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GNAT 23 NEW FEATURES LIST
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Copyright (C) 2021, AdaCore

This file contains a complete list of new features in version 23 of GNAT. A
full description of all GNAT features can be found in the GNAT User's Guide
and GNAT Reference Manual.

An ISO date (YYYY-MM-DD) appears in parentheses after the description line.
This date shows the implementation date of the feature. Any 23.0w wavefront
subsequent to this date will contain the indicated feature, as will any
subsequent 23 or later release.

NF-UA11-002 New generic functions in System.Atomic_Primitives (2021-10-12)

  The System.Atomic_Primitives package now contains a generic
  version of its functions to be instantiated on modular types.

NF-UA06-040 Warn on unused variable in quantified subexpression (2021-10-11)

  It is common that a quantified expression takes the form of a
  conjunction or disjunction. In such a case, it is expected that
  all conjuncts/disjuncts reference the quantified variable. Not
  doing so can be either the symptom of an error, or of a suboptimal
  expression, as that subexpression could be extracted from the
  quantified expression. This is beneficial for both execution
  (speed) and for proof (automation). A warning is now issued in
  such a case.

NF-UA05-029 Better error messages for dot notation in calls (2021-11-12)

  GNAT issues better error messages when dot notation is used
  incorrectly, whether it is because the prefix is a generic package
  (instead of an instantiation of the generic) or because the object
  is not tagged (but using -gnatX would make the use of dot notation
  legal).

NF-U916-043 Extend -gnatX support for casing on composite values (2021-10-20)

  GNAT supports case statements that case on composite values as a
  GNAT-defined language extension. Certain subcomponent types that
  were previously disallowed for such a composite type are now
  allowed, but subject to a restriction that the value of such a
  subcomponent can only be specified in a case choice via a "box"
  (<>) component value. This includes subcomponent types that are
  not discrete, record, or array types (for example, private types),
  subtypes that are subject to a nonstatic constraint or to a
  predicate, and subtypes of array types that have a nonstatic index
  subtype or that are multidimensional.

NF-U903-027 New warning on differing subtypes that fully conform (2021-10-12)

  A warning is now issued when a subprogram has corresponding formal
  parameter or result subtype_marks that fully conform between the
  subprogram's declaration and body but the denoted subtypes come
  from different subtype declarations. This warning is enabled with
  -gnatw_p, a new switch that is intended to cover "pedantic" checks
  (and which currently only includes this one check case).

NF-U521-003 New restriction No_Tagged_Type_Registration (2021-12-04)

  A new restriction, No_Tagged_Type_Registration, is now supported
  that disallows use of class-wide streaming operations and
  operations in Ada.Tags. It also allows restriction
  No_Elaboration_Code in the presence of tagged types, which in turn
  allows the compiler to avoid elaboration code in some cases when
  pragma Elaborate_Body is also used.

NF-U504-045 Expression defaults for generic formal functions (2021-11-18)

  As a language extension, the default for a generic formal function
  can now be specified by an expression, using syntax analogous to
  an expression function (for example, "with function F (Obj : T)
  return T is (Obj)"). This feature is enabled by using the switch
  -gnatX or pragma Extensions_Allowed.

NF-U421-012 Better support for link-time optimization (2021-09-30)

  The declaration of some runtime symbols was changed in order to
  better support LTO.

NF-S821-017 Ada 2022: Class-wide types and formal subprograms (2021-10-19)

  Ada 2022 specifies that when the controlling type of a formal
  abstract subprogram declaration is a formal type, and the actual
  type is a class-wide type T'Class, the actual subprogram can be an
  implicitly declared subprogram corresponding to a primitive
  operation of type T. This feature is documented in AI12-0165-1.

NF-RA02-062 New "task apply" command in debugger (2021-11-01)

  The debugger has a new command, "task apply". This is an Ada task
  analogue of the existing "thread apply" command.