add transformation: if a then {if b then e else d } else e

Author: bobzhang

jscomp/core/js_stmt_make.ml

@@ -281,14 +281,18 @@ let rec if_ ?comment  ?declaration ?else_ (e : J.expression) (then_ : J.block)
 
     (*
        {[ if a then { if b then d else e} else e ]}
-
        => if a && b then d else e 
     *)
     | _,
       [ {statement_desc = If (pred, then_, Some ([else_] as cont)) }],
       [ another_else] when Js_analyzer.eq_statement else_ another_else
       ->
       aux ?comment (E.and_ e pred) then_ cont acc 
+    | _,
+      [ {statement_desc = If (pred, ([ then_ ] as cont), Some ( else_ )) }],
+      [ another_else] when Js_analyzer.eq_statement then_ another_else
+      ->
+      aux ?comment (E.and_ e (E.not pred)) else_ cont acc   
     | _ -> 
       let e = E.ocaml_boolean_under_condition e in 
       { statement_desc =

jscomp/test/exception_rebound_err_test.js

@@ -51,12 +51,8 @@ function test_js_error4() {
       exit$1 = 2;
     }
     if (exit$1 === 2) {
-      if (e[0] === A) {
-        if (e[1] !== 2) {
-          exit = 1;
-        } else {
-          return 4;
-        }
+      if (e[0] === A && e[1] === 2) {
+        return 4;
       } else {
         exit = 1;
       }