Make the file:filename() type more restrictive

The recommended type for filenames is a list of characters (which
may be Unicode characters greater than 255). Change the
file:filename() to reflect that.

For the filename module we still need a type that can be either
a string or a binary, so we need to introduce the type
file:filename_all().

4 files changed, 31 insertions, 27 deletions

diff --git a/lib/dialyzer/test/small_SUITE_data/results/contracts_with_subtypes b/lib/dialyzer/test/small_SUITE_data/results/contracts_with_subtypes
index 4850f3ff0c..173ff3a9f1 100644
--- a/lib/dialyzer/test/small_SUITE_data/results/contracts_with_subtypes
+++ b/lib/dialyzer/test/small_SUITE_data/results/contracts_with_subtypes
@@ -5,18 +5,18 @@ contracts_with_subtypes.erl:108: The call contracts_with_subtypes:rec_arg({'a',{
 contracts_with_subtypes.erl:109: The call contracts_with_subtypes:rec_arg({'b',{'a','b'}}) breaks the contract (Arg) -> 'ok' when is_subtype(Arg,{'a',A} | {'b',B}), is_subtype(A,'a' | {'b',B}), is_subtype(B,'b' | {'a',A})
 contracts_with_subtypes.erl:110: The call contracts_with_subtypes:rec_arg({'a',{'b',{'a','b'}}}) breaks the contract (Arg) -> 'ok' when is_subtype(Arg,{'a',A} | {'b',B}), is_subtype(A,'a' | {'b',B}), is_subtype(B,'b' | {'a',A})
 contracts_with_subtypes.erl:111: The call contracts_with_subtypes:rec_arg({'b',{'a',{'b','a'}}}) breaks the contract (Arg) -> 'ok' when is_subtype(Arg,{'a',A} | {'b',B}), is_subtype(A,'a' | {'b',B}), is_subtype(B,'b' | {'a',A})
-contracts_with_subtypes.erl:142: The pattern 1 can never match the type binary() | string()
-contracts_with_subtypes.erl:145: The pattern 'alpha' can never match the type {'ok',_} | {'ok',_,binary() | string()}
-contracts_with_subtypes.erl:147: The pattern 42 can never match the type {'ok',_} | {'ok',_,binary() | string()}
+contracts_with_subtypes.erl:142: The pattern 1 can never match the type string()
+contracts_with_subtypes.erl:145: The pattern 'alpha' can never match the type {'ok',_} | {'ok',_,string()}
+contracts_with_subtypes.erl:147: The pattern 42 can never match the type {'ok',_} | {'ok',_,string()}
 contracts_with_subtypes.erl:163: The pattern 'alpha' can never match the type {'ok',X}
 contracts_with_subtypes.erl:165: The pattern 42 can never match the type {'ok',X}
 contracts_with_subtypes.erl:183: The pattern 'alpha' can never match the type {'ok',X}
 contracts_with_subtypes.erl:185: The pattern 42 can never match the type {'ok',X}
-contracts_with_subtypes.erl:202: The pattern 1 can never match the type binary() | string()
-contracts_with_subtypes.erl:205: The pattern {'ok', _} can never match the type {'ok',X,binary() | string()}
-contracts_with_subtypes.erl:206: The pattern 'alpha' can never match the type {'ok',X,binary() | string()}
-contracts_with_subtypes.erl:207: The pattern {'ok', 42} can never match the type {'ok',X,binary() | string()}
-contracts_with_subtypes.erl:208: The pattern 42 can never match the type {'ok',X,binary() | string()}
+contracts_with_subtypes.erl:202: The pattern 1 can never match the type string()
+contracts_with_subtypes.erl:205: The pattern {'ok', _} can never match the type {'ok',X,string()}
+contracts_with_subtypes.erl:206: The pattern 'alpha' can never match the type {'ok',X,string()}
+contracts_with_subtypes.erl:207: The pattern {'ok', 42} can never match the type {'ok',X,string()}
+contracts_with_subtypes.erl:208: The pattern 42 can never match the type {'ok',X,string()}
 contracts_with_subtypes.erl:234: Function flat_ets_new_t/0 has no local return
 contracts_with_subtypes.erl:235: The call contracts_with_subtypes:flat_ets_new(12,[]) breaks the contract (Name,Options) -> atom() when is_subtype(Name,atom()), is_subtype(Options,[Option]), is_subtype(Option,'set' | 'ordered_set' | 'bag' | 'duplicate_bag' | 'public' | 'protected' | 'private' | 'named_table' | {'keypos',integer()} | {'heir',pid(),term()} | {'heir','none'} | {'write_concurrency',boolean()} | {'read_concurrency',boolean()} | 'compressed')
 contracts_with_subtypes.erl:23: Invalid type specification for function contracts_with_subtypes:extract2/0. The success typing is () -> 'something'
diff --git a/lib/kernel/doc/src/file.xml b/lib/kernel/doc/src/file.xml
index a96da0fb4e..069b13eacf 100644
--- a/lib/kernel/doc/src/file.xml
+++ b/lib/kernel/doc/src/file.xml
@@ -110,6 +110,9 @@
       <name name="filename"/>
     </datatype>
     <datatype>
+      <name name="filename_all"/>
+    </datatype>
+    <datatype>
       <name name="io_device"/>
       <desc>
         <p>As returned by
diff --git a/lib/kernel/src/file.erl b/lib/kernel/src/file.erl
index 6b92d6c025..5f52f94270 100644
--- a/lib/kernel/src/file.erl
+++ b/lib/kernel/src/file.erl
@@ -67,8 +67,8 @@
 -export([ipread_s32bu_p32bu_int/3]).
 
 %% Types that can be used from other modules -- alphabetically ordered.
--export_type([date_time/0, fd/0, file_info/0, filename/0, io_device/0,
-	      name/0, posix/0]).
+-export_type([date_time/0, fd/0, file_info/0, filename/0, filename_all/0,
+              io_device/0, name/0, posix/0]).
 
 %%% Includes and defines
 -include("file.hrl").
@@ -80,7 +80,8 @@
 -define(RAM_FILE, ram_file).           % Module
 
 %% data types
--type filename()  :: string() | binary().
+-type filename()  :: string().
+-type filename_all() :: string() | binary().
 -type file_info() :: #file_info{}.
 -type fd()        :: #file_descriptor{}.
 -type io_device() :: pid() | fd().
@@ -280,7 +281,7 @@ read_link(Name) ->
 
 -spec read_link_all(Name) -> {ok, Filename} | {error, Reason} when
       Name :: name(),
-      Filename :: filename(),
+      Filename :: filename_all(),
       Reason :: posix() | badarg.
 
 read_link_all(Name) ->
@@ -313,7 +314,7 @@ list_dir(Name) ->
 
 -spec list_dir_all(Dir) -> {ok, Filenames} | {error, Reason} when
       Dir :: name(),
-      Filenames :: [filename()],
+      Filenames :: [filename_all()],
       Reason :: posix() | badarg.
 
 list_dir_all(Name) ->
diff --git a/lib/stdlib/src/filename.erl b/lib/stdlib/src/filename.erl
index 0c50eb34e6..e944dd4c43 100644
--- a/lib/stdlib/src/filename.erl
+++ b/lib/stdlib/src/filename.erl
@@ -61,13 +61,13 @@
 %% (for WIN32): absname("/") -> "D:/"
 
 
--spec absname(Filename) -> file:filename() when
+-spec absname(Filename) -> file:filename_all() when
       Filename :: file:name().
 absname(Name) ->
     {ok, Cwd} = file:get_cwd(),
     absname(Name, Cwd).
 
--spec absname(Filename, Dir) -> file:filename() when
+-spec absname(Filename, Dir) -> file:filename_all() when
       Filename :: file:name(),
       Dir :: file:name().
 absname(Name, AbsBase) when is_binary(Name), is_list(AbsBase) ->
@@ -122,7 +122,7 @@ absname_vr([[X, $:]|Name], _, _AbsBase) ->
 %% This is just a join/2, but assumes that 
 %% AbsBase must be absolute and Name must be relative.
 
--spec absname_join(Dir, Filename) -> file:filename() when
+-spec absname_join(Dir, Filename) -> file:filename_all() when
       Dir :: file:name(),
       Filename :: file:name().
 absname_join(AbsBase, Name) ->
@@ -136,7 +136,7 @@ absname_join(AbsBase, Name) ->
 %%           basename("/usr/foo/") -> "foo"  (trailing slashes ignored)
 %%           basename("/") -> []
 
--spec basename(Filename) -> file:filename() when
+-spec basename(Filename) -> file:filename_all() when
       Filename :: file:name().
 basename(Name) when is_binary(Name) ->
     case os:type() of
@@ -201,7 +201,7 @@ skip_prefix(Name, _) ->
 %%	    rootname(basename("xxx.jam")) -> "xxx"
 %%	    rootname(basename("xxx.erl")) -> "xxx"
 
--spec basename(Filename, Ext) -> file:filename() when
+-spec basename(Filename, Ext) -> file:filename_all() when
       Filename :: file:name(),
       Ext :: file:name().
 basename(Name, Ext) when is_binary(Name), is_list(Ext) ->
@@ -251,7 +251,7 @@ basename([], _Ext, Tail, _DrvSep2) ->
 %% Example: dirname("/usr/src/kalle.erl") -> "/usr/src",
 %%	    dirname("kalle.erl") -> "."
 
--spec dirname(Filename) -> file:filename() when
+-spec dirname(Filename) -> file:filename_all() when
       Filename :: file:name().
 dirname(Name) when is_binary(Name) ->
     {Dsep,Drivesep} = separators(),
@@ -344,7 +344,7 @@ dirjoin1([H|T],Acc,Sep) ->
 %%
 %% On Windows:  fn:dirname("\\usr\\src/kalle.erl") -> "/usr/src"
 
--spec extension(Filename) -> file:filename() when
+-spec extension(Filename) -> file:filename_all() when
       Filename :: file:name().
 extension(Name) when is_binary(Name) ->
     {Dsep,_} = separators(),
@@ -387,7 +387,7 @@ extension([], Result, _OsType) ->
 
 %% Joins a list of filenames with directory separators.
 
--spec join(Components) -> file:filename() when
+-spec join(Components) -> file:filename_all() when
       Components :: [file:name()].
 join([Name1, Name2|Rest]) ->
     join([join(Name1, Name2)|Rest]);
@@ -400,7 +400,7 @@ join([Name]) when is_atom(Name) ->
 
 %% Joins two filenames with directory separators.
 
--spec join(Name1, Name2) -> file:filename() when
+-spec join(Name1, Name2) -> file:filename_all() when
       Name1 :: file:name(),
       Name2 :: file:name().
 join(Name1, Name2) when is_list(Name1), is_list(Name2) ->
@@ -488,7 +488,7 @@ maybe_remove_dirsep(Name, _) ->
 %% a given base directory, which is is assumed to be normalised
 %% by a previous call to join/{1,2}.
 
--spec append(file:filename(), file:name()) -> file:filename().
+-spec append(file:filename_all(), file:name()) -> file:filename_all().
 append(Dir, Name) when is_binary(Dir), is_binary(Name) ->
     <<Dir/binary,$/:8,Name/binary>>;
 append(Dir, Name) when is_binary(Dir) ->
@@ -564,7 +564,7 @@ win32_pathtype(_) 		  -> relative.
 %% Examples: rootname("/jam.src/kalle") -> "/jam.src/kalle"
 %%           rootname("/jam.src/foo.erl") -> "/jam.src/foo"
 
--spec rootname(Filename) -> file:filename() when
+-spec rootname(Filename) -> file:filename_all() when
       Filename :: file:name().
 rootname(Name) when is_binary(Name) ->
     list_to_binary(rootname(binary_to_list(Name))); % No need to handle unicode, . is < 128
@@ -594,7 +594,7 @@ rootname([], Root, _Ext, _OsType) ->
 %% Examples: rootname("/jam.src/kalle.jam", ".erl") -> "/jam.src/kalle.jam"
 %%           rootname("/jam.src/foo.erl", ".erl") -> "/jam.src/foo"
 
--spec rootname(Filename, Ext) -> file:filename() when
+-spec rootname(Filename, Ext) -> file:filename_all() when
       Filename :: file:name(),
       Ext :: file:name().
 rootname(Name, Ext) when is_binary(Name), is_binary(Ext) ->
@@ -717,7 +717,7 @@ split([], Comp, Components, OsType) ->
 %% will be converted to backslashes.  On all platforms, the
 %% name will be normalized as done by join/1.
 
--spec nativename(Path) -> file:filename() when
+-spec nativename(Path) -> file:filename_all() when
       Path :: file:name().
 nativename(Name0) ->
     Name = join([Name0]),			%Normalize.
@@ -921,7 +921,7 @@ major_os_type() ->
 %% flatten(List)
 %%  Flatten a list, also accepting atoms.
 
--spec flatten(Filename) -> file:filename() when
+-spec flatten(Filename) -> file:filename_all() when
       Filename :: file:name().
 flatten(Bin) when is_binary(Bin) ->
     Bin;