Fix redundant branches in generated switch body, fixes #6671 (#6672)

* Fix redundant branches in generated switch body, fixes #6671

Signed-Off-By: Vincenzo Pellegrini <[email protected]>

* Updated changelog

---------

Signed-off-by: Vincenzo Pellegrini <[email protected]>

Author: friedbyalice

CHANGELOG.md

@@ -16,6 +16,7 @@
 
 - Fix making the static import for the dynamic import of external ffi https://github.com/rescript-lang/rescript-compiler/pull/6664
 - Fix local type variables breaking react components. https://github.com/rescript-lang/rescript-compiler/pull/6665
+- Fix remove redundant branches in generated switch body. https://github.com/rescript-lang/rescript-compiler/pull/6672
 
 #### :nail-care: Polish
 

jscomp/core/lam_compile.ml

@@ -573,6 +573,11 @@ and compile_general_cases :
             break still should not be printed (it will be continuned)
            TOOD: disabled temporarily since it's not perfect yet *)
       morph_declare_to_assign cxt (fun cxt declaration ->
+          (* Exclude cases that are the same as the default if the default is defined *)
+          let cases = match default with
+            | Default lam -> List.filter (fun (_, lam1) -> not (Lam.eq_approx lam lam1)) cases
+            | _ -> cases
+          in
           let default =
             match default with
             | Complete -> None

jscomp/test/gpr_1438.js

@@ -46,8 +46,6 @@ function parse_sign_and_base(s) {
     case 43 :
         i = i + 1 | 0;
         break;
-    case 44 :
-        break;
     case 45 :
         sign = -1;
         i = i + 1 | 0;
@@ -417,19 +415,6 @@ function parse_format(fmt) {
             };
             _i = j;
             continue ;
-        case 33 :
-        case 34 :
-        case 36 :
-        case 37 :
-        case 38 :
-        case 39 :
-        case 40 :
-        case 41 :
-        case 42 :
-        case 44 :
-        case 47 :
-            exit = 1;
-            break;
         case 48 :
             f.filter = "0";
             _i = i + 1 | 0;

jscomp/test/gpr_1698_test.js

@@ -240,9 +240,6 @@ function make_lexer(keywords) {
             case 94 :
                 exit = 3;
                 break;
-            case 95 :
-                exit = 2;
-                break;
             case 91 :
             case 93 :
             case 96 :
@@ -535,12 +532,6 @@ function make_lexer(keywords) {
           case 114 :
               Stream.junk(strm__);
               return /* '\r' */13;
-          case 111 :
-          case 112 :
-          case 113 :
-          case 115 :
-              Stream.junk(strm__);
-              return c1;
           case 116 :
               Stream.junk(strm__);
               return /* '\t' */9;
@@ -617,9 +608,6 @@ function make_lexer(keywords) {
                     RE_EXN_ID: Stream.Failure,
                     Error: new Error()
                   };
-          case 41 :
-              Stream.junk(strm__);
-              continue ;
           case 42 :
               Stream.junk(strm__);
               while(true) {