Check that there are no maps in map keys already in type checker

test/aeso_compiler_tests.erl

@@ -468,6 +468,15 @@ failing_contracts() ->
       [<<?Pos(2, 53)
          "Cannot unify int\n         and string\nwhen checking the type of the pattern at line 2, column 53\n  x : int\nagainst the expected type\n  string">>
       ]}
+    , {"map_as_map_key",
+       [<<?Pos(5, 25)
+         "Invalid key type\n"
+         "  map(int, int)\n"
+         "Map keys cannot contain other maps.">>,
+        <<?Pos(6, 25)
+         "Invalid key type\n"
+         "  lm\n"
+         "Map keys cannot contain other maps.">>]}
     ].
 
 -define(Path(File), "code_errors/" ??File).

test/contracts/map_as_map_key.aes

@@ -0,0 +1,6 @@
+contract MapAsMapKey =
+  type t('key) = map('key, int)
+  type lm = list(map(int, int))
+
+  entrypoint foo(m) : t(map(int, int)) = {[m] = 0}
+  entrypoint bar(m) : t(lm) = Map.delete(m, {})