1 //===-- lib/Evaluate/characteristics.cpp ----------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "flang/Evaluate/characteristics.h"
10 #include "flang/Common/indirection.h"
11 #include "flang/Evaluate/check-expression.h"
12 #include "flang/Evaluate/fold.h"
13 #include "flang/Evaluate/intrinsics.h"
14 #include "flang/Evaluate/tools.h"
15 #include "flang/Evaluate/type.h"
16 #include "flang/Parser/message.h"
17 #include "flang/Semantics/scope.h"
18 #include "flang/Semantics/symbol.h"
19 #include "llvm/Support/raw_ostream.h"
20 #include <initializer_list>
21 
22 using namespace Fortran::parser::literals;
23 
24 namespace Fortran::evaluate::characteristics {
25 
26 // Copy attributes from a symbol to dst based on the mapping in pairs.
27 template <typename A, typename B>
28 static void CopyAttrs(const semantics::Symbol &src, A &dst,
29     const std::initializer_list<std::pair<semantics::Attr, B>> &pairs) {
30   for (const auto &pair : pairs) {
31     if (src.attrs().test(pair.first)) {
32       dst.attrs.set(pair.second);
33     }
34   }
35 }
36 
37 // Shapes of function results and dummy arguments have to have
38 // the same rank, the same deferred dimensions, and the same
39 // values for explicit dimensions when constant.
40 bool ShapesAreCompatible(const Shape &x, const Shape &y) {
41   if (x.size() != y.size()) {
42     return false;
43   }
44   auto yIter{y.begin()};
45   for (const auto &xDim : x) {
46     const auto &yDim{*yIter++};
47     if (xDim) {
48       if (!yDim || ToInt64(*xDim) != ToInt64(*yDim)) {
49         return false;
50       }
51     } else if (yDim) {
52       return false;
53     }
54   }
55   return true;
56 }
57 
58 bool TypeAndShape::operator==(const TypeAndShape &that) const {
59   return type_ == that.type_ && ShapesAreCompatible(shape_, that.shape_) &&
60       attrs_ == that.attrs_ && corank_ == that.corank_;
61 }
62 
63 TypeAndShape &TypeAndShape::Rewrite(FoldingContext &context) {
64   LEN_ = Fold(context, std::move(LEN_));
65   shape_ = Fold(context, std::move(shape_));
66   return *this;
67 }
68 
69 std::optional<TypeAndShape> TypeAndShape::Characterize(
70     const semantics::Symbol &symbol, FoldingContext &context) {
71   const auto &ultimate{symbol.GetUltimate()};
72   return std::visit(
73       common::visitors{
74           [&](const semantics::ProcEntityDetails &proc) {
75             const semantics::ProcInterface &interface{proc.interface()};
76             if (interface.type()) {
77               return Characterize(*interface.type(), context);
78             } else if (interface.symbol()) {
79               return Characterize(*interface.symbol(), context);
80             } else {
81               return std::optional<TypeAndShape>{};
82             }
83           },
84           [&](const semantics::AssocEntityDetails &assoc) {
85             return Characterize(assoc, context);
86           },
87           [&](const semantics::ProcBindingDetails &binding) {
88             return Characterize(binding.symbol(), context);
89           },
90           [&](const auto &x) -> std::optional<TypeAndShape> {
91             using Ty = std::decay_t<decltype(x)>;
92             if constexpr (std::is_same_v<Ty, semantics::EntityDetails> ||
93                 std::is_same_v<Ty, semantics::ObjectEntityDetails> ||
94                 std::is_same_v<Ty, semantics::TypeParamDetails>) {
95               if (const semantics::DeclTypeSpec * type{ultimate.GetType()}) {
96                 if (auto dyType{DynamicType::From(*type)}) {
97                   TypeAndShape result{
98                       std::move(*dyType), GetShape(context, ultimate)};
99                   result.AcquireAttrs(ultimate);
100                   result.AcquireLEN(ultimate);
101                   return std::move(result.Rewrite(context));
102                 }
103               }
104             }
105             return std::nullopt;
106           },
107       },
108       // GetUltimate() used here, not ResolveAssociations(), because
109       // we need the type/rank of an associate entity from TYPE IS,
110       // CLASS IS, or RANK statement.
111       ultimate.details());
112 }
113 
114 std::optional<TypeAndShape> TypeAndShape::Characterize(
115     const semantics::AssocEntityDetails &assoc, FoldingContext &context) {
116   std::optional<TypeAndShape> result;
117   if (auto type{DynamicType::From(assoc.type())}) {
118     if (auto rank{assoc.rank()}) {
119       if (*rank >= 0 && *rank <= common::maxRank) {
120         result = TypeAndShape{std::move(*type), Shape(*rank)};
121       }
122     } else if (auto shape{GetShape(context, assoc.expr())}) {
123       result = TypeAndShape{std::move(*type), std::move(*shape)};
124     }
125     if (result && type->category() == TypeCategory::Character) {
126       if (const auto *chExpr{UnwrapExpr<Expr<SomeCharacter>>(assoc.expr())}) {
127         if (auto len{chExpr->LEN()}) {
128           result->set_LEN(std::move(*len));
129         }
130       }
131     }
132   }
133   return Fold(context, std::move(result));
134 }
135 
136 std::optional<TypeAndShape> TypeAndShape::Characterize(
137     const semantics::DeclTypeSpec &spec, FoldingContext &context) {
138   if (auto type{DynamicType::From(spec)}) {
139     return Fold(context, TypeAndShape{std::move(*type)});
140   } else {
141     return std::nullopt;
142   }
143 }
144 
145 std::optional<TypeAndShape> TypeAndShape::Characterize(
146     const ActualArgument &arg, FoldingContext &context) {
147   return Characterize(arg.UnwrapExpr(), context);
148 }
149 
150 bool TypeAndShape::IsCompatibleWith(parser::ContextualMessages &messages,
151     const TypeAndShape &that, const char *thisIs, const char *thatIs,
152     bool isElemental, enum CheckConformanceFlags::Flags flags) const {
153   if (!type_.IsTkCompatibleWith(that.type_)) {
154     messages.Say(
155         "%1$s type '%2$s' is not compatible with %3$s type '%4$s'"_err_en_US,
156         thatIs, that.AsFortran(), thisIs, AsFortran());
157     return false;
158   }
159   return isElemental ||
160       CheckConformance(messages, shape_, that.shape_, flags, thisIs, thatIs)
161           .value_or(true /*fail only when nonconformance is known now*/);
162 }
163 
164 std::optional<Expr<SubscriptInteger>> TypeAndShape::MeasureElementSizeInBytes(
165     FoldingContext &foldingContext, bool align) const {
166   if (LEN_) {
167     CHECK(type_.category() == TypeCategory::Character);
168     return Fold(foldingContext,
169         Expr<SubscriptInteger>{type_.kind()} * Expr<SubscriptInteger>{*LEN_});
170   }
171   if (auto elementBytes{type_.MeasureSizeInBytes(foldingContext, align)}) {
172     return Fold(foldingContext, std::move(*elementBytes));
173   }
174   return std::nullopt;
175 }
176 
177 std::optional<Expr<SubscriptInteger>> TypeAndShape::MeasureSizeInBytes(
178     FoldingContext &foldingContext) const {
179   if (auto elements{GetSize(Shape{shape_})}) {
180     // Sizes of arrays (even with single elements) are multiples of
181     // their alignments.
182     if (auto elementBytes{
183             MeasureElementSizeInBytes(foldingContext, GetRank(shape_) > 0)}) {
184       return Fold(
185           foldingContext, std::move(*elements) * std::move(*elementBytes));
186     }
187   }
188   return std::nullopt;
189 }
190 
191 void TypeAndShape::AcquireAttrs(const semantics::Symbol &symbol) {
192   if (const auto *object{
193           symbol.GetUltimate().detailsIf<semantics::ObjectEntityDetails>()}) {
194     corank_ = object->coshape().Rank();
195     if (object->IsAssumedRank()) {
196       attrs_.set(Attr::AssumedRank);
197     }
198     if (object->IsAssumedShape()) {
199       attrs_.set(Attr::AssumedShape);
200     }
201     if (object->IsAssumedSize()) {
202       attrs_.set(Attr::AssumedSize);
203     }
204     if (object->IsDeferredShape()) {
205       attrs_.set(Attr::DeferredShape);
206     }
207     if (object->IsCoarray()) {
208       attrs_.set(Attr::Coarray);
209     }
210   }
211 }
212 
213 void TypeAndShape::AcquireLEN() {
214   if (auto len{type_.GetCharLength()}) {
215     LEN_ = std::move(len);
216   }
217 }
218 
219 void TypeAndShape::AcquireLEN(const semantics::Symbol &symbol) {
220   if (type_.category() == TypeCategory::Character) {
221     if (auto len{DataRef{symbol}.LEN()}) {
222       LEN_ = std::move(*len);
223     }
224   }
225 }
226 
227 std::string TypeAndShape::AsFortran() const {
228   return type_.AsFortran(LEN_ ? LEN_->AsFortran() : "");
229 }
230 
231 llvm::raw_ostream &TypeAndShape::Dump(llvm::raw_ostream &o) const {
232   o << type_.AsFortran(LEN_ ? LEN_->AsFortran() : "");
233   attrs_.Dump(o, EnumToString);
234   if (!shape_.empty()) {
235     o << " dimension";
236     char sep{'('};
237     for (const auto &expr : shape_) {
238       o << sep;
239       sep = ',';
240       if (expr) {
241         expr->AsFortran(o);
242       } else {
243         o << ':';
244       }
245     }
246     o << ')';
247   }
248   return o;
249 }
250 
251 bool DummyDataObject::operator==(const DummyDataObject &that) const {
252   return type == that.type && attrs == that.attrs && intent == that.intent &&
253       coshape == that.coshape;
254 }
255 
256 static common::Intent GetIntent(const semantics::Attrs &attrs) {
257   if (attrs.test(semantics::Attr::INTENT_IN)) {
258     return common::Intent::In;
259   } else if (attrs.test(semantics::Attr::INTENT_OUT)) {
260     return common::Intent::Out;
261   } else if (attrs.test(semantics::Attr::INTENT_INOUT)) {
262     return common::Intent::InOut;
263   } else {
264     return common::Intent::Default;
265   }
266 }
267 
268 std::optional<DummyDataObject> DummyDataObject::Characterize(
269     const semantics::Symbol &symbol, FoldingContext &context) {
270   if (symbol.has<semantics::ObjectEntityDetails>() ||
271       symbol.has<semantics::EntityDetails>()) {
272     if (auto type{TypeAndShape::Characterize(symbol, context)}) {
273       std::optional<DummyDataObject> result{std::move(*type)};
274       using semantics::Attr;
275       CopyAttrs<DummyDataObject, DummyDataObject::Attr>(symbol, *result,
276           {
277               {Attr::OPTIONAL, DummyDataObject::Attr::Optional},
278               {Attr::ALLOCATABLE, DummyDataObject::Attr::Allocatable},
279               {Attr::ASYNCHRONOUS, DummyDataObject::Attr::Asynchronous},
280               {Attr::CONTIGUOUS, DummyDataObject::Attr::Contiguous},
281               {Attr::VALUE, DummyDataObject::Attr::Value},
282               {Attr::VOLATILE, DummyDataObject::Attr::Volatile},
283               {Attr::POINTER, DummyDataObject::Attr::Pointer},
284               {Attr::TARGET, DummyDataObject::Attr::Target},
285           });
286       result->intent = GetIntent(symbol.attrs());
287       return result;
288     }
289   }
290   return std::nullopt;
291 }
292 
293 bool DummyDataObject::CanBePassedViaImplicitInterface() const {
294   if ((attrs &
295           Attrs{Attr::Allocatable, Attr::Asynchronous, Attr::Optional,
296               Attr::Pointer, Attr::Target, Attr::Value, Attr::Volatile})
297           .any()) {
298     return false; // 15.4.2.2(3)(a)
299   } else if ((type.attrs() &
300                  TypeAndShape::Attrs{TypeAndShape::Attr::AssumedShape,
301                      TypeAndShape::Attr::AssumedRank,
302                      TypeAndShape::Attr::Coarray})
303                  .any()) {
304     return false; // 15.4.2.2(3)(b-d)
305   } else if (type.type().IsPolymorphic()) {
306     return false; // 15.4.2.2(3)(f)
307   } else if (const auto *derived{GetDerivedTypeSpec(type.type())}) {
308     return derived->parameters().empty(); // 15.4.2.2(3)(e)
309   } else {
310     return true;
311   }
312 }
313 
314 llvm::raw_ostream &DummyDataObject::Dump(llvm::raw_ostream &o) const {
315   attrs.Dump(o, EnumToString);
316   if (intent != common::Intent::Default) {
317     o << "INTENT(" << common::EnumToString(intent) << ')';
318   }
319   type.Dump(o);
320   if (!coshape.empty()) {
321     char sep{'['};
322     for (const auto &expr : coshape) {
323       expr.AsFortran(o << sep);
324       sep = ',';
325     }
326   }
327   return o;
328 }
329 
330 DummyProcedure::DummyProcedure(Procedure &&p)
331     : procedure{new Procedure{std::move(p)}} {}
332 
333 bool DummyProcedure::operator==(const DummyProcedure &that) const {
334   return attrs == that.attrs && intent == that.intent &&
335       procedure.value() == that.procedure.value();
336 }
337 
338 static std::string GetSeenProcs(
339     const semantics::UnorderedSymbolSet &seenProcs) {
340   // Sort the symbols so that they appear in the same order on all platforms
341   auto ordered{semantics::OrderBySourcePosition(seenProcs)};
342   std::string result;
343   llvm::interleave(
344       ordered,
345       [&](const SymbolRef p) { result += '\'' + p->name().ToString() + '\''; },
346       [&]() { result += ", "; });
347   return result;
348 }
349 
350 // These functions with arguments of type UnorderedSymbolSet are used with
351 // mutually recursive calls when characterizing a Procedure, a DummyArgument,
352 // or a DummyProcedure to detect circularly defined procedures as required by
353 // 15.4.3.6, paragraph 2.
354 static std::optional<DummyArgument> CharacterizeDummyArgument(
355     const semantics::Symbol &symbol, FoldingContext &context,
356     semantics::UnorderedSymbolSet &seenProcs);
357 
358 static std::optional<Procedure> CharacterizeProcedure(
359     const semantics::Symbol &original, FoldingContext &context,
360     semantics::UnorderedSymbolSet &seenProcs) {
361   Procedure result;
362   const auto &symbol{ResolveAssociations(original)};
363   if (seenProcs.find(symbol) != seenProcs.end()) {
364     std::string procsList{GetSeenProcs(seenProcs)};
365     context.messages().Say(symbol.name(),
366         "Procedure '%s' is recursively defined.  Procedures in the cycle:"
367         " %s"_err_en_US,
368         symbol.name(), procsList);
369     return std::nullopt;
370   }
371   seenProcs.insert(symbol);
372   CopyAttrs<Procedure, Procedure::Attr>(symbol, result,
373       {
374           {semantics::Attr::PURE, Procedure::Attr::Pure},
375           {semantics::Attr::ELEMENTAL, Procedure::Attr::Elemental},
376           {semantics::Attr::BIND_C, Procedure::Attr::BindC},
377       });
378   if (result.attrs.test(Procedure::Attr::Elemental) &&
379       !symbol.attrs().test(semantics::Attr::IMPURE)) {
380     result.attrs.set(Procedure::Attr::Pure); // explicitly flag pure procedures
381   }
382   return std::visit(
383       common::visitors{
384           [&](const semantics::SubprogramDetails &subp)
385               -> std::optional<Procedure> {
386             if (subp.isFunction()) {
387               if (auto fr{
388                       FunctionResult::Characterize(subp.result(), context)}) {
389                 result.functionResult = std::move(fr);
390               } else {
391                 return std::nullopt;
392               }
393             } else {
394               result.attrs.set(Procedure::Attr::Subroutine);
395             }
396             for (const semantics::Symbol *arg : subp.dummyArgs()) {
397               if (!arg) {
398                 if (subp.isFunction()) {
399                   return std::nullopt;
400                 } else {
401                   result.dummyArguments.emplace_back(AlternateReturn{});
402                 }
403               } else if (auto argCharacteristics{CharacterizeDummyArgument(
404                              *arg, context, seenProcs)}) {
405                 result.dummyArguments.emplace_back(
406                     std::move(argCharacteristics.value()));
407               } else {
408                 return std::nullopt;
409               }
410             }
411             return result;
412           },
413           [&](const semantics::ProcEntityDetails &proc)
414               -> std::optional<Procedure> {
415             if (symbol.attrs().test(semantics::Attr::INTRINSIC)) {
416               // Fails when the intrinsic is not a specific intrinsic function
417               // from F'2018 table 16.2.  In order to handle forward references,
418               // attempts to use impermissible intrinsic procedures as the
419               // interfaces of procedure pointers are caught and flagged in
420               // declaration checking in Semantics.
421               return context.intrinsics().IsSpecificIntrinsicFunction(
422                   symbol.name().ToString());
423             }
424             const semantics::ProcInterface &interface{proc.interface()};
425             if (const semantics::Symbol * interfaceSymbol{interface.symbol()}) {
426               return CharacterizeProcedure(
427                   *interfaceSymbol, context, seenProcs);
428             } else {
429               result.attrs.set(Procedure::Attr::ImplicitInterface);
430               const semantics::DeclTypeSpec *type{interface.type()};
431               if (symbol.test(semantics::Symbol::Flag::Subroutine)) {
432                 // ignore any implicit typing
433                 result.attrs.set(Procedure::Attr::Subroutine);
434               } else if (type) {
435                 if (auto resultType{DynamicType::From(*type)}) {
436                   result.functionResult = FunctionResult{*resultType};
437                 } else {
438                   return std::nullopt;
439                 }
440               } else if (symbol.test(semantics::Symbol::Flag::Function)) {
441                 return std::nullopt;
442               }
443               // The PASS name, if any, is not a characteristic.
444               return result;
445             }
446           },
447           [&](const semantics::ProcBindingDetails &binding) {
448             if (auto result{CharacterizeProcedure(
449                     binding.symbol(), context, seenProcs)}) {
450               if (!symbol.attrs().test(semantics::Attr::NOPASS)) {
451                 auto passName{binding.passName()};
452                 for (auto &dummy : result->dummyArguments) {
453                   if (!passName || dummy.name.c_str() == *passName) {
454                     dummy.pass = true;
455                     return result;
456                   }
457                 }
458                 DIE("PASS argument missing");
459               }
460               return result;
461             } else {
462               return std::optional<Procedure>{};
463             }
464           },
465           [&](const semantics::UseDetails &use) {
466             return CharacterizeProcedure(use.symbol(), context, seenProcs);
467           },
468           [&](const semantics::HostAssocDetails &assoc) {
469             return CharacterizeProcedure(assoc.symbol(), context, seenProcs);
470           },
471           [&](const semantics::EntityDetails &) {
472             context.messages().Say(
473                 "Procedure '%s' is referenced before being sufficiently defined in a context where it must be so"_err_en_US,
474                 symbol.name());
475             return std::optional<Procedure>{};
476           },
477           [&](const semantics::SubprogramNameDetails &) {
478             context.messages().Say(
479                 "Procedure '%s' is referenced before being sufficiently defined in a context where it must be so"_err_en_US,
480                 symbol.name());
481             return std::optional<Procedure>{};
482           },
483           [&](const auto &) {
484             context.messages().Say(
485                 "'%s' is not a procedure"_err_en_US, symbol.name());
486             return std::optional<Procedure>{};
487           },
488       },
489       symbol.details());
490 }
491 
492 static std::optional<DummyProcedure> CharacterizeDummyProcedure(
493     const semantics::Symbol &symbol, FoldingContext &context,
494     semantics::UnorderedSymbolSet &seenProcs) {
495   if (auto procedure{CharacterizeProcedure(symbol, context, seenProcs)}) {
496     // Dummy procedures may not be elemental.  Elemental dummy procedure
497     // interfaces are errors when the interface is not intrinsic, and that
498     // error is caught elsewhere.  Elemental intrinsic interfaces are
499     // made non-elemental.
500     procedure->attrs.reset(Procedure::Attr::Elemental);
501     DummyProcedure result{std::move(procedure.value())};
502     CopyAttrs<DummyProcedure, DummyProcedure::Attr>(symbol, result,
503         {
504             {semantics::Attr::OPTIONAL, DummyProcedure::Attr::Optional},
505             {semantics::Attr::POINTER, DummyProcedure::Attr::Pointer},
506         });
507     result.intent = GetIntent(symbol.attrs());
508     return result;
509   } else {
510     return std::nullopt;
511   }
512 }
513 
514 llvm::raw_ostream &DummyProcedure::Dump(llvm::raw_ostream &o) const {
515   attrs.Dump(o, EnumToString);
516   if (intent != common::Intent::Default) {
517     o << "INTENT(" << common::EnumToString(intent) << ')';
518   }
519   procedure.value().Dump(o);
520   return o;
521 }
522 
523 llvm::raw_ostream &AlternateReturn::Dump(llvm::raw_ostream &o) const {
524   return o << '*';
525 }
526 
527 DummyArgument::~DummyArgument() {}
528 
529 bool DummyArgument::operator==(const DummyArgument &that) const {
530   return u == that.u; // name and passed-object usage are not characteristics
531 }
532 
533 static std::optional<DummyArgument> CharacterizeDummyArgument(
534     const semantics::Symbol &symbol, FoldingContext &context,
535     semantics::UnorderedSymbolSet &seenProcs) {
536   auto name{symbol.name().ToString()};
537   if (symbol.has<semantics::ObjectEntityDetails>() ||
538       symbol.has<semantics::EntityDetails>()) {
539     if (auto obj{DummyDataObject::Characterize(symbol, context)}) {
540       return DummyArgument{std::move(name), std::move(obj.value())};
541     }
542   } else if (auto proc{
543                  CharacterizeDummyProcedure(symbol, context, seenProcs)}) {
544     return DummyArgument{std::move(name), std::move(proc.value())};
545   }
546   return std::nullopt;
547 }
548 
549 std::optional<DummyArgument> DummyArgument::FromActual(
550     std::string &&name, const Expr<SomeType> &expr, FoldingContext &context) {
551   return std::visit(
552       common::visitors{
553           [&](const BOZLiteralConstant &) {
554             return std::make_optional<DummyArgument>(std::move(name),
555                 DummyDataObject{
556                     TypeAndShape{DynamicType::TypelessIntrinsicArgument()}});
557           },
558           [&](const NullPointer &) {
559             return std::make_optional<DummyArgument>(std::move(name),
560                 DummyDataObject{
561                     TypeAndShape{DynamicType::TypelessIntrinsicArgument()}});
562           },
563           [&](const ProcedureDesignator &designator) {
564             if (auto proc{Procedure::Characterize(designator, context)}) {
565               return std::make_optional<DummyArgument>(
566                   std::move(name), DummyProcedure{std::move(*proc)});
567             } else {
568               return std::optional<DummyArgument>{};
569             }
570           },
571           [&](const ProcedureRef &call) {
572             if (auto proc{Procedure::Characterize(call, context)}) {
573               return std::make_optional<DummyArgument>(
574                   std::move(name), DummyProcedure{std::move(*proc)});
575             } else {
576               return std::optional<DummyArgument>{};
577             }
578           },
579           [&](const auto &) {
580             if (auto type{TypeAndShape::Characterize(expr, context)}) {
581               return std::make_optional<DummyArgument>(
582                   std::move(name), DummyDataObject{std::move(*type)});
583             } else {
584               return std::optional<DummyArgument>{};
585             }
586           },
587       },
588       expr.u);
589 }
590 
591 bool DummyArgument::IsOptional() const {
592   return std::visit(
593       common::visitors{
594           [](const DummyDataObject &data) {
595             return data.attrs.test(DummyDataObject::Attr::Optional);
596           },
597           [](const DummyProcedure &proc) {
598             return proc.attrs.test(DummyProcedure::Attr::Optional);
599           },
600           [](const AlternateReturn &) { return false; },
601       },
602       u);
603 }
604 
605 void DummyArgument::SetOptional(bool value) {
606   std::visit(common::visitors{
607                  [value](DummyDataObject &data) {
608                    data.attrs.set(DummyDataObject::Attr::Optional, value);
609                  },
610                  [value](DummyProcedure &proc) {
611                    proc.attrs.set(DummyProcedure::Attr::Optional, value);
612                  },
613                  [](AlternateReturn &) { DIE("cannot set optional"); },
614              },
615       u);
616 }
617 
618 void DummyArgument::SetIntent(common::Intent intent) {
619   std::visit(common::visitors{
620                  [intent](DummyDataObject &data) { data.intent = intent; },
621                  [intent](DummyProcedure &proc) { proc.intent = intent; },
622                  [](AlternateReturn &) { DIE("cannot set intent"); },
623              },
624       u);
625 }
626 
627 common::Intent DummyArgument::GetIntent() const {
628   return std::visit(common::visitors{
629                         [](const DummyDataObject &data) { return data.intent; },
630                         [](const DummyProcedure &proc) { return proc.intent; },
631                         [](const AlternateReturn &) -> common::Intent {
632                           DIE("Alternate returns have no intent");
633                         },
634                     },
635       u);
636 }
637 
638 bool DummyArgument::CanBePassedViaImplicitInterface() const {
639   if (const auto *object{std::get_if<DummyDataObject>(&u)}) {
640     return object->CanBePassedViaImplicitInterface();
641   } else {
642     return true;
643   }
644 }
645 
646 bool DummyArgument::IsTypelessIntrinsicDummy() const {
647   const auto *argObj{std::get_if<characteristics::DummyDataObject>(&u)};
648   return argObj && argObj->type.type().IsTypelessIntrinsicArgument();
649 }
650 
651 llvm::raw_ostream &DummyArgument::Dump(llvm::raw_ostream &o) const {
652   if (!name.empty()) {
653     o << name << '=';
654   }
655   if (pass) {
656     o << " PASS";
657   }
658   std::visit([&](const auto &x) { x.Dump(o); }, u);
659   return o;
660 }
661 
662 FunctionResult::FunctionResult(DynamicType t) : u{TypeAndShape{t}} {}
663 FunctionResult::FunctionResult(TypeAndShape &&t) : u{std::move(t)} {}
664 FunctionResult::FunctionResult(Procedure &&p) : u{std::move(p)} {}
665 FunctionResult::~FunctionResult() {}
666 
667 bool FunctionResult::operator==(const FunctionResult &that) const {
668   return attrs == that.attrs && u == that.u;
669 }
670 
671 std::optional<FunctionResult> FunctionResult::Characterize(
672     const Symbol &symbol, FoldingContext &context) {
673   if (symbol.has<semantics::ObjectEntityDetails>()) {
674     if (auto type{TypeAndShape::Characterize(symbol, context)}) {
675       FunctionResult result{std::move(*type)};
676       CopyAttrs<FunctionResult, FunctionResult::Attr>(symbol, result,
677           {
678               {semantics::Attr::ALLOCATABLE, FunctionResult::Attr::Allocatable},
679               {semantics::Attr::CONTIGUOUS, FunctionResult::Attr::Contiguous},
680               {semantics::Attr::POINTER, FunctionResult::Attr::Pointer},
681           });
682       return result;
683     }
684   } else if (auto maybeProc{Procedure::Characterize(symbol, context)}) {
685     FunctionResult result{std::move(*maybeProc)};
686     result.attrs.set(FunctionResult::Attr::Pointer);
687     return result;
688   }
689   return std::nullopt;
690 }
691 
692 bool FunctionResult::IsAssumedLengthCharacter() const {
693   if (const auto *ts{std::get_if<TypeAndShape>(&u)}) {
694     return ts->type().IsAssumedLengthCharacter();
695   } else {
696     return false;
697   }
698 }
699 
700 bool FunctionResult::CanBeReturnedViaImplicitInterface() const {
701   if (attrs.test(Attr::Pointer) || attrs.test(Attr::Allocatable)) {
702     return false; // 15.4.2.2(4)(b)
703   } else if (const auto *typeAndShape{GetTypeAndShape()}) {
704     if (typeAndShape->Rank() > 0) {
705       return false; // 15.4.2.2(4)(a)
706     } else {
707       const DynamicType &type{typeAndShape->type()};
708       switch (type.category()) {
709       case TypeCategory::Character:
710         if (type.knownLength()) {
711           return true;
712         } else if (const auto *param{type.charLengthParamValue()}) {
713           if (const auto &expr{param->GetExplicit()}) {
714             return IsConstantExpr(*expr); // 15.4.2.2(4)(c)
715           } else if (param->isAssumed()) {
716             return true;
717           }
718         }
719         return false;
720       case TypeCategory::Derived:
721         if (!type.IsPolymorphic()) {
722           const auto &spec{type.GetDerivedTypeSpec()};
723           for (const auto &pair : spec.parameters()) {
724             if (const auto &expr{pair.second.GetExplicit()}) {
725               if (!IsConstantExpr(*expr)) {
726                 return false; // 15.4.2.2(4)(c)
727               }
728             }
729           }
730           return true;
731         }
732         return false;
733       default:
734         return true;
735       }
736     }
737   } else {
738     return false; // 15.4.2.2(4)(b) - procedure pointer
739   }
740 }
741 
742 llvm::raw_ostream &FunctionResult::Dump(llvm::raw_ostream &o) const {
743   attrs.Dump(o, EnumToString);
744   std::visit(common::visitors{
745                  [&](const TypeAndShape &ts) { ts.Dump(o); },
746                  [&](const CopyableIndirection<Procedure> &p) {
747                    p.value().Dump(o << " procedure(") << ')';
748                  },
749              },
750       u);
751   return o;
752 }
753 
754 Procedure::Procedure(FunctionResult &&fr, DummyArguments &&args, Attrs a)
755     : functionResult{std::move(fr)}, dummyArguments{std::move(args)}, attrs{a} {
756 }
757 Procedure::Procedure(DummyArguments &&args, Attrs a)
758     : dummyArguments{std::move(args)}, attrs{a} {}
759 Procedure::~Procedure() {}
760 
761 bool Procedure::operator==(const Procedure &that) const {
762   return attrs == that.attrs && functionResult == that.functionResult &&
763       dummyArguments == that.dummyArguments;
764 }
765 
766 int Procedure::FindPassIndex(std::optional<parser::CharBlock> name) const {
767   int argCount{static_cast<int>(dummyArguments.size())};
768   int index{0};
769   if (name) {
770     while (index < argCount && *name != dummyArguments[index].name.c_str()) {
771       ++index;
772     }
773   }
774   CHECK(index < argCount);
775   return index;
776 }
777 
778 bool Procedure::CanOverride(
779     const Procedure &that, std::optional<int> passIndex) const {
780   // A pure procedure may override an impure one (7.5.7.3(2))
781   if ((that.attrs.test(Attr::Pure) && !attrs.test(Attr::Pure)) ||
782       that.attrs.test(Attr::Elemental) != attrs.test(Attr::Elemental) ||
783       functionResult != that.functionResult) {
784     return false;
785   }
786   int argCount{static_cast<int>(dummyArguments.size())};
787   if (argCount != static_cast<int>(that.dummyArguments.size())) {
788     return false;
789   }
790   for (int j{0}; j < argCount; ++j) {
791     if ((!passIndex || j != *passIndex) &&
792         dummyArguments[j] != that.dummyArguments[j]) {
793       return false;
794     }
795   }
796   return true;
797 }
798 
799 std::optional<Procedure> Procedure::Characterize(
800     const semantics::Symbol &original, FoldingContext &context) {
801   semantics::UnorderedSymbolSet seenProcs;
802   return CharacterizeProcedure(original, context, seenProcs);
803 }
804 
805 std::optional<Procedure> Procedure::Characterize(
806     const ProcedureDesignator &proc, FoldingContext &context) {
807   if (const auto *symbol{proc.GetSymbol()}) {
808     if (auto result{characteristics::Procedure::Characterize(
809             ResolveAssociations(*symbol), context)}) {
810       return result;
811     }
812   } else if (const auto *intrinsic{proc.GetSpecificIntrinsic()}) {
813     return intrinsic->characteristics.value();
814   }
815   return std::nullopt;
816 }
817 
818 std::optional<Procedure> Procedure::Characterize(
819     const ProcedureRef &ref, FoldingContext &context) {
820   if (auto callee{Characterize(ref.proc(), context)}) {
821     if (callee->functionResult) {
822       if (const Procedure *
823           proc{callee->functionResult->IsProcedurePointer()}) {
824         return {*proc};
825       }
826     }
827   }
828   return std::nullopt;
829 }
830 
831 bool Procedure::CanBeCalledViaImplicitInterface() const {
832   if (attrs.test(Attr::Elemental) || attrs.test(Attr::BindC)) {
833     return false; // 15.4.2.2(5,6)
834   } else if (IsFunction() &&
835       !functionResult->CanBeReturnedViaImplicitInterface()) {
836     return false;
837   } else {
838     for (const DummyArgument &arg : dummyArguments) {
839       if (!arg.CanBePassedViaImplicitInterface()) {
840         return false;
841       }
842     }
843     return true;
844   }
845 }
846 
847 llvm::raw_ostream &Procedure::Dump(llvm::raw_ostream &o) const {
848   attrs.Dump(o, EnumToString);
849   if (functionResult) {
850     functionResult->Dump(o << "TYPE(") << ") FUNCTION";
851   } else {
852     o << "SUBROUTINE";
853   }
854   char sep{'('};
855   for (const auto &dummy : dummyArguments) {
856     dummy.Dump(o << sep);
857     sep = ',';
858   }
859   return o << (sep == '(' ? "()" : ")");
860 }
861 
862 // Utility class to determine if Procedures, etc. are distinguishable
863 class DistinguishUtils {
864 public:
865   // Are these procedures distinguishable for a generic name?
866   static bool Distinguishable(const Procedure &, const Procedure &);
867   // Are these procedures distinguishable for a generic operator or assignment?
868   static bool DistinguishableOpOrAssign(const Procedure &, const Procedure &);
869 
870 private:
871   struct CountDummyProcedures {
872     CountDummyProcedures(const DummyArguments &args) {
873       for (const DummyArgument &arg : args) {
874         if (std::holds_alternative<DummyProcedure>(arg.u)) {
875           total += 1;
876           notOptional += !arg.IsOptional();
877         }
878       }
879     }
880     int total{0};
881     int notOptional{0};
882   };
883 
884   static bool Rule3Distinguishable(const Procedure &, const Procedure &);
885   static const DummyArgument *Rule1DistinguishingArg(
886       const DummyArguments &, const DummyArguments &);
887   static int FindFirstToDistinguishByPosition(
888       const DummyArguments &, const DummyArguments &);
889   static int FindLastToDistinguishByName(
890       const DummyArguments &, const DummyArguments &);
891   static int CountCompatibleWith(const DummyArgument &, const DummyArguments &);
892   static int CountNotDistinguishableFrom(
893       const DummyArgument &, const DummyArguments &);
894   static bool Distinguishable(const DummyArgument &, const DummyArgument &);
895   static bool Distinguishable(const DummyDataObject &, const DummyDataObject &);
896   static bool Distinguishable(const DummyProcedure &, const DummyProcedure &);
897   static bool Distinguishable(const FunctionResult &, const FunctionResult &);
898   static bool Distinguishable(const TypeAndShape &, const TypeAndShape &);
899   static bool IsTkrCompatible(const DummyArgument &, const DummyArgument &);
900   static bool IsTkrCompatible(const TypeAndShape &, const TypeAndShape &);
901   static const DummyArgument *GetAtEffectivePosition(
902       const DummyArguments &, int);
903   static const DummyArgument *GetPassArg(const Procedure &);
904 };
905 
906 // Simpler distinguishability rules for operators and assignment
907 bool DistinguishUtils::DistinguishableOpOrAssign(
908     const Procedure &proc1, const Procedure &proc2) {
909   auto &args1{proc1.dummyArguments};
910   auto &args2{proc2.dummyArguments};
911   if (args1.size() != args2.size()) {
912     return true; // C1511: distinguishable based on number of arguments
913   }
914   for (std::size_t i{0}; i < args1.size(); ++i) {
915     if (Distinguishable(args1[i], args2[i])) {
916       return true; // C1511, C1512: distinguishable based on this arg
917     }
918   }
919   return false;
920 }
921 
922 bool DistinguishUtils::Distinguishable(
923     const Procedure &proc1, const Procedure &proc2) {
924   auto &args1{proc1.dummyArguments};
925   auto &args2{proc2.dummyArguments};
926   auto count1{CountDummyProcedures(args1)};
927   auto count2{CountDummyProcedures(args2)};
928   if (count1.notOptional > count2.total || count2.notOptional > count1.total) {
929     return true; // distinguishable based on C1514 rule 2
930   }
931   if (Rule3Distinguishable(proc1, proc2)) {
932     return true; // distinguishable based on C1514 rule 3
933   }
934   if (Rule1DistinguishingArg(args1, args2)) {
935     return true; // distinguishable based on C1514 rule 1
936   }
937   int pos1{FindFirstToDistinguishByPosition(args1, args2)};
938   int name1{FindLastToDistinguishByName(args1, args2)};
939   if (pos1 >= 0 && pos1 <= name1) {
940     return true; // distinguishable based on C1514 rule 4
941   }
942   int pos2{FindFirstToDistinguishByPosition(args2, args1)};
943   int name2{FindLastToDistinguishByName(args2, args1)};
944   if (pos2 >= 0 && pos2 <= name2) {
945     return true; // distinguishable based on C1514 rule 4
946   }
947   return false;
948 }
949 
950 // C1514 rule 3: Procedures are distinguishable if both have a passed-object
951 // dummy argument and those are distinguishable.
952 bool DistinguishUtils::Rule3Distinguishable(
953     const Procedure &proc1, const Procedure &proc2) {
954   const DummyArgument *pass1{GetPassArg(proc1)};
955   const DummyArgument *pass2{GetPassArg(proc2)};
956   return pass1 && pass2 && Distinguishable(*pass1, *pass2);
957 }
958 
959 // Find a non-passed-object dummy data object in one of the argument lists
960 // that satisfies C1514 rule 1. I.e. x such that:
961 // - m is the number of dummy data objects in one that are nonoptional,
962 //   are not passed-object, that x is TKR compatible with
963 // - n is the number of non-passed-object dummy data objects, in the other
964 //   that are not distinguishable from x
965 // - m is greater than n
966 const DummyArgument *DistinguishUtils::Rule1DistinguishingArg(
967     const DummyArguments &args1, const DummyArguments &args2) {
968   auto size1{args1.size()};
969   auto size2{args2.size()};
970   for (std::size_t i{0}; i < size1 + size2; ++i) {
971     const DummyArgument &x{i < size1 ? args1[i] : args2[i - size1]};
972     if (!x.pass && std::holds_alternative<DummyDataObject>(x.u)) {
973       if (CountCompatibleWith(x, args1) >
974               CountNotDistinguishableFrom(x, args2) ||
975           CountCompatibleWith(x, args2) >
976               CountNotDistinguishableFrom(x, args1)) {
977         return &x;
978       }
979     }
980   }
981   return nullptr;
982 }
983 
984 // Find the index of the first nonoptional non-passed-object dummy argument
985 // in args1 at an effective position such that either:
986 // - args2 has no dummy argument at that effective position
987 // - the dummy argument at that position is distinguishable from it
988 int DistinguishUtils::FindFirstToDistinguishByPosition(
989     const DummyArguments &args1, const DummyArguments &args2) {
990   int effective{0}; // position of arg1 in list, ignoring passed arg
991   for (std::size_t i{0}; i < args1.size(); ++i) {
992     const DummyArgument &arg1{args1.at(i)};
993     if (!arg1.pass && !arg1.IsOptional()) {
994       const DummyArgument *arg2{GetAtEffectivePosition(args2, effective)};
995       if (!arg2 || Distinguishable(arg1, *arg2)) {
996         return i;
997       }
998     }
999     effective += !arg1.pass;
1000   }
1001   return -1;
1002 }
1003 
1004 // Find the index of the last nonoptional non-passed-object dummy argument
1005 // in args1 whose name is such that either:
1006 // - args2 has no dummy argument with that name
1007 // - the dummy argument with that name is distinguishable from it
1008 int DistinguishUtils::FindLastToDistinguishByName(
1009     const DummyArguments &args1, const DummyArguments &args2) {
1010   std::map<std::string, const DummyArgument *> nameToArg;
1011   for (const auto &arg2 : args2) {
1012     nameToArg.emplace(arg2.name, &arg2);
1013   }
1014   for (int i = args1.size() - 1; i >= 0; --i) {
1015     const DummyArgument &arg1{args1.at(i)};
1016     if (!arg1.pass && !arg1.IsOptional()) {
1017       auto it{nameToArg.find(arg1.name)};
1018       if (it == nameToArg.end() || Distinguishable(arg1, *it->second)) {
1019         return i;
1020       }
1021     }
1022   }
1023   return -1;
1024 }
1025 
1026 // Count the dummy data objects in args that are nonoptional, are not
1027 // passed-object, and that x is TKR compatible with
1028 int DistinguishUtils::CountCompatibleWith(
1029     const DummyArgument &x, const DummyArguments &args) {
1030   return std::count_if(args.begin(), args.end(), [&](const DummyArgument &y) {
1031     return !y.pass && !y.IsOptional() && IsTkrCompatible(x, y);
1032   });
1033 }
1034 
1035 // Return the number of dummy data objects in args that are not
1036 // distinguishable from x and not passed-object.
1037 int DistinguishUtils::CountNotDistinguishableFrom(
1038     const DummyArgument &x, const DummyArguments &args) {
1039   return std::count_if(args.begin(), args.end(), [&](const DummyArgument &y) {
1040     return !y.pass && std::holds_alternative<DummyDataObject>(y.u) &&
1041         !Distinguishable(y, x);
1042   });
1043 }
1044 
1045 bool DistinguishUtils::Distinguishable(
1046     const DummyArgument &x, const DummyArgument &y) {
1047   if (x.u.index() != y.u.index()) {
1048     return true; // different kind: data/proc/alt-return
1049   }
1050   return std::visit(
1051       common::visitors{
1052           [&](const DummyDataObject &z) {
1053             return Distinguishable(z, std::get<DummyDataObject>(y.u));
1054           },
1055           [&](const DummyProcedure &z) {
1056             return Distinguishable(z, std::get<DummyProcedure>(y.u));
1057           },
1058           [&](const AlternateReturn &) { return false; },
1059       },
1060       x.u);
1061 }
1062 
1063 bool DistinguishUtils::Distinguishable(
1064     const DummyDataObject &x, const DummyDataObject &y) {
1065   using Attr = DummyDataObject::Attr;
1066   if (Distinguishable(x.type, y.type)) {
1067     return true;
1068   } else if (x.attrs.test(Attr::Allocatable) && y.attrs.test(Attr::Pointer) &&
1069       y.intent != common::Intent::In) {
1070     return true;
1071   } else if (y.attrs.test(Attr::Allocatable) && x.attrs.test(Attr::Pointer) &&
1072       x.intent != common::Intent::In) {
1073     return true;
1074   } else {
1075     return false;
1076   }
1077 }
1078 
1079 bool DistinguishUtils::Distinguishable(
1080     const DummyProcedure &x, const DummyProcedure &y) {
1081   const Procedure &xProc{x.procedure.value()};
1082   const Procedure &yProc{y.procedure.value()};
1083   if (Distinguishable(xProc, yProc)) {
1084     return true;
1085   } else {
1086     const std::optional<FunctionResult> &xResult{xProc.functionResult};
1087     const std::optional<FunctionResult> &yResult{yProc.functionResult};
1088     return xResult ? !yResult || Distinguishable(*xResult, *yResult)
1089                    : yResult.has_value();
1090   }
1091 }
1092 
1093 bool DistinguishUtils::Distinguishable(
1094     const FunctionResult &x, const FunctionResult &y) {
1095   if (x.u.index() != y.u.index()) {
1096     return true; // one is data object, one is procedure
1097   }
1098   return std::visit(
1099       common::visitors{
1100           [&](const TypeAndShape &z) {
1101             return Distinguishable(z, std::get<TypeAndShape>(y.u));
1102           },
1103           [&](const CopyableIndirection<Procedure> &z) {
1104             return Distinguishable(z.value(),
1105                 std::get<CopyableIndirection<Procedure>>(y.u).value());
1106           },
1107       },
1108       x.u);
1109 }
1110 
1111 bool DistinguishUtils::Distinguishable(
1112     const TypeAndShape &x, const TypeAndShape &y) {
1113   return !IsTkrCompatible(x, y) && !IsTkrCompatible(y, x);
1114 }
1115 
1116 // Compatibility based on type, kind, and rank
1117 bool DistinguishUtils::IsTkrCompatible(
1118     const DummyArgument &x, const DummyArgument &y) {
1119   const auto *obj1{std::get_if<DummyDataObject>(&x.u)};
1120   const auto *obj2{std::get_if<DummyDataObject>(&y.u)};
1121   return obj1 && obj2 && IsTkrCompatible(obj1->type, obj2->type);
1122 }
1123 bool DistinguishUtils::IsTkrCompatible(
1124     const TypeAndShape &x, const TypeAndShape &y) {
1125   return x.type().IsTkCompatibleWith(y.type()) &&
1126       (x.attrs().test(TypeAndShape::Attr::AssumedRank) ||
1127           y.attrs().test(TypeAndShape::Attr::AssumedRank) ||
1128           x.Rank() == y.Rank());
1129 }
1130 
1131 // Return the argument at the given index, ignoring the passed arg
1132 const DummyArgument *DistinguishUtils::GetAtEffectivePosition(
1133     const DummyArguments &args, int index) {
1134   for (const DummyArgument &arg : args) {
1135     if (!arg.pass) {
1136       if (index == 0) {
1137         return &arg;
1138       }
1139       --index;
1140     }
1141   }
1142   return nullptr;
1143 }
1144 
1145 // Return the passed-object dummy argument of this procedure, if any
1146 const DummyArgument *DistinguishUtils::GetPassArg(const Procedure &proc) {
1147   for (const auto &arg : proc.dummyArguments) {
1148     if (arg.pass) {
1149       return &arg;
1150     }
1151   }
1152   return nullptr;
1153 }
1154 
1155 bool Distinguishable(const Procedure &x, const Procedure &y) {
1156   return DistinguishUtils::Distinguishable(x, y);
1157 }
1158 
1159 bool DistinguishableOpOrAssign(const Procedure &x, const Procedure &y) {
1160   return DistinguishUtils::DistinguishableOpOrAssign(x, y);
1161 }
1162 
1163 DEFINE_DEFAULT_CONSTRUCTORS_AND_ASSIGNMENTS(DummyArgument)
1164 DEFINE_DEFAULT_CONSTRUCTORS_AND_ASSIGNMENTS(DummyProcedure)
1165 DEFINE_DEFAULT_CONSTRUCTORS_AND_ASSIGNMENTS(FunctionResult)
1166 DEFINE_DEFAULT_CONSTRUCTORS_AND_ASSIGNMENTS(Procedure)
1167 } // namespace Fortran::evaluate::characteristics
1168 
1169 template class Fortran::common::Indirection<
1170     Fortran::evaluate::characteristics::Procedure, true>;
1171