fix #3880 optimize option pattern match

Author: bobzhang

jscomp/core/js_exp_make.ml

@@ -623,6 +623,10 @@ let rec and_ ?comment (e1 : t) (e2 : t) : t =
   | Var i,  Bin (And , l, ({expression_desc = Var j ; _} as r))
     when Js_op_util.same_vident  i j -> 
     { e2 with expression_desc = Bin(And, r,l)}
+  | Bin(NotEqEq, {expression_desc = Var i}, {expression_desc = Undefined } ),   
+    Bin(EqEqEq, {expression_desc = Var j}, {expression_desc = Str _ | Number _ | Unicode _})
+    when Js_op_util.same_vident i j
+    -> e2
   | _, _ ->     
     { expression_desc = Bin(And, e1,e2) ; comment }
 

jscomp/test/gpr_3875_test.js

@@ -17,13 +17,13 @@ var Xx = {
 function compilerBug(a, b, c, f) {
   var exit = 0;
   var exit$1 = 0;
-  if (a !== undefined && a === "x") {
+  if (a === "x") {
     exit = 2;
   } else {
     exit$1 = 3;
   }
   if (exit$1 === 3) {
-    exit = b !== undefined && b === "x" ? 2 : 1;
+    exit = b === "x" ? 2 : 1;
   }
   switch (exit) {
     case 1 :

jscomp/test/nested_pattern_match_test.js

@@ -61,11 +61,11 @@ function f_opion(x) {
           var match$3 = match$2[1];
           if (match$3) {
             var match$4 = match$3[0];
-            if (match$4 !== undefined && match$4 === 2) {
+            if (match$4 === 2) {
               var match$5 = match$3[1];
               if (match$5) {
                 var match$6 = match$5[0];
-                if (match$6 !== undefined && match$6 === 1) {
+                if (match$6 === 1) {
                   var match$7 = match$5[1];
                   if (match$7 && match$7[0] !== undefined) {
                     return 2;
@@ -99,11 +99,11 @@ function f_opion(x) {
         var match$10 = match$9[1];
         if (match$10) {
           var match$11 = match$10[0];
-          if (match$11 !== undefined && match$11 === 2) {
+          if (match$11 === 2) {
             var match$12 = match$10[1];
             if (match$12) {
               var match$13 = match$12[0];
-              if (match$13 !== undefined && match$13 === 1) {
+              if (match$13 === 1) {
                 var match$14 = match$12[1];
                 if (match$14 && match$14[0] !== undefined) {
                   return 3;

lib/4.02.3/unstable/js_compiler.ml

@@ -82811,6 +82811,10 @@ let rec and_ ?comment (e1 : t) (e2 : t) : t =
   | Var i,  Bin (And , l, ({expression_desc = Var j ; _} as r))
     when Js_op_util.same_vident  i j -> 
     { e2 with expression_desc = Bin(And, r,l)}
+  | Bin(NotEqEq, {expression_desc = Var i}, {expression_desc = Undefined } ),   
+    Bin(EqEqEq, {expression_desc = Var j}, {expression_desc = Str _ | Number _ | Unicode _})
+    when Js_op_util.same_vident i j
+    -> e2
   | _, _ ->     
     { expression_desc = Bin(And, e1,e2) ; comment }
 

lib/4.02.3/whole_compiler.ml

@@ -73003,6 +73003,10 @@ let rec and_ ?comment (e1 : t) (e2 : t) : t =
   | Var i,  Bin (And , l, ({expression_desc = Var j ; _} as r))
     when Js_op_util.same_vident  i j -> 
     { e2 with expression_desc = Bin(And, r,l)}
+  | Bin(NotEqEq, {expression_desc = Var i}, {expression_desc = Undefined } ),   
+    Bin(EqEqEq, {expression_desc = Var j}, {expression_desc = Str _ | Number _ | Unicode _})
+    when Js_op_util.same_vident i j
+    -> e2
   | _, _ ->     
     { expression_desc = Bin(And, e1,e2) ; comment }
 

lib/js/genlex.js

@@ -132,7 +132,7 @@ function make_lexer(keywords) {
                     Stream.junk(strm__);
                     var strm__$1 = strm__;
                     var match$2 = Stream.peek(strm__$1);
-                    if (match$2 !== undefined && match$2 === 42) {
+                    if (match$2 === 42) {
                       Stream.junk(strm__$1);
                       comment(strm__$1);
                       return next_token(strm__$1);