@ -2031,9 +2031,9 @@ case_opt(Arg, Cs0, Sub) ->
case_opt_args([A0|As0], Cs0, Sub, LitExpr, Acc) ->
case case_opt_arg(A0, Sub, Cs0, LitExpr) of
- error ->
+ {error,Cs1} ->
%% Nothing to be done. Move on to the next argument.
- Cs = [{Ps,C,[P|PsAcc],Bs} || {[P|Ps],C,PsAcc,Bs} <- Cs0],
+ Cs = [{Ps,C,[P|PsAcc],Bs} || {[P|Ps],C,PsAcc,Bs} <- Cs1],
case_opt_args(As0, Cs, Sub, LitExpr, [A0|Acc]);
{ok,As1,Cs} ->
%% The argument was either expanded (from tuple/list) or
@@ -2052,7 +2052,7 @@ case_opt_arg(E0, Sub, Cs, LitExpr) ->
E = maybe_replace_var(E0, Sub),
case cerl:is_data(E) of
false ->
- error;
+ {error,Cs};
true ->
case cerl:data_type(E) of
{atomic,_} ->
@@ -2102,35 +2102,44 @@ maybe_replace_var_1(E, #sub{t=Tdb}) ->
%% pattern matching is tricky, so we will give up in that case.
case_opt_lit(Lit, Cs0, LitExpr) ->
- try case_opt_lit_1(Cs0, Lit, LitExpr) of
+ Cs1 = case_opt_lit_1(Lit, Cs0, LitExpr),
+ try case_opt_lit_2(Lit, Cs1) of
Cs ->
{ok,[],Cs}
catch
throw:impossible ->
- error
+ {error,Cs1}
end.
-case_opt_lit_1([{[P|Ps],C,PsAcc,Bs0}|Cs], E, LitExpr) ->
+case_opt_lit_1(E, [{[P|_],C,_,_}=Current|Cs], LitExpr) ->
+ case cerl_clauses:match(P, E) of
+ none ->
+ %% The pattern will not match the literal. Remove the clause.
+ %% Unless the entire case expression is a literal, also
+ %% emit a warning.
+ case LitExpr of
+ false -> add_warning(C, nomatch_clause_type);
+ true -> ok
+ end,
+ case_opt_lit_1(E, Cs, LitExpr);
+ _ ->
+ [Current|case_opt_lit_1(E, Cs, LitExpr)]
+ end;
+case_opt_lit_1(_, [], _) -> [].
+
+case_opt_lit_2(E, [{[P|Ps],C,PsAcc,Bs0}|Cs]) ->
+ %% Non-matching clauses have already been removed in case_opt_lit_1/3.
case cerl_clauses:match(P, E) of
- none ->
- %% The pattern will not match the literal. Remove the clause.
- %% Unless the entire case expression is a literal, also
- %% emit a warning.
- case LitExpr of
- false -> add_warning(C, nomatch_clause_type);
- true -> ok
- end,
- case_opt_lit_1(Cs, E, LitExpr);
{true,Bs} ->
%% The pattern matches the literal. Remove the pattern
%% and update the bindings.
- [{Ps,C,PsAcc,Bs++Bs0}|case_opt_lit_1(Cs, E, LitExpr)];
+ [{Ps,C,PsAcc,Bs++Bs0}|case_opt_lit_2(E, Cs)];
{false,_} ->
%% Binary literal and pattern. We are not sure whether
%% the pattern will match.
throw(impossible)
end;
-case_opt_lit_1([], _, _) -> [].
+case_opt_lit_2(_, []) -> [].
%% case_opt_data(Expr, Clauses0, LitExpr) -> {ok,Exprs,Clauses}
diff --git a/lib/compiler/test/core_fold_SUITE.erl b/lib/compiler/test/core_fold_SUITE.erl
index 9c986576d5..6a7036d728 100644
--- a/lib/compiler/test/core_fold_SUITE.erl
+++ b/lib/compiler/test/core_fold_SUITE.erl
@@ -23,7 +23,7 @@
t_element/1,setelement/1,t_length/1,append/1,t_apply/1,bifs/1,
eq/1,nested_call_in_case/1,guard_try_catch/1,coverage/1,
unused_multiple_values_error/1,unused_multiple_values/1,
- multiple_aliases/1,redundant_boolean_clauses/1]).
+ multiple_aliases/1,redundant_boolean_clauses/1,mixed_matching_clauses/1]).
-export([foo/0,foo/1,foo/2,foo/3]).
@@ -40,7 +40,7 @@ groups() ->
[t_element,setelement,t_length,append,t_apply,bifs,
eq,nested_call_in_case,guard_try_catch,coverage,
unused_multiple_values_error,unused_multiple_values,
- multiple_aliases,redundant_boolean_clauses]}].
+ multiple_aliases,redundant_boolean_clauses,mixed_matching_clauses]}].
init_per_suite(Config) ->
@@ -373,5 +373,15 @@ redundant_boolean_clauses(Config) when is_list(Config) ->
true -> yes
end.
+mixed_matching_clauses(Config) when is_list(Config) ->
+ 0 = case #{} of
+ #{} -> 0;
+ a -> 1
+ end,
+ 0 = case <<>> of
+ <<>> -> 0;
+ a -> 1
+ end,
+ ok.
id(I) -> I.