xref: /llvm-project/flang/lib/Semantics/resolve-names-utils.cpp (revision 4ca111d4cb4c0b425268c86b54fb19c4be2e88dd) 
1 //===-- lib/Semantics/resolve-names-utils.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 "resolve-names-utils.h"
10 #include "flang/Common/Fortran-features.h"
11 #include "flang/Common/Fortran.h"
12 #include "flang/Common/idioms.h"
13 #include "flang/Common/indirection.h"
14 #include "flang/Evaluate/fold.h"
15 #include "flang/Evaluate/tools.h"
16 #include "flang/Evaluate/type.h"
17 #include "flang/Parser/char-block.h"
18 #include "flang/Parser/parse-tree.h"
19 #include "flang/Semantics/expression.h"
20 #include "flang/Semantics/semantics.h"
21 #include "flang/Semantics/tools.h"
22 #include <initializer_list>
23 #include <variant>
24 
25 namespace Fortran::semantics {
26 
27 using common::LanguageFeature;
28 using common::LogicalOperator;
29 using common::NumericOperator;
30 using common::RelationalOperator;
31 using IntrinsicOperator = parser::DefinedOperator::IntrinsicOperator;
32 
33 static constexpr const char *operatorPrefix{"operator("};
34 
35 static GenericKind MapIntrinsicOperator(IntrinsicOperator);
36 
37 Symbol *Resolve(const parser::Name &name, Symbol *symbol) {
38   if (symbol && !name.symbol) {
39     name.symbol = symbol;
40   }
41   return symbol;
42 }
43 Symbol &Resolve(const parser::Name &name, Symbol &symbol) {
44   return *Resolve(name, &symbol);
45 }
46 
47 parser::MessageFixedText WithSeverity(
48     const parser::MessageFixedText &msg, parser::Severity severity) {
49   return parser::MessageFixedText{
50       msg.text().begin(), msg.text().size(), severity};
51 }
52 
53 bool IsIntrinsicOperator(
54     const SemanticsContext &context, const SourceName &name) {
55   std::string str{name.ToString()};
56   for (int i{0}; i != common::LogicalOperator_enumSize; ++i) {
57     auto names{context.languageFeatures().GetNames(LogicalOperator{i})};
58     if (std::find(names.begin(), names.end(), str) != names.end()) {
59       return true;
60     }
61   }
62   for (int i{0}; i != common::RelationalOperator_enumSize; ++i) {
63     auto names{context.languageFeatures().GetNames(RelationalOperator{i})};
64     if (std::find(names.begin(), names.end(), str) != names.end()) {
65       return true;
66     }
67   }
68   return false;
69 }
70 
71 template <typename E>
72 std::forward_list<std::string> GetOperatorNames(
73     const SemanticsContext &context, E opr) {
74   std::forward_list<std::string> result;
75   for (const char *name : context.languageFeatures().GetNames(opr)) {
76     result.emplace_front(std::string{operatorPrefix} + name + ')');
77   }
78   return result;
79 }
80 
81 std::forward_list<std::string> GetAllNames(
82     const SemanticsContext &context, const SourceName &name) {
83   std::string str{name.ToString()};
84   if (!name.empty() && name.end()[-1] == ')' &&
85       name.ToString().rfind(std::string{operatorPrefix}, 0) == 0) {
86     for (int i{0}; i != common::LogicalOperator_enumSize; ++i) {
87       auto names{GetOperatorNames(context, LogicalOperator{i})};
88       if (std::find(names.begin(), names.end(), str) != names.end()) {
89         return names;
90       }
91     }
92     for (int i{0}; i != common::RelationalOperator_enumSize; ++i) {
93       auto names{GetOperatorNames(context, RelationalOperator{i})};
94       if (std::find(names.begin(), names.end(), str) != names.end()) {
95         return names;
96       }
97     }
98   }
99   return {str};
100 }
101 
102 bool IsLogicalConstant(
103     const SemanticsContext &context, const SourceName &name) {
104   std::string str{name.ToString()};
105   return str == ".true." || str == ".false." ||
106       (context.IsEnabled(LanguageFeature::LogicalAbbreviations) &&
107           (str == ".t" || str == ".f."));
108 }
109 
110 void GenericSpecInfo::Resolve(Symbol *symbol) const {
111   if (symbol) {
112     if (auto *details{symbol->detailsIf<GenericDetails>()}) {
113       details->set_kind(kind_);
114     }
115     if (parseName_) {
116       semantics::Resolve(*parseName_, symbol);
117     }
118   }
119 }
120 
121 void GenericSpecInfo::Analyze(const parser::DefinedOpName &name) {
122   kind_ = GenericKind::OtherKind::DefinedOp;
123   parseName_ = &name.v;
124   symbolName_ = name.v.source;
125 }
126 
127 void GenericSpecInfo::Analyze(const parser::GenericSpec &x) {
128   symbolName_ = x.source;
129   kind_ = std::visit(
130       common::visitors{
131           [&](const parser::Name &y) -> GenericKind {
132             parseName_ = &y;
133             symbolName_ = y.source;
134             return GenericKind::OtherKind::Name;
135           },
136           [&](const parser::DefinedOperator &y) {
137             return std::visit(
138                 common::visitors{
139                     [&](const parser::DefinedOpName &z) -> GenericKind {
140                       Analyze(z);
141                       return GenericKind::OtherKind::DefinedOp;
142                     },
143                     [&](const IntrinsicOperator &z) {
144                       return MapIntrinsicOperator(z);
145                     },
146                 },
147                 y.u);
148           },
149           [&](const parser::GenericSpec::Assignment &) -> GenericKind {
150             return GenericKind::OtherKind::Assignment;
151           },
152           [&](const parser::GenericSpec::ReadFormatted &) -> GenericKind {
153             return GenericKind::DefinedIo::ReadFormatted;
154           },
155           [&](const parser::GenericSpec::ReadUnformatted &) -> GenericKind {
156             return GenericKind::DefinedIo::ReadUnformatted;
157           },
158           [&](const parser::GenericSpec::WriteFormatted &) -> GenericKind {
159             return GenericKind::DefinedIo::WriteFormatted;
160           },
161           [&](const parser::GenericSpec::WriteUnformatted &) -> GenericKind {
162             return GenericKind::DefinedIo::WriteUnformatted;
163           },
164       },
165       x.u);
166 }
167 
168 llvm::raw_ostream &operator<<(
169     llvm::raw_ostream &os, const GenericSpecInfo &info) {
170   os << "GenericSpecInfo: kind=" << info.kind_.ToString();
171   os << " parseName="
172      << (info.parseName_ ? info.parseName_->ToString() : "null");
173   os << " symbolName="
174      << (info.symbolName_ ? info.symbolName_->ToString() : "null");
175   return os;
176 }
177 
178 // parser::DefinedOperator::IntrinsicOperator -> GenericKind
179 static GenericKind MapIntrinsicOperator(IntrinsicOperator op) {
180   switch (op) {
181     SWITCH_COVERS_ALL_CASES
182   case IntrinsicOperator::Concat:
183     return GenericKind::OtherKind::Concat;
184   case IntrinsicOperator::Power:
185     return NumericOperator::Power;
186   case IntrinsicOperator::Multiply:
187     return NumericOperator::Multiply;
188   case IntrinsicOperator::Divide:
189     return NumericOperator::Divide;
190   case IntrinsicOperator::Add:
191     return NumericOperator::Add;
192   case IntrinsicOperator::Subtract:
193     return NumericOperator::Subtract;
194   case IntrinsicOperator::AND:
195     return LogicalOperator::And;
196   case IntrinsicOperator::OR:
197     return LogicalOperator::Or;
198   case IntrinsicOperator::EQV:
199     return LogicalOperator::Eqv;
200   case IntrinsicOperator::NEQV:
201     return LogicalOperator::Neqv;
202   case IntrinsicOperator::NOT:
203     return LogicalOperator::Not;
204   case IntrinsicOperator::LT:
205     return RelationalOperator::LT;
206   case IntrinsicOperator::LE:
207     return RelationalOperator::LE;
208   case IntrinsicOperator::EQ:
209     return RelationalOperator::EQ;
210   case IntrinsicOperator::NE:
211     return RelationalOperator::NE;
212   case IntrinsicOperator::GE:
213     return RelationalOperator::GE;
214   case IntrinsicOperator::GT:
215     return RelationalOperator::GT;
216   }
217 }
218 
219 class ArraySpecAnalyzer {
220 public:
221   ArraySpecAnalyzer(SemanticsContext &context) : context_{context} {}
222   ArraySpec Analyze(const parser::ArraySpec &);
223   ArraySpec AnalyzeDeferredShapeSpecList(const parser::DeferredShapeSpecList &);
224   ArraySpec Analyze(const parser::ComponentArraySpec &);
225   ArraySpec Analyze(const parser::CoarraySpec &);
226 
227 private:
228   SemanticsContext &context_;
229   ArraySpec arraySpec_;
230 
231   template <typename T> void Analyze(const std::list<T> &list) {
232     for (const auto &elem : list) {
233       Analyze(elem);
234     }
235   }
236   void Analyze(const parser::AssumedShapeSpec &);
237   void Analyze(const parser::ExplicitShapeSpec &);
238   void Analyze(const parser::AssumedImpliedSpec &);
239   void Analyze(const parser::DeferredShapeSpecList &);
240   void Analyze(const parser::AssumedRankSpec &);
241   void MakeExplicit(const std::optional<parser::SpecificationExpr> &,
242       const parser::SpecificationExpr &);
243   void MakeImplied(const std::optional<parser::SpecificationExpr> &);
244   void MakeDeferred(int);
245   Bound GetBound(const std::optional<parser::SpecificationExpr> &);
246   Bound GetBound(const parser::SpecificationExpr &);
247 };
248 
249 ArraySpec AnalyzeArraySpec(
250     SemanticsContext &context, const parser::ArraySpec &arraySpec) {
251   return ArraySpecAnalyzer{context}.Analyze(arraySpec);
252 }
253 ArraySpec AnalyzeArraySpec(
254     SemanticsContext &context, const parser::ComponentArraySpec &arraySpec) {
255   return ArraySpecAnalyzer{context}.Analyze(arraySpec);
256 }
257 ArraySpec AnalyzeDeferredShapeSpecList(SemanticsContext &context,
258     const parser::DeferredShapeSpecList &deferredShapeSpecs) {
259   return ArraySpecAnalyzer{context}.AnalyzeDeferredShapeSpecList(
260       deferredShapeSpecs);
261 }
262 ArraySpec AnalyzeCoarraySpec(
263     SemanticsContext &context, const parser::CoarraySpec &coarraySpec) {
264   return ArraySpecAnalyzer{context}.Analyze(coarraySpec);
265 }
266 
267 ArraySpec ArraySpecAnalyzer::Analyze(const parser::ComponentArraySpec &x) {
268   std::visit([this](const auto &y) { Analyze(y); }, x.u);
269   CHECK(!arraySpec_.empty());
270   return arraySpec_;
271 }
272 ArraySpec ArraySpecAnalyzer::Analyze(const parser::ArraySpec &x) {
273   std::visit(common::visitors{
274                  [&](const parser::AssumedSizeSpec &y) {
275                    Analyze(std::get<std::list<parser::ExplicitShapeSpec>>(y.t));
276                    Analyze(std::get<parser::AssumedImpliedSpec>(y.t));
277                  },
278                  [&](const parser::ImpliedShapeSpec &y) { Analyze(y.v); },
279                  [&](const auto &y) { Analyze(y); },
280              },
281       x.u);
282   CHECK(!arraySpec_.empty());
283   return arraySpec_;
284 }
285 ArraySpec ArraySpecAnalyzer::AnalyzeDeferredShapeSpecList(
286     const parser::DeferredShapeSpecList &x) {
287   Analyze(x);
288   CHECK(!arraySpec_.empty());
289   return arraySpec_;
290 }
291 ArraySpec ArraySpecAnalyzer::Analyze(const parser::CoarraySpec &x) {
292   std::visit(
293       common::visitors{
294           [&](const parser::DeferredCoshapeSpecList &y) { MakeDeferred(y.v); },
295           [&](const parser::ExplicitCoshapeSpec &y) {
296             Analyze(std::get<std::list<parser::ExplicitShapeSpec>>(y.t));
297             MakeImplied(
298                 std::get<std::optional<parser::SpecificationExpr>>(y.t));
299           },
300       },
301       x.u);
302   CHECK(!arraySpec_.empty());
303   return arraySpec_;
304 }
305 
306 void ArraySpecAnalyzer::Analyze(const parser::AssumedShapeSpec &x) {
307   arraySpec_.push_back(ShapeSpec::MakeAssumedShape(GetBound(x.v)));
308 }
309 void ArraySpecAnalyzer::Analyze(const parser::ExplicitShapeSpec &x) {
310   MakeExplicit(std::get<std::optional<parser::SpecificationExpr>>(x.t),
311       std::get<parser::SpecificationExpr>(x.t));
312 }
313 void ArraySpecAnalyzer::Analyze(const parser::AssumedImpliedSpec &x) {
314   MakeImplied(x.v);
315 }
316 void ArraySpecAnalyzer::Analyze(const parser::DeferredShapeSpecList &x) {
317   MakeDeferred(x.v);
318 }
319 void ArraySpecAnalyzer::Analyze(const parser::AssumedRankSpec &) {
320   arraySpec_.push_back(ShapeSpec::MakeAssumedRank());
321 }
322 
323 void ArraySpecAnalyzer::MakeExplicit(
324     const std::optional<parser::SpecificationExpr> &lb,
325     const parser::SpecificationExpr &ub) {
326   arraySpec_.push_back(ShapeSpec::MakeExplicit(GetBound(lb), GetBound(ub)));
327 }
328 void ArraySpecAnalyzer::MakeImplied(
329     const std::optional<parser::SpecificationExpr> &lb) {
330   arraySpec_.push_back(ShapeSpec::MakeImplied(GetBound(lb)));
331 }
332 void ArraySpecAnalyzer::MakeDeferred(int n) {
333   for (int i = 0; i < n; ++i) {
334     arraySpec_.push_back(ShapeSpec::MakeDeferred());
335   }
336 }
337 
338 Bound ArraySpecAnalyzer::GetBound(
339     const std::optional<parser::SpecificationExpr> &x) {
340   return x ? GetBound(*x) : Bound{1};
341 }
342 Bound ArraySpecAnalyzer::GetBound(const parser::SpecificationExpr &x) {
343   MaybeSubscriptIntExpr expr;
344   if (MaybeExpr maybeExpr{AnalyzeExpr(context_, x.v)}) {
345     if (auto *intExpr{evaluate::UnwrapExpr<SomeIntExpr>(*maybeExpr)}) {
346       expr = evaluate::Fold(context_.foldingContext(),
347           evaluate::ConvertToType<evaluate::SubscriptInteger>(
348               std::move(*intExpr)));
349     }
350   }
351   return Bound{std::move(expr)};
352 }
353 
354 // If SAVE is set on src, set it on all members of dst
355 static void PropagateSaveAttr(
356     const EquivalenceObject &src, EquivalenceSet &dst) {
357   if (src.symbol.attrs().test(Attr::SAVE)) {
358     for (auto &obj : dst) {
359       obj.symbol.attrs().set(Attr::SAVE);
360     }
361   }
362 }
363 static void PropagateSaveAttr(const EquivalenceSet &src, EquivalenceSet &dst) {
364   if (!src.empty()) {
365     PropagateSaveAttr(src.front(), dst);
366   }
367 }
368 
369 void EquivalenceSets::AddToSet(const parser::Designator &designator) {
370   if (CheckDesignator(designator)) {
371     Symbol &symbol{*currObject_.symbol};
372     if (!currSet_.empty()) {
373       // check this symbol against first of set for compatibility
374       Symbol &first{currSet_.front().symbol};
375       CheckCanEquivalence(designator.source, first, symbol) &&
376           CheckCanEquivalence(designator.source, symbol, first);
377     }
378     auto subscripts{currObject_.subscripts};
379     if (subscripts.empty() && symbol.IsObjectArray()) {
380       // record a whole array as its first element
381       for (const ShapeSpec &spec : symbol.get<ObjectEntityDetails>().shape()) {
382         auto &lbound{spec.lbound().GetExplicit().value()};
383         subscripts.push_back(evaluate::ToInt64(lbound).value());
384       }
385     }
386     auto substringStart{currObject_.substringStart};
387     currSet_.emplace_back(
388         symbol, subscripts, substringStart, designator.source);
389     PropagateSaveAttr(currSet_.back(), currSet_);
390   }
391   currObject_ = {};
392 }
393 
394 void EquivalenceSets::FinishSet(const parser::CharBlock &source) {
395   std::set<std::size_t> existing; // indices of sets intersecting this one
396   for (auto &obj : currSet_) {
397     auto it{objectToSet_.find(obj)};
398     if (it != objectToSet_.end()) {
399       existing.insert(it->second); // symbol already in this set
400     }
401   }
402   if (existing.empty()) {
403     sets_.push_back({}); // create a new equivalence set
404     MergeInto(source, currSet_, sets_.size() - 1);
405   } else {
406     auto it{existing.begin()};
407     std::size_t dstIndex{*it};
408     MergeInto(source, currSet_, dstIndex);
409     while (++it != existing.end()) {
410       MergeInto(source, sets_[*it], dstIndex);
411     }
412   }
413   currSet_.clear();
414 }
415 
416 // Report an error or warning if sym1 and sym2 cannot be in the same equivalence
417 // set.
418 bool EquivalenceSets::CheckCanEquivalence(
419     const parser::CharBlock &source, const Symbol &sym1, const Symbol &sym2) {
420   std::optional<parser::MessageFixedText> msg;
421   const DeclTypeSpec *type1{sym1.GetType()};
422   const DeclTypeSpec *type2{sym2.GetType()};
423   bool isDefaultNum1{IsDefaultNumericSequenceType(type1)};
424   bool isAnyNum1{IsAnyNumericSequenceType(type1)};
425   bool isDefaultNum2{IsDefaultNumericSequenceType(type2)};
426   bool isAnyNum2{IsAnyNumericSequenceType(type2)};
427   bool isChar1{IsCharacterSequenceType(type1)};
428   bool isChar2{IsCharacterSequenceType(type2)};
429   if (sym1.attrs().test(Attr::PROTECTED) &&
430       !sym2.attrs().test(Attr::PROTECTED)) { // C8114
431     msg = "Equivalence set cannot contain '%s'"
432           " with PROTECTED attribute and '%s' without"_err_en_US;
433   } else if ((isDefaultNum1 && isDefaultNum2) || (isChar1 && isChar2)) {
434     // ok & standard conforming
435   } else if (!(isAnyNum1 || isChar1) &&
436       !(isAnyNum2 || isChar2)) { // C8110 - C8113
437     if (AreTkCompatibleTypes(type1, type2)) {
438       if (context_.ShouldWarn(LanguageFeature::EquivalenceSameNonSequence)) {
439         msg =
440             "nonstandard: Equivalence set contains '%s' and '%s' with same "
441             "type that is neither numeric nor character sequence type"_port_en_US;
442       }
443     } else {
444       msg = "Equivalence set cannot contain '%s' and '%s' with distinct types "
445             "that are not both numeric or character sequence types"_err_en_US;
446     }
447   } else if (isAnyNum1) {
448     if (isChar2) {
449       if (context_.ShouldWarn(
450               LanguageFeature::EquivalenceNumericWithCharacter)) {
451         msg = "nonstandard: Equivalence set contains '%s' that is numeric "
452               "sequence type and '%s' that is character"_port_en_US;
453       }
454     } else if (isAnyNum2 &&
455         context_.ShouldWarn(LanguageFeature::EquivalenceNonDefaultNumeric)) {
456       if (isDefaultNum1) {
457         msg =
458             "nonstandard: Equivalence set contains '%s' that is a default "
459             "numeric sequence type and '%s' that is numeric with non-default kind"_port_en_US;
460       } else if (!isDefaultNum2) {
461         msg = "nonstandard: Equivalence set contains '%s' and '%s' that are "
462               "numeric sequence types with non-default kinds"_port_en_US;
463       }
464     }
465   }
466   if (msg) {
467     context_.Say(source, std::move(*msg), sym1.name(), sym2.name());
468     return false;
469   }
470   return true;
471 }
472 
473 // Move objects from src to sets_[dstIndex]
474 void EquivalenceSets::MergeInto(const parser::CharBlock &source,
475     EquivalenceSet &src, std::size_t dstIndex) {
476   EquivalenceSet &dst{sets_[dstIndex]};
477   PropagateSaveAttr(dst, src);
478   for (const auto &obj : src) {
479     dst.push_back(obj);
480     objectToSet_[obj] = dstIndex;
481   }
482   PropagateSaveAttr(src, dst);
483   src.clear();
484 }
485 
486 // If set has an object with this symbol, return it.
487 const EquivalenceObject *EquivalenceSets::Find(
488     const EquivalenceSet &set, const Symbol &symbol) {
489   for (const auto &obj : set) {
490     if (obj.symbol == symbol) {
491       return &obj;
492     }
493   }
494   return nullptr;
495 }
496 
497 bool EquivalenceSets::CheckDesignator(const parser::Designator &designator) {
498   return std::visit(
499       common::visitors{
500           [&](const parser::DataRef &x) {
501             return CheckDataRef(designator.source, x);
502           },
503           [&](const parser::Substring &x) {
504             const auto &dataRef{std::get<parser::DataRef>(x.t)};
505             const auto &range{std::get<parser::SubstringRange>(x.t)};
506             bool ok{CheckDataRef(designator.source, dataRef)};
507             if (const auto &lb{std::get<0>(range.t)}) {
508               ok &= CheckSubstringBound(lb->thing.thing.value(), true);
509             } else {
510               currObject_.substringStart = 1;
511             }
512             if (const auto &ub{std::get<1>(range.t)}) {
513               ok &= CheckSubstringBound(ub->thing.thing.value(), false);
514             }
515             return ok;
516           },
517       },
518       designator.u);
519 }
520 
521 bool EquivalenceSets::CheckDataRef(
522     const parser::CharBlock &source, const parser::DataRef &x) {
523   return std::visit(
524       common::visitors{
525           [&](const parser::Name &name) { return CheckObject(name); },
526           [&](const common::Indirection<parser::StructureComponent> &) {
527             context_.Say(source, // C8107
528                 "Derived type component '%s' is not allowed in an equivalence set"_err_en_US,
529                 source);
530             return false;
531           },
532           [&](const common::Indirection<parser::ArrayElement> &elem) {
533             bool ok{CheckDataRef(source, elem.value().base)};
534             for (const auto &subscript : elem.value().subscripts) {
535               ok &= std::visit(
536                   common::visitors{
537                       [&](const parser::SubscriptTriplet &) {
538                         context_.Say(source, // C924, R872
539                             "Array section '%s' is not allowed in an equivalence set"_err_en_US,
540                             source);
541                         return false;
542                       },
543                       [&](const parser::IntExpr &y) {
544                         return CheckArrayBound(y.thing.value());
545                       },
546                   },
547                   subscript.u);
548             }
549             return ok;
550           },
551           [&](const common::Indirection<parser::CoindexedNamedObject> &) {
552             context_.Say(source, // C924 (R872)
553                 "Coindexed object '%s' is not allowed in an equivalence set"_err_en_US,
554                 source);
555             return false;
556           },
557       },
558       x.u);
559 }
560 
561 static bool InCommonWithBind(const Symbol &symbol) {
562   if (const auto *details{symbol.detailsIf<ObjectEntityDetails>()}) {
563     const Symbol *commonBlock{details->commonBlock()};
564     return commonBlock && commonBlock->attrs().test(Attr::BIND_C);
565   } else {
566     return false;
567   }
568 }
569 
570 // If symbol can't be in equivalence set report error and return false;
571 bool EquivalenceSets::CheckObject(const parser::Name &name) {
572   if (!name.symbol) {
573     return false; // an error has already occurred
574   }
575   currObject_.symbol = name.symbol;
576   parser::MessageFixedText msg;
577   const Symbol &symbol{*name.symbol};
578   if (symbol.owner().IsDerivedType()) { // C8107
579     msg = "Derived type component '%s'"
580           " is not allowed in an equivalence set"_err_en_US;
581   } else if (IsDummy(symbol)) { // C8106
582     msg = "Dummy argument '%s' is not allowed in an equivalence set"_err_en_US;
583   } else if (symbol.IsFuncResult()) { // C8106
584     msg = "Function result '%s' is not allow in an equivalence set"_err_en_US;
585   } else if (IsPointer(symbol)) { // C8106
586     msg = "Pointer '%s' is not allowed in an equivalence set"_err_en_US;
587   } else if (IsAllocatable(symbol)) { // C8106
588     msg = "Allocatable variable '%s'"
589           " is not allowed in an equivalence set"_err_en_US;
590   } else if (symbol.Corank() > 0) { // C8106
591     msg = "Coarray '%s' is not allowed in an equivalence set"_err_en_US;
592   } else if (symbol.has<UseDetails>()) { // C8115
593     msg = "Use-associated variable '%s'"
594           " is not allowed in an equivalence set"_err_en_US;
595   } else if (symbol.attrs().test(Attr::BIND_C)) { // C8106
596     msg = "Variable '%s' with BIND attribute"
597           " is not allowed in an equivalence set"_err_en_US;
598   } else if (symbol.attrs().test(Attr::TARGET)) { // C8108
599     msg = "Variable '%s' with TARGET attribute"
600           " is not allowed in an equivalence set"_err_en_US;
601   } else if (IsNamedConstant(symbol)) { // C8106
602     msg = "Named constant '%s' is not allowed in an equivalence set"_err_en_US;
603   } else if (InCommonWithBind(symbol)) { // C8106
604     msg = "Variable '%s' in common block with BIND attribute"
605           " is not allowed in an equivalence set"_err_en_US;
606   } else if (const auto *type{symbol.GetType()}) {
607     if (const auto *derived{type->AsDerived()}) {
608       if (const auto *comp{FindUltimateComponent(
609               *derived, IsAllocatableOrPointer)}) { // C8106
610         msg = IsPointer(*comp)
611             ? "Derived type object '%s' with pointer ultimate component"
612               " is not allowed in an equivalence set"_err_en_US
613             : "Derived type object '%s' with allocatable ultimate component"
614               " is not allowed in an equivalence set"_err_en_US;
615       } else if (!derived->typeSymbol().get<DerivedTypeDetails>().sequence()) {
616         msg = "Nonsequence derived type object '%s'"
617               " is not allowed in an equivalence set"_err_en_US;
618       }
619     } else if (IsAutomatic(symbol)) {
620       msg = "Automatic object '%s'"
621             " is not allowed in an equivalence set"_err_en_US;
622     }
623   }
624   if (!msg.text().empty()) {
625     context_.Say(name.source, std::move(msg), name.source);
626     return false;
627   }
628   return true;
629 }
630 
631 bool EquivalenceSets::CheckArrayBound(const parser::Expr &bound) {
632   MaybeExpr expr{
633       evaluate::Fold(context_.foldingContext(), AnalyzeExpr(context_, bound))};
634   if (!expr) {
635     return false;
636   }
637   if (expr->Rank() > 0) {
638     context_.Say(bound.source, // C924, R872
639         "Array with vector subscript '%s' is not allowed in an equivalence set"_err_en_US,
640         bound.source);
641     return false;
642   }
643   auto subscript{evaluate::ToInt64(*expr)};
644   if (!subscript) {
645     context_.Say(bound.source, // C8109
646         "Array with nonconstant subscript '%s' is not allowed in an equivalence set"_err_en_US,
647         bound.source);
648     return false;
649   }
650   currObject_.subscripts.push_back(*subscript);
651   return true;
652 }
653 
654 bool EquivalenceSets::CheckSubstringBound(
655     const parser::Expr &bound, bool isStart) {
656   MaybeExpr expr{
657       evaluate::Fold(context_.foldingContext(), AnalyzeExpr(context_, bound))};
658   if (!expr) {
659     return false;
660   }
661   auto subscript{evaluate::ToInt64(*expr)};
662   if (!subscript) {
663     context_.Say(bound.source, // C8109
664         "Substring with nonconstant bound '%s' is not allowed in an equivalence set"_err_en_US,
665         bound.source);
666     return false;
667   }
668   if (!isStart) {
669     auto start{currObject_.substringStart};
670     if (*subscript < (start ? *start : 1)) {
671       context_.Say(bound.source, // C8116
672           "Substring with zero length is not allowed in an equivalence set"_err_en_US);
673       return false;
674     }
675   } else if (*subscript != 1) {
676     currObject_.substringStart = *subscript;
677   }
678   return true;
679 }
680 
681 bool EquivalenceSets::IsCharacterSequenceType(const DeclTypeSpec *type) {
682   return IsSequenceType(type, [&](const IntrinsicTypeSpec &type) {
683     auto kind{evaluate::ToInt64(type.kind())};
684     return type.category() == TypeCategory::Character && kind &&
685         kind.value() == context_.GetDefaultKind(TypeCategory::Character);
686   });
687 }
688 
689 // Numeric or logical type of default kind or DOUBLE PRECISION or DOUBLE COMPLEX
690 bool EquivalenceSets::IsDefaultKindNumericType(const IntrinsicTypeSpec &type) {
691   if (auto kind{evaluate::ToInt64(type.kind())}) {
692     switch (type.category()) {
693     case TypeCategory::Integer:
694     case TypeCategory::Logical:
695       return *kind == context_.GetDefaultKind(TypeCategory::Integer);
696     case TypeCategory::Real:
697     case TypeCategory::Complex:
698       return *kind == context_.GetDefaultKind(TypeCategory::Real) ||
699           *kind == context_.doublePrecisionKind();
700     default:
701       return false;
702     }
703   }
704   return false;
705 }
706 
707 bool EquivalenceSets::IsDefaultNumericSequenceType(const DeclTypeSpec *type) {
708   return IsSequenceType(type, [&](const IntrinsicTypeSpec &type) {
709     return IsDefaultKindNumericType(type);
710   });
711 }
712 
713 bool EquivalenceSets::IsAnyNumericSequenceType(const DeclTypeSpec *type) {
714   return IsSequenceType(type, [&](const IntrinsicTypeSpec &type) {
715     return type.category() == TypeCategory::Logical ||
716         common::IsNumericTypeCategory(type.category());
717   });
718 }
719 
720 // Is type an intrinsic type that satisfies predicate or a sequence type
721 // whose components do.
722 bool EquivalenceSets::IsSequenceType(const DeclTypeSpec *type,
723     std::function<bool(const IntrinsicTypeSpec &)> predicate) {
724   if (!type) {
725     return false;
726   } else if (const IntrinsicTypeSpec * intrinsic{type->AsIntrinsic()}) {
727     return predicate(*intrinsic);
728   } else if (const DerivedTypeSpec * derived{type->AsDerived()}) {
729     for (const auto &pair : *derived->typeSymbol().scope()) {
730       const Symbol &component{*pair.second};
731       if (IsAllocatableOrPointer(component) ||
732           !IsSequenceType(component.GetType(), predicate)) {
733         return false;
734       }
735     }
736     return true;
737   } else {
738     return false;
739   }
740 }
741 
742 } // namespace Fortran::semantics
743