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-rw-r--r--lib/compiler/src/sys_core_fold.erl15
-rw-r--r--lib/compiler/test/warnings_SUITE.erl10
2 files changed, 22 insertions, 3 deletions
diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl
index c870bb68c8..9360556e00 100644
--- a/lib/compiler/src/sys_core_fold.erl
+++ b/lib/compiler/src/sys_core_fold.erl
@@ -1969,13 +1969,22 @@ case_tuple_pat([#c_tuple{es=Ps}], Arity) when length(Ps) =:= Arity ->
case_tuple_pat([#c_literal{val=T}], Arity) when tuple_size(T) =:= Arity ->
Ps = [#c_literal{val=E} || E <- tuple_to_list(T)],
{ok,Ps,[]};
-case_tuple_pat([#c_var{anno=Anno}=V], Arity) ->
- Vars = make_vars(Anno, 1, Arity),
+case_tuple_pat([#c_var{anno=Anno0}=V], Arity) ->
+ Vars = make_vars(Anno0, 1, Arity),
+
+ %% If the entire case statement is evaluated in an effect
+ %% context (e.g. "case {A,B} of ... end, ok"), there will
+ %% be a warning that a term is constructed but never used.
+ %% To avoid that warning, we must annotate the tuple as
+ %% compiler generated.
+
+ Anno = [compiler_generated|Anno0],
{ok,Vars,[{V,#c_tuple{anno=Anno,es=Vars}}]};
case_tuple_pat([#c_alias{var=V,pat=P}], Arity) ->
case case_tuple_pat([P], Arity) of
{ok,Ps,Avs} ->
- Anno = core_lib:get_anno(P),
+ Anno0 = core_lib:get_anno(P),
+ Anno = [compiler_generated|Anno0],
{ok,Ps,[{V,#c_tuple{anno=Anno,es=unalias_pat_list(Ps)}}|Avs]};
error ->
error
diff --git a/lib/compiler/test/warnings_SUITE.erl b/lib/compiler/test/warnings_SUITE.erl
index 8cc3ca4199..dd18a6e1a3 100644
--- a/lib/compiler/test/warnings_SUITE.erl
+++ b/lib/compiler/test/warnings_SUITE.erl
@@ -453,6 +453,16 @@ effect(Config) when is_list(Config) ->
true -> ok
end,
ok.
+
+ m8(A, B) ->
+ case {A,B} of
+ V -> V
+ end,
+ ok.
+
+ m9(Bs) ->
+ [{B,ok} = {B,foo:bar(B)} || B <- Bs],
+ ok.
">>,
[],
{warnings,[{5,sys_core_fold,{no_effect,{erlang,is_integer,1}}},