Pattern guards for functions and switch statements (#339)

* Add case guards to parser

* Add pattern guards to infer types and fcode generation

* Add functions guards

* Add test for patterns guards

* Update docs

* Update CHANGELOG.md

* Remove stateful context from Env for guards

* Elaborate on guards

* Add failing test for stateful pattern guards

* Implement multiple guards

* Fix tests

* Disable aevm related tests

* Split the sentence before if and otherwise

* Fix type in docs

* Implement multiple exprs in the same guard

* Fix pretty printing

* Change tests to include multiple guards

* Add test for non-boolean guards

* Desugar clauses with guards

* Fix incomplete patterns bug

* Fix docs

* Compile to icode when no guards are used

* Revert "Disable aevm related tests"

This reverts commit e828099bd97dffe11438f2e48f3a92ce3641e85b.

src/aeso_compiler.erl

@@ -475,9 +475,9 @@ error_missing_call_function() ->
 get_call_type([{Contract, _, _, Defs}]) when ?IS_CONTRACT_HEAD(Contract) ->
     case [ {lists:last(QFunName), FunType}
           || {letfun, _, {id, _, ?CALL_NAME}, [], _Ret,
-                {typed, _,
-                    {app, _,
-                        {typed, _, {qid, _, QFunName}, FunType}, _}, _}} <- Defs ] of
+                [{guarded, _, [], {typed, _,
+                     {app, _,
+                         {typed, _, {qid, _, QFunName}, FunType}, _}, _}}]} <- Defs ] of
         [Call] -> {ok, Call};
         []     -> error_missing_call_function()
     end;