This expression has type Sast.var_decl but an expression was expected of type Ast.var_decl (write a compile with Ocaml )?

It's hard to tell from only that little bit of code, but it sounds like Sast.Id expects a value of type Sast. Var_decl as its argument, but find_variable produces a value of type Ast. Var_decl so that's the type of vdecl .

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