Infer scalar types with let generalization

test/test_harness.mli

@@ -9,3 +9,15 @@ val expect_diagnostic : string -> (unit -> unit) -> unit
 val run_suite : string -> case list -> unit
 val failure_count : unit -> int
 val case_count : unit -> int
+
+val root : unit -> string
+val fixture : string -> string
+val read_fixture : string -> string
+val error_of : (unit -> 'a) -> Diagnostic.t option
+val parse : string -> Syntax.program
+val resolve : string -> Resolve.program
+val infer : string -> Typed.program
+val parse_error : string -> Diagnostic.t option
+val resolve_error : string -> Diagnostic.t option
+val infer_error : string -> Diagnostic.t option
+val check_message : string -> string -> (unit -> 'a) -> unit