check-expression.h

//===-- include/flang/Evaluate/check-expression.h ---------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
 
// Static expression checking
 
#ifndef FORTRAN_EVALUATE_CHECK_EXPRESSION_H_
#define FORTRAN_EVALUATE_CHECK_EXPRESSION_H_
 
#include "expression.h"
#include "intrinsics.h"
#include "type.h"
#include <optional>
 
namespace Fortran::parser {
class ContextualMessages;
}
namespace Fortran::semantics {
class Scope;
}
 
namespace Fortran::evaluate {
 
// Predicate: true when an expression is a constant expression (in the
// strict sense of the Fortran standard); it may not (yet) be a hard
// constant value.
// The FoldingContext pointer, if not null, prevents a "free" implied
// DO index from being allowed in a constant expression or initial data
// target if it is not registered in the FoldingContext.  (Array constructor
// implied DO indices are always allowed when the implied DO is within
// the expression.)
template <typename A>
bool IsConstantExpr(const A &, const FoldingContext * = nullptr);
extern template bool IsConstantExpr(
    const Expr<SomeType> &, const FoldingContext *);
extern template bool IsConstantExpr(
    const Expr<SubscriptInteger> &, const FoldingContext *);
extern template bool IsConstantExpr(
    const StructureConstructor &, const FoldingContext *);
 
// Predicate: true when an expression is a constant expression (in the
// strict sense of the Fortran standard) or a dummy argument with
// INTENT(IN) and no VALUE.  This is useful for representing explicit
// shapes of other dummy arguments.
template <typename A>
bool IsScopeInvariantExpr(const A &, const FoldingContext * = nullptr);
extern template bool IsScopeInvariantExpr(
    const Expr<SomeType> &, const FoldingContext *);
extern template bool IsScopeInvariantExpr(
    const Expr<SubscriptInteger> &, const FoldingContext *);
 
// Predicate: true when an expression actually is a typed Constant<T>,
// perhaps with parentheses and wrapping around it.  False for all typeless
// expressions, including BOZ literals.
template <typename A> bool IsActuallyConstant(const A &);
extern template bool IsActuallyConstant(const Expr<SomeType> &);
extern template bool IsActuallyConstant(const Expr<SubscriptInteger> &);
extern template bool IsActuallyConstant(
    const std::optional<Expr<SubscriptInteger>> &);
 
// Checks whether an expression is an object designator with
// constant addressing and no vector-valued subscript.
// If a non-null ContextualMessages pointer is passed, an error message
// will be generated if and only if the result of the function is false.
bool IsInitialDataTarget(const Expr<SomeType> &,
    parser::ContextualMessages * = nullptr, const FoldingContext * = nullptr);
 
bool IsInitialProcedureTarget(const Symbol &);
bool IsInitialProcedureTarget(const ProcedureDesignator &);
bool IsInitialProcedureTarget(const Expr<SomeType> &);
 
// Emit warnings about default REAL literal constants in contexts that
// will be converted to a higher precision REAL kind than the default.
void CheckRealWidening(
    const Expr<SomeType> &, const DynamicType &toType, FoldingContext &);
void CheckRealWidening(const Expr<SomeType> &,
    const std::optional<DynamicType> &, FoldingContext &);
 
// Validate the value of a named constant, the static initial
// value of a non-pointer non-allocatable non-dummy variable, or the
// default initializer of a component of a derived type (or instantiation
// of a derived type).  Converts type and expands scalars as necessary.
std::optional<Expr<SomeType>> NonPointerInitializationExpr(const Symbol &,
    Expr<SomeType> &&, FoldingContext &,
    const semantics::Scope *instantiation = nullptr);
 
// Check whether an expression is a specification expression
// (10.1.11(2), C1010).  Constant expressions are always valid
// specification expressions.
 
template <typename A>
void CheckSpecificationExpr(const A &, const semantics::Scope &,
    FoldingContext &, bool forElementalFunctionResult);
extern template void CheckSpecificationExpr(const Expr<SomeType> &x,
    const semantics::Scope &, FoldingContext &,
    bool forElementalFunctionResult);
extern template void CheckSpecificationExpr(const Expr<SubscriptInteger> &x,
    const semantics::Scope &, FoldingContext &,
    bool forElementalFunctionResult);
extern template void CheckSpecificationExpr(
    const std::optional<Expr<SomeType>> &x, const semantics::Scope &,
    FoldingContext &, bool forElementalFunctionResult);
extern template void CheckSpecificationExpr(
    const std::optional<Expr<SubscriptInteger>> &x, const semantics::Scope &,
    FoldingContext &, bool forElementalFunctionResult);
 
// Contiguity & "simple contiguity" (9.5.4)
// Named constant sections are expressions, and as such their evaluation is
// considered to be contiguous. This avoids funny situations where
// IS_CONTIGUOUS(cst(1:10:2)) would fold to true because `cst(1:10:2)` is
// folded into an array constructor literal, but IS_CONTIGUOUS(cst(i:i+9:2))
// folds to false because the named constant reference cannot be folded.
// Note that these IS_CONTIGUOUS usages are not portable (can probably be
// considered to fall into F2023 8.5.7 (4)), and existing compilers are not
// consistent here.
// However, the compiler may very well decide to create a descriptor over
// `cst(i:i+9:2)` when it can to avoid copies, and as such it needs internally
// to be able to tell the actual contiguity of that array section over the
// read-only data.
template <typename A>
std::optional<bool> IsContiguous(const A &, FoldingContext &,
    bool namedConstantSectionsAreContiguous = true,
    bool firstDimensionStride1 = false);
extern template std::optional<bool> IsContiguous(const Expr<SomeType> &,
    FoldingContext &, bool namedConstantSectionsAreContiguous,
    bool firstDimensionStride1);
extern template std::optional<bool> IsContiguous(const ActualArgument &,
    FoldingContext &, bool namedConstantSectionsAreContiguous,
    bool firstDimensionStride1);
extern template std::optional<bool> IsContiguous(const ArrayRef &,
    FoldingContext &, bool namedConstantSectionsAreContiguous,
    bool firstDimensionStride1);
extern template std::optional<bool> IsContiguous(const Substring &,
    FoldingContext &, bool namedConstantSectionsAreContiguous,
    bool firstDimensionStride1);
extern template std::optional<bool> IsContiguous(const Component &,
    FoldingContext &, bool namedConstantSectionsAreContiguous,
    bool firstDimensionStride1);
extern template std::optional<bool> IsContiguous(const ComplexPart &,
    FoldingContext &, bool namedConstantSectionsAreContiguous,
    bool firstDimensionStride1);
extern template std::optional<bool> IsContiguous(const CoarrayRef &,
    FoldingContext &, bool namedConstantSectionsAreContiguous,
    bool firstDimensionStride1);
extern template std::optional<bool> IsContiguous(const Symbol &,
    FoldingContext &, bool namedConstantSectionsAreContiguous,
    bool firstDimensionStride1);
static inline std::optional<bool> IsContiguous(const SymbolRef &s,
    FoldingContext &c, bool namedConstantSectionsAreContiguous = true) {
  return IsContiguous(s.get(), c, namedConstantSectionsAreContiguous);
}
template <typename A>
bool IsSimplyContiguous(const A &x, FoldingContext &context,
    bool namedConstantSectionsAreContiguous = true) {
  return IsContiguous(x, context, namedConstantSectionsAreContiguous)
      .value_or(false);
}
 
template <typename A> bool IsErrorExpr(const A &);
extern template bool IsErrorExpr(const Expr<SomeType> &);
 
std::optional<parser::Message> CheckStatementFunction(
    const Symbol &, const Expr<SomeType> &, FoldingContext &);
 
// Actual arguments of procedure references may retain designators of named
// constants (rather than their folded values) so that lowering can associate
// dummy arguments with the named constant's storage.  Intrinsic argument
// matching, checking, and folding inspect constant values structurally, so
// such arguments must be folded back to values once a call is known to
// resolve to an intrinsic procedure.
bool IsNamedConstantDesignator(const Expr<SomeType> &);
bool AnyNamedConstantActualArguments(const ActualArguments &);
void FoldNamedConstantActualArguments(FoldingContext &, ActualArguments &);
 
std::optional<bool> ActualArgNeedsCopy(const ActualArgument *,
    const characteristics::DummyArgument *, FoldingContext &, bool forCopyOut);
 
// Scan expressions and note uses of values of symbols.
semantics::UnorderedSymbolSet CollectUsedSymbolValues(
    semantics::SemanticsContext &, const Expr<SomeType> &,
    bool isDefinition = false);
semantics::UnorderedSymbolSet CollectUsedSymbolValues(
    semantics::SemanticsContext &, const ProcedureRef &);
semantics::UnorderedSymbolSet CollectUsedSymbolValues(
    semantics::SemanticsContext &, const Assignment &);
 
} // namespace Fortran::evaluate
#endif