Add punning for object copying expressions.

From: Jeremy Yallop <yallop@gmail.com>

git-svn-id: http://caml.inria.fr/svn/ocaml/trunk@15580 f963ae5c-01c2-4b8c-9fe0-0dff7051ff02

2 files changed, 19 insertions, 11 deletions

diff --git a/Changes b/Changes
index 3b5035b8e..cea1d08c3 100644
--- a/Changes
+++ b/Changes
@@ -1,6 +1,12 @@
 OCaml 4.03.0:
 -------------
 
+Language features:
+- PR#6374: allow "_ t" as a short-hand for "(_, _, ..) t" for n-ary type
+  constructors (Alain Frisch)
+- allow field punning in object copying expressions: {< x; >} for {< x = x; >}
+  (Jeremy Yallop)
+
 Compilers:
 - PR#6501: harden the native-code generator against certain uses of "%identity"
   (Xavier Leroy, report by Antoine Miné).
@@ -16,8 +22,6 @@ Standard library:
 - PR#6585: fix memory leak in win32unix/createprocess.c
 
 Type system:
-- PR#6374: allow "_ t" as a short-hand for "(_, _, ..) t" for n-ary type
-  constructors (Alain Frisch)
 * PR#6465: allow incremental weakening of module aliases (Jacques Garrigue).
   This is done by adding equations to submodules when expanding aliases.
   In theory this may be incompatible is some corner cases defining a module
diff --git a/parsing/parser.mly b/parsing/parser.mly
index 7366fd747..3210c4a0e 100644
--- a/parsing/parser.mly
+++ b/parsing/parser.mly
@@ -1264,15 +1264,15 @@ simple_expr:
       { mkexp(Pexp_apply(mkoperator "!" 1, ["",$2])) }
   | NEW ext_attributes class_longident
       { mkexp_attrs (Pexp_new(mkrhs $3 3)) $2 }
-  | LBRACELESS field_expr_list opt_semi GREATERRBRACE
-      { mkexp (Pexp_override(List.rev $2)) }
-  | LBRACELESS field_expr_list opt_semi error
+  | LBRACELESS field_expr_list GREATERRBRACE
+      { mkexp (Pexp_override $2) }
+  | LBRACELESS field_expr_list error
       { unclosed "{<" 1 ">}" 4 }
   | LBRACELESS GREATERRBRACE
       { mkexp (Pexp_override [])}
-  | mod_longident DOT LBRACELESS field_expr_list opt_semi GREATERRBRACE
-      { mkexp(Pexp_open(Fresh, mkrhs $1 1, mkexp (Pexp_override(List.rev $4))))}
-  | mod_longident DOT LBRACELESS field_expr_list opt_semi error
+  | mod_longident DOT LBRACELESS field_expr_list GREATERRBRACE
+      { mkexp(Pexp_open(Fresh, mkrhs $1 1, mkexp (Pexp_override $4)))}
+  | mod_longident DOT LBRACELESS field_expr_list error
       { unclosed "{<" 3 ">}" 6 }
   | simple_expr SHARP label
       { mkexp(Pexp_send($1, $3)) }
@@ -1412,10 +1412,14 @@ lbl_expr:
       { (mkrhs $1 1, exp_of_label $1 1) }
 ;
 field_expr_list:
+    field_expr opt_semi { [$1] }
+  | field_expr SEMI field_expr_list { $1 :: $3 }
+;
+field_expr:
     label EQUAL expr
-      { [mkrhs $1 1,$3] }
-  | field_expr_list SEMI label EQUAL expr
-      { (mkrhs $3 3, $5) :: $1 }
+      { (mkrhs $1 1, $3) }
+  | label
+      { (mkrhs $1 1, exp_of_label (Lident $1) 1) }
 ;
 expr_semi_list:
     expr                                        { [$1] }