From af2fe4515ca741977e88b8bcc75722b33ab423df Mon Sep 17 00:00:00 2001
From: Gaith Hallak <gaithhallak@gmail.com>
Date: Mon, 23 May 2022 20:33:13 +0400
Subject: [PATCH] Ban empty record declarations

---
 CHANGELOG.md                                | 1 +
 src/aeso_ast_infer_types.erl                | 6 ++++++
 test/aeso_compiler_tests.erl                | 4 ++++
 test/contracts/empty_record_declaration.aes | 3 +++
 4 files changed, 14 insertions(+)
 create mode 100644 test/contracts/empty_record_declaration.aes

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 925053c..86bcadb 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ```
 ### Changed
 - Error messages have been restructured (less newlines) to provide more unified errors. Also `pp_oneline/1` has been added.
+- Ban empty record declarations (e.g. `record r = {}` would give an error).
 ### Removed
 - Support for AEVM has been entirely wiped
 
diff --git a/src/aeso_ast_infer_types.erl b/src/aeso_ast_infer_types.erl
index 9490117..ef94924 100644
--- a/src/aeso_ast_infer_types.erl
+++ b/src/aeso_ast_infer_types.erl
@@ -1018,6 +1018,9 @@ check_typedef_sccs(Env, TypeMap, [{acyclic, Name} | SCCs], Acc) ->
             Env1 = bind_type(Name, Ann, {Xs, Def}, Env),
             case Def of
                 {alias_t, _}  -> check_typedef_sccs(Env1, TypeMap, SCCs, Acc1);
+                {record_t, []} ->
+                    type_error({empty_record_declaration, Ann, Name}),
+                    check_typedef_sccs(Env1, TypeMap, SCCs, Acc1);
                 {record_t, Fields} ->
                     %% check_type to get qualified name
                     RecTy = check_type(Env1, app_t(Ann, D, Xs)),
@@ -3279,6 +3282,9 @@ mk_error({using_undefined_namespace_parts, Ann, Namespace, Parts}) ->
 mk_error({unknown_warning, Warning}) ->
     Msg = io_lib:format("Trying to report unknown warning: ~p", [Warning]),
     mk_t_err(pos(0, 0), Msg);
+mk_error({empty_record_declaration, Ann, Name}) ->
+    Msg = io_lib:format("Empty record declarations are not allowed. Cannot declare the record `~s`", [Name]),
+    mk_t_err(pos(Ann), Msg);
 mk_error(Err) ->
     Msg = io_lib:format("Unknown error: ~p", [Err]),
     mk_t_err(pos(0, 0), Msg).
diff --git a/test/aeso_compiler_tests.erl b/test/aeso_compiler_tests.erl
index 6e547b3..6db76f5 100644
--- a/test/aeso_compiler_tests.erl
+++ b/test/aeso_compiler_tests.erl
@@ -791,6 +791,10 @@ failing_contracts() ->
                      "when checking the type of the expression `\"y\" : string` "
                      "against the expected type `bool`">>
                   ])
+    , ?TYPE_ERROR(empty_record_declaration,
+                  [<<?Pos(2,5)
+                     "Empty record declarations are not allowed. Cannot declare the record `r`">>
+                  ])
     , ?TYPE_ERROR(warnings,
                   [<<?Pos(0, 0)
                       "The file `Triple.aes` is included but not used.">>,
diff --git a/test/contracts/empty_record_declaration.aes b/test/contracts/empty_record_declaration.aes
new file mode 100644
index 0000000..df45e8c
--- /dev/null
+++ b/test/contracts/empty_record_declaration.aes
@@ -0,0 +1,3 @@
+contract C =
+    record r = {}
+    entrypoint init() = ()