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authorHans Bolinder <[email protected]>2018-05-02 10:36:09 +0200
committerHans Bolinder <[email protected]>2018-05-13 09:06:30 +0200
commitac35ee08779884728d67d804cc80b0c210c29fd8 (patch)
tree7cf09cec5736ee1b8acbc955a7597ae34cc56a3e
parent837fe8bf4bf3a567c66afec0f0ec3dd70d248cd8 (diff)
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dialyzer: Do not emit warnings for unreachable funs
Warnings are not generated for funs residing in dead code. In particular, warnings like "The created fun has no local return" are no longer generated for funs declared in clauses or functions that cannot be run.
-rw-r--r--lib/dialyzer/src/dialyzer_dataflow.erl44
-rw-r--r--lib/dialyzer/test/small_SUITE_data/results/unused_funs5
-rw-r--r--lib/dialyzer/test/small_SUITE_data/src/unused_funs.erl21
3 files changed, 60 insertions, 10 deletions
diff --git a/lib/dialyzer/src/dialyzer_dataflow.erl b/lib/dialyzer/src/dialyzer_dataflow.erl
index c5f93a3392..45b4abb253 100644
--- a/lib/dialyzer/src/dialyzer_dataflow.erl
+++ b/lib/dialyzer/src/dialyzer_dataflow.erl
@@ -102,6 +102,8 @@
| 'undefined', % race
fun_homes :: dict:dict(label(), mfa())
| 'undefined', % race
+ reachable_funs :: sets:set(label())
+ | 'undefined', % race
plt :: dialyzer_plt:plt()
| 'undefined', % race
opaques :: [type()]
@@ -269,9 +271,11 @@ traverse(Tree, Map, State) ->
case state__warning_mode(State) of
true -> {State, Map, Type};
false ->
- State2 = state__add_work(get_label(Tree), State),
+ FunLbl = get_label(Tree),
+ State2 = state__add_work(FunLbl, State),
State3 = state__update_fun_env(Tree, Map, State2),
- {State3, Map, Type}
+ State4 = state__add_reachable(FunLbl, State3),
+ {State4, Map, Type}
end;
'let' ->
handle_let(Tree, Map, State);
@@ -3039,25 +3043,35 @@ state__new(Callgraph, Codeserver, Tree, Plt, Module, Records) ->
{TreeMap, FunHomes} = build_tree_map(Tree, Callgraph),
Funs = dict:fetch_keys(TreeMap),
FunTab = init_fun_tab(Funs, dict:new(), TreeMap, Callgraph, Plt),
- ExportedFuns =
- [Fun || Fun <- Funs--[top], dialyzer_callgraph:is_escaping(Fun, Callgraph)],
- Work = init_work(ExportedFuns),
+ ExportedFunctions =
+ [Fun ||
+ Fun <- Funs--[top],
+ dialyzer_callgraph:is_escaping(Fun, Callgraph),
+ dialyzer_callgraph:lookup_name(Fun, Callgraph) =/= error
+ ],
+ Work = init_work(ExportedFunctions),
Env = lists:foldl(fun(Fun, Env) -> dict:store(Fun, map__new(), Env) end,
dict:new(), Funs),
#state{callgraph = Callgraph, codeserver = Codeserver,
envs = Env, fun_tab = FunTab, fun_homes = FunHomes, opaques = Opaques,
plt = Plt, races = dialyzer_races:new(), records = Records,
warning_mode = false, warnings = [], work = Work, tree_map = TreeMap,
- module = Module}.
+ module = Module, reachable_funs = sets:new()}.
state__warning_mode(#state{warning_mode = WM}) ->
WM.
state__set_warning_mode(#state{tree_map = TreeMap, fun_tab = FunTab,
- races = Races} = State) ->
+ races = Races, callgraph = Callgraph,
+ reachable_funs = ReachableFuns} = State) ->
?debug("==========\nStarting warning pass\n==========\n", []),
Funs = dict:fetch_keys(TreeMap),
- State#state{work = init_work([top|Funs--[top]]),
+ Work =
+ [Fun ||
+ Fun <- Funs--[top],
+ dialyzer_callgraph:lookup_name(Fun, Callgraph) =/= error orelse
+ sets:is_element(Fun, ReachableFuns)],
+ State#state{work = init_work(Work),
fun_tab = FunTab, warning_mode = true,
races = dialyzer_races:put_race_analysis(true, Races)}.
@@ -3149,7 +3163,8 @@ state__get_race_warnings(#state{races = Races} = State) ->
State1#state{races = Races1}.
state__get_warnings(#state{tree_map = TreeMap, fun_tab = FunTab,
- callgraph = Callgraph, plt = Plt} = State) ->
+ callgraph = Callgraph, plt = Plt,
+ reachable_funs = ReachableFuns} = State) ->
FoldFun =
fun({top, _}, AccState) -> AccState;
({FunLbl, Fun}, AccState) ->
@@ -3184,7 +3199,12 @@ state__get_warnings(#state{tree_map = TreeMap, fun_tab = FunTab,
GenRet = dialyzer_contracts:get_contract_return(C),
not t_is_unit(GenRet)
end,
- case Warn of
+ %% Do not output warnings for unreachable funs.
+ case
+ Warn andalso
+ (dialyzer_callgraph:lookup_name(FunLbl, Callgraph) =/= error
+ orelse sets:is_element(FunLbl, ReachableFuns))
+ of
true ->
case classify_returns(Fun) of
no_match ->
@@ -3255,6 +3275,10 @@ state__get_args_and_status(Tree, #state{fun_tab = FunTab}) ->
{ok, {ArgTypes, _}} -> {ArgTypes, true}
end.
+state__add_reachable(FunLbl, #state{reachable_funs = ReachableFuns}=State) ->
+ NewReachableFuns = sets:add_element(FunLbl, ReachableFuns),
+ State#state{reachable_funs = NewReachableFuns}.
+
build_tree_map(Tree, Callgraph) ->
Fun =
fun(T, {Dict, Homes, FunLbls} = Acc) ->
diff --git a/lib/dialyzer/test/small_SUITE_data/results/unused_funs b/lib/dialyzer/test/small_SUITE_data/results/unused_funs
new file mode 100644
index 0000000000..c468457ead
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/results/unused_funs
@@ -0,0 +1,5 @@
+
+unused_funs.erl:10: The pattern 'error' can never match the type 'other_error'
+unused_funs.erl:15: Function not_used/0 will never be called
+unused_funs.erl:19: Function foo/1 will never be called
+unused_funs.erl:7: Function test/0 has no local return
diff --git a/lib/dialyzer/test/small_SUITE_data/src/unused_funs.erl b/lib/dialyzer/test/small_SUITE_data/src/unused_funs.erl
new file mode 100644
index 0000000000..c24cf3ea81
--- /dev/null
+++ b/lib/dialyzer/test/small_SUITE_data/src/unused_funs.erl
@@ -0,0 +1,21 @@
+%% See also ERL-593.
+
+-module(unused_funs).
+
+-export([test/0]).
+
+test() -> % "has no local return"
+ Var = outer_scope,
+ case other_error of
+ error -> % "can never match"
+ %% No warnings "no local return" and "_ = 1 can never match 0" (!)
+ foo(fun() -> {Var, 1 = 0} end)
+ end.
+
+not_used() -> % "will never be called"
+ %% No warnings "no local return" and "1 can never match 0".
+ foo(fun() -> 1 = 0 end).
+
+foo(Fun) -> % "will never be called"
+ 1 = 0, % No pattern match warning (foo/1 is not traversed at all).
+ Fun().