# Module Location

    module Location: sig .. end

## Source code locations (ranges of positions), used in parsetree

Warning: this module is unstable and part of compiler-libs.

    type t = Warnings.loc = {

`` | `loc_start : `Lexing.position`;`
`` | `loc_end : `Lexing.position`;`
`` | `loc_ghost : `bool`;`

`}`

Note on the use of Lexing.position in this module. If `pos_fname = ""`, then use `!input_name` instead. If `pos_lnum = -1`, then `pos_bol = 0`. Use `pos_cnum` and re-parse the file to get the line and character numbers. Else all fields are correct.

    val none : t

An arbitrary value of type `t`; describes an empty ghost range.

    val is_none : t -> bool

True for `Location.none`, false any other location

    val in_file : string -> t

Return an empty ghost range located in a given file.

    val init : Lexing.lexbuf -> string -> unit

Set the file name and line number of the `lexbuf` to be the start of the named file.

    val curr : Lexing.lexbuf -> t

Get the location of the current token from the `lexbuf`.

    val symbol_rloc : unit -> t

    val symbol_gloc : unit -> t

    val rhs_loc : int -> t

`rhs_loc n` returns the location of the symbol at position `n`, starting at 1, in the current parser rule.

    val rhs_interval : int -> int -> t

    val get_pos_info : Lexing.position -> string * int * int

file, line, char

    type 'a loc = {

`` | `txt : `'a`;`
`` | `loc : `t`;`

`}`

    val mknoloc : 'a -> 'a loc

    val mkloc : 'a -> t -> 'a loc

## Input info

    val input_name : string ref

    val input_lexbuf : Lexing.lexbuf option ref

    val input_phrase_buffer : Buffer.t option ref

## Toplevel-specific functions

    val echo_eof : unit -> unit

    val reset : unit -> unit

## Printing locations

    val rewrite_absolute_path : string -> string

rewrite absolute path to honor the BUILD_PATH_PREFIX_MAP variable (https://reproducible-builds.org/specs/build-path-prefix-map/) if it is set.

    val absolute_path : string -> string

    val show_filename : string -> string

In -absname mode, return the absolute path for this filename. Otherwise, returns the filename unchanged.

    val print_filename : Format.formatter -> string -> unit

    val print_loc : Format.formatter -> t -> unit

    val print_locs : Format.formatter -> t list -> unit

## Toplevel-specific location highlighting

    val highlight_terminfo : Lexing.lexbuf -> Format.formatter -> t list -> unit

## Reporting errors and warnings

### The type of reports and report printers

    type msg = (Format.formatter -> unit) loc

    val msg : ?loc:t ->
           ('a, Format.formatter, unit, msg) format4 -> 'a

    type report_kind =

`|` | `Report_error`
`|` | `Report_warning of `string``
`|` | `Report_warning_as_error of `string``
`|` | `Report_alert of `string``
`|` | `Report_alert_as_error of `string``

    type report = {

`` | `kind : `report_kind`;`
`` | `main : `msg`;`
`` | `sub : `msg list`;`

`}`

    type report_printer = {

`` | `pp : `report_printer -> Format.formatter -> report -> unit`;`
`` | `pp_report_kind : `report_printer -> report -> Format.formatter -> report_kind -> unit`;`
`` | `pp_main_loc : `report_printer -> report -> Format.formatter -> t -> unit`;`
`` | `pp_main_txt : `report_printer -> report -> Format.formatter -> (Format.formatter -> unit) -> unit`;`
`` | `pp_submsgs : `report_printer -> report -> Format.formatter -> msg list -> unit`;`
`` | `pp_submsg : `report_printer -> report -> Format.formatter -> msg -> unit`;`
`` | `pp_submsg_loc : `report_printer -> report -> Format.formatter -> t -> unit`;`
`` | `pp_submsg_txt : `report_printer -> report -> Format.formatter -> (Format.formatter -> unit) -> unit`;`

`}`

A printer for `report`s, defined using open-recursion. The goal is to make it easy to define new printers by re-using code from existing ones.

### Report printers used in the compiler

    val batch_mode_printer : report_printer

    val terminfo_toplevel_printer : Lexing.lexbuf -> report_printer

    val best_toplevel_printer : unit -> report_printer

Detects the terminal capabilities and selects an adequate printer

### Printing a `report`

    val print_report : Format.formatter -> report -> unit

Display an error or warning report.

    val report_printer : (unit -> report_printer) ref

Hook for redefining the printer of reports.

The hook is a `unit -> report_printer` and not simply a `report_printer`: this is useful so that it can detect the type of the output (a file, a terminal, ...) and select a printer accordingly.

    val default_report_printer : unit -> report_printer

Original report printer for use in hooks.

## Reporting warnings

### Converting a `Warnings.t` into a `report`

    val report_warning : t -> Warnings.t -> report option

`report_warning loc w` produces a report for the given warning `w`, or `None` if the warning is not to be printed.

    val warning_reporter : (t -> Warnings.t -> report option) ref

Hook for intercepting warnings.

    val default_warning_reporter : t -> Warnings.t -> report option

Original warning reporter for use in hooks.

### Printing warnings

    val formatter_for_warnings : Format.formatter ref

    val print_warning : t -> Format.formatter -> Warnings.t -> unit

Prints a warning. This is simply the composition of `report_warning` and `print_report`.

    val prerr_warning : t -> Warnings.t -> unit

Same as `print_warning`, but uses `!formatter_for_warnings` as output formatter.

## Reporting alerts

### Converting an `Alert.t` into a `report`

    val report_alert : t -> Warnings.alert -> report option

`report_alert loc w` produces a report for the given alert `w`, or `None` if the alert is not to be printed.

    val alert_reporter : (t -> Warnings.alert -> report option) ref

Hook for intercepting alerts.

    val default_alert_reporter : t -> Warnings.alert -> report option

Original alert reporter for use in hooks.

### Printing alerts

    val print_alert : t -> Format.formatter -> Warnings.alert -> unit

Prints an alert. This is simply the composition of `report_alert` and `print_report`.

    val prerr_alert : t -> Warnings.alert -> unit

Same as `print_alert`, but uses `!formatter_for_warnings` as output formatter.

    val deprecated : ?def:t -> ?use:t -> t -> string -> unit

Prints a deprecation alert.

    val alert : ?def:t ->
           ?use:t -> kind:string -> t -> string -> unit

Prints an arbitrary alert.

## Reporting errors

    type error = report

An `error` is a `report` which `report_kind` must be `Report_error`.

    val error : ?loc:t -> ?sub:msg list -> string -> error

    val errorf : ?loc:t ->
           ?sub:msg list ->
           ('a, Format.formatter, unit, error) format4 -> 'a

    val error_of_printer : ?loc:t ->
           ?sub:msg list ->
           (Format.formatter -> 'a -> unit) -> 'a -> error

    val error_of_printer_file : (Format.formatter -> 'a -> unit) -> 'a -> error

## Automatically reporting errors for raised exceptions

    val register_error_of_exn : (exn -> error option) -> unit

Each compiler module which defines a custom type of exception which can surface as a user-visible error should register a "printer" for this exception using `register_error_of_exn`. The result of the printer is an `error` value containing a location, a message, and optionally sub-messages (each of them being located as well).

    val error_of_exn : exn -> [ `Already_displayed | `Ok of error ] option

    exception Error of error

Raising `Error e` signals an error `e`; the exception will be caught and the error will be printed.

    exception Already_displayed_error

Raising `Already_displayed_error` signals an error which has already been printed. The exception will be caught, but nothing will be printed

    val raise_errorf : ?loc:t ->
           ?sub:msg list ->
           ('a, Format.formatter, unit, 'b) format4 -> 'a

    val report_exception : Format.formatter -> exn -> unit

Reraise the exception if it is unknown.