Improve and correct types and specifications in Kernel and STDLIB

Running Dialyzer on the test suites revealed a few type errors.

5 files changed, 19 insertions, 13 deletions

diff --git a/lib/stdlib/src/dets.erl b/lib/stdlib/src/dets.erl
index 671b5a9dd4..fa0641ffd9 100644
--- a/lib/stdlib/src/dets.erl
+++ b/lib/stdlib/src/dets.erl
@@ -411,7 +411,8 @@ init_table(Tab, InitFun) ->
       InitFun :: fun((Arg) -> Res),
       Arg :: read | close,
       Res :: end_of_input | {[object()], InitFun} | {Data, InitFun} | term(),
-      Options :: [{min_no_slots,no_slots()} | {format,term | bchunk}],
+      Options :: Option | [Option],
+      Option :: {min_no_slots,no_slots()} | {format,term | bchunk},
       Reason :: term(),
       Data :: binary() | tuple().
 
@@ -871,11 +872,15 @@ to_ets(DTab, ETab) ->
 -spec traverse(Name, Fun) -> Return | {'error', Reason} when
       Name :: tab_name(),
       Fun :: fun((Object) -> FunReturn),
-      FunReturn :: 'continue' | {'continue', Val} | {'done', Value},
+      Object :: object(),
+      FunReturn :: 'continue'
+                 | {'continue', Val}
+                 | {'done', Value}
+                 | OtherValue,
+      Return :: [term()] | OtherValue,
       Val :: term(),
       Value :: term(),
-      Object :: object(),
-      Return :: [term()],
+      OtherValue :: term(),
       Reason :: term().
 
 traverse(Tab, Fun) ->
diff --git a/lib/stdlib/src/escript.erl b/lib/stdlib/src/escript.erl
index d67617260e..cd1bacd2f5 100644
--- a/lib/stdlib/src/escript.erl
+++ b/lib/stdlib/src/escript.erl
@@ -62,10 +62,10 @@
 -type zip_create_option() :: term().
 -type section() ::
 	  shebang
-	| {shebang, shebang()}
+	| {shebang, shebang() | default | undefined}
 	| comment
-	| {comment, comment()}
-	| {emu_args, emu_args()}
+	| {comment, comment() | default | undefined}
+	| {emu_args, emu_args() | undefined}
 	| {source, file:filename() | binary()}
 	| {beam, file:filename() | binary()}
 	| {archive, file:filename() | binary()}
diff --git a/lib/stdlib/src/io_lib.erl b/lib/stdlib/src/io_lib.erl
index 165e03e506..0252cdf742 100644
--- a/lib/stdlib/src/io_lib.erl
+++ b/lib/stdlib/src/io_lib.erl
@@ -109,9 +109,9 @@ fwrite(Format, Args) ->
 fread(Chars, Format) ->
     io_lib_fread:fread(Chars, Format).
 
--spec fread(Continuation, String, Format) -> Return when
+-spec fread(Continuation, CharSpec, Format) -> Return when
       Continuation :: continuation() | [],
-      String :: string(),
+      CharSpec :: string() | eof,
       Format :: string(),
       Return :: {'more', Continuation1 :: continuation()}
               | {'done', Result, LeftOverChars :: string()},
diff --git a/lib/stdlib/src/sofs.erl b/lib/stdlib/src/sofs.erl
index d38b8ab37a..34eb224647 100644
--- a/lib/stdlib/src/sofs.erl
+++ b/lib/stdlib/src/sofs.erl
@@ -81,7 +81,8 @@
 -define(ORDTAG, 'OrdSet').
 
 -record(?TAG, {data = [] :: list(), type = type :: term()}).
--record(?ORDTAG, {orddata = {} :: tuple(), ordtype = type :: term()}).
+-record(?ORDTAG, {orddata = {} :: tuple() | atom(),
+                  ordtype = type :: term()}).
 
 -define(LIST(S), (S)#?TAG.data).
 -define(TYPE(S), (S)#?TAG.type).
@@ -375,7 +376,7 @@ to_sets(S) when ?IS_ORDSET(S) ->
 
 -spec(no_elements(ASet) -> NoElements when
       ASet :: a_set() | ordset(),
-      NoElements :: pos_integer()).
+      NoElements :: non_neg_integer()).
 no_elements(S) when ?IS_SET(S) ->
     length(?LIST(S));
 no_elements(S) when ?IS_ORDSET(S), is_tuple(?ORDTYPE(S)) ->
diff --git a/lib/stdlib/src/sys.erl b/lib/stdlib/src/sys.erl
index 8ab72c9b50..f34201604c 100644
--- a/lib/stdlib/src/sys.erl
+++ b/lib/stdlib/src/sys.erl
@@ -154,7 +154,7 @@ log_to_file(Name, FileName, Timeout) ->
 -spec statistics(Name, Flag) -> 'ok' | {'ok', Statistics} when
       Name :: name(),
       Flag :: 'true' | 'false' | 'get',
-      Statistics :: [StatisticsTuple],
+      Statistics :: [StatisticsTuple] | no_statistics,
       StatisticsTuple :: {'start_time', DateTime1}
                        | {'current_time', DateTime2}
                        | {'reductions', non_neg_integer()}
@@ -168,7 +168,7 @@ statistics(Name, Flag) ->
 -spec statistics(Name, Flag, Timeout) -> 'ok' | {'ok', Statistics} when
       Name :: name(),
       Flag :: 'true' | 'false' | 'get',
-      Statistics :: [StatisticsTuple],
+      Statistics :: [StatisticsTuple] | no_statistics,
       StatisticsTuple :: {'start_time', DateTime1}
                        | {'current_time', DateTime2}
                        | {'reductions', non_neg_integer()}