flang/lib/Semantics/definable.h

   1 //===-- lib/Semantics/definable.h -------------------------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8
   9 #ifndef FORTRAN_SEMANTICS_DEFINABLE_H_
  10 #define FORTRAN_SEMANTICS_DEFINABLE_H_
  11
  12 // Utilities for checking the definability of variables and pointers in context,
  13 // including checks for attempted definitions in PURE subprograms.
  14 // Fortran 2018 C1101, C1158, C1594, &c.
  15
  16 #include "flang/Common/enum-set.h"
  17 #include "flang/Common/idioms.h"
  18 #include "flang/Evaluate/expression.h"
  19 #include "flang/Parser/char-block.h"
  20 #include "flang/Parser/message.h"
  21 #include <optional>
  22
  23 namespace Fortran::semantics {
  24
  25 class Symbol;
  26 class Scope;
  27
  28 ENUM_CLASS(DefinabilityFlag,
  29     VectorSubscriptIsOk, // a vector subscript may appear (i.e., assignment)
  30     PointerDefinition, // a pointer is being defined, not its target
  31     AcceptAllocatable, // treat allocatable as if it were a pointer
  32     PolymorphicOkInPure) // don't check for polymorphic type in pure subprogram
  33
  34 using DefinabilityFlags =
  35     common::EnumSet<DefinabilityFlag, DefinabilityFlag_enumSize>;
  36
  37 // Tests a symbol or LHS variable or pointer for definability in a given scope.
  38 // When the entity is not definable, returns a "because:" Message suitable for
  39 // attachment to an error message to explain why the entity cannot be defined.
  40 // When the entity can be defined in that context, returns std::nullopt.
  41 std::optional<parser::Message> WhyNotDefinable(
  42     parser::CharBlock, const Scope &, DefinabilityFlags, const Symbol &);
  43 std::optional<parser::Message> WhyNotDefinable(parser::CharBlock, const Scope &,
  44     DefinabilityFlags, const evaluate::Expr<evaluate::SomeType> &);
  45
  46 // If a symbol would not be definable in a pure scope, or not be usable as the
  47 // target of a pointer assignment in a pure scope, return a constant string
  48 // describing why.
  49 const char *WhyBaseObjectIsSuspicious(const Symbol &, const Scope &);
  50
  51 } // namespace Fortran::semantics
  52 #endif // FORTRAN_SEMANTICS_DEFINABLE_H_