I extended left-hand sides of assignments to have qualified paths.

Note: In loops over integers, the initial assignment has still a
variable (the index) as left-hand side.

A qualified path is of the form "x" or "x.y.z" or "x.y.z[t]".

AST.ml

@@ -388,11 +388,15 @@ and case = {
 }
 
 and assignment = {
-  path   : path;
+  lhs    : lhs;
   assign : assign;
   expr   : expr
 }
 
+and lhs =
+  Path    of path
+| MapPath of map_lookup reg
+
 and loop =
   While of while_loop reg
 | For   of for_loop
@@ -409,7 +413,7 @@ and for_loop =
 
 and for_int = {
   kwd_for : kwd_for;
-  assign  : assignment reg;
+  assign  : var_assign reg;
   down    : kwd_down option;
   kwd_to  : kwd_to;
   bound   : expr;
@@ -417,6 +421,12 @@ and for_int = {
   block   : block reg
 }
 
+and var_assign = {
+  name   : variable;
+  assign : assign;
+  expr   : expr
+}
+
 and for_collect = {
   kwd_for : kwd_for;
   var     : variable;
@@ -713,6 +723,10 @@ let local_decl_to_region = function
 | LocalConst         {region; _}
 | LocalVar           {region; _} -> region
 
+let lhs_to_region = function
+  Path path -> path_to_region path
+| MapPath {region; _} -> region
+
 (* Printing the tokens with their source regions *)
 
 let printf = Printf.printf
@@ -1014,11 +1028,15 @@ and print_case {value; _} =
   print_instruction instr
 
 and print_assignment {value; _} =
-  let {path; assign; expr} = value in
-  print_path path;
+  let {lhs; assign; expr} = value in
+  print_lhs lhs;
   print_token assign ":=";
   print_expr expr
 
+and print_lhs = function
+  Path path -> print_path path
+| MapPath {value; _} -> print_map_lookup value
+
 and print_loop = function
   While {value; _} -> print_while_loop value
 | For     for_loop -> print_for_loop for_loop
@@ -1037,13 +1055,19 @@ and print_for_int ({value; _} : for_int reg) =
   let {kwd_for; assign; down; kwd_to;
        bound; step; block} = value in
   print_token      kwd_for "for";
-  print_assignment assign;
+  print_var_assign assign;
   print_down       down;
   print_token      kwd_to "to";
   print_expr       bound;
   print_step       step;
   print_block      block
 
+and print_var_assign {value; _} =
+  let {name; assign; expr} = value in
+  print_var name;
+  print_token assign ":=";
+  print_expr expr
+
 and print_down = function
   Some kwd_down -> print_token kwd_down "down"
 | None -> ()
@@ -1086,15 +1110,16 @@ and print_expr = function
 | ParExpr e    -> print_par_expr e
 
 and print_map_expr = function
-  MapLookUp {value; _} ->
-    let {path; index} = value in
+  MapLookUp {value; _} -> print_map_lookup value
+| MapInj inj ->
+    print_map_injection inj
+
+and print_map_lookup {path; index} =
   let {lbracket; inside; rbracket} = index.value in
   print_path  path;
   print_token lbracket "[";
   print_expr  inside;
   print_token rbracket "]"
-| MapInj inj ->
-    print_map_injection inj
 
 and print_path = function
   Name var        -> print_var var

AST.mli

@@ -372,11 +372,15 @@ and case = {
 }
 
 and assignment = {
-  path   : path;
+  lhs    : lhs;
   assign : assign;
   expr   : expr
 }
 
+and lhs =
+  Path    of path
+| MapPath of map_lookup reg
+
 and loop =
   While of while_loop reg
 | For   of for_loop
@@ -393,7 +397,7 @@ and for_loop =
 
 and for_int = {
   kwd_for : kwd_for;
-  assign  : assignment reg;
+  assign  : var_assign reg;
   down    : kwd_down option;
   kwd_to  : kwd_to;
   bound   : expr;
@@ -401,6 +405,12 @@ and for_int = {
   block   : block reg
 }
 
+and var_assign = {
+  name   : variable;
+  assign : assign;
+  expr   : expr
+}
+
 and for_collect = {
   kwd_for : kwd_for;
   var     : variable;
@@ -582,6 +592,7 @@ val instr_to_region      : instruction -> Region.t
 val pattern_to_region    : pattern -> Region.t
 val local_decl_to_region : local_decl -> Region.t
 val path_to_region       : path -> Region.t
+val lhs_to_region        : lhs -> Region.t
 
 (* Printing *)
 

Parser.mly

@@ -543,12 +543,16 @@ case:
   }
 
 assignment:
-  path ASS expr {
-    let region = cover (path_to_region $1) (expr_to_region $3)
-    and value  = {path = $1; assign = $2; expr = $3}
+  lhs ASS expr {
+    let region = cover (lhs_to_region $1) (expr_to_region $3)
+    and value  = {lhs = $1; assign = $2; expr = $3}
     in {region; value}
   }
 
+lhs:
+  path       {    Path $1 }
+| map_lookup { MapPath $1 }
+
 loop:
   while_loop { $1 }
 | for_loop   { $1 }
@@ -564,7 +568,7 @@ while_loop:
   }
 
 for_loop:
-  For assignment Down? To expr option(step_clause) block {
+  For var_assign Down? To expr option(step_clause) block {
     let region = cover $1 $7.region in
     let value = {
       kwd_for  = $1;
@@ -589,6 +593,13 @@ for_loop:
     in For (ForCollect {region; value})
   }
 
+var_assign:
+  var ASS expr {
+    let region = cover $1.region (expr_to_region $3)
+    and value  = {name = $1; assign = $2; expr = $3}
+    in {region; value}
+  }
+
 step_clause:
   Step expr { $1,$2 }
 
@@ -768,13 +779,13 @@ core_expr:
   }
 
 map_expr:
-  map_selection { MapLookUp $1 }
+  map_lookup { MapLookUp $1 }
 
 path:
   var               {       Name $1 }
 | record_projection { RecordPath $1 }
 
-map_selection:
+map_lookup:
   path brackets(expr) {
     let region = cover (path_to_region $1) $2.region in
     let value  = {

Tests/crowdfunding.ligo

@@ -18,9 +18,8 @@ entrypoint contribute (storage store : store;
       fail "Deadline passed"
     else
       case store.backers[sender] of
-        None ->
-//           store.backers[sender] := Some (amount)
-          patch store.backers with map sender -> amount end
+        None -> store.backers[sender] := Some (amount)
+//        patch store.backers with map sender -> amount end
       |    _ -> skip
       end
   end with (store, operations)
@@ -59,7 +58,7 @@ entrypoint claim (storage store : store; const sender : address)
           else
             begin
               operations := [Transfer (sender, amount)];
-//              store.backers[sender] := None
+              store.backers[sender] := (None : option (nat))
             end
       end
   end with (store, operations)