dialyzer: Rename t_is_none_or_unit/1 to t_is_impossible/1

Calling this function t_is_none_or_unit/1 is like saying
t_is_integer_or_float/1 instead of t_is_number/1. I wouldn't be
the least bit surprised if this weird naming was the root cause of
GH-6580.

lib/dialyzer/src/dialyzer_contracts.erl

@@ -346,11 +346,11 @@ check_contract_inf_list(List, SuccType, Opaques) ->
 
 check_contract_inf_list([{Contract, FunType}|Left], SuccType, Opaques, OM) ->
   FunArgs = erl_types:t_fun_args(FunType),
-  case lists:any(fun erl_types:t_is_none_or_unit/1, FunArgs) of
+  case lists:any(fun erl_types:t_is_impossible/1, FunArgs) of
     true -> check_contract_inf_list(Left, SuccType, Opaques, OM);
     false ->
       STRange = erl_types:t_fun_range(SuccType),
-      case erl_types:t_is_none_or_unit(STRange) of
+      case erl_types:t_is_impossible(STRange) of
 	true -> ok;
 	false ->
 	  Range = erl_types:t_fun_range(FunType),

lib/dialyzer/src/dialyzer_dataflow.erl

@@ -43,7 +43,7 @@
 	 t_is_any/1, t_is_atom/1, t_is_atom/2, t_is_any_atom/3,
          t_is_boolean/2,
 	 t_is_integer/2, t_is_list/1,
-	 t_is_nil/2, t_is_none/1, t_is_none_or_unit/1,
+	 t_is_nil/2, t_is_none/1, t_is_impossible/1,
 	 t_is_number/2, t_is_reference/2, t_is_pid/2, t_is_port/2,
          t_is_unit/1,
 	 t_limit/2, t_list/0, t_list_elements/2,
@@ -256,7 +256,7 @@ traverse(Tree, Map, State) ->
       Arg = cerl:seq_arg(Tree),
       Body = cerl:seq_body(Tree),
       {State1, Map1, ArgType} = SMA = traverse(Arg, Map, State),
-      case t_is_none_or_unit(ArgType) of
+      case t_is_impossible(ArgType) of
 	true ->
 	  SMA;
 	false ->
@@ -924,7 +924,7 @@ handle_case(Tree, Map, State) ->
   Arg = cerl:case_arg(Tree),
   Clauses = cerl:case_clauses(Tree),
   {State1, Map1, ArgType} = SMA = traverse(Arg, Map, State),
-  case t_is_none_or_unit(ArgType) of
+  case t_is_impossible(ArgType) of
     true -> SMA;
     false ->
       Map2 = join_maps_begin(Map1),
@@ -974,7 +974,7 @@ handle_let(Tree, Map, State) ->
     end,
   Body = cerl:let_body(Tree),
   {State1, Map1, ArgTypes} = SMA = traverse(Arg, Map0, State0),
-  case t_is_none_or_unit(ArgTypes) of
+  case t_is_impossible(ArgTypes) of
     true -> SMA;
     false ->
       Map2 = enter_type_lists(Vars, t_to_tlist(ArgTypes), Map1),
@@ -1059,7 +1059,7 @@ handle_map(Tree,Map,State) ->
   Arg = cerl:map_arg(Tree),
   {State1, Map1, ArgType} = traverse(Arg, Map, State),
   ArgType1 = t_inf(t_map(), ArgType),
-  case t_is_none_or_unit(ArgType1) of
+  case t_is_impossible(ArgType1) of
     true ->
       {State1, Map1, ArgType1};
     false ->
@@ -1681,7 +1681,7 @@ bitstr_bitsize_type(Size) ->
 %% possible value (not 'none' or 'unit'), otherwise raise a bind_error().
 bind_checked_inf(Pat, ExpectedType, Type, Opaques) ->
   Inf = t_inf(ExpectedType, Type, Opaques),
-  case t_is_none_or_unit(Inf) of
+  case t_is_impossible(Inf) of
     true ->
       case t_find_opaque_mismatch(ExpectedType, Type, Opaques) of
         {ok, T1, T2} ->
@@ -2411,7 +2411,7 @@ handle_guard_map(Guard, Map, Env, State) ->
   Arg = cerl:map_arg(Guard),
   {Map1, ArgType0} = bind_guard(Arg, Map, Env, dont_know, State),
   ArgType1 = t_inf(t_map(), ArgType0),
-  case t_is_none_or_unit(ArgType1) of
+  case t_is_impossible(ArgType1) of
     true -> {Map1, t_none()};
     false ->
       {Map2, TypePairs} = bind_guard_map_pairs(Pairs, Map1, Env, State, []),

lib/dialyzer/src/dialyzer_typesig.erl

@@ -42,7 +42,7 @@
 	 t_is_float/1, t_is_fun/1,
 	 t_is_integer/1, t_non_neg_integer/0,
 	 t_is_list/1, t_is_nil/1, t_is_none/1, t_is_number/1,
-	 t_is_singleton/1, t_is_none_or_unit/1,
+	 t_is_singleton/1, t_is_impossible/1,
 
          t_limit/2, t_list/0, t_list/1,
 	 t_list_elements/1, t_nonempty_list/1, t_maybe_improper_list/0,
@@ -534,14 +534,14 @@ traverse(Tree, DefinedVars, State) ->
 		    false -> t_any();
 		    true ->
 		      MT = t_inf(lookup_type(MapVar, Map), t_map()),
-		      case t_is_none_or_unit(MT) of
+		      case t_is_impossible(MT) of
 			true -> t_none();
 			false ->
 			  DisjointFromKeyType =
 			    fun(ShadowKey) ->
                                 ST = t_inf(lookup_type(ShadowKey, Map),
                                            KeyType),
-				t_is_none_or_unit(ST)
+				t_is_impossible(ST)
 			    end,
 			  case lists:all(DisjointFromKeyType, ShadowKeys) of
 			    true -> t_map_get(KeyType, MT);
@@ -575,7 +575,7 @@ traverse(Tree, DefinedVars, State) ->
 			    cerl:concrete(OpTree) =:= exact of
 			    true ->
                               ST = t_inf(ShadowedKeys, KeyType),
-                              case t_is_none_or_unit(ST) of
+                              case t_is_impossible(ST) of
 				true ->
 				  t_map_put({KeyType, t_any()}, AccType);
 				false ->

lib/dialyzer/src/erl_bif_types.erl

@@ -67,10 +67,10 @@
 		    t_is_cons/2,
 		    t_is_float/2,
 		    t_is_fun/2,
+		    t_is_impossible/1,
 		    t_is_integer/2,
 		    t_is_nil/1, t_is_nil/2,
 		    t_is_none/1,
-		    t_is_none_or_unit/1,
 		    t_is_number/2,
 		    t_is_pid/2,
 		    t_is_port/2,
@@ -1680,7 +1680,7 @@ list_replace(1, E, [_X | Xs]) ->
   [E | Xs].
 
 any_is_none_or_unit(Ts) ->
-  lists:any(fun erl_types:t_is_none_or_unit/1, Ts).
+  lists:any(fun erl_types:t_is_impossible/1, Ts).
 
 check_guard([X], Test, Type, Opaques) ->
   check_guard_single(X, Test, Type, Opaques).
@@ -2565,15 +2565,15 @@ check_fun_application(Fun, Args, Opaques) ->
     true ->
       case t_fun_args(Fun, Opaques) of
 	unknown ->
-	  case t_is_none_or_unit(t_fun_range(Fun, Opaques)) of
+	  case t_is_impossible(t_fun_range(Fun, Opaques)) of
 	    true -> error;
 	    false -> ok
 	  end;
 	FunDom when length(FunDom) =:= length(Args) ->
 	  case any_is_none_or_unit(inf_lists(FunDom, Args, Opaques)) of
 	    true -> error;
 	    false ->
-	      case t_is_none_or_unit(t_fun_range(Fun, Opaques)) of
+	      case t_is_impossible(t_fun_range(Fun, Opaques)) of
 		true -> error;
 		false -> ok
 	      end

lib/dialyzer/src/erl_types.erl

@@ -116,6 +116,7 @@
 	 t_is_float/1, t_is_float/2,
 	 t_is_fun/1, t_is_fun/2,
          t_is_identifier/1,
+         t_is_impossible/1,
 	 t_is_instance/2,
 	 t_is_integer/1, t_is_integer/2,
 	 t_is_list/1,
@@ -794,11 +795,15 @@ t_unit() ->
 t_is_unit(?unit) -> true;
 t_is_unit(_) -> false.
 
+-spec t_is_impossible(erl_type()) -> boolean().
+
+t_is_impossible(?none) -> true;
+t_is_impossible(?unit) -> true;
+t_is_impossible(_) -> false.
+
 -spec t_is_none_or_unit(erl_type()) -> boolean().
 
-t_is_none_or_unit(?none) -> true;
-t_is_none_or_unit(?unit) -> true;
-t_is_none_or_unit(_) -> false.
+t_is_none_or_unit(T) -> t_is_impossible(T).
 
 %%-----------------------------------------------------------------------------
 %% Atoms and the derived type boolean
@@ -1679,7 +1684,7 @@ t_map(L) ->
 t_map(Pairs0, DefK0, DefV0) ->
   DefK1 = lists:foldl(fun({K,_,_},Acc)->t_subtract(Acc,K)end, DefK0, Pairs0),
   {DefK2, DefV1} =
-    case t_is_none_or_unit(DefK1) orelse t_is_none_or_unit(DefV0) of
+    case t_is_impossible(DefK1) orelse t_is_impossible(DefV0) of
       true  -> {?none, ?none};
       false -> {DefK1, DefV0}
     end,
@@ -1940,7 +1945,7 @@ t_map_put(KV, Map, Opaques) ->
 map_put(_, ?none, _) -> ?none;
 map_put(_, ?unit, _) -> ?none;
 map_put({Key, Value}, ?map(Pairs,DefK,DefV), Opaques) ->
-  case t_is_none_or_unit(Key) orelse t_is_none_or_unit(Value) of
+  case t_is_impossible(Key) orelse t_is_impossible(Value) of
     true -> ?none;
     false ->
       case is_singleton_type(Key) of
@@ -3994,7 +3999,7 @@ t_is_instance(ConcreteType, Type) ->
 -spec t_do_overlap(erl_type(), erl_type()) -> boolean().
 
 t_do_overlap(TypeA, TypeB) ->
-  not (t_is_none_or_unit(t_inf(TypeA, TypeB))).
+  not (t_is_impossible(t_inf(TypeA, TypeB))).
 
 -spec t_unopaque(erl_type()) -> erl_type().