caml_js_get and caml_js_delete should not be eliminated even if their result is not used

Author: alainfrisch

CHANGES.md

@@ -32,6 +32,7 @@
 * Compiler: fix rewriter bug in share_constant (fix #1247)
 * Compiler: fix miscompilation of mutually recursive functions in loop (#1321)
 * Compiler: fix bug while minifying/renaming try-catch blocks
+* Compiler: no dead code elimination for caml_js_get
 * Runtime: fix ocamlyacc parse engine (#1307)
 * Runtime: fix Out_channel.is_buffered, set_buffered
 * Runtime: fix format wrt alternative

compiler/lib/generate.ml

@@ -965,7 +965,9 @@ let _ =
 
   register_tern_prim "caml_js_set" (fun cx cy cz _ ->
       J.EBin (J.Eq, J.EAccess (cx, cy), cz));
-  register_bin_prim "caml_js_get" `Mutable (fun cx cy _ -> J.EAccess (cx, cy));
+  (* [caml_js_get] can have side effect, we declare it as mutator.
+     see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/get *)
+  register_bin_prim "caml_js_get" `Mutator (fun cx cy _ -> J.EAccess (cx, cy));
   register_bin_prim "caml_js_delete" `Mutator (fun cx cy _ ->
       J.EUn (J.Delete, J.EAccess (cx, cy)));
   register_bin_prim "caml_js_equals" `Mutable (fun cx cy _ ->

runtime/jslib.js

@@ -24,7 +24,7 @@ function caml_js_pure_expr (f) { return f(); }
 
 //Provides: caml_js_set (mutable, const, const)
 function caml_js_set(o,f,v) { o[f]=v;return 0}
-//Provides: caml_js_get mutable (const, const)
+//Provides: caml_js_get (const, const)
 function caml_js_get(o,f) { return o[f]; }
 //Provides: caml_js_delete (mutable, const)
 function caml_js_delete(o,f) { delete o[f]; return 0}