[jvm] get unboxed types when figuring binop result type (#9870)

src/generators/genjvm.ml

@@ -884,13 +884,12 @@ class texpr_to_jvm gctx (jc : JvmClass.builder) (jm : JvmMethod.builder) (return
 		f2();
 		jm#cast ~allow_to_string:true cast_type;
 
-	method get_binop_type_sig jsig1 jsig2 = match jsig1,jsig2 with
+	method get_binop_type_sig jsig1 jsig2 =
+		match get_unboxed_type jsig1, get_unboxed_type jsig2 with
 		| TObject((["java";"lang"],"String"),_),_
 		| _,TObject((["java";"lang"],"String"),_) ->
 			string_sig
 		| TLong,_ | _,TLong -> TLong
-		| _,TObject((["java";"lang"],"Double"),_)
-		| TObject((["java";"lang"],"Double"),_),_
 		| TDouble,_ | _,TDouble -> TDouble
 		| TFloat,_ | _,TFloat -> TFloat
 		| TInt,_ | _,TInt -> TInt