diff options
| -rw-r--r-- | lib/compiler/src/sys_core_fold.erl | 17 | ||||
| -rw-r--r-- | lib/compiler/src/v3_core.erl | 26 | ||||
| -rw-r--r-- | lib/compiler/test/match_SUITE.erl | 16 | ||||
| -rw-r--r-- | lib/compiler/test/warnings_SUITE.erl | 7 |
4 files changed, 51 insertions, 15 deletions
diff --git a/lib/compiler/src/sys_core_fold.erl b/lib/compiler/src/sys_core_fold.erl index 068478496b..3b374be015 100644 --- a/lib/compiler/src/sys_core_fold.erl +++ b/lib/compiler/src/sys_core_fold.erl @@ -602,15 +602,23 @@ count_bits_1(Int, Bits) -> count_bits_1(Int bsr 64, Bits+64). %% a rewritten expression consisting of a sequence of %% the arguments only is returned. -useless_call(effect, #c_call{module=#c_literal{val=Mod}, +useless_call(effect, #c_call{anno=Anno, + module=#c_literal{val=Mod}, name=#c_literal{val=Name}, args=Args}=Call) -> A = length(Args), case erl_bifs:is_safe(Mod, Name, A) of false -> case erl_bifs:is_pure(Mod, Name, A) of - true -> add_warning(Call, result_ignored); - false -> ok + true -> + case member(result_not_wanted, Anno) of + false -> + add_warning(Call, result_ignored); + true -> + ok + end; + false -> + ok end, no; true -> @@ -2806,7 +2814,8 @@ format_error({no_effect,{erlang,F,A}}) -> end, flatten(io_lib:format(Fmt, Args)); format_error(result_ignored) -> - "the result of the expression is ignored"; + "the result of the expression is ignored " + "(suppress the warning by assigning the expression to the _ variable)"; format_error(useless_building) -> "a term is constructed, but never used"; format_error(bin_opt_alias) -> diff --git a/lib/compiler/src/v3_core.erl b/lib/compiler/src/v3_core.erl index 4ac2196d79..b2f0ac75c7 100644 --- a/lib/compiler/src/v3_core.erl +++ b/lib/compiler/src/v3_core.erl @@ -128,6 +128,7 @@ -record(core, {vcount=0 :: non_neg_integer(), %Variable counter fcount=0 :: non_neg_integer(), %Function counter in_guard=false :: boolean(), %In guard or not. + wanted=true :: boolean(), %Result wanted or not. opts :: [compile:option()], %Options. es=[] :: [error()], %Errors. ws=[] :: [warning()], %Warnings. @@ -580,10 +581,14 @@ expr({'fun',L,{function,F,A},{_,_,_}=Id}, St) -> {#c_var{anno=Lanno++[{id,Id}],name={F,A}},[],St}; expr({'fun',L,{clauses,Cs},Id}, St) -> fun_tq(Id, Cs, L, St); -expr({call,L,{remote,_,M,F},As0}, St0) -> +expr({call,L,{remote,_,M,F},As0}, #core{wanted=Wanted}=St0) -> {[M1,F1|As1],Aps,St1} = safe_list([M,F|As0], St0), Lanno = lineno_anno(L, St1), - {#icall{anno=#a{anno=Lanno},module=M1,name=F1,args=As1},Aps,St1}; + Anno = case Wanted of + false -> [result_not_wanted|Lanno]; + true -> Lanno + end, + {#icall{anno=#a{anno=Anno},module=M1,name=F1,args=As1},Aps,St1}; expr({call,Lc,{atom,Lf,F},As0}, St0) -> {As1,Aps,St1} = safe_list(As0, St0), Op = #c_var{anno=lineno_anno(Lf, St1),name={F,length(As1)}}, @@ -596,23 +601,28 @@ expr({call,L,FunExp,As0}, St0) -> expr({match,L,P0,E0}, St0) -> %% First fold matches together to create aliases. {P1,E1} = fold_match(E0, P0), - {E2,Eps,St1} = novars(E1, St0), + St1 = case P1 of + {var,_,'_'} -> St0#core{wanted=false}; + _ -> St0 + end, + {E2,Eps,St2} = novars(E1, St1), + St3 = St2#core{wanted=St0#core.wanted}, P2 = try - pattern(P1, St1) + pattern(P1, St3) catch throw:Thrown -> Thrown end, - {Fpat,St2} = new_var(St1), + {Fpat,St4} = new_var(St3), Fc = fail_clause([Fpat], c_tuple([#c_literal{val=badmatch},Fpat])), - Lanno = lineno_anno(L, St2), + Lanno = lineno_anno(L, St4), case P2 of nomatch -> - St = add_warning(L, nomatch, St2), + St = add_warning(L, nomatch, St4), {#icase{anno=#a{anno=Lanno}, args=[E2],clauses=[],fc=Fc},Eps,St}; Other when not is_atom(Other) -> - {#imatch{anno=#a{anno=Lanno},pat=P2,arg=E2,fc=Fc},Eps,St2} + {#imatch{anno=#a{anno=Lanno},pat=P2,arg=E2,fc=Fc},Eps,St4} end; expr({op,_,'++',{lc,Llc,E,Qs},More}, St0) -> %% Optimise '++' here because of the list comprehension algorithm. diff --git a/lib/compiler/test/match_SUITE.erl b/lib/compiler/test/match_SUITE.erl index 20969c0b26..7d5669025c 100644 --- a/lib/compiler/test/match_SUITE.erl +++ b/lib/compiler/test/match_SUITE.erl @@ -21,14 +21,14 @@ -export([all/1, pmatch/1,mixed/1,aliases/1,match_in_call/1, untuplify/1,shortcut_boolean/1,letify_guard/1, - selectify/1]). + selectify/1,underscore/1]). -include("test_server.hrl"). all(suite) -> test_lib:recompile(?MODULE), [pmatch,mixed,aliases,match_in_call,untuplify,shortcut_boolean, - letify_guard,selectify]. + letify_guard,selectify,underscore]. pmatch(Config) when is_list(Config) -> ?line ok = doit(1), @@ -352,4 +352,16 @@ sel_same_value2(V) when V =:= 42; V =:= 43 -> sel_same_value2(_) -> error. +underscore(Config) when is_list(Config) -> + case Config of + [] -> + %% Assignment to _ at the end of a construct. + _ = length(Config); + [_|_] -> + %% Assignment to _ at the end of a construct. + _ = list_to_tuple(Config) + end, + _ = is_list(Config), + ok. + id(I) -> I. diff --git a/lib/compiler/test/warnings_SUITE.erl b/lib/compiler/test/warnings_SUITE.erl index 6e60ab88cb..8b98db54f2 100644 --- a/lib/compiler/test/warnings_SUITE.erl +++ b/lib/compiler/test/warnings_SUITE.erl @@ -375,7 +375,12 @@ effect(Config) when is_list(Config) -> comp_op -> X =:= 2; cookie -> - erlang:get_cookie() + erlang:get_cookie(); + result_ignore -> + _ = list_to_integer(X); + warn_lc_4 -> + %% No warning because of assignment to _. + [_ = abs(Z) || Z <- [1,2,3]] end, ok. |