Ban using contracts as namespaces (#428)

* Ban calling contracts functions as functions namespaces

* Ban using contracts as namespaces

* Add tests

* Update CHANGELOG

* Separate guards with a semicolon

test/aeso_compiler_tests.erl

@@ -1175,6 +1175,13 @@ failing_contracts() ->
                   [<<?Pos(5,16)
                      "`f` must be payable because the entrypoint `f` in the interface `I` is payable">>
                   ])
+    , ?TYPE_ERROR(calling_child_contract_entrypoint,
+                  [<<?Pos(5,20)
+                     "Invalid call to contract entrypoint `F.g`.\n"
+                     "It must be called as `c.g` for some `c : F`.">>])
+    , ?TYPE_ERROR(using_contract_as_namespace,
+                  [<<?Pos(5,3)
+                     "Cannot use undefined namespace F">>])
     ].
 
 validation_test_() ->

test/contracts/calling_child_contract_entrypoint.aes

@@ -0,0 +1,5 @@
+contract F =
+  entrypoint g() = 1
+
+main contract C =
+  entrypoint f() = F.g()

test/contracts/using_contract_as_namespace.aes

@@ -0,0 +1,7 @@
+contract F =
+  entrypoint g() = 1
+
+main contract C =
+  using F for [g]
+
+  entrypoint f() = g()