Fix issue with uninitialized _param in recursive functions with unit argument.

Fixes #6719

Author: cristianoc

CHANGELOG.md

@@ -49,6 +49,7 @@
 - Avoid generation of `Curry` with reverse application `|>`. https://github.com/rescript-lang/rescript-compiler/pull/6876
 - Fix issue where the internal ppx for pipe `->` would not use uncurried application in uncurried mode. https://github.com/rescript-lang/rescript-compiler/pull/6878
 - Fix build after calling without `-warn-error`, see https://github.com/rescript-lang/rescript-compiler/issues/6868 for more details. https://github.com/rescript-lang/rescript-compiler/pull/6877
+- Fix issue with uninitialized `_param` in recursive functions with unit argument. https://github.com/rescript-lang/rescript-compiler/pull/6907
 
 #### :house: Internal
 

jscomp/core/lam_compile.ml

@@ -327,6 +327,7 @@ and compile_recursive_let ~all_bindings (cxt : Lam_compile_context.t)
          ]}
           [Alias] may not be exact
       *)
+      let params = if one_unit_arg then [] else params in
       let ret : Lam_compile_context.return_label =
         {
           id;

jscomp/test/ocaml_re_test.js

@@ -266,7 +266,6 @@ function iter(f, strm) {
       }
       junk(strm);
       f(Caml_option.valFromOption(a));
-      _param = undefined;
       continue;
     };
   };

jscomp/test/uncurry_test.js

@@ -266,7 +266,6 @@ function iter(f, strm) {
       }
       junk(strm);
       f(Caml_option.valFromOption(a));
-      _param = undefined;
       continue;
     };
   };