Change syntax tree and parser

src/aeso_parser.erl

@@ -224,6 +224,9 @@ arg() -> choice(
     ?RULE(id(),                   {arg, get_ann(_1), _1, type_wildcard(get_ann(_1))}),
     ?RULE(id(), tok(':'), type(), {arg, get_ann(_1), _1, _3})).
 
+letpat() ->
+    ?RULE(keyword('('), id(), tok('='), pattern(), tok(')'), {letpat, get_ann(_1), _2, _4}).
+
 %% -- Types ------------------------------------------------------------------
 
 type_vars() -> paren_list(tvar()).
@@ -328,6 +331,7 @@ exprAtom() ->
         , ?RULE(keyword('['), Expr, token('|'), comma_sep(comprehension_exp()), tok(']'), list_comp_e(_1, _2, _4))
         , ?RULE(tok('['), Expr, binop('..'), Expr, tok(']'), _3(_2, _4))
         , ?RULE(keyword('('), comma_sep(Expr), tok(')'), tuple_e(_1, _2))
+        , letpat()
         ])
     end).
 
@@ -588,6 +592,8 @@ tuple_e(Ann, Exprs)   -> {tuple, Ann, Exprs}.
 list_comp_e(Ann, Expr, Binds) -> {list_comp, Ann, Expr, Binds}.
 
 -spec parse_pattern(aeso_syntax:expr()) -> aeso_parse_lib:parser(aeso_syntax:pat()).
+parse_pattern({letpat, Ann, Id, Pat}) ->
+    {letpat, Ann, Id, parse_pattern(Pat)};
 parse_pattern({app, Ann, Con = {'::', _}, Es}) ->
     {app, Ann, Con, lists:map(fun parse_pattern/1, Es)};
 parse_pattern({app, Ann, {'-', _}, [{int, _, N}]}) ->

src/aeso_pretty.erl

@@ -299,6 +299,8 @@ tuple_type(Factors) ->
       ]).
 
 -spec expr_p(integer(), aeso_syntax:arg_expr()) -> doc().
+expr_p(P, {letpat, _, Id, Pat}) ->
+    paren(P > 100, follow(hsep(expr(Id), text("=")), expr(Pat)));
 expr_p(P, {named_arg, _, Name, E}) ->
     paren(P > 100, follow(hsep(expr(Name), text("=")), expr(E)));
 expr_p(P, {lam, _, Args, E}) ->

src/aeso_syntax.erl

@@ -58,6 +58,7 @@
 
 -type letval()  :: {letval, ann(), pat(), expr()}.
 -type letfun()  :: {letfun, ann(), id(), [pat()], type(), expr()}.
+-type letpat()  :: {letpat, ann(), id(), pat()}.
 -type fundecl() :: {fun_decl, ann(), id(), type()}.
 
 -type letbind()
@@ -122,7 +123,8 @@
      | {block, ann(), [stmt()]}
      | {op(), ann()}
      | id() | qid() | con() | qcon()
-     | constant().
+     | constant()
+     | letpat().
 
 -type record_or_map() :: record | map | record_or_map_error.
 
@@ -156,6 +158,7 @@
              | {list, ann(), [pat()]}
              | {typed, ann(), pat(), type()}
              | {record, ann(), [field(pat())]}
+             | letpat()
              | constant()
              | con()
              | id().