1 //===-- lib/Semantics/check-declarations.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 // Static declaration checking
10 
11 #include "check-declarations.h"
12 #include "pointer-assignment.h"
13 #include "flang/Evaluate/check-expression.h"
14 #include "flang/Evaluate/fold.h"
15 #include "flang/Evaluate/tools.h"
16 #include "flang/Semantics/scope.h"
17 #include "flang/Semantics/semantics.h"
18 #include "flang/Semantics/symbol.h"
19 #include "flang/Semantics/tools.h"
20 #include "flang/Semantics/type.h"
21 #include <algorithm>
22 #include <map>
23 #include <string>
24 
25 namespace Fortran::semantics {
26 
27 namespace characteristics = evaluate::characteristics;
28 using characteristics::DummyArgument;
29 using characteristics::DummyDataObject;
30 using characteristics::DummyProcedure;
31 using characteristics::FunctionResult;
32 using characteristics::Procedure;
33 
34 class CheckHelper {
35 public:
36   explicit CheckHelper(SemanticsContext &c) : context_{c} {}
37   CheckHelper(SemanticsContext &c, const Scope &s) : context_{c}, scope_{&s} {}
38 
39   SemanticsContext &context() { return context_; }
40   void Check() { Check(context_.globalScope()); }
41   void Check(const ParamValue &, bool canBeAssumed);
42   void Check(const Bound &bound) { CheckSpecExpr(bound.GetExplicit()); }
43   void Check(const ShapeSpec &spec) {
44     Check(spec.lbound());
45     Check(spec.ubound());
46   }
47   void Check(const ArraySpec &);
48   void Check(const DeclTypeSpec &, bool canHaveAssumedTypeParameters);
49   void Check(const Symbol &);
50   void Check(const Scope &);
51   const Procedure *Characterize(const Symbol &);
52 
53 private:
54   template <typename A> void CheckSpecExpr(const A &x) {
55     evaluate::CheckSpecificationExpr(x, DEREF(scope_), foldingContext_);
56   }
57   void CheckValue(const Symbol &, const DerivedTypeSpec *);
58   void CheckVolatile(const Symbol &, const DerivedTypeSpec *);
59   void CheckPointer(const Symbol &);
60   void CheckPassArg(
61       const Symbol &proc, const Symbol *interface, const WithPassArg &);
62   void CheckProcBinding(const Symbol &, const ProcBindingDetails &);
63   void CheckObjectEntity(const Symbol &, const ObjectEntityDetails &);
64   void CheckPointerInitialization(const Symbol &);
65   void CheckArraySpec(const Symbol &, const ArraySpec &);
66   void CheckProcEntity(const Symbol &, const ProcEntityDetails &);
67   void CheckSubprogram(const Symbol &, const SubprogramDetails &);
68   void CheckAssumedTypeEntity(const Symbol &, const ObjectEntityDetails &);
69   void CheckDerivedType(const Symbol &, const DerivedTypeDetails &);
70   bool CheckFinal(
71       const Symbol &subroutine, SourceName, const Symbol &derivedType);
72   bool CheckDistinguishableFinals(const Symbol &f1, SourceName f1name,
73       const Symbol &f2, SourceName f2name, const Symbol &derivedType);
74   void CheckGeneric(const Symbol &, const GenericDetails &);
75   void CheckHostAssoc(const Symbol &, const HostAssocDetails &);
76   bool CheckDefinedOperator(
77       SourceName, GenericKind, const Symbol &, const Procedure &);
78   std::optional<parser::MessageFixedText> CheckNumberOfArgs(
79       const GenericKind &, std::size_t);
80   bool CheckDefinedOperatorArg(
81       const SourceName &, const Symbol &, const Procedure &, std::size_t);
82   bool CheckDefinedAssignment(const Symbol &, const Procedure &);
83   bool CheckDefinedAssignmentArg(const Symbol &, const DummyArgument &, int);
84   void CheckSpecificsAreDistinguishable(const Symbol &, const GenericDetails &);
85   void CheckEquivalenceSet(const EquivalenceSet &);
86   void CheckBlockData(const Scope &);
87   void CheckGenericOps(const Scope &);
88   bool CheckConflicting(const Symbol &, Attr, Attr);
89   void WarnMissingFinal(const Symbol &);
90   bool InPure() const {
91     return innermostSymbol_ && IsPureProcedure(*innermostSymbol_);
92   }
93   bool InElemental() const {
94     return innermostSymbol_ && innermostSymbol_->attrs().test(Attr::ELEMENTAL);
95   }
96   bool InFunction() const {
97     return innermostSymbol_ && IsFunction(*innermostSymbol_);
98   }
99   template <typename... A>
100   void SayWithDeclaration(const Symbol &symbol, A &&...x) {
101     if (parser::Message * msg{messages_.Say(std::forward<A>(x)...)}) {
102       if (messages_.at().begin() != symbol.name().begin()) {
103         evaluate::AttachDeclaration(*msg, symbol);
104       }
105     }
106   }
107   bool IsResultOkToDiffer(const FunctionResult &);
108   void CheckBindCName(const Symbol &);
109   // Check functions for defined I/O procedures
110   void CheckDefinedIoProc(
111       const Symbol &, const GenericDetails &, GenericKind::DefinedIo);
112   bool CheckDioDummyIsData(const Symbol &, const Symbol *, std::size_t);
113   void CheckDioDummyIsDerived(
114       const Symbol &, const Symbol &, GenericKind::DefinedIo ioKind);
115   void CheckDioDummyIsDefaultInteger(const Symbol &, const Symbol &);
116   void CheckDioDummyIsScalar(const Symbol &, const Symbol &);
117   void CheckDioDummyAttrs(const Symbol &, const Symbol &, Attr);
118   void CheckDioDtvArg(const Symbol &, const Symbol *, GenericKind::DefinedIo);
119   void CheckDefaultIntegerArg(const Symbol &, const Symbol *, Attr);
120   void CheckDioAssumedLenCharacterArg(
121       const Symbol &, const Symbol *, std::size_t, Attr);
122   void CheckDioVlistArg(const Symbol &, const Symbol *, std::size_t);
123   void CheckDioArgCount(
124       const Symbol &, GenericKind::DefinedIo ioKind, std::size_t);
125   struct TypeWithDefinedIo {
126     const DerivedTypeSpec *type;
127     GenericKind::DefinedIo ioKind;
128     const Symbol &proc;
129   };
130   void CheckAlreadySeenDefinedIo(
131       const DerivedTypeSpec *, GenericKind::DefinedIo, const Symbol &);
132 
133   SemanticsContext &context_;
134   evaluate::FoldingContext &foldingContext_{context_.foldingContext()};
135   parser::ContextualMessages &messages_{foldingContext_.messages()};
136   const Scope *scope_{nullptr};
137   bool scopeIsUninstantiatedPDT_{false};
138   // This symbol is the one attached to the innermost enclosing scope
139   // that has a symbol.
140   const Symbol *innermostSymbol_{nullptr};
141   // Cache of calls to Procedure::Characterize(Symbol)
142   std::map<SymbolRef, std::optional<Procedure>, SymbolAddressCompare>
143       characterizeCache_;
144   // Collection of symbols with BIND(C) names
145   std::map<std::string, SymbolRef> bindC_;
146   // Derived types that have defined input/output procedures
147   std::vector<TypeWithDefinedIo> seenDefinedIoTypes_;
148 };
149 
150 class DistinguishabilityHelper {
151 public:
152   DistinguishabilityHelper(SemanticsContext &context) : context_{context} {}
153   void Add(const Symbol &, GenericKind, const Symbol &, const Procedure &);
154   void Check(const Scope &);
155 
156 private:
157   void SayNotDistinguishable(const Scope &, const SourceName &, GenericKind,
158       const Symbol &, const Symbol &);
159   void AttachDeclaration(parser::Message &, const Scope &, const Symbol &);
160 
161   SemanticsContext &context_;
162   struct ProcedureInfo {
163     GenericKind kind;
164     const Symbol &symbol;
165     const Procedure &procedure;
166   };
167   std::map<SourceName, std::vector<ProcedureInfo>> nameToInfo_;
168 };
169 
170 void CheckHelper::Check(const ParamValue &value, bool canBeAssumed) {
171   if (value.isAssumed()) {
172     if (!canBeAssumed) { // C795, C721, C726
173       messages_.Say(
174           "An assumed (*) type parameter may be used only for a (non-statement"
175           " function) dummy argument, associate name, named constant, or"
176           " external function result"_err_en_US);
177     }
178   } else {
179     CheckSpecExpr(value.GetExplicit());
180   }
181 }
182 
183 void CheckHelper::Check(const ArraySpec &shape) {
184   for (const auto &spec : shape) {
185     Check(spec);
186   }
187 }
188 
189 void CheckHelper::Check(
190     const DeclTypeSpec &type, bool canHaveAssumedTypeParameters) {
191   if (type.category() == DeclTypeSpec::Character) {
192     Check(type.characterTypeSpec().length(), canHaveAssumedTypeParameters);
193   } else if (const DerivedTypeSpec * derived{type.AsDerived()}) {
194     for (auto &parm : derived->parameters()) {
195       Check(parm.second, canHaveAssumedTypeParameters);
196     }
197   }
198 }
199 
200 void CheckHelper::Check(const Symbol &symbol) {
201   if (context_.HasError(symbol)) {
202     return;
203   }
204   auto restorer{messages_.SetLocation(symbol.name())};
205   context_.set_location(symbol.name());
206   const DeclTypeSpec *type{symbol.GetType()};
207   const DerivedTypeSpec *derived{type ? type->AsDerived() : nullptr};
208   bool isDone{false};
209   std::visit(
210       common::visitors{
211           [&](const UseDetails &x) { isDone = true; },
212           [&](const HostAssocDetails &x) {
213             CheckHostAssoc(symbol, x);
214             isDone = true;
215           },
216           [&](const ProcBindingDetails &x) {
217             CheckProcBinding(symbol, x);
218             isDone = true;
219           },
220           [&](const ObjectEntityDetails &x) { CheckObjectEntity(symbol, x); },
221           [&](const ProcEntityDetails &x) { CheckProcEntity(symbol, x); },
222           [&](const SubprogramDetails &x) { CheckSubprogram(symbol, x); },
223           [&](const DerivedTypeDetails &x) { CheckDerivedType(symbol, x); },
224           [&](const GenericDetails &x) { CheckGeneric(symbol, x); },
225           [](const auto &) {},
226       },
227       symbol.details());
228   if (symbol.attrs().test(Attr::VOLATILE)) {
229     CheckVolatile(symbol, derived);
230   }
231   CheckBindCName(symbol);
232   if (isDone) {
233     return; // following checks do not apply
234   }
235   if (IsPointer(symbol)) {
236     CheckPointer(symbol);
237   }
238   if (InPure()) {
239     if (IsSaved(symbol)) {
240       messages_.Say(
241           "A pure subprogram may not have a variable with the SAVE attribute"_err_en_US);
242     }
243     if (symbol.attrs().test(Attr::VOLATILE)) {
244       messages_.Say(
245           "A pure subprogram may not have a variable with the VOLATILE attribute"_err_en_US);
246     }
247     if (IsProcedure(symbol) && !IsPureProcedure(symbol) && IsDummy(symbol)) {
248       messages_.Say(
249           "A dummy procedure of a pure subprogram must be pure"_err_en_US);
250     }
251     if (!IsDummy(symbol) && !IsFunctionResult(symbol)) {
252       if (IsPolymorphicAllocatable(symbol)) {
253         SayWithDeclaration(symbol,
254             "Deallocation of polymorphic object '%s' is not permitted in a pure subprogram"_err_en_US,
255             symbol.name());
256       } else if (derived) {
257         if (auto bad{FindPolymorphicAllocatableUltimateComponent(*derived)}) {
258           SayWithDeclaration(*bad,
259               "Deallocation of polymorphic object '%s%s' is not permitted in a pure subprogram"_err_en_US,
260               symbol.name(), bad.BuildResultDesignatorName());
261         }
262       }
263     }
264   }
265   if (type) { // Section 7.2, paragraph 7
266     bool canHaveAssumedParameter{IsNamedConstant(symbol) ||
267         (IsAssumedLengthCharacter(symbol) && // C722
268             IsExternal(symbol)) ||
269         symbol.test(Symbol::Flag::ParentComp)};
270     if (!IsStmtFunctionDummy(symbol)) { // C726
271       if (const auto *object{symbol.detailsIf<ObjectEntityDetails>()}) {
272         canHaveAssumedParameter |= object->isDummy() ||
273             (object->isFuncResult() &&
274                 type->category() == DeclTypeSpec::Character) ||
275             IsStmtFunctionResult(symbol); // Avoids multiple messages
276       } else {
277         canHaveAssumedParameter |= symbol.has<AssocEntityDetails>();
278       }
279     }
280     Check(*type, canHaveAssumedParameter);
281     if (InPure() && InFunction() && IsFunctionResult(symbol)) {
282       if (derived && HasImpureFinal(*derived)) { // C1584
283         messages_.Say(
284             "Result of pure function may not have an impure FINAL subroutine"_err_en_US);
285       }
286       if (type->IsPolymorphic() && IsAllocatable(symbol)) { // C1585
287         messages_.Say(
288             "Result of pure function may not be both polymorphic and ALLOCATABLE"_err_en_US);
289       }
290       if (derived) {
291         if (auto bad{FindPolymorphicAllocatableUltimateComponent(*derived)}) {
292           SayWithDeclaration(*bad,
293               "Result of pure function may not have polymorphic ALLOCATABLE ultimate component '%s'"_err_en_US,
294               bad.BuildResultDesignatorName());
295         }
296       }
297     }
298   }
299   if (IsAssumedLengthCharacter(symbol) && IsExternal(symbol)) { // C723
300     if (symbol.attrs().test(Attr::RECURSIVE)) {
301       messages_.Say(
302           "An assumed-length CHARACTER(*) function cannot be RECURSIVE"_err_en_US);
303     }
304     if (symbol.Rank() > 0) {
305       messages_.Say(
306           "An assumed-length CHARACTER(*) function cannot return an array"_err_en_US);
307     }
308     if (symbol.attrs().test(Attr::PURE)) {
309       messages_.Say(
310           "An assumed-length CHARACTER(*) function cannot be PURE"_err_en_US);
311     }
312     if (symbol.attrs().test(Attr::ELEMENTAL)) {
313       messages_.Say(
314           "An assumed-length CHARACTER(*) function cannot be ELEMENTAL"_err_en_US);
315     }
316     if (const Symbol * result{FindFunctionResult(symbol)}) {
317       if (IsPointer(*result)) {
318         messages_.Say(
319             "An assumed-length CHARACTER(*) function cannot return a POINTER"_err_en_US);
320       }
321     }
322   }
323   if (symbol.attrs().test(Attr::VALUE)) {
324     CheckValue(symbol, derived);
325   }
326   if (symbol.attrs().test(Attr::CONTIGUOUS) && IsPointer(symbol) &&
327       symbol.Rank() == 0) { // C830
328     messages_.Say("CONTIGUOUS POINTER must be an array"_err_en_US);
329   }
330   if (IsDummy(symbol)) {
331     if (IsNamedConstant(symbol)) {
332       messages_.Say(
333           "A dummy argument may not also be a named constant"_err_en_US);
334     }
335     if (!symbol.test(Symbol::Flag::InDataStmt) /*caught elsewhere*/ &&
336         IsSaved(symbol)) {
337       messages_.Say(
338           "A dummy argument may not have the SAVE attribute"_err_en_US);
339     }
340   } else if (IsFunctionResult(symbol)) {
341     if (!symbol.test(Symbol::Flag::InDataStmt) /*caught elsewhere*/ &&
342         IsSaved(symbol)) {
343       messages_.Say(
344           "A function result may not have the SAVE attribute"_err_en_US);
345     }
346   }
347   if (symbol.owner().IsDerivedType() &&
348       (symbol.attrs().test(Attr::CONTIGUOUS) &&
349           !(IsPointer(symbol) && symbol.Rank() > 0))) { // C752
350     messages_.Say(
351         "A CONTIGUOUS component must be an array with the POINTER attribute"_err_en_US);
352   }
353   if (symbol.owner().IsModule() && IsAutomatic(symbol)) {
354     messages_.Say(
355         "Automatic data object '%s' may not appear in the specification part"
356         " of a module"_err_en_US,
357         symbol.name());
358   }
359 }
360 
361 void CheckHelper::CheckValue(
362     const Symbol &symbol, const DerivedTypeSpec *derived) { // C863 - C865
363   if (!IsDummy(symbol)) {
364     messages_.Say(
365         "VALUE attribute may apply only to a dummy argument"_err_en_US);
366   }
367   if (IsProcedure(symbol)) {
368     messages_.Say(
369         "VALUE attribute may apply only to a dummy data object"_err_en_US);
370   }
371   if (IsAssumedSizeArray(symbol)) {
372     messages_.Say(
373         "VALUE attribute may not apply to an assumed-size array"_err_en_US);
374   }
375   if (IsCoarray(symbol)) {
376     messages_.Say("VALUE attribute may not apply to a coarray"_err_en_US);
377   }
378   if (IsAllocatable(symbol)) {
379     messages_.Say("VALUE attribute may not apply to an ALLOCATABLE"_err_en_US);
380   } else if (IsPointer(symbol)) {
381     messages_.Say("VALUE attribute may not apply to a POINTER"_err_en_US);
382   }
383   if (IsIntentInOut(symbol)) {
384     messages_.Say(
385         "VALUE attribute may not apply to an INTENT(IN OUT) argument"_err_en_US);
386   } else if (IsIntentOut(symbol)) {
387     messages_.Say(
388         "VALUE attribute may not apply to an INTENT(OUT) argument"_err_en_US);
389   }
390   if (symbol.attrs().test(Attr::VOLATILE)) {
391     messages_.Say("VALUE attribute may not apply to a VOLATILE"_err_en_US);
392   }
393   if (innermostSymbol_ && IsBindCProcedure(*innermostSymbol_) &&
394       IsOptional(symbol)) {
395     messages_.Say(
396         "VALUE attribute may not apply to an OPTIONAL in a BIND(C) procedure"_err_en_US);
397   }
398   if (derived) {
399     if (FindCoarrayUltimateComponent(*derived)) {
400       messages_.Say(
401           "VALUE attribute may not apply to a type with a coarray ultimate component"_err_en_US);
402     }
403   }
404 }
405 
406 void CheckHelper::CheckAssumedTypeEntity( // C709
407     const Symbol &symbol, const ObjectEntityDetails &details) {
408   if (const DeclTypeSpec * type{symbol.GetType()};
409       type && type->category() == DeclTypeSpec::TypeStar) {
410     if (!IsDummy(symbol)) {
411       messages_.Say(
412           "Assumed-type entity '%s' must be a dummy argument"_err_en_US,
413           symbol.name());
414     } else {
415       if (symbol.attrs().test(Attr::ALLOCATABLE)) {
416         messages_.Say("Assumed-type argument '%s' cannot have the ALLOCATABLE"
417                       " attribute"_err_en_US,
418             symbol.name());
419       }
420       if (symbol.attrs().test(Attr::POINTER)) {
421         messages_.Say("Assumed-type argument '%s' cannot have the POINTER"
422                       " attribute"_err_en_US,
423             symbol.name());
424       }
425       if (symbol.attrs().test(Attr::VALUE)) {
426         messages_.Say("Assumed-type argument '%s' cannot have the VALUE"
427                       " attribute"_err_en_US,
428             symbol.name());
429       }
430       if (symbol.attrs().test(Attr::INTENT_OUT)) {
431         messages_.Say(
432             "Assumed-type argument '%s' cannot be INTENT(OUT)"_err_en_US,
433             symbol.name());
434       }
435       if (IsCoarray(symbol)) {
436         messages_.Say(
437             "Assumed-type argument '%s' cannot be a coarray"_err_en_US,
438             symbol.name());
439       }
440       if (details.IsArray() && details.shape().IsExplicitShape()) {
441         messages_.Say(
442             "Assumed-type array argument 'arg8' must be assumed shape,"
443             " assumed size, or assumed rank"_err_en_US,
444             symbol.name());
445       }
446     }
447   }
448 }
449 
450 void CheckHelper::CheckObjectEntity(
451     const Symbol &symbol, const ObjectEntityDetails &details) {
452   CheckArraySpec(symbol, details.shape());
453   Check(details.shape());
454   Check(details.coshape());
455   CheckAssumedTypeEntity(symbol, details);
456   WarnMissingFinal(symbol);
457   if (!details.coshape().empty()) {
458     bool isDeferredShape{details.coshape().IsDeferredShape()};
459     if (IsAllocatable(symbol)) {
460       if (!isDeferredShape) { // C827
461         messages_.Say("'%s' is an ALLOCATABLE coarray and must have a deferred"
462                       " coshape"_err_en_US,
463             symbol.name());
464       }
465     } else if (symbol.owner().IsDerivedType()) { // C746
466       std::string deferredMsg{
467           isDeferredShape ? "" : " and have a deferred coshape"};
468       messages_.Say("Component '%s' is a coarray and must have the ALLOCATABLE"
469                     " attribute%s"_err_en_US,
470           symbol.name(), deferredMsg);
471     } else {
472       if (!details.coshape().IsAssumedSize()) { // C828
473         messages_.Say(
474             "Component '%s' is a non-ALLOCATABLE coarray and must have"
475             " an explicit coshape"_err_en_US,
476             symbol.name());
477       }
478     }
479   }
480   if (details.isDummy()) {
481     if (symbol.attrs().test(Attr::INTENT_OUT)) {
482       if (FindUltimateComponent(symbol, [](const Symbol &x) {
483             return IsCoarray(x) && IsAllocatable(x);
484           })) { // C846
485         messages_.Say(
486             "An INTENT(OUT) dummy argument may not be, or contain, an ALLOCATABLE coarray"_err_en_US);
487       }
488       if (IsOrContainsEventOrLockComponent(symbol)) { // C847
489         messages_.Say(
490             "An INTENT(OUT) dummy argument may not be, or contain, EVENT_TYPE or LOCK_TYPE"_err_en_US);
491       }
492     }
493     if (InPure() && !IsStmtFunction(DEREF(innermostSymbol_)) &&
494         !IsPointer(symbol) && !IsIntentIn(symbol) &&
495         !symbol.attrs().test(Attr::VALUE)) {
496       if (InFunction()) { // C1583
497         messages_.Say(
498             "non-POINTER dummy argument of pure function must be INTENT(IN) or VALUE"_err_en_US);
499       } else if (IsIntentOut(symbol)) {
500         if (const DeclTypeSpec * type{details.type()}) {
501           if (type && type->IsPolymorphic()) { // C1588
502             messages_.Say(
503                 "An INTENT(OUT) dummy argument of a pure subroutine may not be polymorphic"_err_en_US);
504           } else if (const DerivedTypeSpec * derived{type->AsDerived()}) {
505             if (FindUltimateComponent(*derived, [](const Symbol &x) {
506                   const DeclTypeSpec *type{x.GetType()};
507                   return type && type->IsPolymorphic();
508                 })) { // C1588
509               messages_.Say(
510                   "An INTENT(OUT) dummy argument of a pure subroutine may not have a polymorphic ultimate component"_err_en_US);
511             }
512             if (HasImpureFinal(*derived)) { // C1587
513               messages_.Say(
514                   "An INTENT(OUT) dummy argument of a pure subroutine may not have an impure FINAL subroutine"_err_en_US);
515             }
516           }
517         }
518       } else if (!IsIntentInOut(symbol)) { // C1586
519         messages_.Say(
520             "non-POINTER dummy argument of pure subroutine must have INTENT() or VALUE attribute"_err_en_US);
521       }
522     }
523   } else if (symbol.attrs().test(Attr::INTENT_IN) ||
524       symbol.attrs().test(Attr::INTENT_OUT) ||
525       symbol.attrs().test(Attr::INTENT_INOUT)) {
526     messages_.Say("INTENT attributes may apply only to a dummy "
527                   "argument"_err_en_US); // C843
528   } else if (IsOptional(symbol)) {
529     messages_.Say("OPTIONAL attribute may apply only to a dummy "
530                   "argument"_err_en_US); // C849
531   }
532   if (InElemental()) {
533     if (details.isDummy()) { // C15100
534       if (details.shape().Rank() > 0) {
535         messages_.Say(
536             "A dummy argument of an ELEMENTAL procedure must be scalar"_err_en_US);
537       }
538       if (IsAllocatable(symbol)) {
539         messages_.Say(
540             "A dummy argument of an ELEMENTAL procedure may not be ALLOCATABLE"_err_en_US);
541       }
542       if (IsCoarray(symbol)) {
543         messages_.Say(
544             "A dummy argument of an ELEMENTAL procedure may not be a coarray"_err_en_US);
545       }
546       if (IsPointer(symbol)) {
547         messages_.Say(
548             "A dummy argument of an ELEMENTAL procedure may not be a POINTER"_err_en_US);
549       }
550       if (!symbol.attrs().HasAny(Attrs{Attr::VALUE, Attr::INTENT_IN,
551               Attr::INTENT_INOUT, Attr::INTENT_OUT})) { // C15102
552         messages_.Say(
553             "A dummy argument of an ELEMENTAL procedure must have an INTENT() or VALUE attribute"_err_en_US);
554       }
555     } else if (IsFunctionResult(symbol)) { // C15101
556       if (details.shape().Rank() > 0) {
557         messages_.Say(
558             "The result of an ELEMENTAL function must be scalar"_err_en_US);
559       }
560       if (IsAllocatable(symbol)) {
561         messages_.Say(
562             "The result of an ELEMENTAL function may not be ALLOCATABLE"_err_en_US);
563       }
564       if (IsPointer(symbol)) {
565         messages_.Say(
566             "The result of an ELEMENTAL function may not be a POINTER"_err_en_US);
567       }
568     }
569   }
570   if (HasDeclarationInitializer(symbol)) { // C808; ignore DATA initialization
571     CheckPointerInitialization(symbol);
572     if (IsAutomatic(symbol)) {
573       messages_.Say(
574           "An automatic variable or component must not be initialized"_err_en_US);
575     } else if (IsDummy(symbol)) {
576       messages_.Say("A dummy argument must not be initialized"_err_en_US);
577     } else if (IsFunctionResult(symbol)) {
578       messages_.Say("A function result must not be initialized"_err_en_US);
579     } else if (IsInBlankCommon(symbol)) {
580       messages_.Say(
581           "A variable in blank COMMON should not be initialized"_en_US);
582     }
583   }
584   if (symbol.owner().kind() == Scope::Kind::BlockData) {
585     if (IsAllocatable(symbol)) {
586       messages_.Say(
587           "An ALLOCATABLE variable may not appear in a BLOCK DATA subprogram"_err_en_US);
588     } else if (IsInitialized(symbol) && !FindCommonBlockContaining(symbol)) {
589       messages_.Say(
590           "An initialized variable in BLOCK DATA must be in a COMMON block"_err_en_US);
591     }
592   }
593   if (const DeclTypeSpec * type{details.type()}) { // C708
594     if (type->IsPolymorphic() &&
595         !(type->IsAssumedType() || IsAllocatableOrPointer(symbol) ||
596             IsDummy(symbol))) {
597       messages_.Say("CLASS entity '%s' must be a dummy argument or have "
598                     "ALLOCATABLE or POINTER attribute"_err_en_US,
599           symbol.name());
600     }
601   }
602 }
603 
604 void CheckHelper::CheckPointerInitialization(const Symbol &symbol) {
605   if (IsPointer(symbol) && !context_.HasError(symbol) &&
606       !scopeIsUninstantiatedPDT_) {
607     if (const auto *object{symbol.detailsIf<ObjectEntityDetails>()}) {
608       if (object->init()) { // C764, C765; C808
609         if (auto designator{evaluate::AsGenericExpr(symbol)}) {
610           auto restorer{messages_.SetLocation(symbol.name())};
611           context_.set_location(symbol.name());
612           CheckInitialTarget(foldingContext_, *designator, *object->init());
613         }
614       }
615     } else if (const auto *proc{symbol.detailsIf<ProcEntityDetails>()}) {
616       if (proc->init() && *proc->init()) {
617         // C1519 - must be nonelemental external or module procedure,
618         // or an unrestricted specific intrinsic function.
619         const Symbol &ultimate{(*proc->init())->GetUltimate()};
620         if (ultimate.attrs().test(Attr::INTRINSIC)) {
621           if (!context_.intrinsics().IsSpecificIntrinsicFunction(
622                   ultimate.name().ToString())) { // C1030
623             context_.Say(
624                 "Intrinsic procedure '%s' is not a specific intrinsic permitted for use as the initializer for procedure pointer '%s'"_err_en_US,
625                 ultimate.name(), symbol.name());
626           }
627         } else if (!ultimate.attrs().test(Attr::EXTERNAL) &&
628             ultimate.owner().kind() != Scope::Kind::Module) {
629           context_.Say("Procedure pointer '%s' initializer '%s' is neither "
630                        "an external nor a module procedure"_err_en_US,
631               symbol.name(), ultimate.name());
632         } else if (ultimate.attrs().test(Attr::ELEMENTAL)) {
633           context_.Say("Procedure pointer '%s' cannot be initialized with the "
634                        "elemental procedure '%s"_err_en_US,
635               symbol.name(), ultimate.name());
636         } else {
637           // TODO: Check the "shalls" in the 15.4.3.6 paragraphs 7-10.
638         }
639       }
640     }
641   }
642 }
643 
644 // The six different kinds of array-specs:
645 //   array-spec     -> explicit-shape-list | deferred-shape-list
646 //                     | assumed-shape-list | implied-shape-list
647 //                     | assumed-size | assumed-rank
648 //   explicit-shape -> [ lb : ] ub
649 //   deferred-shape -> :
650 //   assumed-shape  -> [ lb ] :
651 //   implied-shape  -> [ lb : ] *
652 //   assumed-size   -> [ explicit-shape-list , ] [ lb : ] *
653 //   assumed-rank   -> ..
654 // Note:
655 // - deferred-shape is also an assumed-shape
656 // - A single "*" or "lb:*" might be assumed-size or implied-shape-list
657 void CheckHelper::CheckArraySpec(
658     const Symbol &symbol, const ArraySpec &arraySpec) {
659   if (arraySpec.Rank() == 0) {
660     return;
661   }
662   bool isExplicit{arraySpec.IsExplicitShape()};
663   bool isDeferred{arraySpec.IsDeferredShape()};
664   bool isImplied{arraySpec.IsImpliedShape()};
665   bool isAssumedShape{arraySpec.IsAssumedShape()};
666   bool isAssumedSize{arraySpec.IsAssumedSize()};
667   bool isAssumedRank{arraySpec.IsAssumedRank()};
668   std::optional<parser::MessageFixedText> msg;
669   if (symbol.test(Symbol::Flag::CrayPointee) && !isExplicit && !isAssumedSize) {
670     msg = "Cray pointee '%s' must have must have explicit shape or"
671           " assumed size"_err_en_US;
672   } else if (IsAllocatableOrPointer(symbol) && !isDeferred && !isAssumedRank) {
673     if (symbol.owner().IsDerivedType()) { // C745
674       if (IsAllocatable(symbol)) {
675         msg = "Allocatable array component '%s' must have"
676               " deferred shape"_err_en_US;
677       } else {
678         msg = "Array pointer component '%s' must have deferred shape"_err_en_US;
679       }
680     } else {
681       if (IsAllocatable(symbol)) { // C832
682         msg = "Allocatable array '%s' must have deferred shape or"
683               " assumed rank"_err_en_US;
684       } else {
685         msg = "Array pointer '%s' must have deferred shape or"
686               " assumed rank"_err_en_US;
687       }
688     }
689   } else if (IsDummy(symbol)) {
690     if (isImplied && !isAssumedSize) { // C836
691       msg = "Dummy array argument '%s' may not have implied shape"_err_en_US;
692     }
693   } else if (isAssumedShape && !isDeferred) {
694     msg = "Assumed-shape array '%s' must be a dummy argument"_err_en_US;
695   } else if (isAssumedSize && !isImplied) { // C833
696     msg = "Assumed-size array '%s' must be a dummy argument"_err_en_US;
697   } else if (isAssumedRank) { // C837
698     msg = "Assumed-rank array '%s' must be a dummy argument"_err_en_US;
699   } else if (isImplied) {
700     if (!IsNamedConstant(symbol)) { // C835, C836
701       msg = "Implied-shape array '%s' must be a named constant or a "
702             "dummy argument"_err_en_US;
703     }
704   } else if (IsNamedConstant(symbol)) {
705     if (!isExplicit && !isImplied) {
706       msg = "Named constant '%s' array must have constant or"
707             " implied shape"_err_en_US;
708     }
709   } else if (!IsAllocatableOrPointer(symbol) && !isExplicit) {
710     if (symbol.owner().IsDerivedType()) { // C749
711       msg = "Component array '%s' without ALLOCATABLE or POINTER attribute must"
712             " have explicit shape"_err_en_US;
713     } else { // C816
714       msg = "Array '%s' without ALLOCATABLE or POINTER attribute must have"
715             " explicit shape"_err_en_US;
716     }
717   }
718   if (msg) {
719     context_.Say(std::move(*msg), symbol.name());
720   }
721 }
722 
723 void CheckHelper::CheckProcEntity(
724     const Symbol &symbol, const ProcEntityDetails &details) {
725   if (details.isDummy()) {
726     if (!symbol.attrs().test(Attr::POINTER) && // C843
727         (symbol.attrs().test(Attr::INTENT_IN) ||
728             symbol.attrs().test(Attr::INTENT_OUT) ||
729             symbol.attrs().test(Attr::INTENT_INOUT))) {
730       messages_.Say("A dummy procedure without the POINTER attribute"
731                     " may not have an INTENT attribute"_err_en_US);
732     }
733     if (InElemental()) { // C15100
734       messages_.Say(
735           "An ELEMENTAL subprogram may not have a dummy procedure"_err_en_US);
736     }
737     const Symbol *interface { details.interface().symbol() };
738     if (!symbol.attrs().test(Attr::INTRINSIC) &&
739         (symbol.attrs().test(Attr::ELEMENTAL) ||
740             (interface && !interface->attrs().test(Attr::INTRINSIC) &&
741                 interface->attrs().test(Attr::ELEMENTAL)))) {
742       // There's no explicit constraint or "shall" that we can find in the
743       // standard for this check, but it seems to be implied in multiple
744       // sites, and ELEMENTAL non-intrinsic actual arguments *are*
745       // explicitly forbidden.  But we allow "PROCEDURE(SIN)::dummy"
746       // because it is explicitly legal to *pass* the specific intrinsic
747       // function SIN as an actual argument.
748       messages_.Say("A dummy procedure may not be ELEMENTAL"_err_en_US);
749     }
750   } else if (symbol.attrs().test(Attr::INTENT_IN) ||
751       symbol.attrs().test(Attr::INTENT_OUT) ||
752       symbol.attrs().test(Attr::INTENT_INOUT)) {
753     messages_.Say("INTENT attributes may apply only to a dummy "
754                   "argument"_err_en_US); // C843
755   } else if (IsOptional(symbol)) {
756     messages_.Say("OPTIONAL attribute may apply only to a dummy "
757                   "argument"_err_en_US); // C849
758   } else if (symbol.owner().IsDerivedType()) {
759     if (!symbol.attrs().test(Attr::POINTER)) { // C756
760       const auto &name{symbol.name()};
761       messages_.Say(name,
762           "Procedure component '%s' must have POINTER attribute"_err_en_US,
763           name);
764     }
765     CheckPassArg(symbol, details.interface().symbol(), details);
766   }
767   if (symbol.attrs().test(Attr::POINTER)) {
768     CheckPointerInitialization(symbol);
769     if (const Symbol * interface{details.interface().symbol()}) {
770       if (interface->attrs().test(Attr::INTRINSIC)) {
771         if (!context_.intrinsics().IsSpecificIntrinsicFunction(
772                 interface->name().ToString())) { // C1515
773           messages_.Say(
774               "Intrinsic procedure '%s' is not a specific intrinsic permitted for use as the definition of the interface to procedure pointer '%s'"_err_en_US,
775               interface->name(), symbol.name());
776         }
777       } else if (interface->attrs().test(Attr::ELEMENTAL)) {
778         messages_.Say("Procedure pointer '%s' may not be ELEMENTAL"_err_en_US,
779             symbol.name()); // C1517
780       }
781     }
782   } else if (symbol.attrs().test(Attr::SAVE)) {
783     messages_.Say(
784         "Procedure '%s' with SAVE attribute must also have POINTER attribute"_err_en_US,
785         symbol.name());
786   }
787 }
788 
789 // When a module subprogram has the MODULE prefix the following must match
790 // with the corresponding separate module procedure interface body:
791 // - C1549: characteristics and dummy argument names
792 // - C1550: binding label
793 // - C1551: NON_RECURSIVE prefix
794 class SubprogramMatchHelper {
795 public:
796   explicit SubprogramMatchHelper(CheckHelper &checkHelper)
797       : checkHelper{checkHelper} {}
798 
799   void Check(const Symbol &, const Symbol &);
800 
801 private:
802   SemanticsContext &context() { return checkHelper.context(); }
803   void CheckDummyArg(const Symbol &, const Symbol &, const DummyArgument &,
804       const DummyArgument &);
805   void CheckDummyDataObject(const Symbol &, const Symbol &,
806       const DummyDataObject &, const DummyDataObject &);
807   void CheckDummyProcedure(const Symbol &, const Symbol &,
808       const DummyProcedure &, const DummyProcedure &);
809   bool CheckSameIntent(
810       const Symbol &, const Symbol &, common::Intent, common::Intent);
811   template <typename... A>
812   void Say(
813       const Symbol &, const Symbol &, parser::MessageFixedText &&, A &&...);
814   template <typename ATTRS>
815   bool CheckSameAttrs(const Symbol &, const Symbol &, ATTRS, ATTRS);
816   bool ShapesAreCompatible(const DummyDataObject &, const DummyDataObject &);
817   evaluate::Shape FoldShape(const evaluate::Shape &);
818   std::string AsFortran(DummyDataObject::Attr attr) {
819     return parser::ToUpperCaseLetters(DummyDataObject::EnumToString(attr));
820   }
821   std::string AsFortran(DummyProcedure::Attr attr) {
822     return parser::ToUpperCaseLetters(DummyProcedure::EnumToString(attr));
823   }
824 
825   CheckHelper &checkHelper;
826 };
827 
828 // 15.6.2.6 para 3 - can the result of an ENTRY differ from its function?
829 bool CheckHelper::IsResultOkToDiffer(const FunctionResult &result) {
830   if (result.attrs.test(FunctionResult::Attr::Allocatable) ||
831       result.attrs.test(FunctionResult::Attr::Pointer)) {
832     return false;
833   }
834   const auto *typeAndShape{result.GetTypeAndShape()};
835   if (!typeAndShape || typeAndShape->Rank() != 0) {
836     return false;
837   }
838   auto category{typeAndShape->type().category()};
839   if (category == TypeCategory::Character ||
840       category == TypeCategory::Derived) {
841     return false;
842   }
843   int kind{typeAndShape->type().kind()};
844   return kind == context_.GetDefaultKind(category) ||
845       (category == TypeCategory::Real &&
846           kind == context_.doublePrecisionKind());
847 }
848 
849 void CheckHelper::CheckSubprogram(
850     const Symbol &symbol, const SubprogramDetails &details) {
851   if (const Symbol * iface{FindSeparateModuleSubprogramInterface(&symbol)}) {
852     SubprogramMatchHelper{*this}.Check(symbol, *iface);
853   }
854   if (const Scope * entryScope{details.entryScope()}) {
855     // ENTRY 15.6.2.6, esp. C1571
856     std::optional<parser::MessageFixedText> error;
857     const Symbol *subprogram{entryScope->symbol()};
858     const SubprogramDetails *subprogramDetails{nullptr};
859     if (subprogram) {
860       subprogramDetails = subprogram->detailsIf<SubprogramDetails>();
861     }
862     if (entryScope->kind() != Scope::Kind::Subprogram) {
863       error = "ENTRY may appear only in a subroutine or function"_err_en_US;
864     } else if (!(entryScope->parent().IsGlobal() ||
865                    entryScope->parent().IsModule() ||
866                    entryScope->parent().IsSubmodule())) {
867       error = "ENTRY may not appear in an internal subprogram"_err_en_US;
868     } else if (FindSeparateModuleSubprogramInterface(subprogram)) {
869       error = "ENTRY may not appear in a separate module procedure"_err_en_US;
870     } else if (subprogramDetails && details.isFunction() &&
871         subprogramDetails->isFunction() &&
872         !context_.HasError(details.result()) &&
873         !context_.HasError(subprogramDetails->result())) {
874       auto result{FunctionResult::Characterize(
875           details.result(), context_.foldingContext())};
876       auto subpResult{FunctionResult::Characterize(
877           subprogramDetails->result(), context_.foldingContext())};
878       if (result && subpResult && *result != *subpResult &&
879           (!IsResultOkToDiffer(*result) || !IsResultOkToDiffer(*subpResult))) {
880         error =
881             "Result of ENTRY is not compatible with result of containing function"_err_en_US;
882       }
883     }
884     if (error) {
885       if (auto *msg{messages_.Say(symbol.name(), *error)}) {
886         if (subprogram) {
887           msg->Attach(subprogram->name(), "Containing subprogram"_en_US);
888         }
889       }
890     }
891   }
892   if (symbol.attrs().test(Attr::ELEMENTAL)) {
893     // See comment on the similar check in CheckProcEntity()
894     if (details.isDummy()) {
895       messages_.Say("A dummy procedure may not be ELEMENTAL"_err_en_US);
896     } else if (details.dummyArgs().empty()) {
897       messages_.Say(
898           "An ELEMENTAL subprogram must have at least one dummy argument"_err_en_US);
899     } else {
900       for (const Symbol *dummy : details.dummyArgs()) {
901         if (!dummy) { // C15100
902           messages_.Say(
903               "An ELEMENTAL subroutine may not have an alternate return dummy argument"_err_en_US);
904         }
905       }
906     }
907   }
908 }
909 
910 void CheckHelper::CheckDerivedType(
911     const Symbol &derivedType, const DerivedTypeDetails &details) {
912   if (details.isForwardReferenced() && !context_.HasError(derivedType)) {
913     messages_.Say("The derived type '%s' has not been defined"_err_en_US,
914         derivedType.name());
915   }
916   const Scope *scope{derivedType.scope()};
917   if (!scope) {
918     CHECK(details.isForwardReferenced());
919     return;
920   }
921   CHECK(scope->symbol() == &derivedType);
922   CHECK(scope->IsDerivedType());
923   if (derivedType.attrs().test(Attr::ABSTRACT) && // C734
924       (derivedType.attrs().test(Attr::BIND_C) || details.sequence())) {
925     messages_.Say("An ABSTRACT derived type must be extensible"_err_en_US);
926   }
927   if (const DeclTypeSpec * parent{FindParentTypeSpec(derivedType)}) {
928     const DerivedTypeSpec *parentDerived{parent->AsDerived()};
929     if (!IsExtensibleType(parentDerived)) { // C705
930       messages_.Say("The parent type is not extensible"_err_en_US);
931     }
932     if (!derivedType.attrs().test(Attr::ABSTRACT) && parentDerived &&
933         parentDerived->typeSymbol().attrs().test(Attr::ABSTRACT)) {
934       ScopeComponentIterator components{*parentDerived};
935       for (const Symbol &component : components) {
936         if (component.attrs().test(Attr::DEFERRED)) {
937           if (scope->FindComponent(component.name()) == &component) {
938             SayWithDeclaration(component,
939                 "Non-ABSTRACT extension of ABSTRACT derived type '%s' lacks a binding for DEFERRED procedure '%s'"_err_en_US,
940                 parentDerived->typeSymbol().name(), component.name());
941           }
942         }
943       }
944     }
945     DerivedTypeSpec derived{derivedType.name(), derivedType};
946     derived.set_scope(*scope);
947     if (FindCoarrayUltimateComponent(derived) && // C736
948         !(parentDerived && FindCoarrayUltimateComponent(*parentDerived))) {
949       messages_.Say(
950           "Type '%s' has a coarray ultimate component so the type at the base "
951           "of its type extension chain ('%s') must be a type that has a "
952           "coarray ultimate component"_err_en_US,
953           derivedType.name(), scope->GetDerivedTypeBase().GetSymbol()->name());
954     }
955     if (FindEventOrLockPotentialComponent(derived) && // C737
956         !(FindEventOrLockPotentialComponent(*parentDerived) ||
957             IsEventTypeOrLockType(parentDerived))) {
958       messages_.Say(
959           "Type '%s' has an EVENT_TYPE or LOCK_TYPE component, so the type "
960           "at the base of its type extension chain ('%s') must either have an "
961           "EVENT_TYPE or LOCK_TYPE component, or be EVENT_TYPE or "
962           "LOCK_TYPE"_err_en_US,
963           derivedType.name(), scope->GetDerivedTypeBase().GetSymbol()->name());
964     }
965   }
966   if (HasIntrinsicTypeName(derivedType)) { // C729
967     messages_.Say("A derived type name cannot be the name of an intrinsic"
968                   " type"_err_en_US);
969   }
970   std::map<SourceName, SymbolRef> previous;
971   for (const auto &pair : details.finals()) {
972     SourceName source{pair.first};
973     const Symbol &ref{*pair.second};
974     if (CheckFinal(ref, source, derivedType) &&
975         std::all_of(previous.begin(), previous.end(),
976             [&](std::pair<SourceName, SymbolRef> prev) {
977               return CheckDistinguishableFinals(
978                   ref, source, *prev.second, prev.first, derivedType);
979             })) {
980       previous.emplace(source, ref);
981     }
982   }
983 }
984 
985 // C786
986 bool CheckHelper::CheckFinal(
987     const Symbol &subroutine, SourceName finalName, const Symbol &derivedType) {
988   if (!IsModuleProcedure(subroutine)) {
989     SayWithDeclaration(subroutine, finalName,
990         "FINAL subroutine '%s' of derived type '%s' must be a module procedure"_err_en_US,
991         subroutine.name(), derivedType.name());
992     return false;
993   }
994   const Procedure *proc{Characterize(subroutine)};
995   if (!proc) {
996     return false; // error recovery
997   }
998   if (!proc->IsSubroutine()) {
999     SayWithDeclaration(subroutine, finalName,
1000         "FINAL subroutine '%s' of derived type '%s' must be a subroutine"_err_en_US,
1001         subroutine.name(), derivedType.name());
1002     return false;
1003   }
1004   if (proc->dummyArguments.size() != 1) {
1005     SayWithDeclaration(subroutine, finalName,
1006         "FINAL subroutine '%s' of derived type '%s' must have a single dummy argument"_err_en_US,
1007         subroutine.name(), derivedType.name());
1008     return false;
1009   }
1010   const auto &arg{proc->dummyArguments[0]};
1011   const Symbol *errSym{&subroutine};
1012   if (const auto *details{subroutine.detailsIf<SubprogramDetails>()}) {
1013     if (!details->dummyArgs().empty()) {
1014       if (const Symbol * argSym{details->dummyArgs()[0]}) {
1015         errSym = argSym;
1016       }
1017     }
1018   }
1019   const auto *ddo{std::get_if<DummyDataObject>(&arg.u)};
1020   if (!ddo) {
1021     SayWithDeclaration(subroutine, finalName,
1022         "FINAL subroutine '%s' of derived type '%s' must have a single dummy argument that is a data object"_err_en_US,
1023         subroutine.name(), derivedType.name());
1024     return false;
1025   }
1026   bool ok{true};
1027   if (arg.IsOptional()) {
1028     SayWithDeclaration(*errSym, finalName,
1029         "FINAL subroutine '%s' of derived type '%s' must not have an OPTIONAL dummy argument"_err_en_US,
1030         subroutine.name(), derivedType.name());
1031     ok = false;
1032   }
1033   if (ddo->attrs.test(DummyDataObject::Attr::Allocatable)) {
1034     SayWithDeclaration(*errSym, finalName,
1035         "FINAL subroutine '%s' of derived type '%s' must not have an ALLOCATABLE dummy argument"_err_en_US,
1036         subroutine.name(), derivedType.name());
1037     ok = false;
1038   }
1039   if (ddo->attrs.test(DummyDataObject::Attr::Pointer)) {
1040     SayWithDeclaration(*errSym, finalName,
1041         "FINAL subroutine '%s' of derived type '%s' must not have a POINTER dummy argument"_err_en_US,
1042         subroutine.name(), derivedType.name());
1043     ok = false;
1044   }
1045   if (ddo->intent == common::Intent::Out) {
1046     SayWithDeclaration(*errSym, finalName,
1047         "FINAL subroutine '%s' of derived type '%s' must not have a dummy argument with INTENT(OUT)"_err_en_US,
1048         subroutine.name(), derivedType.name());
1049     ok = false;
1050   }
1051   if (ddo->attrs.test(DummyDataObject::Attr::Value)) {
1052     SayWithDeclaration(*errSym, finalName,
1053         "FINAL subroutine '%s' of derived type '%s' must not have a dummy argument with the VALUE attribute"_err_en_US,
1054         subroutine.name(), derivedType.name());
1055     ok = false;
1056   }
1057   if (ddo->type.corank() > 0) {
1058     SayWithDeclaration(*errSym, finalName,
1059         "FINAL subroutine '%s' of derived type '%s' must not have a coarray dummy argument"_err_en_US,
1060         subroutine.name(), derivedType.name());
1061     ok = false;
1062   }
1063   if (ddo->type.type().IsPolymorphic()) {
1064     SayWithDeclaration(*errSym, finalName,
1065         "FINAL subroutine '%s' of derived type '%s' must not have a polymorphic dummy argument"_err_en_US,
1066         subroutine.name(), derivedType.name());
1067     ok = false;
1068   } else if (ddo->type.type().category() != TypeCategory::Derived ||
1069       &ddo->type.type().GetDerivedTypeSpec().typeSymbol() != &derivedType) {
1070     SayWithDeclaration(*errSym, finalName,
1071         "FINAL subroutine '%s' of derived type '%s' must have a TYPE(%s) dummy argument"_err_en_US,
1072         subroutine.name(), derivedType.name(), derivedType.name());
1073     ok = false;
1074   } else { // check that all LEN type parameters are assumed
1075     for (auto ref : OrderParameterDeclarations(derivedType)) {
1076       if (IsLenTypeParameter(*ref)) {
1077         const auto *value{
1078             ddo->type.type().GetDerivedTypeSpec().FindParameter(ref->name())};
1079         if (!value || !value->isAssumed()) {
1080           SayWithDeclaration(*errSym, finalName,
1081               "FINAL subroutine '%s' of derived type '%s' must have a dummy argument with an assumed LEN type parameter '%s=*'"_err_en_US,
1082               subroutine.name(), derivedType.name(), ref->name());
1083           ok = false;
1084         }
1085       }
1086     }
1087   }
1088   return ok;
1089 }
1090 
1091 bool CheckHelper::CheckDistinguishableFinals(const Symbol &f1,
1092     SourceName f1Name, const Symbol &f2, SourceName f2Name,
1093     const Symbol &derivedType) {
1094   const Procedure *p1{Characterize(f1)};
1095   const Procedure *p2{Characterize(f2)};
1096   if (p1 && p2) {
1097     if (characteristics::Distinguishable(*p1, *p2)) {
1098       return true;
1099     }
1100     if (auto *msg{messages_.Say(f1Name,
1101             "FINAL subroutines '%s' and '%s' of derived type '%s' cannot be distinguished by rank or KIND type parameter value"_err_en_US,
1102             f1Name, f2Name, derivedType.name())}) {
1103       msg->Attach(f2Name, "FINAL declaration of '%s'"_en_US, f2.name())
1104           .Attach(f1.name(), "Definition of '%s'"_en_US, f1Name)
1105           .Attach(f2.name(), "Definition of '%s'"_en_US, f2Name);
1106     }
1107   }
1108   return false;
1109 }
1110 
1111 void CheckHelper::CheckHostAssoc(
1112     const Symbol &symbol, const HostAssocDetails &details) {
1113   const Symbol &hostSymbol{details.symbol()};
1114   if (hostSymbol.test(Symbol::Flag::ImplicitOrError)) {
1115     if (details.implicitOrSpecExprError) {
1116       messages_.Say("Implicitly typed local entity '%s' not allowed in"
1117                     " specification expression"_err_en_US,
1118           symbol.name());
1119     } else if (details.implicitOrExplicitTypeError) {
1120       messages_.Say(
1121           "No explicit type declared for '%s'"_err_en_US, symbol.name());
1122     }
1123   }
1124 }
1125 
1126 void CheckHelper::CheckGeneric(
1127     const Symbol &symbol, const GenericDetails &details) {
1128   CheckSpecificsAreDistinguishable(symbol, details);
1129   std::visit(common::visitors{
1130                  [&](const GenericKind::DefinedIo &io) {
1131                    CheckDefinedIoProc(symbol, details, io);
1132                  },
1133                  [](const auto &) {},
1134              },
1135       details.kind().u);
1136 }
1137 
1138 // Check that the specifics of this generic are distinguishable from each other
1139 void CheckHelper::CheckSpecificsAreDistinguishable(
1140     const Symbol &generic, const GenericDetails &details) {
1141   GenericKind kind{details.kind()};
1142   const SymbolVector &specifics{details.specificProcs()};
1143   std::size_t count{specifics.size()};
1144   if (count < 2 || !kind.IsName()) {
1145     return;
1146   }
1147   DistinguishabilityHelper helper{context_};
1148   for (const Symbol &specific : specifics) {
1149     if (const Procedure * procedure{Characterize(specific)}) {
1150       helper.Add(generic, kind, specific, *procedure);
1151     }
1152   }
1153   helper.Check(generic.owner());
1154 }
1155 
1156 static bool ConflictsWithIntrinsicAssignment(const Procedure &proc) {
1157   auto lhs{std::get<DummyDataObject>(proc.dummyArguments[0].u).type};
1158   auto rhs{std::get<DummyDataObject>(proc.dummyArguments[1].u).type};
1159   return Tristate::No ==
1160       IsDefinedAssignment(lhs.type(), lhs.Rank(), rhs.type(), rhs.Rank());
1161 }
1162 
1163 static bool ConflictsWithIntrinsicOperator(
1164     const GenericKind &kind, const Procedure &proc) {
1165   if (!kind.IsIntrinsicOperator()) {
1166     return false;
1167   }
1168   auto arg0{std::get<DummyDataObject>(proc.dummyArguments[0].u).type};
1169   auto type0{arg0.type()};
1170   if (proc.dummyArguments.size() == 1) { // unary
1171     return std::visit(
1172         common::visitors{
1173             [&](common::NumericOperator) { return IsIntrinsicNumeric(type0); },
1174             [&](common::LogicalOperator) { return IsIntrinsicLogical(type0); },
1175             [](const auto &) -> bool { DIE("bad generic kind"); },
1176         },
1177         kind.u);
1178   } else { // binary
1179     int rank0{arg0.Rank()};
1180     auto arg1{std::get<DummyDataObject>(proc.dummyArguments[1].u).type};
1181     auto type1{arg1.type()};
1182     int rank1{arg1.Rank()};
1183     return std::visit(
1184         common::visitors{
1185             [&](common::NumericOperator) {
1186               return IsIntrinsicNumeric(type0, rank0, type1, rank1);
1187             },
1188             [&](common::LogicalOperator) {
1189               return IsIntrinsicLogical(type0, rank0, type1, rank1);
1190             },
1191             [&](common::RelationalOperator opr) {
1192               return IsIntrinsicRelational(opr, type0, rank0, type1, rank1);
1193             },
1194             [&](GenericKind::OtherKind x) {
1195               CHECK(x == GenericKind::OtherKind::Concat);
1196               return IsIntrinsicConcat(type0, rank0, type1, rank1);
1197             },
1198             [](const auto &) -> bool { DIE("bad generic kind"); },
1199         },
1200         kind.u);
1201   }
1202 }
1203 
1204 // Check if this procedure can be used for defined operators (see 15.4.3.4.2).
1205 bool CheckHelper::CheckDefinedOperator(SourceName opName, GenericKind kind,
1206     const Symbol &specific, const Procedure &proc) {
1207   if (context_.HasError(specific)) {
1208     return false;
1209   }
1210   std::optional<parser::MessageFixedText> msg;
1211   auto checkDefinedOperatorArgs{
1212       [&](SourceName opName, const Symbol &specific, const Procedure &proc) {
1213         bool arg0Defined{CheckDefinedOperatorArg(opName, specific, proc, 0)};
1214         bool arg1Defined{CheckDefinedOperatorArg(opName, specific, proc, 1)};
1215         return arg0Defined && arg1Defined;
1216       }};
1217   if (specific.attrs().test(Attr::NOPASS)) { // C774
1218     msg = "%s procedure '%s' may not have NOPASS attribute"_err_en_US;
1219   } else if (!proc.functionResult.has_value()) {
1220     msg = "%s procedure '%s' must be a function"_err_en_US;
1221   } else if (proc.functionResult->IsAssumedLengthCharacter()) {
1222     msg = "%s function '%s' may not have assumed-length CHARACTER(*)"
1223           " result"_err_en_US;
1224   } else if (auto m{CheckNumberOfArgs(kind, proc.dummyArguments.size())}) {
1225     msg = std::move(m);
1226   } else if (!checkDefinedOperatorArgs(opName, specific, proc)) {
1227     return false; // error was reported
1228   } else if (ConflictsWithIntrinsicOperator(kind, proc)) {
1229     msg = "%s function '%s' conflicts with intrinsic operator"_err_en_US;
1230   } else {
1231     return true; // OK
1232   }
1233   SayWithDeclaration(
1234       specific, std::move(*msg), MakeOpName(opName), specific.name());
1235   context_.SetError(specific);
1236   return false;
1237 }
1238 
1239 // If the number of arguments is wrong for this intrinsic operator, return
1240 // false and return the error message in msg.
1241 std::optional<parser::MessageFixedText> CheckHelper::CheckNumberOfArgs(
1242     const GenericKind &kind, std::size_t nargs) {
1243   if (!kind.IsIntrinsicOperator()) {
1244     return std::nullopt;
1245   }
1246   std::size_t min{2}, max{2}; // allowed number of args; default is binary
1247   std::visit(common::visitors{
1248                  [&](const common::NumericOperator &x) {
1249                    if (x == common::NumericOperator::Add ||
1250                        x == common::NumericOperator::Subtract) {
1251                      min = 1; // + and - are unary or binary
1252                    }
1253                  },
1254                  [&](const common::LogicalOperator &x) {
1255                    if (x == common::LogicalOperator::Not) {
1256                      min = 1; // .NOT. is unary
1257                      max = 1;
1258                    }
1259                  },
1260                  [](const common::RelationalOperator &) {
1261                    // all are binary
1262                  },
1263                  [](const GenericKind::OtherKind &x) {
1264                    CHECK(x == GenericKind::OtherKind::Concat);
1265                  },
1266                  [](const auto &) { DIE("expected intrinsic operator"); },
1267              },
1268       kind.u);
1269   if (nargs >= min && nargs <= max) {
1270     return std::nullopt;
1271   } else if (max == 1) {
1272     return "%s function '%s' must have one dummy argument"_err_en_US;
1273   } else if (min == 2) {
1274     return "%s function '%s' must have two dummy arguments"_err_en_US;
1275   } else {
1276     return "%s function '%s' must have one or two dummy arguments"_err_en_US;
1277   }
1278 }
1279 
1280 bool CheckHelper::CheckDefinedOperatorArg(const SourceName &opName,
1281     const Symbol &symbol, const Procedure &proc, std::size_t pos) {
1282   if (pos >= proc.dummyArguments.size()) {
1283     return true;
1284   }
1285   auto &arg{proc.dummyArguments.at(pos)};
1286   std::optional<parser::MessageFixedText> msg;
1287   if (arg.IsOptional()) {
1288     msg = "In %s function '%s', dummy argument '%s' may not be"
1289           " OPTIONAL"_err_en_US;
1290   } else if (const auto *dataObject{std::get_if<DummyDataObject>(&arg.u)};
1291              dataObject == nullptr) {
1292     msg = "In %s function '%s', dummy argument '%s' must be a"
1293           " data object"_err_en_US;
1294   } else if (dataObject->intent != common::Intent::In &&
1295       !dataObject->attrs.test(DummyDataObject::Attr::Value)) {
1296     msg = "In %s function '%s', dummy argument '%s' must have INTENT(IN)"
1297           " or VALUE attribute"_err_en_US;
1298   }
1299   if (msg) {
1300     SayWithDeclaration(symbol, std::move(*msg),
1301         parser::ToUpperCaseLetters(opName.ToString()), symbol.name(), arg.name);
1302     return false;
1303   }
1304   return true;
1305 }
1306 
1307 // Check if this procedure can be used for defined assignment (see 15.4.3.4.3).
1308 bool CheckHelper::CheckDefinedAssignment(
1309     const Symbol &specific, const Procedure &proc) {
1310   if (context_.HasError(specific)) {
1311     return false;
1312   }
1313   std::optional<parser::MessageFixedText> msg;
1314   if (specific.attrs().test(Attr::NOPASS)) { // C774
1315     msg = "Defined assignment procedure '%s' may not have"
1316           " NOPASS attribute"_err_en_US;
1317   } else if (!proc.IsSubroutine()) {
1318     msg = "Defined assignment procedure '%s' must be a subroutine"_err_en_US;
1319   } else if (proc.dummyArguments.size() != 2) {
1320     msg = "Defined assignment subroutine '%s' must have"
1321           " two dummy arguments"_err_en_US;
1322   } else if (!CheckDefinedAssignmentArg(specific, proc.dummyArguments[0], 0) |
1323       !CheckDefinedAssignmentArg(specific, proc.dummyArguments[1], 1)) {
1324     return false; // error was reported
1325   } else if (ConflictsWithIntrinsicAssignment(proc)) {
1326     msg = "Defined assignment subroutine '%s' conflicts with"
1327           " intrinsic assignment"_err_en_US;
1328   } else {
1329     return true; // OK
1330   }
1331   SayWithDeclaration(specific, std::move(msg.value()), specific.name());
1332   context_.SetError(specific);
1333   return false;
1334 }
1335 
1336 bool CheckHelper::CheckDefinedAssignmentArg(
1337     const Symbol &symbol, const DummyArgument &arg, int pos) {
1338   std::optional<parser::MessageFixedText> msg;
1339   if (arg.IsOptional()) {
1340     msg = "In defined assignment subroutine '%s', dummy argument '%s'"
1341           " may not be OPTIONAL"_err_en_US;
1342   } else if (const auto *dataObject{std::get_if<DummyDataObject>(&arg.u)}) {
1343     if (pos == 0) {
1344       if (dataObject->intent != common::Intent::Out &&
1345           dataObject->intent != common::Intent::InOut) {
1346         msg = "In defined assignment subroutine '%s', first dummy argument '%s'"
1347               " must have INTENT(OUT) or INTENT(INOUT)"_err_en_US;
1348       }
1349     } else if (pos == 1) {
1350       if (dataObject->intent != common::Intent::In &&
1351           !dataObject->attrs.test(DummyDataObject::Attr::Value)) {
1352         msg =
1353             "In defined assignment subroutine '%s', second dummy"
1354             " argument '%s' must have INTENT(IN) or VALUE attribute"_err_en_US;
1355       }
1356     } else {
1357       DIE("pos must be 0 or 1");
1358     }
1359   } else {
1360     msg = "In defined assignment subroutine '%s', dummy argument '%s'"
1361           " must be a data object"_err_en_US;
1362   }
1363   if (msg) {
1364     SayWithDeclaration(symbol, std::move(*msg), symbol.name(), arg.name);
1365     context_.SetError(symbol);
1366     return false;
1367   }
1368   return true;
1369 }
1370 
1371 // Report a conflicting attribute error if symbol has both of these attributes
1372 bool CheckHelper::CheckConflicting(const Symbol &symbol, Attr a1, Attr a2) {
1373   if (symbol.attrs().test(a1) && symbol.attrs().test(a2)) {
1374     messages_.Say("'%s' may not have both the %s and %s attributes"_err_en_US,
1375         symbol.name(), AttrToString(a1), AttrToString(a2));
1376     return true;
1377   } else {
1378     return false;
1379   }
1380 }
1381 
1382 void CheckHelper::WarnMissingFinal(const Symbol &symbol) {
1383   const auto *object{symbol.detailsIf<ObjectEntityDetails>()};
1384   if (!object || IsPointer(symbol)) {
1385     return;
1386   }
1387   const DeclTypeSpec *type{object->type()};
1388   const DerivedTypeSpec *derived{type ? type->AsDerived() : nullptr};
1389   const Symbol *derivedSym{derived ? &derived->typeSymbol() : nullptr};
1390   int rank{object->shape().Rank()};
1391   const Symbol *initialDerivedSym{derivedSym};
1392   while (const auto *derivedDetails{
1393       derivedSym ? derivedSym->detailsIf<DerivedTypeDetails>() : nullptr}) {
1394     if (!derivedDetails->finals().empty() &&
1395         !derivedDetails->GetFinalForRank(rank)) {
1396       if (auto *msg{derivedSym == initialDerivedSym
1397                   ? messages_.Say(symbol.name(),
1398                         "'%s' of derived type '%s' does not have a FINAL subroutine for its rank (%d)"_en_US,
1399                         symbol.name(), derivedSym->name(), rank)
1400                   : messages_.Say(symbol.name(),
1401                         "'%s' of derived type '%s' extended from '%s' does not have a FINAL subroutine for its rank (%d)"_en_US,
1402                         symbol.name(), initialDerivedSym->name(),
1403                         derivedSym->name(), rank)}) {
1404         msg->Attach(derivedSym->name(),
1405             "Declaration of derived type '%s'"_en_US, derivedSym->name());
1406       }
1407       return;
1408     }
1409     derived = derivedSym->GetParentTypeSpec();
1410     derivedSym = derived ? &derived->typeSymbol() : nullptr;
1411   }
1412 }
1413 
1414 const Procedure *CheckHelper::Characterize(const Symbol &symbol) {
1415   auto it{characterizeCache_.find(symbol)};
1416   if (it == characterizeCache_.end()) {
1417     auto pair{characterizeCache_.emplace(SymbolRef{symbol},
1418         Procedure::Characterize(symbol, context_.foldingContext()))};
1419     it = pair.first;
1420   }
1421   return common::GetPtrFromOptional(it->second);
1422 }
1423 
1424 void CheckHelper::CheckVolatile(const Symbol &symbol,
1425     const DerivedTypeSpec *derived) { // C866 - C868
1426   if (IsIntentIn(symbol)) {
1427     messages_.Say(
1428         "VOLATILE attribute may not apply to an INTENT(IN) argument"_err_en_US);
1429   }
1430   if (IsProcedure(symbol)) {
1431     messages_.Say("VOLATILE attribute may apply only to a variable"_err_en_US);
1432   }
1433   if (symbol.has<UseDetails>() || symbol.has<HostAssocDetails>()) {
1434     const Symbol &ultimate{symbol.GetUltimate()};
1435     if (IsCoarray(ultimate)) {
1436       messages_.Say(
1437           "VOLATILE attribute may not apply to a coarray accessed by USE or host association"_err_en_US);
1438     }
1439     if (derived) {
1440       if (FindCoarrayUltimateComponent(*derived)) {
1441         messages_.Say(
1442             "VOLATILE attribute may not apply to a type with a coarray ultimate component accessed by USE or host association"_err_en_US);
1443       }
1444     }
1445   }
1446 }
1447 
1448 void CheckHelper::CheckPointer(const Symbol &symbol) { // C852
1449   CheckConflicting(symbol, Attr::POINTER, Attr::TARGET);
1450   CheckConflicting(symbol, Attr::POINTER, Attr::ALLOCATABLE); // C751
1451   CheckConflicting(symbol, Attr::POINTER, Attr::INTRINSIC);
1452   // Prohibit constant pointers.  The standard does not explicitly prohibit
1453   // them, but the PARAMETER attribute requires a entity-decl to have an
1454   // initialization that is a constant-expr, and the only form of
1455   // initialization that allows a constant-expr is the one that's not a "=>"
1456   // pointer initialization.  See C811, C807, and section 8.5.13.
1457   CheckConflicting(symbol, Attr::POINTER, Attr::PARAMETER);
1458   if (symbol.Corank() > 0) {
1459     messages_.Say(
1460         "'%s' may not have the POINTER attribute because it is a coarray"_err_en_US,
1461         symbol.name());
1462   }
1463 }
1464 
1465 // C760 constraints on the passed-object dummy argument
1466 // C757 constraints on procedure pointer components
1467 void CheckHelper::CheckPassArg(
1468     const Symbol &proc, const Symbol *interface, const WithPassArg &details) {
1469   if (proc.attrs().test(Attr::NOPASS)) {
1470     return;
1471   }
1472   const auto &name{proc.name()};
1473   if (!interface) {
1474     messages_.Say(name,
1475         "Procedure component '%s' must have NOPASS attribute or explicit interface"_err_en_US,
1476         name);
1477     return;
1478   }
1479   const auto *subprogram{interface->detailsIf<SubprogramDetails>()};
1480   if (!subprogram) {
1481     messages_.Say(name,
1482         "Procedure component '%s' has invalid interface '%s'"_err_en_US, name,
1483         interface->name());
1484     return;
1485   }
1486   std::optional<SourceName> passName{details.passName()};
1487   const auto &dummyArgs{subprogram->dummyArgs()};
1488   if (!passName) {
1489     if (dummyArgs.empty()) {
1490       messages_.Say(name,
1491           proc.has<ProcEntityDetails>()
1492               ? "Procedure component '%s' with no dummy arguments"
1493                 " must have NOPASS attribute"_err_en_US
1494               : "Procedure binding '%s' with no dummy arguments"
1495                 " must have NOPASS attribute"_err_en_US,
1496           name);
1497       context_.SetError(*interface);
1498       return;
1499     }
1500     Symbol *argSym{dummyArgs[0]};
1501     if (!argSym) {
1502       messages_.Say(interface->name(),
1503           "Cannot use an alternate return as the passed-object dummy "
1504           "argument"_err_en_US);
1505       return;
1506     }
1507     passName = dummyArgs[0]->name();
1508   }
1509   std::optional<int> passArgIndex{};
1510   for (std::size_t i{0}; i < dummyArgs.size(); ++i) {
1511     if (dummyArgs[i] && dummyArgs[i]->name() == *passName) {
1512       passArgIndex = i;
1513       break;
1514     }
1515   }
1516   if (!passArgIndex) { // C758
1517     messages_.Say(*passName,
1518         "'%s' is not a dummy argument of procedure interface '%s'"_err_en_US,
1519         *passName, interface->name());
1520     return;
1521   }
1522   const Symbol &passArg{*dummyArgs[*passArgIndex]};
1523   std::optional<parser::MessageFixedText> msg;
1524   if (!passArg.has<ObjectEntityDetails>()) {
1525     msg = "Passed-object dummy argument '%s' of procedure '%s'"
1526           " must be a data object"_err_en_US;
1527   } else if (passArg.attrs().test(Attr::POINTER)) {
1528     msg = "Passed-object dummy argument '%s' of procedure '%s'"
1529           " may not have the POINTER attribute"_err_en_US;
1530   } else if (passArg.attrs().test(Attr::ALLOCATABLE)) {
1531     msg = "Passed-object dummy argument '%s' of procedure '%s'"
1532           " may not have the ALLOCATABLE attribute"_err_en_US;
1533   } else if (passArg.attrs().test(Attr::VALUE)) {
1534     msg = "Passed-object dummy argument '%s' of procedure '%s'"
1535           " may not have the VALUE attribute"_err_en_US;
1536   } else if (passArg.Rank() > 0) {
1537     msg = "Passed-object dummy argument '%s' of procedure '%s'"
1538           " must be scalar"_err_en_US;
1539   }
1540   if (msg) {
1541     messages_.Say(name, std::move(*msg), passName.value(), name);
1542     return;
1543   }
1544   const DeclTypeSpec *type{passArg.GetType()};
1545   if (!type) {
1546     return; // an error already occurred
1547   }
1548   const Symbol &typeSymbol{*proc.owner().GetSymbol()};
1549   const DerivedTypeSpec *derived{type->AsDerived()};
1550   if (!derived || derived->typeSymbol() != typeSymbol) {
1551     messages_.Say(name,
1552         "Passed-object dummy argument '%s' of procedure '%s'"
1553         " must be of type '%s' but is '%s'"_err_en_US,
1554         passName.value(), name, typeSymbol.name(), type->AsFortran());
1555     return;
1556   }
1557   if (IsExtensibleType(derived) != type->IsPolymorphic()) {
1558     messages_.Say(name,
1559         type->IsPolymorphic()
1560             ? "Passed-object dummy argument '%s' of procedure '%s'"
1561               " may not be polymorphic because '%s' is not extensible"_err_en_US
1562             : "Passed-object dummy argument '%s' of procedure '%s'"
1563               " must be polymorphic because '%s' is extensible"_err_en_US,
1564         passName.value(), name, typeSymbol.name());
1565     return;
1566   }
1567   for (const auto &[paramName, paramValue] : derived->parameters()) {
1568     if (paramValue.isLen() && !paramValue.isAssumed()) {
1569       messages_.Say(name,
1570           "Passed-object dummy argument '%s' of procedure '%s'"
1571           " has non-assumed length parameter '%s'"_err_en_US,
1572           passName.value(), name, paramName);
1573     }
1574   }
1575 }
1576 
1577 void CheckHelper::CheckProcBinding(
1578     const Symbol &symbol, const ProcBindingDetails &binding) {
1579   const Scope &dtScope{symbol.owner()};
1580   CHECK(dtScope.kind() == Scope::Kind::DerivedType);
1581   if (symbol.attrs().test(Attr::DEFERRED)) {
1582     if (const Symbol * dtSymbol{dtScope.symbol()}) {
1583       if (!dtSymbol->attrs().test(Attr::ABSTRACT)) { // C733
1584         SayWithDeclaration(*dtSymbol,
1585             "Procedure bound to non-ABSTRACT derived type '%s' may not be DEFERRED"_err_en_US,
1586             dtSymbol->name());
1587       }
1588     }
1589     if (symbol.attrs().test(Attr::NON_OVERRIDABLE)) {
1590       messages_.Say(
1591           "Type-bound procedure '%s' may not be both DEFERRED and NON_OVERRIDABLE"_err_en_US,
1592           symbol.name());
1593     }
1594   }
1595   if (binding.symbol().attrs().test(Attr::INTRINSIC) &&
1596       !context_.intrinsics().IsSpecificIntrinsicFunction(
1597           binding.symbol().name().ToString())) {
1598     messages_.Say(
1599         "Intrinsic procedure '%s' is not a specific intrinsic permitted for use in the definition of binding '%s'"_err_en_US,
1600         binding.symbol().name(), symbol.name());
1601   }
1602   if (const Symbol * overridden{FindOverriddenBinding(symbol)}) {
1603     if (overridden->attrs().test(Attr::NON_OVERRIDABLE)) {
1604       SayWithDeclaration(*overridden,
1605           "Override of NON_OVERRIDABLE '%s' is not permitted"_err_en_US,
1606           symbol.name());
1607     }
1608     if (const auto *overriddenBinding{
1609             overridden->detailsIf<ProcBindingDetails>()}) {
1610       if (!IsPureProcedure(symbol) && IsPureProcedure(*overridden)) {
1611         SayWithDeclaration(*overridden,
1612             "An overridden pure type-bound procedure binding must also be pure"_err_en_US);
1613         return;
1614       }
1615       if (!binding.symbol().attrs().test(Attr::ELEMENTAL) &&
1616           overriddenBinding->symbol().attrs().test(Attr::ELEMENTAL)) {
1617         SayWithDeclaration(*overridden,
1618             "A type-bound procedure and its override must both, or neither, be ELEMENTAL"_err_en_US);
1619         return;
1620       }
1621       bool isNopass{symbol.attrs().test(Attr::NOPASS)};
1622       if (isNopass != overridden->attrs().test(Attr::NOPASS)) {
1623         SayWithDeclaration(*overridden,
1624             isNopass
1625                 ? "A NOPASS type-bound procedure may not override a passed-argument procedure"_err_en_US
1626                 : "A passed-argument type-bound procedure may not override a NOPASS procedure"_err_en_US);
1627       } else {
1628         const auto *bindingChars{Characterize(binding.symbol())};
1629         const auto *overriddenChars{Characterize(overriddenBinding->symbol())};
1630         if (bindingChars && overriddenChars) {
1631           if (isNopass) {
1632             if (!bindingChars->CanOverride(*overriddenChars, std::nullopt)) {
1633               SayWithDeclaration(*overridden,
1634                   "A type-bound procedure and its override must have compatible interfaces"_err_en_US);
1635             }
1636           } else if (!context_.HasError(binding.symbol())) {
1637             int passIndex{bindingChars->FindPassIndex(binding.passName())};
1638             int overriddenPassIndex{
1639                 overriddenChars->FindPassIndex(overriddenBinding->passName())};
1640             if (passIndex != overriddenPassIndex) {
1641               SayWithDeclaration(*overridden,
1642                   "A type-bound procedure and its override must use the same PASS argument"_err_en_US);
1643             } else if (!bindingChars->CanOverride(
1644                            *overriddenChars, passIndex)) {
1645               SayWithDeclaration(*overridden,
1646                   "A type-bound procedure and its override must have compatible interfaces apart from their passed argument"_err_en_US);
1647             }
1648           }
1649         }
1650       }
1651       if (symbol.attrs().test(Attr::PRIVATE) &&
1652           overridden->attrs().test(Attr::PUBLIC)) {
1653         SayWithDeclaration(*overridden,
1654             "A PRIVATE procedure may not override a PUBLIC procedure"_err_en_US);
1655       }
1656     } else {
1657       SayWithDeclaration(*overridden,
1658           "A type-bound procedure binding may not have the same name as a parent component"_err_en_US);
1659     }
1660   }
1661   CheckPassArg(symbol, &binding.symbol(), binding);
1662 }
1663 
1664 void CheckHelper::Check(const Scope &scope) {
1665   scope_ = &scope;
1666   common::Restorer<const Symbol *> restorer{innermostSymbol_, innermostSymbol_};
1667   if (const Symbol * symbol{scope.symbol()}) {
1668     innermostSymbol_ = symbol;
1669   }
1670   if (scope.IsParameterizedDerivedTypeInstantiation()) {
1671     auto restorer{common::ScopedSet(scopeIsUninstantiatedPDT_, false)};
1672     auto restorer2{context_.foldingContext().messages().SetContext(
1673         scope.instantiationContext().get())};
1674     for (const auto &pair : scope) {
1675       CheckPointerInitialization(*pair.second);
1676     }
1677   } else {
1678     auto restorer{common::ScopedSet(
1679         scopeIsUninstantiatedPDT_, scope.IsParameterizedDerivedType())};
1680     for (const auto &set : scope.equivalenceSets()) {
1681       CheckEquivalenceSet(set);
1682     }
1683     for (const auto &pair : scope) {
1684       Check(*pair.second);
1685     }
1686     for (const Scope &child : scope.children()) {
1687       Check(child);
1688     }
1689     if (scope.kind() == Scope::Kind::BlockData) {
1690       CheckBlockData(scope);
1691     }
1692     CheckGenericOps(scope);
1693   }
1694 }
1695 
1696 void CheckHelper::CheckEquivalenceSet(const EquivalenceSet &set) {
1697   auto iter{
1698       std::find_if(set.begin(), set.end(), [](const EquivalenceObject &object) {
1699         return FindCommonBlockContaining(object.symbol) != nullptr;
1700       })};
1701   if (iter != set.end()) {
1702     const Symbol &commonBlock{DEREF(FindCommonBlockContaining(iter->symbol))};
1703     for (auto &object : set) {
1704       if (&object != &*iter) {
1705         if (auto *details{object.symbol.detailsIf<ObjectEntityDetails>()}) {
1706           if (details->commonBlock()) {
1707             if (details->commonBlock() != &commonBlock) { // 8.10.3 paragraph 1
1708               if (auto *msg{messages_.Say(object.symbol.name(),
1709                       "Two objects in the same EQUIVALENCE set may not be members of distinct COMMON blocks"_err_en_US)}) {
1710                 msg->Attach(iter->symbol.name(),
1711                        "Other object in EQUIVALENCE set"_en_US)
1712                     .Attach(details->commonBlock()->name(),
1713                         "COMMON block containing '%s'"_en_US,
1714                         object.symbol.name())
1715                     .Attach(commonBlock.name(),
1716                         "COMMON block containing '%s'"_en_US,
1717                         iter->symbol.name());
1718               }
1719             }
1720           } else {
1721             // Mark all symbols in the equivalence set with the same COMMON
1722             // block to prevent spurious error messages about initialization
1723             // in BLOCK DATA outside COMMON
1724             details->set_commonBlock(commonBlock);
1725           }
1726         }
1727       }
1728     }
1729   }
1730   // TODO: Move C8106 (&al.) checks here from resolve-names-utils.cpp
1731 }
1732 
1733 void CheckHelper::CheckBlockData(const Scope &scope) {
1734   // BLOCK DATA subprograms should contain only named common blocks.
1735   // C1415 presents a list of statements that shouldn't appear in
1736   // BLOCK DATA, but so long as the subprogram contains no executable
1737   // code and allocates no storage outside named COMMON, we're happy
1738   // (e.g., an ENUM is strictly not allowed).
1739   for (const auto &pair : scope) {
1740     const Symbol &symbol{*pair.second};
1741     if (!(symbol.has<CommonBlockDetails>() || symbol.has<UseDetails>() ||
1742             symbol.has<UseErrorDetails>() || symbol.has<DerivedTypeDetails>() ||
1743             symbol.has<SubprogramDetails>() ||
1744             symbol.has<ObjectEntityDetails>() ||
1745             (symbol.has<ProcEntityDetails>() &&
1746                 !symbol.attrs().test(Attr::POINTER)))) {
1747       messages_.Say(symbol.name(),
1748           "'%s' may not appear in a BLOCK DATA subprogram"_err_en_US,
1749           symbol.name());
1750     }
1751   }
1752 }
1753 
1754 // Check distinguishability of generic assignment and operators.
1755 // For these, generics and generic bindings must be considered together.
1756 void CheckHelper::CheckGenericOps(const Scope &scope) {
1757   DistinguishabilityHelper helper{context_};
1758   auto addSpecifics{[&](const Symbol &generic) {
1759     const auto *details{generic.GetUltimate().detailsIf<GenericDetails>()};
1760     if (!details) {
1761       return;
1762     }
1763     GenericKind kind{details->kind()};
1764     if (!kind.IsAssignment() && !kind.IsOperator()) {
1765       return;
1766     }
1767     const SymbolVector &specifics{details->specificProcs()};
1768     const std::vector<SourceName> &bindingNames{details->bindingNames()};
1769     for (std::size_t i{0}; i < specifics.size(); ++i) {
1770       const Symbol &specific{*specifics[i]};
1771       if (const Procedure * proc{Characterize(specific)}) {
1772         auto restorer{messages_.SetLocation(bindingNames[i])};
1773         if (kind.IsAssignment()) {
1774           if (!CheckDefinedAssignment(specific, *proc)) {
1775             continue;
1776           }
1777         } else {
1778           if (!CheckDefinedOperator(generic.name(), kind, specific, *proc)) {
1779             continue;
1780           }
1781         }
1782         helper.Add(generic, kind, specific, *proc);
1783       }
1784     }
1785   }};
1786   for (const auto &pair : scope) {
1787     const Symbol &symbol{*pair.second};
1788     addSpecifics(symbol);
1789     const Symbol &ultimate{symbol.GetUltimate()};
1790     if (ultimate.has<DerivedTypeDetails>()) {
1791       if (const Scope * typeScope{ultimate.scope()}) {
1792         for (const auto &pair2 : *typeScope) {
1793           addSpecifics(*pair2.second);
1794         }
1795       }
1796     }
1797   }
1798   helper.Check(scope);
1799 }
1800 
1801 static const std::string *DefinesBindCName(const Symbol &symbol) {
1802   const auto *subp{symbol.detailsIf<SubprogramDetails>()};
1803   if ((subp && !subp->isInterface()) || symbol.has<ObjectEntityDetails>()) {
1804     // Symbol defines data or entry point
1805     return symbol.GetBindName();
1806   } else {
1807     return nullptr;
1808   }
1809 }
1810 
1811 // Check that BIND(C) names are distinct
1812 void CheckHelper::CheckBindCName(const Symbol &symbol) {
1813   if (const std::string * name{DefinesBindCName(symbol)}) {
1814     auto pair{bindC_.emplace(*name, symbol)};
1815     if (!pair.second) {
1816       const Symbol &other{*pair.first->second};
1817       if (DefinesBindCName(other) && !context_.HasError(other)) {
1818         if (auto *msg{messages_.Say(
1819                 "Two symbols have the same BIND(C) name '%s'"_err_en_US,
1820                 *name)}) {
1821           msg->Attach(other.name(), "Conflicting symbol"_en_US);
1822         }
1823         context_.SetError(symbol);
1824         context_.SetError(other);
1825       }
1826     }
1827   }
1828 }
1829 
1830 bool CheckHelper::CheckDioDummyIsData(
1831     const Symbol &subp, const Symbol *arg, std::size_t position) {
1832   if (arg && arg->detailsIf<ObjectEntityDetails>()) {
1833     return true;
1834   } else {
1835     if (arg) {
1836       messages_.Say(arg->name(),
1837           "Dummy argument '%s' must be a data object"_err_en_US, arg->name());
1838     } else {
1839       messages_.Say(subp.name(),
1840           "Dummy argument %d of '%s' must be a data object"_err_en_US, position,
1841           subp.name());
1842     }
1843     return false;
1844   }
1845 }
1846 
1847 void CheckHelper::CheckAlreadySeenDefinedIo(const DerivedTypeSpec *derivedType,
1848     GenericKind::DefinedIo ioKind, const Symbol &proc) {
1849   for (TypeWithDefinedIo definedIoType : seenDefinedIoTypes_) {
1850     if (*derivedType == *definedIoType.type && ioKind == definedIoType.ioKind &&
1851         proc != definedIoType.proc) {
1852       SayWithDeclaration(proc, definedIoType.proc.name(),
1853           "Derived type '%s' already has defined input/output procedure"
1854           " '%s'"_err_en_US,
1855           derivedType->name(),
1856           parser::ToUpperCaseLetters(GenericKind::EnumToString(ioKind)));
1857       return;
1858     }
1859   }
1860   seenDefinedIoTypes_.emplace_back(
1861       TypeWithDefinedIo{derivedType, ioKind, proc});
1862 }
1863 
1864 void CheckHelper::CheckDioDummyIsDerived(
1865     const Symbol &subp, const Symbol &arg, GenericKind::DefinedIo ioKind) {
1866   if (const DeclTypeSpec * type{arg.GetType()}) {
1867     if (const DerivedTypeSpec * derivedType{type->AsDerived()}) {
1868       CheckAlreadySeenDefinedIo(derivedType, ioKind, subp);
1869       bool isPolymorphic{type->IsPolymorphic()};
1870       if (isPolymorphic != IsExtensibleType(derivedType)) {
1871         messages_.Say(arg.name(),
1872             "Dummy argument '%s' of a defined input/output procedure must be %s when the derived type is %s"_err_en_US,
1873             arg.name(), isPolymorphic ? "TYPE()" : "CLASS()",
1874             isPolymorphic ? "not extensible" : "extensible");
1875       }
1876     } else {
1877       messages_.Say(arg.name(),
1878           "Dummy argument '%s' of a defined input/output procedure must have a"
1879           " derived type"_err_en_US,
1880           arg.name());
1881     }
1882   }
1883 }
1884 
1885 void CheckHelper::CheckDioDummyIsDefaultInteger(
1886     const Symbol &subp, const Symbol &arg) {
1887   if (const DeclTypeSpec * type{arg.GetType()};
1888       type && type->IsNumeric(TypeCategory::Integer)) {
1889     if (const auto kind{evaluate::ToInt64(type->numericTypeSpec().kind())};
1890         kind && *kind == context_.GetDefaultKind(TypeCategory::Integer)) {
1891       return;
1892     }
1893   }
1894   messages_.Say(arg.name(),
1895       "Dummy argument '%s' of a defined input/output procedure"
1896       " must be an INTEGER of default KIND"_err_en_US,
1897       arg.name());
1898 }
1899 
1900 void CheckHelper::CheckDioDummyIsScalar(const Symbol &subp, const Symbol &arg) {
1901   if (arg.Rank() > 0 || arg.Corank() > 0) {
1902     messages_.Say(arg.name(),
1903         "Dummy argument '%s' of a defined input/output procedure"
1904         " must be a scalar"_err_en_US,
1905         arg.name());
1906   }
1907 }
1908 
1909 void CheckHelper::CheckDioDtvArg(
1910     const Symbol &subp, const Symbol *arg, GenericKind::DefinedIo ioKind) {
1911   // Dtv argument looks like: dtv-type-spec, INTENT(INOUT) :: dtv
1912   if (CheckDioDummyIsData(subp, arg, 0)) {
1913     CheckDioDummyIsDerived(subp, *arg, ioKind);
1914     CheckDioDummyAttrs(subp, *arg,
1915         ioKind == GenericKind::DefinedIo::ReadFormatted ||
1916                 ioKind == GenericKind::DefinedIo::ReadUnformatted
1917             ? Attr::INTENT_INOUT
1918             : Attr::INTENT_IN);
1919   }
1920 }
1921 
1922 void CheckHelper::CheckDefaultIntegerArg(
1923     const Symbol &subp, const Symbol *arg, Attr intent) {
1924   // Argument looks like: INTEGER, INTENT(intent) :: arg
1925   if (CheckDioDummyIsData(subp, arg, 1)) {
1926     CheckDioDummyIsDefaultInteger(subp, *arg);
1927     CheckDioDummyIsScalar(subp, *arg);
1928     CheckDioDummyAttrs(subp, *arg, intent);
1929   }
1930 }
1931 
1932 void CheckHelper::CheckDioAssumedLenCharacterArg(const Symbol &subp,
1933     const Symbol *arg, std::size_t argPosition, Attr intent) {
1934   // Argument looks like: CHARACTER (LEN=*), INTENT(intent) :: (iotype OR iomsg)
1935   if (CheckDioDummyIsData(subp, arg, argPosition)) {
1936     CheckDioDummyAttrs(subp, *arg, intent);
1937     if (!IsAssumedLengthCharacter(*arg)) {
1938       messages_.Say(arg->name(),
1939           "Dummy argument '%s' of a defined input/output procedure"
1940           " must be assumed-length CHARACTER"_err_en_US,
1941           arg->name());
1942     }
1943   }
1944 }
1945 
1946 void CheckHelper::CheckDioVlistArg(
1947     const Symbol &subp, const Symbol *arg, std::size_t argPosition) {
1948   // Vlist argument looks like: INTEGER, INTENT(IN) :: v_list(:)
1949   if (CheckDioDummyIsData(subp, arg, argPosition)) {
1950     CheckDioDummyIsDefaultInteger(subp, *arg);
1951     CheckDioDummyAttrs(subp, *arg, Attr::INTENT_IN);
1952     if (const auto *objectDetails{arg->detailsIf<ObjectEntityDetails>()}) {
1953       if (objectDetails->shape().IsDeferredShape()) {
1954         return;
1955       }
1956     }
1957     messages_.Say(arg->name(),
1958         "Dummy argument '%s' of a defined input/output procedure must be"
1959         " deferred shape"_err_en_US,
1960         arg->name());
1961   }
1962 }
1963 
1964 void CheckHelper::CheckDioArgCount(
1965     const Symbol &subp, GenericKind::DefinedIo ioKind, std::size_t argCount) {
1966   const std::size_t requiredArgCount{
1967       (std::size_t)(ioKind == GenericKind::DefinedIo::ReadFormatted ||
1968                   ioKind == GenericKind::DefinedIo::WriteFormatted
1969               ? 6
1970               : 4)};
1971   if (argCount != requiredArgCount) {
1972     SayWithDeclaration(subp,
1973         "Defined input/output procedure '%s' must have"
1974         " %d dummy arguments rather than %d"_err_en_US,
1975         subp.name(), requiredArgCount, argCount);
1976     context_.SetError(subp);
1977   }
1978 }
1979 
1980 void CheckHelper::CheckDioDummyAttrs(
1981     const Symbol &subp, const Symbol &arg, Attr goodIntent) {
1982   // Defined I/O procedures can't have attributes other than INTENT
1983   Attrs attrs{arg.attrs()};
1984   if (!attrs.test(goodIntent)) {
1985     messages_.Say(arg.name(),
1986         "Dummy argument '%s' of a defined input/output procedure"
1987         " must have intent '%s'"_err_en_US,
1988         arg.name(), AttrToString(goodIntent));
1989   }
1990   attrs = attrs - Attr::INTENT_IN - Attr::INTENT_OUT - Attr::INTENT_INOUT;
1991   if (!attrs.empty()) {
1992     messages_.Say(arg.name(),
1993         "Dummy argument '%s' of a defined input/output procedure may not have"
1994         " any attributes"_err_en_US,
1995         arg.name());
1996   }
1997 }
1998 
1999 // Enforce semantics for defined input/output procedures (12.6.4.8.2) and C777
2000 void CheckHelper::CheckDefinedIoProc(const Symbol &symbol,
2001     const GenericDetails &details, GenericKind::DefinedIo ioKind) {
2002   for (auto ref : details.specificProcs()) {
2003     const auto *binding{ref->detailsIf<ProcBindingDetails>()};
2004     const Symbol &specific{*(binding ? &binding->symbol() : &*ref)};
2005     if (ref->attrs().test(Attr::NOPASS)) { // C774
2006       messages_.Say("Defined input/output procedure '%s' may not have NOPASS "
2007                     "attribute"_err_en_US,
2008           ref->name());
2009       context_.SetError(*ref);
2010     }
2011     if (const auto *subpDetails{specific.detailsIf<SubprogramDetails>()}) {
2012       const std::vector<Symbol *> &dummyArgs{subpDetails->dummyArgs()};
2013       CheckDioArgCount(specific, ioKind, dummyArgs.size());
2014       int argCount{0};
2015       for (auto *arg : dummyArgs) {
2016         switch (argCount++) {
2017         case 0:
2018           // dtv-type-spec, INTENT(INOUT) :: dtv
2019           CheckDioDtvArg(specific, arg, ioKind);
2020           break;
2021         case 1:
2022           // INTEGER, INTENT(IN) :: unit
2023           CheckDefaultIntegerArg(specific, arg, Attr::INTENT_IN);
2024           break;
2025         case 2:
2026           if (ioKind == GenericKind::DefinedIo::ReadFormatted ||
2027               ioKind == GenericKind::DefinedIo::WriteFormatted) {
2028             // CHARACTER (LEN=*), INTENT(IN) :: iotype
2029             CheckDioAssumedLenCharacterArg(
2030                 specific, arg, argCount, Attr::INTENT_IN);
2031           } else {
2032             // INTEGER, INTENT(OUT) :: iostat
2033             CheckDefaultIntegerArg(specific, arg, Attr::INTENT_OUT);
2034           }
2035           break;
2036         case 3:
2037           if (ioKind == GenericKind::DefinedIo::ReadFormatted ||
2038               ioKind == GenericKind::DefinedIo::WriteFormatted) {
2039             // INTEGER, INTENT(IN) :: v_list(:)
2040             CheckDioVlistArg(specific, arg, argCount);
2041           } else {
2042             // CHARACTER (LEN=*), INTENT(INOUT) :: iomsg
2043             CheckDioAssumedLenCharacterArg(
2044                 specific, arg, argCount, Attr::INTENT_INOUT);
2045           }
2046           break;
2047         case 4:
2048           // INTEGER, INTENT(OUT) :: iostat
2049           CheckDefaultIntegerArg(specific, arg, Attr::INTENT_OUT);
2050           break;
2051         case 5:
2052           // CHARACTER (LEN=*), INTENT(INOUT) :: iomsg
2053           CheckDioAssumedLenCharacterArg(
2054               specific, arg, argCount, Attr::INTENT_INOUT);
2055           break;
2056         default:;
2057         }
2058       }
2059     }
2060   }
2061 }
2062 
2063 void SubprogramMatchHelper::Check(
2064     const Symbol &symbol1, const Symbol &symbol2) {
2065   const auto details1{symbol1.get<SubprogramDetails>()};
2066   const auto details2{symbol2.get<SubprogramDetails>()};
2067   if (details1.isFunction() != details2.isFunction()) {
2068     Say(symbol1, symbol2,
2069         details1.isFunction()
2070             ? "Module function '%s' was declared as a subroutine in the"
2071               " corresponding interface body"_err_en_US
2072             : "Module subroutine '%s' was declared as a function in the"
2073               " corresponding interface body"_err_en_US);
2074     return;
2075   }
2076   const auto &args1{details1.dummyArgs()};
2077   const auto &args2{details2.dummyArgs()};
2078   int nargs1{static_cast<int>(args1.size())};
2079   int nargs2{static_cast<int>(args2.size())};
2080   if (nargs1 != nargs2) {
2081     Say(symbol1, symbol2,
2082         "Module subprogram '%s' has %d args but the corresponding interface"
2083         " body has %d"_err_en_US,
2084         nargs1, nargs2);
2085     return;
2086   }
2087   bool nonRecursive1{symbol1.attrs().test(Attr::NON_RECURSIVE)};
2088   if (nonRecursive1 != symbol2.attrs().test(Attr::NON_RECURSIVE)) { // C1551
2089     Say(symbol1, symbol2,
2090         nonRecursive1
2091             ? "Module subprogram '%s' has NON_RECURSIVE prefix but"
2092               " the corresponding interface body does not"_err_en_US
2093             : "Module subprogram '%s' does not have NON_RECURSIVE prefix but "
2094               "the corresponding interface body does"_err_en_US);
2095   }
2096   const std::string *bindName1{details1.bindName()};
2097   const std::string *bindName2{details2.bindName()};
2098   if (!bindName1 && !bindName2) {
2099     // OK - neither has a binding label
2100   } else if (!bindName1) {
2101     Say(symbol1, symbol2,
2102         "Module subprogram '%s' does not have a binding label but the"
2103         " corresponding interface body does"_err_en_US);
2104   } else if (!bindName2) {
2105     Say(symbol1, symbol2,
2106         "Module subprogram '%s' has a binding label but the"
2107         " corresponding interface body does not"_err_en_US);
2108   } else if (*bindName1 != *bindName2) {
2109     Say(symbol1, symbol2,
2110         "Module subprogram '%s' has binding label '%s' but the corresponding"
2111         " interface body has '%s'"_err_en_US,
2112         *details1.bindName(), *details2.bindName());
2113   }
2114   const Procedure *proc1{checkHelper.Characterize(symbol1)};
2115   const Procedure *proc2{checkHelper.Characterize(symbol2)};
2116   if (!proc1 || !proc2) {
2117     return;
2118   }
2119   if (proc1->functionResult && proc2->functionResult &&
2120       *proc1->functionResult != *proc2->functionResult) {
2121     Say(symbol1, symbol2,
2122         "Return type of function '%s' does not match return type of"
2123         " the corresponding interface body"_err_en_US);
2124   }
2125   for (int i{0}; i < nargs1; ++i) {
2126     const Symbol *arg1{args1[i]};
2127     const Symbol *arg2{args2[i]};
2128     if (arg1 && !arg2) {
2129       Say(symbol1, symbol2,
2130           "Dummy argument %2$d of '%1$s' is not an alternate return indicator"
2131           " but the corresponding argument in the interface body is"_err_en_US,
2132           i + 1);
2133     } else if (!arg1 && arg2) {
2134       Say(symbol1, symbol2,
2135           "Dummy argument %2$d of '%1$s' is an alternate return indicator but"
2136           " the corresponding argument in the interface body is not"_err_en_US,
2137           i + 1);
2138     } else if (arg1 && arg2) {
2139       SourceName name1{arg1->name()};
2140       SourceName name2{arg2->name()};
2141       if (name1 != name2) {
2142         Say(*arg1, *arg2,
2143             "Dummy argument name '%s' does not match corresponding name '%s'"
2144             " in interface body"_err_en_US,
2145             name2);
2146       } else {
2147         CheckDummyArg(
2148             *arg1, *arg2, proc1->dummyArguments[i], proc2->dummyArguments[i]);
2149       }
2150     }
2151   }
2152 }
2153 
2154 void SubprogramMatchHelper::CheckDummyArg(const Symbol &symbol1,
2155     const Symbol &symbol2, const DummyArgument &arg1,
2156     const DummyArgument &arg2) {
2157   std::visit(common::visitors{
2158                  [&](const DummyDataObject &obj1, const DummyDataObject &obj2) {
2159                    CheckDummyDataObject(symbol1, symbol2, obj1, obj2);
2160                  },
2161                  [&](const DummyProcedure &proc1, const DummyProcedure &proc2) {
2162                    CheckDummyProcedure(symbol1, symbol2, proc1, proc2);
2163                  },
2164                  [&](const DummyDataObject &, const auto &) {
2165                    Say(symbol1, symbol2,
2166                        "Dummy argument '%s' is a data object; the corresponding"
2167                        " argument in the interface body is not"_err_en_US);
2168                  },
2169                  [&](const DummyProcedure &, const auto &) {
2170                    Say(symbol1, symbol2,
2171                        "Dummy argument '%s' is a procedure; the corresponding"
2172                        " argument in the interface body is not"_err_en_US);
2173                  },
2174                  [&](const auto &, const auto &) {
2175                    llvm_unreachable("Dummy arguments are not data objects or"
2176                                     "procedures");
2177                  },
2178              },
2179       arg1.u, arg2.u);
2180 }
2181 
2182 void SubprogramMatchHelper::CheckDummyDataObject(const Symbol &symbol1,
2183     const Symbol &symbol2, const DummyDataObject &obj1,
2184     const DummyDataObject &obj2) {
2185   if (!CheckSameIntent(symbol1, symbol2, obj1.intent, obj2.intent)) {
2186   } else if (!CheckSameAttrs(symbol1, symbol2, obj1.attrs, obj2.attrs)) {
2187   } else if (obj1.type.type() != obj2.type.type()) {
2188     Say(symbol1, symbol2,
2189         "Dummy argument '%s' has type %s; the corresponding argument in the"
2190         " interface body has type %s"_err_en_US,
2191         obj1.type.type().AsFortran(), obj2.type.type().AsFortran());
2192   } else if (!ShapesAreCompatible(obj1, obj2)) {
2193     Say(symbol1, symbol2,
2194         "The shape of dummy argument '%s' does not match the shape of the"
2195         " corresponding argument in the interface body"_err_en_US);
2196   }
2197   // TODO: coshape
2198 }
2199 
2200 void SubprogramMatchHelper::CheckDummyProcedure(const Symbol &symbol1,
2201     const Symbol &symbol2, const DummyProcedure &proc1,
2202     const DummyProcedure &proc2) {
2203   if (!CheckSameIntent(symbol1, symbol2, proc1.intent, proc2.intent)) {
2204   } else if (!CheckSameAttrs(symbol1, symbol2, proc1.attrs, proc2.attrs)) {
2205   } else if (proc1 != proc2) {
2206     Say(symbol1, symbol2,
2207         "Dummy procedure '%s' does not match the corresponding argument in"
2208         " the interface body"_err_en_US);
2209   }
2210 }
2211 
2212 bool SubprogramMatchHelper::CheckSameIntent(const Symbol &symbol1,
2213     const Symbol &symbol2, common::Intent intent1, common::Intent intent2) {
2214   if (intent1 == intent2) {
2215     return true;
2216   } else {
2217     Say(symbol1, symbol2,
2218         "The intent of dummy argument '%s' does not match the intent"
2219         " of the corresponding argument in the interface body"_err_en_US);
2220     return false;
2221   }
2222 }
2223 
2224 // Report an error referring to first symbol with declaration of second symbol
2225 template <typename... A>
2226 void SubprogramMatchHelper::Say(const Symbol &symbol1, const Symbol &symbol2,
2227     parser::MessageFixedText &&text, A &&...args) {
2228   auto &message{context().Say(symbol1.name(), std::move(text), symbol1.name(),
2229       std::forward<A>(args)...)};
2230   evaluate::AttachDeclaration(message, symbol2);
2231 }
2232 
2233 template <typename ATTRS>
2234 bool SubprogramMatchHelper::CheckSameAttrs(
2235     const Symbol &symbol1, const Symbol &symbol2, ATTRS attrs1, ATTRS attrs2) {
2236   if (attrs1 == attrs2) {
2237     return true;
2238   }
2239   attrs1.IterateOverMembers([&](auto attr) {
2240     if (!attrs2.test(attr)) {
2241       Say(symbol1, symbol2,
2242           "Dummy argument '%s' has the %s attribute; the corresponding"
2243           " argument in the interface body does not"_err_en_US,
2244           AsFortran(attr));
2245     }
2246   });
2247   attrs2.IterateOverMembers([&](auto attr) {
2248     if (!attrs1.test(attr)) {
2249       Say(symbol1, symbol2,
2250           "Dummy argument '%s' does not have the %s attribute; the"
2251           " corresponding argument in the interface body does"_err_en_US,
2252           AsFortran(attr));
2253     }
2254   });
2255   return false;
2256 }
2257 
2258 bool SubprogramMatchHelper::ShapesAreCompatible(
2259     const DummyDataObject &obj1, const DummyDataObject &obj2) {
2260   return characteristics::ShapesAreCompatible(
2261       FoldShape(obj1.type.shape()), FoldShape(obj2.type.shape()));
2262 }
2263 
2264 evaluate::Shape SubprogramMatchHelper::FoldShape(const evaluate::Shape &shape) {
2265   evaluate::Shape result;
2266   for (const auto &extent : shape) {
2267     result.emplace_back(
2268         evaluate::Fold(context().foldingContext(), common::Clone(extent)));
2269   }
2270   return result;
2271 }
2272 
2273 void DistinguishabilityHelper::Add(const Symbol &generic, GenericKind kind,
2274     const Symbol &specific, const Procedure &procedure) {
2275   if (!context_.HasError(specific)) {
2276     nameToInfo_[generic.name()].emplace_back(
2277         ProcedureInfo{kind, specific, procedure});
2278   }
2279 }
2280 
2281 void DistinguishabilityHelper::Check(const Scope &scope) {
2282   for (const auto &[name, info] : nameToInfo_) {
2283     auto count{info.size()};
2284     for (std::size_t i1{0}; i1 < count - 1; ++i1) {
2285       const auto &[kind, symbol, proc]{info[i1]};
2286       for (std::size_t i2{i1 + 1}; i2 < count; ++i2) {
2287         auto distinguishable{kind.IsName()
2288                 ? evaluate::characteristics::Distinguishable
2289                 : evaluate::characteristics::DistinguishableOpOrAssign};
2290         if (!distinguishable(proc, info[i2].procedure)) {
2291           SayNotDistinguishable(GetTopLevelUnitContaining(scope), name, kind,
2292               symbol, info[i2].symbol);
2293         }
2294       }
2295     }
2296   }
2297 }
2298 
2299 void DistinguishabilityHelper::SayNotDistinguishable(const Scope &scope,
2300     const SourceName &name, GenericKind kind, const Symbol &proc1,
2301     const Symbol &proc2) {
2302   std::string name1{proc1.name().ToString()};
2303   std::string name2{proc2.name().ToString()};
2304   if (kind.IsOperator() || kind.IsAssignment()) {
2305     // proc1 and proc2 may come from different scopes so qualify their names
2306     if (proc1.owner().IsDerivedType()) {
2307       name1 = proc1.owner().GetName()->ToString() + '%' + name1;
2308     }
2309     if (proc2.owner().IsDerivedType()) {
2310       name2 = proc2.owner().GetName()->ToString() + '%' + name2;
2311     }
2312   }
2313   parser::Message *msg;
2314   if (scope.sourceRange().Contains(name)) {
2315     msg = &context_.Say(name,
2316         "Generic '%s' may not have specific procedures '%s' and"
2317         " '%s' as their interfaces are not distinguishable"_err_en_US,
2318         MakeOpName(name), name1, name2);
2319   } else {
2320     msg = &context_.Say(*GetTopLevelUnitContaining(proc1).GetName(),
2321         "USE-associated generic '%s' may not have specific procedures '%s' "
2322         "and"
2323         " '%s' as their interfaces are not distinguishable"_err_en_US,
2324         MakeOpName(name), name1, name2);
2325   }
2326   AttachDeclaration(*msg, scope, proc1);
2327   AttachDeclaration(*msg, scope, proc2);
2328 }
2329 
2330 // `evaluate::AttachDeclaration` doesn't handle the generic case where `proc`
2331 // comes from a different module but is not necessarily use-associated.
2332 void DistinguishabilityHelper::AttachDeclaration(
2333     parser::Message &msg, const Scope &scope, const Symbol &proc) {
2334   const Scope &unit{GetTopLevelUnitContaining(proc)};
2335   if (unit == scope) {
2336     evaluate::AttachDeclaration(msg, proc);
2337   } else {
2338     msg.Attach(unit.GetName().value(),
2339         "'%s' is USE-associated from module '%s'"_en_US, proc.name(),
2340         unit.GetName().value());
2341   }
2342 }
2343 
2344 void CheckDeclarations(SemanticsContext &context) {
2345   CheckHelper{context}.Check();
2346 }
2347 } // namespace Fortran::semantics
2348