Improve error message for invalid patterns in guards and matches

Closes #1092

Author: José Valim

lib/elixir/src/elixir_dispatch.erl

@@ -264,7 +264,7 @@ munge_stacktrace(_, [], _) ->
 %% ERROR HANDLING
 
 format_error({ unrequired_module, { Receiver, Name, Arity, Required }}) ->
-  String = string:join([elixir_errors:inspect(R) || R <- Required], ", "),
+  String = 'Elixir.Enum':join([elixir_errors:inspect(R) || R <- Required], ", "),
   io_lib:format("tried to invoke macro ~ts.~ts/~B but module was not required. Required: ~ts",
     [elixir_errors:inspect(Receiver), Name, Arity, String]);
 

lib/elixir/src/elixir_errors.erl

@@ -14,15 +14,7 @@
 %% Handle inspecting for exceptions
 
 inspect(Atom) when is_atom(Atom) ->
-  case atom_to_list(Atom) of
-    "Elixir-" ++ Rest -> [to_dot(R) || R <- Rest];
-    Else -> Else
-  end;
-
-inspect(Other) -> Other.
-
-to_dot($-) -> $.;
-to_dot(L)  -> L.
+  'Elixir.Binary.Inspect.Atom':inspect(Atom, []).
 
 %% Raised during macros translation.
 

lib/elixir/src/elixir_translator.erl

@@ -389,10 +389,12 @@ translate_each({ Atom, Meta, Args } = Original, S) when is_atom(Atom) ->
           Callback = fun() ->
             case S#elixir_scope.context of
               match ->
+                syntax_error(Meta, S#elixir_scope.file, "cannot invoke function ~ts/~B inside match", [Atom, length(Args)]);
+              guard ->
                 Arity = length(Args),
                 File  = S#elixir_scope.file,
                 case Arity of
-                  0 -> syntax_error(Meta, File, "unknown variable ~ts or cannot invoke local ~ts/~B inside guard", [Atom, Atom, Arity]);
+                  0 -> syntax_error(Meta, File, "unknown variable ~ts or cannot invoke function ~ts/~B inside guard", [Atom, Atom, Arity]);
                   _ -> syntax_error(Meta, File, "cannot invoke local ~ts/~B inside guard", [Atom, Arity])
                 end;
               _ ->
@@ -423,9 +425,23 @@ translate_each({ { '.', _, [Left, Right] }, Meta, Args } = Original, S) when is_
 
           case TLeft of
             { atom, _, Receiver } ->
-              elixir_dispatch:dispatch_require(Meta, Receiver, Right, Args, umergev(SL, SR), Callback);
+              elixir_dispatch:dispatch_require(Meta, Receiver, Right, Args, umergev(SL, SR), fun() ->
+                case S#elixir_scope.context of
+                  Context when Receiver /= erlang, (Context == match) orelse (Context == guard) ->
+                    syntax_error(Meta, S#elixir_scope.file, "cannot invoke remote function ~ts.~ts/~B inside ~ts",
+                      [elixir_errors:inspect(Receiver), Right, length(Args), Context]);
+                  _ ->
+                    Callback()
+                end
+              end);
             _ ->
-              Callback()
+              case S#elixir_scope.context of
+                Context when Context == match; Context == guard ->
+                  syntax_error(Meta, S#elixir_scope.file, "cannot invoke remote function ~ts/~B inside ~ts",
+                    [Right, length(Args), Context]);
+                _ ->
+                  Callback()
+              end
           end;
         Else -> Else
       end;

lib/elixir/test/elixir/kernel/errors_test.exs

@@ -109,7 +109,7 @@ defmodule Kernel.ErrorsTest do
   end
 
   test :function_import_conflict do
-    assert "nofile:2: function exit/1 imported from both erlang and Kernel, call is ambiguous" ==
+    assert "nofile:2: function exit/1 imported from both :erlang and Kernel, call is ambiguous" ==
       format_rescue 'defmodule Foo do import :erlang\n def foo, do: exit(:test)\nend'
   end
 
@@ -134,7 +134,7 @@ defmodule Kernel.ErrorsTest do
   end
 
   test :no_macros do
-    assert "nofile:2: could not load macros from module lists" ==
+    assert "nofile:2: could not load macros from module :lists" ==
       format_rescue 'defmodule Foo do\nimport :macros, :lists\nend'
   end
 
@@ -259,6 +259,26 @@ defmodule Kernel.ErrorsTest do
       format_rescue 'if true do\n  foo = [],\n  baz\nend'
   end
 
+  test :invalid_var_or_function_on_guard do
+    assert "nofile:1: unknown variable something_that_does_not_exist or cannot invoke function something_that_does_not_exist/0 inside guard" =
+      format_rescue('case [] do; [] when something_that_does_not_exist == [] -> :ok; end')
+  end
+
+  test :invalid_function_on_match do
+    assert "nofile:1: cannot invoke function something_that_does_not_exist/0 inside match" =
+      format_rescue('case [] do; something_that_does_not_exist() -> :ok; end')
+  end
+
+  test :invalid_remote_on_match do
+    assert "nofile:1: cannot invoke remote function Hello.something_that_does_not_exist/0 inside match" =
+      format_rescue('case [] do; Hello.something_that_does_not_exist() -> :ok; end')
+  end
+
+  test :invalid_remote_on_guard do
+    assert "nofile:1: cannot invoke remote function Hello.something_that_does_not_exist/0 inside guard" =
+      format_rescue('case [] do; [] when Hello.something_that_does_not_exist == [] -> :ok; end')
+  end
+
   test :macros_error_stacktrace do
     assert [{:erlang,:+,[1,:foo],_},{Foo,:sample,1,_}|_] =
       rescue_stacktrace("defmodule Foo do\ndefmacro sample(num), do: num + :foo\ndef other, do: sample(1)\nend")