Safe call operators ?.

.gitignore

@@ -27,3 +27,5 @@ _esybuild
 _esyinstall
 .merlin
 _release
+**/*.swp
+**/*.swo

src/reason-parser/reason_lexer.mll

@@ -486,6 +486,8 @@ rule token = parse
  | "#=" { SHARPEQUAL }
  | "#" operator_chars+
  { SHARPOP(lexeme_operator lexbuf) }
+ | "?" operator_chars+
+ { OPTIONALACCESS(lexeme_operator lexbuf) }
  | "#" [' ' '\t']* (['0'-'9']+ as num) [' ' '\t']*
  ("\"" ([^ '\010' '\013' '"' ] * as name) "\"")?
  [^ '\010' '\013'] * newline

src/reason-parser/reason_parser.mly

@@ -1239,6 +1239,7 @@ let package_type_of_module_type pmty =
 %token SEMISEMI
 %token SHARP
 %token <string> SHARPOP
+%token <string> OPTIONALACCESS
 %token SHARPEQUAL
 %token SIG
 %token STAR
@@ -1386,6 +1387,8 @@ conflicts.
 (* PREFIXOP and BANG precedence *)
 %nonassoc below_DOT_AND_SHARP (* practically same as below_SHARP but we convey purpose *)
 %nonassoc SHARP (* simple_expr/toplevel_directive *)
+
+%right OPTIONALACCESS
 %nonassoc below_DOT
 
 (* We need SHARPEQUAL to have lower precedence than `[` to make e.g.
@@ -1405,6 +1408,7 @@ conflicts.
 (* Entry points *)
 
 %start implementation (* for implementation files *)
+
 %type <Ast_404.Parsetree.structure> implementation
 %start interface (* for interface files *)
 %type <Ast_404.Parsetree.signature> interface
@@ -3138,6 +3142,84 @@ parenthesized_expr:
  { mkexp (Pexp_send($1, $3)) }
  | E as_loc(SHARPOP) simple_expr_no_call
  { mkinfixop $1 (mkoperator $2) $3 }
+ (*
+ * let res = a?.b;
+ *
+ * --generates-->
+ *
+ * let res = switch a {
+ * | Some(a) => Some(a.b)
+ * | None => None
+ * };
+ *
+ * let res = c?.+d;
+ *
+ * -generates->
+ *
+ * let res = switch c {
+ * | Some(c) => c.d <-- assuming d is optional
+ * | None => None
+ * };
+ *
+ * Same goes for ?# and ?#+ for JS objects
+ *)
+ | E OPTIONALACCESS simple_expr_no_call 
+ {
+ let loc_exp = mklocation $startpos($1) $endpos($1) in
+ let record_name = match $1.pexp_desc with Pexp_ident({txt = Lident(str); loc;}) -> str | _ -> "x" in
+ let prop_name = match $3.pexp_desc with 
+ | Pexp_ident({txt = Lident(str); loc;}) -> str 
+ | Pexp_match({pexp_desc = Pexp_ident({txt = Lident(str); loc;})}, _) -> str
+ | _ -> syntax_error ()
+ in
+ let access_property = match $2 with
+ | "?." | "?.+" -> 
+ mkexp (Pexp_field (
+ mkexp (Pexp_ident({
+ txt = Lident(record_name);
+ loc = loc_exp;
+ })), {
+ txt = Lident(prop_name); 
+ loc = loc_exp;
+ }))
+ | "?#" | "?#+" -> 
+ mkexp (Pexp_apply(
+ mkexp (Pexp_ident({
+ txt = Lident("##");
+ loc = loc_exp;
+ })), [
+ Nolabel, mkexp (Pexp_ident({ txt = Lident(record_name); loc = loc_exp}));
+ Nolabel, mkexp (Pexp_ident({ txt = Lident(prop_name); loc = loc_exp }));
+ ]
+ )) 
+ | _ -> syntax_error ()
+ in
+ let access_property_exp = match $2 with 
+ | "?." | "?#" -> mkexp (Pexp_construct ({txt = Lident("Some"); loc = loc_exp}, Some(access_property)))
+ | "?.+" | "?#+" -> access_property
+ | _ -> syntax_error ()
+ in
+ let some_exp = match $3.pexp_desc with
+ | Pexp_ident(_) -> access_property_exp
+ | Pexp_match(_, _) -> mkexp (Pexp_let(Nonrecursive, [{ 
+ pvb_pat = mkpat (Ppat_var(mkloc prop_name loc_exp));
+ pvb_expr = access_property_exp;
+ pvb_attributes = [];
+ pvb_loc = loc_exp; 
+ }], $3));
+ | _ -> syntax_error () in
+ let some_pat =
+ Pat.mk ~loc:loc_exp (Ppat_construct({ txt = Lident("Some"); loc = loc_exp}, Some(mkpat (Ppat_var(mkloc record_name loc_exp))))) in
+ let none_pat = 
+ Pat.mk ~loc:loc_exp (Ppat_construct({ txt = Lident("None"); loc = loc_exp;}, None)) in
+ let some_case = 
+ Exp.case some_pat some_exp
+ in
+ let none_case =
+ Exp.case none_pat (mkexp (Pexp_construct({ txt = Lident("None"); loc = loc_exp;}, None)));
+ in
+ mkexp (Pexp_match ($1, [some_case; none_case]))
+ }
  | E as_loc(SHARPEQUAL) simple_expr
  { let op = { $2 with txt = "#=" } in
  mkinfixop $1 (mkoperator op) $3 }
@@ -3758,6 +3840,7 @@ mark_position_pat
 
  | LPAREN COLONCOLON RPAREN LPAREN pattern_without_or COMMA pattern_without_or RPAREN
  { let loc_coloncolon = mklocation $startpos($2) $endpos($2) in
+
  let loc = mklocation $symbolstartpos $endpos in
  mkpat_cons loc_coloncolon (mkpat ~ghost:true ~loc (Ppat_tuple[$5;$7])) loc
  }