Better error reporting for invalid type specifications

Closes #818

Author: yrashk

lib/elixir/lib/kernel/typespec.ex

@@ -350,10 +350,17 @@ defmodule Kernel.Typespec do
     do_deftype(kind, type, definition, caller)
   end
 
-  def deftype(kind, type, caller) do
+  def deftype(kind, {name, _meta, args} = type, caller) when 
+                                                        is_atom(name) and
+                                                        not is_list(args) do
     do_deftype(kind, type, { :term, [line: caller.line], nil }, caller)
   end
 
+  def deftype(_kind, other, _caller) do
+    type_spec = Macro.to_binary(other)
+    raise ArgumentError, message: "invalid type specification #{type_spec}"
+  end
+
   defp do_deftype(kind, { name, _, args }, definition, caller) do
     args =
       if is_atom(args) do
@@ -390,6 +397,11 @@ defmodule Kernel.Typespec do
     code
   end
 
+  def defspec(_type, other, _caller) do
+    spec = Macro.to_binary(other)
+    raise ArgumentError, message: "invalid function type specification #{spec}"
+  end
+
   defp guard_to_constraints({ :is_subtype, meta, [{ name, _, _ }, type] }, caller) do
     line = line(meta)
     contraints = [{ :atom, line, :is_subtype }, [{:var, line, name}, typespec(type, [], caller)]]

lib/elixir/test/elixir/typespec_test.exs

@@ -17,6 +17,32 @@ defmodule Typespec.TypeTest do
     end
   end
 
+  test "invalid type specification" do
+    assert_raise ArgumentError, "invalid type specification mytype = 1", fn ->
+      test_module do
+        @type mytype = 1
+      end
+    end
+    assert_raise ArgumentError, "invalid type specification mytype = 1", fn ->
+      test_module do
+        @typep mytype = 1
+      end
+    end
+    assert_raise ArgumentError, "invalid type specification mytype = 1", fn ->
+      test_module do
+        @opaque mytype = 1
+      end
+    end
+  end
+
+  test "invalid function specification" do
+    assert_raise ArgumentError, "invalid function type specification myfun = 1", fn ->
+      test_module do
+        @spec myfun = 1
+      end
+    end
+  end
+
   test "@type with no body (defaults to 'term')" do
     spec = test_module do
       @type mytype