xref: /llvm-project/flang/lib/Evaluate/check-expression.cpp (revision 7ea78643fe1577afb60bfc670357a79be53a31e8) 
1 //===-- lib/Evaluate/check-expression.cpp ---------------------------------===//
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 #include "flang/Evaluate/check-expression.h"
10 #include "flang/Evaluate/characteristics.h"
11 #include "flang/Evaluate/intrinsics.h"
12 #include "flang/Evaluate/tools.h"
13 #include "flang/Evaluate/traverse.h"
14 #include "flang/Evaluate/type.h"
15 #include "flang/Semantics/semantics.h"
16 #include "flang/Semantics/symbol.h"
17 #include "flang/Semantics/tools.h"
18 #include <set>
19 #include <string>
20 
21 namespace Fortran::evaluate {
22 
23 // Constant expression predicates IsConstantExpr() & IsScopeInvariantExpr().
24 // This code determines whether an expression is a "constant expression"
25 // in the sense of section 10.1.12.  This is not the same thing as being
26 // able to fold it (yet) into a known constant value; specifically,
27 // the expression may reference derived type kind parameters whose values
28 // are not yet known.
29 //
30 // The variant form (IsScopeInvariantExpr()) also accepts symbols that are
31 // INTENT(IN) dummy arguments without the VALUE attribute.
32 template <bool INVARIANT>
33 class IsConstantExprHelper
34     : public AllTraverse<IsConstantExprHelper<INVARIANT>, true> {
35 public:
36   using Base = AllTraverse<IsConstantExprHelper, true>;
37   IsConstantExprHelper() : Base{*this} {}
38   using Base::operator();
39 
40   // A missing expression is not considered to be constant.
41   template <typename A> bool operator()(const std::optional<A> &x) const {
42     return x && (*this)(*x);
43   }
44 
45   bool operator()(const TypeParamInquiry &inq) const {
46     return INVARIANT || semantics::IsKindTypeParameter(inq.parameter());
47   }
48   bool operator()(const semantics::Symbol &symbol) const {
49     const auto &ultimate{GetAssociationRoot(symbol)};
50     return IsNamedConstant(ultimate) || IsImpliedDoIndex(ultimate) ||
51         IsInitialProcedureTarget(ultimate) ||
52         ultimate.has<semantics::TypeParamDetails>() ||
53         (INVARIANT && IsIntentIn(symbol) && !IsOptional(symbol) &&
54             !symbol.attrs().test(semantics::Attr::VALUE));
55   }
56   bool operator()(const CoarrayRef &) const { return false; }
57   bool operator()(const semantics::ParamValue &param) const {
58     return param.isExplicit() && (*this)(param.GetExplicit());
59   }
60   bool operator()(const ProcedureRef &) const;
61   bool operator()(const StructureConstructor &constructor) const {
62     for (const auto &[symRef, expr] : constructor) {
63       if (!IsConstantStructureConstructorComponent(*symRef, expr.value())) {
64         return false;
65       }
66     }
67     return true;
68   }
69   bool operator()(const Component &component) const {
70     return (*this)(component.base());
71   }
72   // Forbid integer division by zero in constants.
73   template <int KIND>
74   bool operator()(
75       const Divide<Type<TypeCategory::Integer, KIND>> &division) const {
76     using T = Type<TypeCategory::Integer, KIND>;
77     if (const auto divisor{GetScalarConstantValue<T>(division.right())}) {
78       return !divisor->IsZero() && (*this)(division.left());
79     } else {
80       return false;
81     }
82   }
83 
84   bool operator()(const Constant<SomeDerived> &) const { return true; }
85   bool operator()(const DescriptorInquiry &x) const {
86     const Symbol &sym{x.base().GetLastSymbol()};
87     return INVARIANT && !IsAllocatable(sym) &&
88         (!IsDummy(sym) ||
89             (IsIntentIn(sym) && !IsOptional(sym) &&
90                 !sym.attrs().test(semantics::Attr::VALUE)));
91   }
92 
93 private:
94   bool IsConstantStructureConstructorComponent(
95       const Symbol &, const Expr<SomeType> &) const;
96   bool IsConstantExprShape(const Shape &) const;
97 };
98 
99 template <bool INVARIANT>
100 bool IsConstantExprHelper<INVARIANT>::IsConstantStructureConstructorComponent(
101     const Symbol &component, const Expr<SomeType> &expr) const {
102   if (IsAllocatable(component)) {
103     return IsNullObjectPointer(expr);
104   } else if (IsPointer(component)) {
105     return IsNullPointer(expr) || IsInitialDataTarget(expr) ||
106         IsInitialProcedureTarget(expr);
107   } else {
108     return (*this)(expr);
109   }
110 }
111 
112 template <bool INVARIANT>
113 bool IsConstantExprHelper<INVARIANT>::operator()(
114     const ProcedureRef &call) const {
115   // LBOUND, UBOUND, and SIZE with truly constant DIM= arguments will have
116   // been rewritten into DescriptorInquiry operations.
117   if (const auto *intrinsic{std::get_if<SpecificIntrinsic>(&call.proc().u)}) {
118     const characteristics::Procedure &proc{intrinsic->characteristics.value()};
119     if (intrinsic->name == "kind" ||
120         intrinsic->name == IntrinsicProcTable::InvalidName ||
121         call.arguments().empty() || !call.arguments()[0]) {
122       // kind is always a constant, and we avoid cascading errors by considering
123       // invalid calls to intrinsics to be constant
124       return true;
125     } else if (intrinsic->name == "lbound") {
126       auto base{ExtractNamedEntity(call.arguments()[0]->UnwrapExpr())};
127       return base && IsConstantExprShape(GetLBOUNDs(*base));
128     } else if (intrinsic->name == "ubound") {
129       auto base{ExtractNamedEntity(call.arguments()[0]->UnwrapExpr())};
130       return base && IsConstantExprShape(GetUBOUNDs(*base));
131     } else if (intrinsic->name == "shape" || intrinsic->name == "size") {
132       auto shape{GetShape(call.arguments()[0]->UnwrapExpr())};
133       return shape && IsConstantExprShape(*shape);
134     } else if (proc.IsPure()) {
135       for (const auto &arg : call.arguments()) {
136         if (!arg) {
137           return false;
138         } else if (const auto *expr{arg->UnwrapExpr()};
139                    !expr || !(*this)(*expr)) {
140           return false;
141         }
142       }
143       return true;
144     }
145     // TODO: STORAGE_SIZE
146   }
147   return false;
148 }
149 
150 template <bool INVARIANT>
151 bool IsConstantExprHelper<INVARIANT>::IsConstantExprShape(
152     const Shape &shape) const {
153   for (const auto &extent : shape) {
154     if (!(*this)(extent)) {
155       return false;
156     }
157   }
158   return true;
159 }
160 
161 template <typename A> bool IsConstantExpr(const A &x) {
162   return IsConstantExprHelper<false>{}(x);
163 }
164 template bool IsConstantExpr(const Expr<SomeType> &);
165 template bool IsConstantExpr(const Expr<SomeInteger> &);
166 template bool IsConstantExpr(const Expr<SubscriptInteger> &);
167 template bool IsConstantExpr(const StructureConstructor &);
168 
169 // IsScopeInvariantExpr()
170 template <typename A> bool IsScopeInvariantExpr(const A &x) {
171   return IsConstantExprHelper<true>{}(x);
172 }
173 template bool IsScopeInvariantExpr(const Expr<SomeType> &);
174 template bool IsScopeInvariantExpr(const Expr<SomeInteger> &);
175 template bool IsScopeInvariantExpr(const Expr<SubscriptInteger> &);
176 
177 // IsActuallyConstant()
178 struct IsActuallyConstantHelper {
179   template <typename A> bool operator()(const A &) { return false; }
180   template <typename T> bool operator()(const Constant<T> &) { return true; }
181   template <typename T> bool operator()(const Parentheses<T> &x) {
182     return (*this)(x.left());
183   }
184   template <typename T> bool operator()(const Expr<T> &x) {
185     return common::visit([=](const auto &y) { return (*this)(y); }, x.u);
186   }
187   bool operator()(const Expr<SomeType> &x) {
188     return common::visit([this](const auto &y) { return (*this)(y); }, x.u);
189   }
190   bool operator()(const StructureConstructor &x) {
191     for (const auto &pair : x) {
192       const Expr<SomeType> &y{pair.second.value()};
193       const auto sym{pair.first};
194       const bool compIsConstant{(*this)(y)};
195       // If an allocatable component is initialized by a constant,
196       // the structure constructor is not a constant.
197       if ((!compIsConstant && !IsNullPointer(y)) ||
198           (compIsConstant && IsAllocatable(sym))) {
199         return false;
200       }
201     }
202     return true;
203   }
204   template <typename A> bool operator()(const A *x) { return x && (*this)(*x); }
205   template <typename A> bool operator()(const std::optional<A> &x) {
206     return x && (*this)(*x);
207   }
208 };
209 
210 template <typename A> bool IsActuallyConstant(const A &x) {
211   return IsActuallyConstantHelper{}(x);
212 }
213 
214 template bool IsActuallyConstant(const Expr<SomeType> &);
215 template bool IsActuallyConstant(const Expr<SomeInteger> &);
216 template bool IsActuallyConstant(const Expr<SubscriptInteger> &);
217 template bool IsActuallyConstant(const std::optional<Expr<SubscriptInteger>> &);
218 
219 // Object pointer initialization checking predicate IsInitialDataTarget().
220 // This code determines whether an expression is allowable as the static
221 // data address used to initialize a pointer with "=> x".  See C765.
222 class IsInitialDataTargetHelper
223     : public AllTraverse<IsInitialDataTargetHelper, true> {
224 public:
225   using Base = AllTraverse<IsInitialDataTargetHelper, true>;
226   using Base::operator();
227   explicit IsInitialDataTargetHelper(parser::ContextualMessages *m)
228       : Base{*this}, messages_{m} {}
229 
230   bool emittedMessage() const { return emittedMessage_; }
231 
232   bool operator()(const BOZLiteralConstant &) const { return false; }
233   bool operator()(const NullPointer &) const { return true; }
234   template <typename T> bool operator()(const Constant<T> &) const {
235     return false;
236   }
237   bool operator()(const semantics::Symbol &symbol) {
238     // This function checks only base symbols, not components.
239     const Symbol &ultimate{symbol.GetUltimate()};
240     if (const auto *assoc{
241             ultimate.detailsIf<semantics::AssocEntityDetails>()}) {
242       if (const auto &expr{assoc->expr()}) {
243         if (IsVariable(*expr)) {
244           return (*this)(*expr);
245         } else if (messages_) {
246           messages_->Say(
247               "An initial data target may not be an associated expression ('%s')"_err_en_US,
248               ultimate.name());
249           emittedMessage_ = true;
250         }
251       }
252       return false;
253     } else if (!CheckVarOrComponent(ultimate)) {
254       return false;
255     } else if (!ultimate.attrs().test(semantics::Attr::TARGET)) {
256       if (messages_) {
257         messages_->Say(
258             "An initial data target may not be a reference to an object '%s' that lacks the TARGET attribute"_err_en_US,
259             ultimate.name());
260         emittedMessage_ = true;
261       }
262       return false;
263     } else if (!IsSaved(ultimate)) {
264       if (messages_) {
265         messages_->Say(
266             "An initial data target may not be a reference to an object '%s' that lacks the SAVE attribute"_err_en_US,
267             ultimate.name());
268         emittedMessage_ = true;
269       }
270       return false;
271     } else {
272       return true;
273     }
274   }
275   bool operator()(const StaticDataObject &) const { return false; }
276   bool operator()(const TypeParamInquiry &) const { return false; }
277   bool operator()(const Triplet &x) const {
278     return IsConstantExpr(x.lower()) && IsConstantExpr(x.upper()) &&
279         IsConstantExpr(x.stride());
280   }
281   bool operator()(const Subscript &x) const {
282     return common::visit(common::visitors{
283                              [&](const Triplet &t) { return (*this)(t); },
284                              [&](const auto &y) {
285                                return y.value().Rank() == 0 &&
286                                    IsConstantExpr(y.value());
287                              },
288                          },
289         x.u);
290   }
291   bool operator()(const CoarrayRef &) const { return false; }
292   bool operator()(const Component &x) {
293     return CheckVarOrComponent(x.GetLastSymbol()) && (*this)(x.base());
294   }
295   bool operator()(const Substring &x) const {
296     return IsConstantExpr(x.lower()) && IsConstantExpr(x.upper()) &&
297         (*this)(x.parent());
298   }
299   bool operator()(const DescriptorInquiry &) const { return false; }
300   template <typename T> bool operator()(const ArrayConstructor<T> &) const {
301     return false;
302   }
303   bool operator()(const StructureConstructor &) const { return false; }
304   template <typename D, typename R, typename... O>
305   bool operator()(const Operation<D, R, O...> &) const {
306     return false;
307   }
308   template <typename T> bool operator()(const Parentheses<T> &x) const {
309     return (*this)(x.left());
310   }
311   bool operator()(const ProcedureRef &x) const {
312     if (const SpecificIntrinsic * intrinsic{x.proc().GetSpecificIntrinsic()}) {
313       return intrinsic->characteristics.value().attrs.test(
314           characteristics::Procedure::Attr::NullPointer);
315     }
316     return false;
317   }
318   bool operator()(const Relational<SomeType> &) const { return false; }
319 
320 private:
321   bool CheckVarOrComponent(const semantics::Symbol &symbol) {
322     const Symbol &ultimate{symbol.GetUltimate()};
323     const char *unacceptable{nullptr};
324     if (ultimate.Corank() > 0) {
325       unacceptable = "a coarray";
326     } else if (IsAllocatable(ultimate)) {
327       unacceptable = "an ALLOCATABLE";
328     } else if (IsPointer(ultimate)) {
329       unacceptable = "a POINTER";
330     } else {
331       return true;
332     }
333     if (messages_) {
334       messages_->Say(
335           "An initial data target may not be a reference to %s '%s'"_err_en_US,
336           unacceptable, ultimate.name());
337       emittedMessage_ = true;
338     }
339     return false;
340   }
341 
342   parser::ContextualMessages *messages_;
343   bool emittedMessage_{false};
344 };
345 
346 bool IsInitialDataTarget(
347     const Expr<SomeType> &x, parser::ContextualMessages *messages) {
348   IsInitialDataTargetHelper helper{messages};
349   bool result{helper(x)};
350   if (!result && messages && !helper.emittedMessage()) {
351     messages->Say(
352         "An initial data target must be a designator with constant subscripts"_err_en_US);
353   }
354   return result;
355 }
356 
357 bool IsInitialProcedureTarget(const semantics::Symbol &symbol) {
358   const auto &ultimate{symbol.GetUltimate()};
359   return common::visit(
360       common::visitors{
361           [&](const semantics::SubprogramDetails &subp) {
362             return !subp.isDummy() && !subp.stmtFunction() &&
363                 symbol.owner().kind() != semantics::Scope::Kind::MainProgram &&
364                 symbol.owner().kind() != semantics::Scope::Kind::Subprogram;
365           },
366           [](const semantics::SubprogramNameDetails &x) {
367             return x.kind() != semantics::SubprogramKind::Internal;
368           },
369           [&](const semantics::ProcEntityDetails &proc) {
370             return !semantics::IsPointer(ultimate) && !proc.isDummy();
371           },
372           [](const auto &) { return false; },
373       },
374       ultimate.details());
375 }
376 
377 bool IsInitialProcedureTarget(const ProcedureDesignator &proc) {
378   if (const auto *intrin{proc.GetSpecificIntrinsic()}) {
379     return !intrin->isRestrictedSpecific;
380   } else if (proc.GetComponent()) {
381     return false;
382   } else {
383     return IsInitialProcedureTarget(DEREF(proc.GetSymbol()));
384   }
385 }
386 
387 bool IsInitialProcedureTarget(const Expr<SomeType> &expr) {
388   if (const auto *proc{std::get_if<ProcedureDesignator>(&expr.u)}) {
389     return IsInitialProcedureTarget(*proc);
390   } else {
391     return IsNullProcedurePointer(expr);
392   }
393 }
394 
395 // Converts, folds, and then checks type, rank, and shape of an
396 // initialization expression for a named constant, a non-pointer
397 // variable static initialization, a component default initializer,
398 // a type parameter default value, or instantiated type parameter value.
399 std::optional<Expr<SomeType>> NonPointerInitializationExpr(const Symbol &symbol,
400     Expr<SomeType> &&x, FoldingContext &context,
401     const semantics::Scope *instantiation) {
402   CHECK(!IsPointer(symbol));
403   if (auto symTS{
404           characteristics::TypeAndShape::Characterize(symbol, context)}) {
405     auto xType{x.GetType()};
406     auto converted{ConvertToType(symTS->type(), Expr<SomeType>{x})};
407     if (!converted &&
408         symbol.owner().context().IsEnabled(
409             common::LanguageFeature::LogicalIntegerAssignment)) {
410       converted = DataConstantConversionExtension(context, symTS->type(), x);
411       if (converted &&
412           symbol.owner().context().ShouldWarn(
413               common::LanguageFeature::LogicalIntegerAssignment)) {
414         context.messages().Say(
415             "nonstandard usage: initialization of %s with %s"_port_en_US,
416             symTS->type().AsFortran(), x.GetType().value().AsFortran());
417       }
418     }
419     if (converted) {
420       auto folded{Fold(context, std::move(*converted))};
421       if (IsActuallyConstant(folded)) {
422         int symRank{symTS->Rank()};
423         if (IsImpliedShape(symbol)) {
424           if (folded.Rank() == symRank) {
425             return ArrayConstantBoundChanger{
426                 std::move(*AsConstantExtents(
427                     context, GetRawLowerBounds(context, NamedEntity{symbol})))}
428                 .ChangeLbounds(std::move(folded));
429           } else {
430             context.messages().Say(
431                 "Implied-shape parameter '%s' has rank %d but its initializer has rank %d"_err_en_US,
432                 symbol.name(), symRank, folded.Rank());
433           }
434         } else if (auto extents{AsConstantExtents(context, symTS->shape())}) {
435           if (folded.Rank() == 0 && symRank == 0) {
436             // symbol and constant are both scalars
437             return {std::move(folded)};
438           } else if (folded.Rank() == 0 && symRank > 0) {
439             // expand the scalar constant to an array
440             return ScalarConstantExpander{std::move(*extents),
441                 AsConstantExtents(
442                     context, GetRawLowerBounds(context, NamedEntity{symbol}))}
443                 .Expand(std::move(folded));
444           } else if (auto resultShape{GetShape(context, folded)}) {
445             CHECK(symTS->shape()); // Assumed-ranks cannot be initialized.
446             if (CheckConformance(context.messages(), *symTS->shape(),
447                     *resultShape, CheckConformanceFlags::None,
448                     "initialized object", "initialization expression")
449                     .value_or(false /*fail if not known now to conform*/)) {
450               // make a constant array with adjusted lower bounds
451               return ArrayConstantBoundChanger{
452                   std::move(*AsConstantExtents(context,
453                       GetRawLowerBounds(context, NamedEntity{symbol})))}
454                   .ChangeLbounds(std::move(folded));
455             }
456           }
457         } else if (IsNamedConstant(symbol)) {
458           if (IsExplicitShape(symbol)) {
459             context.messages().Say(
460                 "Named constant '%s' array must have constant shape"_err_en_US,
461                 symbol.name());
462           } else {
463             // Declaration checking handles other cases
464           }
465         } else {
466           context.messages().Say(
467               "Shape of initialized object '%s' must be constant"_err_en_US,
468               symbol.name());
469         }
470       } else if (IsErrorExpr(folded)) {
471       } else if (IsLenTypeParameter(symbol)) {
472         return {std::move(folded)};
473       } else if (IsKindTypeParameter(symbol)) {
474         if (instantiation) {
475           context.messages().Say(
476               "Value of kind type parameter '%s' (%s) must be a scalar INTEGER constant"_err_en_US,
477               symbol.name(), folded.AsFortran());
478         } else {
479           return {std::move(folded)};
480         }
481       } else if (IsNamedConstant(symbol)) {
482         if (symbol.name() == "numeric_storage_size" &&
483             symbol.owner().IsModule() &&
484             DEREF(symbol.owner().symbol()).name() == "iso_fortran_env") {
485           // Very special case: numeric_storage_size is not folded until
486           // it read from the iso_fortran_env module file, as its value
487           // depends on compilation options.
488           return {std::move(folded)};
489         }
490         context.messages().Say(
491             "Value of named constant '%s' (%s) cannot be computed as a constant value"_err_en_US,
492             symbol.name(), folded.AsFortran());
493       } else {
494         context.messages().Say(
495             "Initialization expression for '%s' (%s) cannot be computed as a constant value"_err_en_US,
496             symbol.name(), x.AsFortran());
497       }
498     } else if (xType) {
499       context.messages().Say(
500           "Initialization expression cannot be converted to declared type of '%s' from %s"_err_en_US,
501           symbol.name(), xType->AsFortran());
502     } else {
503       context.messages().Say(
504           "Initialization expression cannot be converted to declared type of '%s'"_err_en_US,
505           symbol.name());
506     }
507   }
508   return std::nullopt;
509 }
510 
511 // Specification expression validation (10.1.11(2), C1010)
512 class CheckSpecificationExprHelper
513     : public AnyTraverse<CheckSpecificationExprHelper,
514           std::optional<std::string>> {
515 public:
516   using Result = std::optional<std::string>;
517   using Base = AnyTraverse<CheckSpecificationExprHelper, Result>;
518   explicit CheckSpecificationExprHelper(const semantics::Scope &s,
519       FoldingContext &context, bool forElementalFunctionResult)
520       : Base{*this}, scope_{s}, context_{context},
521         forElementalFunctionResult_{forElementalFunctionResult} {}
522   using Base::operator();
523 
524   Result operator()(const CoarrayRef &) const { return "coindexed reference"; }
525 
526   Result operator()(const semantics::Symbol &symbol) const {
527     const auto &ultimate{symbol.GetUltimate()};
528     if (const auto *assoc{
529             ultimate.detailsIf<semantics::AssocEntityDetails>()}) {
530       return (*this)(assoc->expr());
531     } else if (semantics::IsNamedConstant(ultimate) ||
532         ultimate.owner().IsModule() || ultimate.owner().IsSubmodule()) {
533       return std::nullopt;
534     } else if (scope_.IsDerivedType() &&
535         IsVariableName(ultimate)) { // C750, C754
536       return "derived type component or type parameter value not allowed to "
537              "reference variable '"s +
538           ultimate.name().ToString() + "'";
539     } else if (IsDummy(ultimate)) {
540       if (!inInquiry_ && forElementalFunctionResult_) {
541         return "dependence on value of dummy argument '"s +
542             ultimate.name().ToString() + "'";
543       } else if (ultimate.attrs().test(semantics::Attr::OPTIONAL)) {
544         return "reference to OPTIONAL dummy argument '"s +
545             ultimate.name().ToString() + "'";
546       } else if (!inInquiry_ &&
547           ultimate.attrs().test(semantics::Attr::INTENT_OUT)) {
548         return "reference to INTENT(OUT) dummy argument '"s +
549             ultimate.name().ToString() + "'";
550       } else if (ultimate.has<semantics::ObjectEntityDetails>()) {
551         return std::nullopt;
552       } else {
553         return "dummy procedure argument";
554       }
555     } else if (&symbol.owner() != &scope_ || &ultimate.owner() != &scope_) {
556       return std::nullopt; // host association is in play
557     } else if (const auto *object{
558                    ultimate.detailsIf<semantics::ObjectEntityDetails>()}) {
559       if (object->commonBlock()) {
560         return std::nullopt;
561       }
562     }
563     if (inInquiry_) {
564       return std::nullopt;
565     } else {
566       return "reference to local entity '"s + ultimate.name().ToString() + "'";
567     }
568   }
569 
570   Result operator()(const Component &x) const {
571     // Don't look at the component symbol.
572     return (*this)(x.base());
573   }
574   Result operator()(const ArrayRef &x) const {
575     if (auto result{(*this)(x.base())}) {
576       return result;
577     }
578     // The subscripts don't get special protection for being in a
579     // specification inquiry context;
580     auto restorer{common::ScopedSet(inInquiry_, false)};
581     return (*this)(x.subscript());
582   }
583   Result operator()(const Substring &x) const {
584     if (auto result{(*this)(x.parent())}) {
585       return result;
586     }
587     // The bounds don't get special protection for being in a
588     // specification inquiry context;
589     auto restorer{common::ScopedSet(inInquiry_, false)};
590     if (auto result{(*this)(x.lower())}) {
591       return result;
592     }
593     return (*this)(x.upper());
594   }
595   Result operator()(const DescriptorInquiry &x) const {
596     // Many uses of SIZE(), LBOUND(), &c. that are valid in specification
597     // expressions will have been converted to expressions over descriptor
598     // inquiries by Fold().
599     // Catch REAL, ALLOCATABLE :: X(:); REAL :: Y(SIZE(X))
600     if (IsPermissibleInquiry(
601             x.base().GetFirstSymbol(), x.base().GetLastSymbol(), x.field())) {
602       auto restorer{common::ScopedSet(inInquiry_, true)};
603       return (*this)(x.base());
604     } else if (IsConstantExpr(x)) {
605       return std::nullopt;
606     } else {
607       return "non-constant descriptor inquiry not allowed for local object";
608     }
609   }
610 
611   Result operator()(const TypeParamInquiry &inq) const {
612     if (scope_.IsDerivedType()) {
613       if (!IsConstantExpr(inq) &&
614           inq.base() /* X%T, not local T */) { // C750, C754
615         return "non-constant reference to a type parameter inquiry not allowed "
616                "for derived type components or type parameter values";
617       }
618     } else if (inq.base() &&
619         IsInquiryAlwaysPermissible(inq.base()->GetFirstSymbol())) {
620       auto restorer{common::ScopedSet(inInquiry_, true)};
621       return (*this)(inq.base());
622     } else if (!IsConstantExpr(inq)) {
623       return "non-constant type parameter inquiry not allowed for local object";
624     }
625     return std::nullopt;
626   }
627 
628   Result operator()(const ProcedureRef &x) const {
629     bool inInquiry{false};
630     if (const auto *symbol{x.proc().GetSymbol()}) {
631       const Symbol &ultimate{symbol->GetUltimate()};
632       if (!semantics::IsPureProcedure(ultimate)) {
633         return "reference to impure function '"s + ultimate.name().ToString() +
634             "'";
635       }
636       if (semantics::IsStmtFunction(ultimate)) {
637         return "reference to statement function '"s +
638             ultimate.name().ToString() + "'";
639       }
640       if (scope_.IsDerivedType()) { // C750, C754
641         return "reference to function '"s + ultimate.name().ToString() +
642             "' not allowed for derived type components or type parameter"
643             " values";
644       }
645       if (auto procChars{characteristics::Procedure::Characterize(
646               x.proc(), context_, /*emitError=*/true)}) {
647         const auto iter{std::find_if(procChars->dummyArguments.begin(),
648             procChars->dummyArguments.end(),
649             [](const characteristics::DummyArgument &dummy) {
650               return std::holds_alternative<characteristics::DummyProcedure>(
651                   dummy.u);
652             })};
653         if (iter != procChars->dummyArguments.end() &&
654             ultimate.name().ToString() != "__builtin_c_funloc") {
655           return "reference to function '"s + ultimate.name().ToString() +
656               "' with dummy procedure argument '" + iter->name + '\'';
657         }
658       }
659       // References to internal functions are caught in expression semantics.
660       // TODO: other checks for standard module procedures
661     } else { // intrinsic
662       const SpecificIntrinsic &intrin{DEREF(x.proc().GetSpecificIntrinsic())};
663       inInquiry = context_.intrinsics().GetIntrinsicClass(intrin.name) ==
664           IntrinsicClass::inquiryFunction;
665       if (scope_.IsDerivedType()) { // C750, C754
666         if ((context_.intrinsics().IsIntrinsic(intrin.name) &&
667                 badIntrinsicsForComponents_.find(intrin.name) !=
668                     badIntrinsicsForComponents_.end())) {
669           return "reference to intrinsic '"s + intrin.name +
670               "' not allowed for derived type components or type parameter"
671               " values";
672         }
673         if (inInquiry && !IsConstantExpr(x)) {
674           return "non-constant reference to inquiry intrinsic '"s +
675               intrin.name +
676               "' not allowed for derived type components or type"
677               " parameter values";
678         }
679       }
680       // Type-determined inquiries (DIGITS, HUGE, &c.) will have already been
681       // folded and won't arrive here.  Inquiries that are represented with
682       // DescriptorInquiry operations (LBOUND) are checked elsewhere.  If a
683       // call that makes it to here satisfies the requirements of a constant
684       // expression (as Fortran defines it), it's fine.
685       if (IsConstantExpr(x)) {
686         return std::nullopt;
687       }
688       if (intrin.name == "present") {
689         return std::nullopt; // always ok
690       }
691       // Catch CHARACTER(:), ALLOCATABLE :: X; CHARACTER(LEN(X)) :: Y
692       if (inInquiry && x.arguments().size() >= 1) {
693         if (const auto &arg{x.arguments().at(0)}) {
694           if (auto dataRef{ExtractDataRef(*arg, true, true)}) {
695             if (intrin.name == "allocated" || intrin.name == "associated" ||
696                 intrin.name == "is_contiguous") { // ok
697             } else if (intrin.name == "len" &&
698                 IsPermissibleInquiry(dataRef->GetFirstSymbol(),
699                     dataRef->GetLastSymbol(),
700                     DescriptorInquiry::Field::Len)) { // ok
701             } else if (intrin.name == "lbound" &&
702                 IsPermissibleInquiry(dataRef->GetFirstSymbol(),
703                     dataRef->GetLastSymbol(),
704                     DescriptorInquiry::Field::LowerBound)) { // ok
705             } else if ((intrin.name == "shape" || intrin.name == "size" ||
706                            intrin.name == "sizeof" ||
707                            intrin.name == "storage_size" ||
708                            intrin.name == "ubound") &&
709                 IsPermissibleInquiry(dataRef->GetFirstSymbol(),
710                     dataRef->GetLastSymbol(),
711                     DescriptorInquiry::Field::Extent)) { // ok
712             } else {
713               return "non-constant inquiry function '"s + intrin.name +
714                   "' not allowed for local object";
715             }
716           }
717         }
718       }
719     }
720     auto restorer{common::ScopedSet(inInquiry_, inInquiry)};
721     return (*this)(x.arguments());
722   }
723 
724 private:
725   const semantics::Scope &scope_;
726   FoldingContext &context_;
727   // Contextual information: this flag is true when in an argument to
728   // an inquiry intrinsic like SIZE().
729   mutable bool inInquiry_{false};
730   bool forElementalFunctionResult_{false}; // F'2023 C15121
731   const std::set<std::string> badIntrinsicsForComponents_{
732       "allocated", "associated", "extends_type_of", "present", "same_type_as"};
733 
734   bool IsInquiryAlwaysPermissible(const semantics::Symbol &) const;
735   bool IsPermissibleInquiry(const semantics::Symbol &firstSymbol,
736       const semantics::Symbol &lastSymbol,
737       DescriptorInquiry::Field field) const;
738 };
739 
740 bool CheckSpecificationExprHelper::IsInquiryAlwaysPermissible(
741     const semantics::Symbol &symbol) const {
742   if (&symbol.owner() != &scope_ || symbol.has<semantics::UseDetails>() ||
743       symbol.owner().kind() == semantics::Scope::Kind::Module ||
744       semantics::FindCommonBlockContaining(symbol) ||
745       symbol.has<semantics::HostAssocDetails>()) {
746     return true; // it's nonlocal
747   } else if (semantics::IsDummy(symbol) && !forElementalFunctionResult_) {
748     return true;
749   } else {
750     return false;
751   }
752 }
753 
754 bool CheckSpecificationExprHelper::IsPermissibleInquiry(
755     const semantics::Symbol &firstSymbol, const semantics::Symbol &lastSymbol,
756     DescriptorInquiry::Field field) const {
757   if (IsInquiryAlwaysPermissible(firstSymbol)) {
758     return true;
759   }
760   // Inquiries on local objects may not access a deferred bound or length.
761   // (This code used to be a switch, but it proved impossible to write it
762   // thus without running afoul of bogus warnings from different C++
763   // compilers.)
764   if (field == DescriptorInquiry::Field::Rank) {
765     return true; // always known
766   }
767   const auto *object{lastSymbol.detailsIf<semantics::ObjectEntityDetails>()};
768   if (field == DescriptorInquiry::Field::LowerBound ||
769       field == DescriptorInquiry::Field::Extent ||
770       field == DescriptorInquiry::Field::Stride) {
771     return object && !object->shape().CanBeDeferredShape();
772   }
773   if (field == DescriptorInquiry::Field::Len) {
774     return object && object->type() &&
775         object->type()->category() == semantics::DeclTypeSpec::Character &&
776         !object->type()->characterTypeSpec().length().isDeferred();
777   }
778   return false;
779 }
780 
781 template <typename A>
782 void CheckSpecificationExpr(const A &x, const semantics::Scope &scope,
783     FoldingContext &context, bool forElementalFunctionResult) {
784   if (auto why{CheckSpecificationExprHelper{
785           scope, context, forElementalFunctionResult}(x)}) {
786     context.messages().Say("Invalid specification expression%s: %s"_err_en_US,
787         forElementalFunctionResult ? " for elemental function result" : "",
788         *why);
789   }
790 }
791 
792 template void CheckSpecificationExpr(const Expr<SomeType> &,
793     const semantics::Scope &, FoldingContext &,
794     bool forElementalFunctionResult);
795 template void CheckSpecificationExpr(const Expr<SomeInteger> &,
796     const semantics::Scope &, FoldingContext &,
797     bool forElementalFunctionResult);
798 template void CheckSpecificationExpr(const Expr<SubscriptInteger> &,
799     const semantics::Scope &, FoldingContext &,
800     bool forElementalFunctionResult);
801 template void CheckSpecificationExpr(const std::optional<Expr<SomeType>> &,
802     const semantics::Scope &, FoldingContext &,
803     bool forElementalFunctionResult);
804 template void CheckSpecificationExpr(const std::optional<Expr<SomeInteger>> &,
805     const semantics::Scope &, FoldingContext &,
806     bool forElementalFunctionResult);
807 template void CheckSpecificationExpr(
808     const std::optional<Expr<SubscriptInteger>> &, const semantics::Scope &,
809     FoldingContext &, bool forElementalFunctionResult);
810 
811 // IsContiguous() -- 9.5.4
812 class IsContiguousHelper
813     : public AnyTraverse<IsContiguousHelper, std::optional<bool>> {
814 public:
815   using Result = std::optional<bool>; // tri-state
816   using Base = AnyTraverse<IsContiguousHelper, Result>;
817   explicit IsContiguousHelper(FoldingContext &c) : Base{*this}, context_{c} {}
818   using Base::operator();
819 
820   template <typename T> Result operator()(const Constant<T> &) const {
821     return true;
822   }
823   Result operator()(const StaticDataObject &) const { return true; }
824   Result operator()(const semantics::Symbol &symbol) const {
825     const auto &ultimate{symbol.GetUltimate()};
826     if (ultimate.attrs().test(semantics::Attr::CONTIGUOUS)) {
827       return true;
828     } else if (!IsVariable(symbol)) {
829       return true;
830     } else if (ultimate.Rank() == 0) {
831       // Extension: accept scalars as a degenerate case of
832       // simple contiguity to allow their use in contexts like
833       // data targets in pointer assignments with remapping.
834       return true;
835     } else if (const auto *details{
836                    ultimate.detailsIf<semantics::AssocEntityDetails>()}) {
837       // RANK(*) associating entity is contiguous.
838       if (details->IsAssumedSize()) {
839         return true;
840       } else {
841         return Base::operator()(ultimate); // use expr
842       }
843     } else if (semantics::IsPointer(ultimate) ||
844         semantics::IsAssumedShape(ultimate) || IsAssumedRank(ultimate)) {
845       return std::nullopt;
846     } else if (ultimate.has<semantics::ObjectEntityDetails>()) {
847       return true;
848     } else {
849       return Base::operator()(ultimate);
850     }
851   }
852 
853   Result operator()(const ArrayRef &x) const {
854     if (x.Rank() == 0) {
855       return true; // scalars considered contiguous
856     }
857     int subscriptRank{0};
858     auto baseLbounds{GetLBOUNDs(context_, x.base())};
859     auto baseUbounds{GetUBOUNDs(context_, x.base())};
860     auto subscripts{CheckSubscripts(
861         x.subscript(), subscriptRank, &baseLbounds, &baseUbounds)};
862     if (!subscripts.value_or(false)) {
863       return subscripts; // subscripts not known to be contiguous
864     } else if (subscriptRank > 0) {
865       // a(1)%b(:,:) is contiguous if and only if a(1)%b is contiguous.
866       return (*this)(x.base());
867     } else {
868       // a(:)%b(1,1) is (probably) not contiguous.
869       return std::nullopt;
870     }
871   }
872   Result operator()(const CoarrayRef &x) const {
873     int rank{0};
874     return CheckSubscripts(x.subscript(), rank).has_value();
875   }
876   Result operator()(const Component &x) const {
877     if (x.base().Rank() == 0) {
878       return (*this)(x.GetLastSymbol());
879     } else {
880       if (Result baseIsContiguous{(*this)(x.base())}) {
881         if (!*baseIsContiguous) {
882           return false;
883         }
884         // TODO could be true if base contiguous and this is only component, or
885         // if base has only one element?
886       }
887       return std::nullopt;
888     }
889   }
890   Result operator()(const ComplexPart &x) const {
891     return x.complex().Rank() == 0;
892   }
893   Result operator()(const Substring &) const { return std::nullopt; }
894 
895   Result operator()(const ProcedureRef &x) const {
896     if (auto chars{characteristics::Procedure::Characterize(
897             x.proc(), context_, /*emitError=*/true)}) {
898       if (chars->functionResult) {
899         const auto &result{*chars->functionResult};
900         if (!result.IsProcedurePointer()) {
901           if (result.attrs.test(
902                   characteristics::FunctionResult::Attr::Contiguous)) {
903             return true;
904           }
905           if (!result.attrs.test(
906                   characteristics::FunctionResult::Attr::Pointer)) {
907             return true;
908           }
909           if (const auto *type{result.GetTypeAndShape()};
910               type && type->Rank() == 0) {
911             return true; // pointer to scalar
912           }
913           // Must be non-CONTIGUOUS pointer to array
914         }
915       }
916     }
917     return std::nullopt;
918   }
919 
920   Result operator()(const NullPointer &) const { return true; }
921 
922 private:
923   // Returns "true" for a provably empty or simply contiguous array section;
924   // return "false" for a provably nonempty discontiguous section or for use
925   // of a vector subscript.
926   std::optional<bool> CheckSubscripts(const std::vector<Subscript> &subscript,
927       int &rank, const Shape *baseLbounds = nullptr,
928       const Shape *baseUbounds = nullptr) const {
929     bool anyTriplet{false};
930     rank = 0;
931     // Detect any provably empty dimension in this array section, which would
932     // render the whole section empty and therefore vacuously contiguous.
933     std::optional<bool> result;
934     bool mayBeEmpty{false};
935     auto dims{subscript.size()};
936     std::vector<bool> knownPartialSlice(dims, false);
937     for (auto j{dims}; j-- > 0;) {
938       std::optional<ConstantSubscript> dimLbound;
939       std::optional<ConstantSubscript> dimUbound;
940       std::optional<ConstantSubscript> dimExtent;
941       if (baseLbounds && j < baseLbounds->size()) {
942         if (const auto &lb{baseLbounds->at(j)}) {
943           dimLbound = ToInt64(Fold(context_, Expr<SubscriptInteger>{*lb}));
944         }
945       }
946       if (baseUbounds && j < baseUbounds->size()) {
947         if (const auto &ub{baseUbounds->at(j)}) {
948           dimUbound = ToInt64(Fold(context_, Expr<SubscriptInteger>{*ub}));
949         }
950       }
951       if (dimLbound && dimUbound) {
952         if (*dimLbound <= *dimUbound) {
953           dimExtent = *dimUbound - *dimLbound + 1;
954         } else {
955           // This is an empty dimension.
956           result = true;
957           dimExtent = 0;
958         }
959       }
960 
961       if (const auto *triplet{std::get_if<Triplet>(&subscript[j].u)}) {
962         ++rank;
963         if (auto stride{ToInt64(triplet->stride())}) {
964           const Expr<SubscriptInteger> *lowerBound{triplet->GetLower()};
965           const Expr<SubscriptInteger> *upperBound{triplet->GetUpper()};
966           std::optional<ConstantSubscript> lowerVal{lowerBound
967                   ? ToInt64(Fold(context_, Expr<SubscriptInteger>{*lowerBound}))
968                   : dimLbound};
969           std::optional<ConstantSubscript> upperVal{upperBound
970                   ? ToInt64(Fold(context_, Expr<SubscriptInteger>{*upperBound}))
971                   : dimUbound};
972           if (lowerVal && upperVal) {
973             if (*lowerVal < *upperVal) {
974               if (*stride < 0) {
975                 result = true; // empty dimension
976               } else if (!result && *stride > 1 &&
977                   *lowerVal + *stride <= *upperVal) {
978                 result = false; // discontiguous if not empty
979               }
980             } else if (*lowerVal > *upperVal) {
981               if (*stride > 0) {
982                 result = true; // empty dimension
983               } else if (!result && *stride < 0 &&
984                   *lowerVal + *stride >= *upperVal) {
985                 result = false; // discontiguous if not empty
986               }
987             } else {
988               mayBeEmpty = true;
989             }
990           } else {
991             mayBeEmpty = true;
992           }
993         } else {
994           mayBeEmpty = true;
995         }
996       } else if (subscript[j].Rank() > 0) {
997         ++rank;
998         if (!result) {
999           result = false; // vector subscript
1000         }
1001         mayBeEmpty = true;
1002       } else {
1003         // Scalar subscript.
1004         if (dimExtent && *dimExtent > 1) {
1005           knownPartialSlice[j] = true;
1006         }
1007       }
1008     }
1009     if (rank == 0) {
1010       result = true; // scalar
1011     }
1012     if (result) {
1013       return result;
1014     }
1015     // Not provably discontiguous at this point.
1016     // Return "true" if simply contiguous, otherwise nullopt.
1017     for (auto j{subscript.size()}; j-- > 0;) {
1018       if (const auto *triplet{std::get_if<Triplet>(&subscript[j].u)}) {
1019         auto stride{ToInt64(triplet->stride())};
1020         if (!stride || stride != 1) {
1021           return std::nullopt;
1022         } else if (anyTriplet) {
1023           if (triplet->GetLower() || triplet->GetUpper()) {
1024             // all triplets before the last one must be just ":" for
1025             // simple contiguity
1026             return std::nullopt;
1027           }
1028         } else {
1029           anyTriplet = true;
1030         }
1031         ++rank;
1032       } else if (anyTriplet) {
1033         // If the section cannot be empty, and this dimension's
1034         // scalar subscript is known not to cover the whole
1035         // dimension, then the array section is provably
1036         // discontiguous.
1037         return (mayBeEmpty || !knownPartialSlice[j])
1038             ? std::nullopt
1039             : std::make_optional(false);
1040       }
1041     }
1042     return true; // simply contiguous
1043   }
1044 
1045   FoldingContext &context_;
1046 };
1047 
1048 template <typename A>
1049 std::optional<bool> IsContiguous(const A &x, FoldingContext &context) {
1050   return IsContiguousHelper{context}(x);
1051 }
1052 
1053 template std::optional<bool> IsContiguous(
1054     const Expr<SomeType> &, FoldingContext &);
1055 template std::optional<bool> IsContiguous(const ArrayRef &, FoldingContext &);
1056 template std::optional<bool> IsContiguous(const Substring &, FoldingContext &);
1057 template std::optional<bool> IsContiguous(const Component &, FoldingContext &);
1058 template std::optional<bool> IsContiguous(
1059     const ComplexPart &, FoldingContext &);
1060 template std::optional<bool> IsContiguous(const CoarrayRef &, FoldingContext &);
1061 template std::optional<bool> IsContiguous(const Symbol &, FoldingContext &);
1062 
1063 // IsErrorExpr()
1064 struct IsErrorExprHelper : public AnyTraverse<IsErrorExprHelper, bool> {
1065   using Result = bool;
1066   using Base = AnyTraverse<IsErrorExprHelper, Result>;
1067   IsErrorExprHelper() : Base{*this} {}
1068   using Base::operator();
1069 
1070   bool operator()(const SpecificIntrinsic &x) {
1071     return x.name == IntrinsicProcTable::InvalidName;
1072   }
1073 };
1074 
1075 template <typename A> bool IsErrorExpr(const A &x) {
1076   return IsErrorExprHelper{}(x);
1077 }
1078 
1079 template bool IsErrorExpr(const Expr<SomeType> &);
1080 
1081 // C1577
1082 // TODO: Also check C1579 & C1582 here
1083 class StmtFunctionChecker
1084     : public AnyTraverse<StmtFunctionChecker, std::optional<parser::Message>> {
1085 public:
1086   using Result = std::optional<parser::Message>;
1087   using Base = AnyTraverse<StmtFunctionChecker, Result>;
1088   StmtFunctionChecker(const Symbol &sf, FoldingContext &context)
1089       : Base{*this}, sf_{sf}, context_{context} {
1090     if (!context_.languageFeatures().IsEnabled(
1091             common::LanguageFeature::StatementFunctionExtensions)) {
1092       severity_ = parser::Severity::Error;
1093     } else if (context_.languageFeatures().ShouldWarn(
1094                    common::LanguageFeature::StatementFunctionExtensions)) {
1095       severity_ = parser::Severity::Portability;
1096     }
1097   }
1098   using Base::operator();
1099 
1100   template <typename T> Result operator()(const ArrayConstructor<T> &) const {
1101     if (severity_) {
1102       auto msg{
1103           "Statement function '%s' should not contain an array constructor"_port_en_US};
1104       msg.set_severity(*severity_);
1105       return parser::Message{sf_.name(), std::move(msg), sf_.name()};
1106     } else {
1107       return std::nullopt;
1108     }
1109   }
1110   Result operator()(const StructureConstructor &) const {
1111     if (severity_) {
1112       auto msg{
1113           "Statement function '%s' should not contain a structure constructor"_port_en_US};
1114       msg.set_severity(*severity_);
1115       return parser::Message{sf_.name(), std::move(msg), sf_.name()};
1116     } else {
1117       return std::nullopt;
1118     }
1119   }
1120   Result operator()(const TypeParamInquiry &) const {
1121     if (severity_) {
1122       auto msg{
1123           "Statement function '%s' should not contain a type parameter inquiry"_port_en_US};
1124       msg.set_severity(*severity_);
1125       return parser::Message{sf_.name(), std::move(msg), sf_.name()};
1126     } else {
1127       return std::nullopt;
1128     }
1129   }
1130   Result operator()(const ProcedureDesignator &proc) const {
1131     if (const Symbol * symbol{proc.GetSymbol()}) {
1132       const Symbol &ultimate{symbol->GetUltimate()};
1133       if (const auto *subp{
1134               ultimate.detailsIf<semantics::SubprogramDetails>()}) {
1135         if (subp->stmtFunction() && &ultimate.owner() == &sf_.owner()) {
1136           if (ultimate.name().begin() > sf_.name().begin()) {
1137             return parser::Message{sf_.name(),
1138                 "Statement function '%s' may not reference another statement function '%s' that is defined later"_err_en_US,
1139                 sf_.name(), ultimate.name()};
1140           }
1141         }
1142       }
1143       if (auto chars{characteristics::Procedure::Characterize(
1144               proc, context_, /*emitError=*/true)}) {
1145         if (!chars->CanBeCalledViaImplicitInterface()) {
1146           if (severity_) {
1147             auto msg{
1148                 "Statement function '%s' should not reference function '%s' that requires an explicit interface"_port_en_US};
1149             msg.set_severity(*severity_);
1150             return parser::Message{
1151                 sf_.name(), std::move(msg), sf_.name(), symbol->name()};
1152           }
1153         }
1154       }
1155     }
1156     if (proc.Rank() > 0) {
1157       if (severity_) {
1158         auto msg{
1159             "Statement function '%s' should not reference a function that returns an array"_port_en_US};
1160         msg.set_severity(*severity_);
1161         return parser::Message{sf_.name(), std::move(msg), sf_.name()};
1162       }
1163     }
1164     return std::nullopt;
1165   }
1166   Result operator()(const ActualArgument &arg) const {
1167     if (const auto *expr{arg.UnwrapExpr()}) {
1168       if (auto result{(*this)(*expr)}) {
1169         return result;
1170       }
1171       if (expr->Rank() > 0 && !UnwrapWholeSymbolOrComponentDataRef(*expr)) {
1172         if (severity_) {
1173           auto msg{
1174               "Statement function '%s' should not pass an array argument that is not a whole array"_port_en_US};
1175           msg.set_severity(*severity_);
1176           return parser::Message{sf_.name(), std::move(msg), sf_.name()};
1177         }
1178       }
1179     }
1180     return std::nullopt;
1181   }
1182 
1183 private:
1184   const Symbol &sf_;
1185   FoldingContext &context_;
1186   std::optional<parser::Severity> severity_;
1187 };
1188 
1189 std::optional<parser::Message> CheckStatementFunction(
1190     const Symbol &sf, const Expr<SomeType> &expr, FoldingContext &context) {
1191   return StmtFunctionChecker{sf, context}(expr);
1192 }
1193 
1194 } // namespace Fortran::evaluate
1195