xref: /llvm-project/flang/lib/Semantics/resolve-labels.cpp (revision 210e675cfd7be3d7e0d93c29368acd27b51f9a17) 
1 //===-- lib/Semantics/resolve-labels.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-labels.h"
10 #include "flang/Common/enum-set.h"
11 #include "flang/Common/template.h"
12 #include "flang/Parser/parse-tree-visitor.h"
13 #include "flang/Semantics/semantics.h"
14 #include <cstdarg>
15 #include <type_traits>
16 
17 namespace Fortran::semantics {
18 
19 using namespace parser::literals;
20 
21 ENUM_CLASS(
22     TargetStatementEnum, Do, Branch, Format, CompatibleDo, CompatibleBranch)
23 using LabeledStmtClassificationSet =
24     common::EnumSet<TargetStatementEnum, TargetStatementEnum_enumSize>;
25 
26 using IndexList = std::vector<std::pair<parser::CharBlock, parser::CharBlock>>;
27 // A ProxyForScope is an integral proxy for a Fortran scope. This is required
28 // because the parse tree does not actually have the scopes required.
29 using ProxyForScope = unsigned;
30 // Minimal scope information
31 struct ScopeInfo {
32   ProxyForScope parent{};
33   bool isExteriorGotoFatal{false};
34   int depth{0};
35 };
36 struct LabeledStatementInfoTuplePOD {
37   ProxyForScope proxyForScope;
38   parser::CharBlock parserCharBlock;
39   LabeledStmtClassificationSet labeledStmtClassificationSet;
40   bool isExecutableConstructEndStmt;
41 };
42 using TargetStmtMap = std::map<parser::Label, LabeledStatementInfoTuplePOD>;
43 struct SourceStatementInfoTuplePOD {
44   SourceStatementInfoTuplePOD(const parser::Label &parserLabel,
45       const ProxyForScope &proxyForScope,
46       const parser::CharBlock &parserCharBlock)
47       : parserLabel{parserLabel}, proxyForScope{proxyForScope},
48         parserCharBlock{parserCharBlock} {}
49   parser::Label parserLabel;
50   ProxyForScope proxyForScope;
51   parser::CharBlock parserCharBlock;
52 };
53 using SourceStmtList = std::vector<SourceStatementInfoTuplePOD>;
54 enum class Legality { never, always, formerly };
55 
56 bool HasScope(ProxyForScope scope) { return scope != ProxyForScope{0u}; }
57 
58 // F18:R1131
59 template <typename A>
60 constexpr Legality IsLegalDoTerm(const parser::Statement<A> &) {
61   if (std::is_same_v<A, common::Indirection<parser::EndDoStmt>> ||
62       std::is_same_v<A, parser::EndDoStmt>) {
63     return Legality::always;
64   } else if (std::is_same_v<A, parser::EndForallStmt> ||
65       std::is_same_v<A, parser::EndWhereStmt>) {
66     // Executable construct end statements are also supported as
67     // an extension but they need special care because the associated
68     // construct create their own scope.
69     return Legality::formerly;
70   } else {
71     return Legality::never;
72   }
73 }
74 
75 constexpr Legality IsLegalDoTerm(
76     const parser::Statement<parser::ActionStmt> &actionStmt) {
77   if (std::holds_alternative<parser::ContinueStmt>(actionStmt.statement.u)) {
78     // See F08:C816
79     return Legality::always;
80   } else if (!(std::holds_alternative<
81                    common::Indirection<parser::ArithmeticIfStmt>>(
82                    actionStmt.statement.u) ||
83                  std::holds_alternative<common::Indirection<parser::CycleStmt>>(
84                      actionStmt.statement.u) ||
85                  std::holds_alternative<common::Indirection<parser::ExitStmt>>(
86                      actionStmt.statement.u) ||
87                  std::holds_alternative<common::Indirection<parser::StopStmt>>(
88                      actionStmt.statement.u) ||
89                  std::holds_alternative<common::Indirection<parser::GotoStmt>>(
90                      actionStmt.statement.u) ||
91                  std::holds_alternative<
92                      common::Indirection<parser::ReturnStmt>>(
93                      actionStmt.statement.u))) {
94     return Legality::formerly;
95   } else {
96     return Legality::never;
97   }
98 }
99 
100 template <typename A> constexpr bool IsFormat(const parser::Statement<A> &) {
101   return std::is_same_v<A, common::Indirection<parser::FormatStmt>>;
102 }
103 
104 template <typename A>
105 constexpr Legality IsLegalBranchTarget(const parser::Statement<A> &) {
106   if (std::is_same_v<A, parser::ActionStmt> ||
107       std::is_same_v<A, parser::AssociateStmt> ||
108       std::is_same_v<A, parser::EndAssociateStmt> ||
109       std::is_same_v<A, parser::IfThenStmt> ||
110       std::is_same_v<A, parser::EndIfStmt> ||
111       std::is_same_v<A, parser::SelectCaseStmt> ||
112       std::is_same_v<A, parser::EndSelectStmt> ||
113       std::is_same_v<A, parser::SelectRankStmt> ||
114       std::is_same_v<A, parser::SelectTypeStmt> ||
115       std::is_same_v<A, common::Indirection<parser::LabelDoStmt>> ||
116       std::is_same_v<A, parser::NonLabelDoStmt> ||
117       std::is_same_v<A, parser::EndDoStmt> ||
118       std::is_same_v<A, common::Indirection<parser::EndDoStmt>> ||
119       std::is_same_v<A, parser::BlockStmt> ||
120       std::is_same_v<A, parser::EndBlockStmt> ||
121       std::is_same_v<A, parser::CriticalStmt> ||
122       std::is_same_v<A, parser::EndCriticalStmt> ||
123       std::is_same_v<A, parser::ForallConstructStmt> ||
124       std::is_same_v<A, parser::WhereConstructStmt> ||
125       std::is_same_v<A, parser::ChangeTeamStmt> ||
126       std::is_same_v<A, parser::EndChangeTeamStmt> ||
127       std::is_same_v<A, parser::EndFunctionStmt> ||
128       std::is_same_v<A, parser::EndMpSubprogramStmt> ||
129       std::is_same_v<A, parser::EndProgramStmt> ||
130       std::is_same_v<A, parser::EndSubroutineStmt>) {
131     return Legality::always;
132   } else {
133     return Legality::never;
134   }
135 }
136 
137 template <typename A>
138 constexpr LabeledStmtClassificationSet ConstructBranchTargetFlags(
139     const parser::Statement<A> &statement) {
140   LabeledStmtClassificationSet labeledStmtClassificationSet{};
141   if (IsLegalDoTerm(statement) == Legality::always) {
142     labeledStmtClassificationSet.set(TargetStatementEnum::Do);
143   } else if (IsLegalDoTerm(statement) == Legality::formerly) {
144     labeledStmtClassificationSet.set(TargetStatementEnum::CompatibleDo);
145   }
146   if (IsLegalBranchTarget(statement) == Legality::always) {
147     labeledStmtClassificationSet.set(TargetStatementEnum::Branch);
148   } else if (IsLegalBranchTarget(statement) == Legality::formerly) {
149     labeledStmtClassificationSet.set(TargetStatementEnum::CompatibleBranch);
150   }
151   if (IsFormat(statement)) {
152     labeledStmtClassificationSet.set(TargetStatementEnum::Format);
153   }
154   return labeledStmtClassificationSet;
155 }
156 
157 static unsigned SayLabel(parser::Label label) {
158   return static_cast<unsigned>(label);
159 }
160 
161 struct UnitAnalysis {
162   UnitAnalysis() { scopeModel.emplace_back(); }
163 
164   SourceStmtList doStmtSources;
165   SourceStmtList formatStmtSources;
166   SourceStmtList otherStmtSources;
167   SourceStmtList assignStmtSources;
168   TargetStmtMap targetStmts;
169   std::vector<ScopeInfo> scopeModel;
170 };
171 
172 // Some parse tree record for statements simply wrap construct names;
173 // others include them as tuple components.  Given a statement,
174 // return a pointer to its name if it has one.
175 template <typename A>
176 const parser::CharBlock *GetStmtName(const parser::Statement<A> &stmt) {
177   const std::optional<parser::Name> *name{nullptr};
178   if constexpr (WrapperTrait<A>) {
179     if constexpr (std::is_same_v<decltype(A::v), parser::Name>) {
180       return &stmt.statement.v.source;
181     } else {
182       name = &stmt.statement.v;
183     }
184   } else if constexpr (std::is_same_v<A, parser::SelectRankStmt> ||
185       std::is_same_v<A, parser::SelectTypeStmt>) {
186     name = &std::get<0>(stmt.statement.t);
187   } else if constexpr (common::HasMember<parser::Name,
188                            decltype(stmt.statement.t)>) {
189     return &std::get<parser::Name>(stmt.statement.t).source;
190   } else {
191     name = &std::get<std::optional<parser::Name>>(stmt.statement.t);
192   }
193   if (name && *name) {
194     return &(*name)->source;
195   }
196   return nullptr;
197 }
198 
199 class ParseTreeAnalyzer {
200 public:
201   ParseTreeAnalyzer(ParseTreeAnalyzer &&that) = default;
202   ParseTreeAnalyzer(SemanticsContext &context) : context_{context} {}
203 
204   template <typename A> constexpr bool Pre(const A &x) {
205     using LabeledProgramUnitStmts =
206         std::tuple<parser::MainProgram, parser::FunctionSubprogram,
207             parser::SubroutineSubprogram, parser::SeparateModuleSubprogram>;
208     if constexpr (common::HasMember<A, LabeledProgramUnitStmts>) {
209       const auto &endStmt{std::get<std::tuple_size_v<decltype(x.t)> - 1>(x.t)};
210       if (endStmt.label) {
211         // The END statement for a subprogram appears after any internal
212         // subprograms.  Visit that statement in advance so that results
213         // are placed in the correct programUnits_ slot.
214         auto targetFlags{ConstructBranchTargetFlags(endStmt)};
215         AddTargetLabelDefinition(endStmt.label.value(), targetFlags,
216             currentScope_,
217             /*isExecutableConstructEndStmt=*/false);
218       }
219     }
220     return true;
221   }
222   template <typename A> constexpr void Post(const A &) {}
223 
224   template <typename A> bool Pre(const parser::Statement<A> &statement) {
225     currentPosition_ = statement.source;
226     const auto &label = statement.label;
227     if (!label) {
228       return true;
229     }
230     using LabeledConstructStmts = std::tuple<parser::AssociateStmt,
231         parser::BlockStmt, parser::ChangeTeamStmt, parser::CriticalStmt,
232         parser::IfThenStmt, parser::NonLabelDoStmt, parser::SelectCaseStmt,
233         parser::SelectRankStmt, parser::SelectTypeStmt,
234         parser::ForallConstructStmt, parser::WhereConstructStmt>;
235     using LabeledConstructEndStmts = std::tuple<parser::EndAssociateStmt,
236         parser::EndBlockStmt, parser::EndChangeTeamStmt,
237         parser::EndCriticalStmt, parser::EndDoStmt, parser::EndForallStmt,
238         parser::EndIfStmt, parser::EndWhereStmt>;
239     using LabeledProgramUnitEndStmts =
240         std::tuple<parser::EndFunctionStmt, parser::EndMpSubprogramStmt,
241             parser::EndProgramStmt, parser::EndSubroutineStmt>;
242     auto targetFlags{ConstructBranchTargetFlags(statement)};
243     if constexpr (common::HasMember<A, LabeledConstructStmts>) {
244       AddTargetLabelDefinition(label.value(), targetFlags, ParentScope(),
245           /*isExecutableConstructEndStmt=*/false);
246     } else if constexpr (std::is_same_v<A, parser::EndIfStmt> ||
247         std::is_same_v<A, parser::EndSelectStmt>) {
248       // the label on an END IF/SELECT is not in the last part/case
249       AddTargetLabelDefinition(label.value(), targetFlags, ParentScope(),
250           /*isExecutableConstructEndStmt=*/true);
251     } else if constexpr (common::HasMember<A, LabeledConstructEndStmts>) {
252       AddTargetLabelDefinition(label.value(), targetFlags, currentScope_,
253           /*isExecutableConstructEndStmt=*/true);
254     } else if constexpr (!common::HasMember<A, LabeledProgramUnitEndStmts>) {
255       // Program unit END statements have already been processed.
256       AddTargetLabelDefinition(label.value(), targetFlags, currentScope_,
257           /*isExecutableConstructEndStmt=*/false);
258     }
259     return true;
260   }
261 
262   // see 11.1.1
263   bool Pre(const parser::ProgramUnit &) { return InitializeNewScopeContext(); }
264   bool Pre(const parser::InternalSubprogram &) {
265     return InitializeNewScopeContext();
266   }
267   bool Pre(const parser::ModuleSubprogram &) {
268     return InitializeNewScopeContext();
269   }
270   bool Pre(const parser::AssociateConstruct &associateConstruct) {
271     return PushConstructName(associateConstruct);
272   }
273   bool Pre(const parser::BlockConstruct &blockConstruct) {
274     return PushConstructName(blockConstruct);
275   }
276   bool Pre(const parser::ChangeTeamConstruct &changeTeamConstruct) {
277     return PushConstructName(changeTeamConstruct);
278   }
279   bool Pre(const parser::CriticalConstruct &criticalConstruct) {
280     return PushConstructName(criticalConstruct);
281   }
282   bool Pre(const parser::DoConstruct &doConstruct) {
283     const auto &optionalName{std::get<std::optional<parser::Name>>(
284         std::get<parser::Statement<parser::NonLabelDoStmt>>(doConstruct.t)
285             .statement.t)};
286     if (optionalName) {
287       constructNames_.emplace_back(optionalName->ToString());
288     }
289     // Allow FORTRAN '66 extended DO ranges
290     PushScope(false);
291     // Process labels of the DO and END DO statements, but not the
292     // statements themselves, so that a non-construct END DO
293     // can be distinguished (below).
294     Pre(std::get<parser::Statement<parser::NonLabelDoStmt>>(doConstruct.t));
295     Walk(std::get<parser::Block>(doConstruct.t), *this);
296     Pre(std::get<parser::Statement<parser::EndDoStmt>>(doConstruct.t));
297     PopConstructName(doConstruct);
298     return false;
299   }
300   void Post(const parser::EndDoStmt &endDoStmt) {
301     // Visited only for non-construct labeled DO termination
302     if (const auto &name{endDoStmt.v}) {
303       context_.Say(name->source, "Unexpected DO construct name '%s'"_err_en_US,
304           name->source);
305     }
306   }
307   bool Pre(const parser::IfConstruct &ifConstruct) {
308     return PushConstructName(ifConstruct);
309   }
310   void Post(const parser::IfThenStmt &) { PushScope(false); }
311   bool Pre(const parser::IfConstruct::ElseIfBlock &) {
312     return SwitchToNewScope();
313   }
314   bool Pre(const parser::IfConstruct::ElseBlock &) {
315     return SwitchToNewScope();
316   }
317   bool Pre(const parser::EndIfStmt &) {
318     PopScope();
319     return true;
320   }
321   bool Pre(const parser::CaseConstruct &caseConstruct) {
322     return PushConstructName(caseConstruct);
323   }
324   void Post(const parser::SelectCaseStmt &) { PushScope(false); }
325   bool Pre(const parser::CaseConstruct::Case &) { return SwitchToNewScope(); }
326   bool Pre(const parser::SelectRankConstruct &selectRankConstruct) {
327     return PushConstructName(selectRankConstruct);
328   }
329   void Post(const parser::SelectRankStmt &) { PushScope(true); }
330   bool Pre(const parser::SelectRankConstruct::RankCase &) {
331     return SwitchToNewScope();
332   }
333   bool Pre(const parser::SelectTypeConstruct &selectTypeConstruct) {
334     return PushConstructName(selectTypeConstruct);
335   }
336   void Post(const parser::SelectTypeStmt &) { PushScope(true); }
337   bool Pre(const parser::SelectTypeConstruct::TypeCase &) {
338     return SwitchToNewScope();
339   }
340   void Post(const parser::EndSelectStmt &) { PopScope(); }
341   bool Pre(const parser::WhereConstruct &whereConstruct) {
342     return PushConstructName(whereConstruct);
343   }
344   bool Pre(const parser::ForallConstruct &forallConstruct) {
345     return PushConstructName(forallConstruct);
346   }
347 
348   void Post(const parser::AssociateConstruct &associateConstruct) {
349     PopConstructName(associateConstruct);
350   }
351   void Post(const parser::BlockConstruct &blockConstruct) {
352     PopConstructName(blockConstruct);
353   }
354   void Post(const parser::ChangeTeamConstruct &changeTeamConstruct) {
355     PopConstructName(changeTeamConstruct);
356   }
357   void Post(const parser::CriticalConstruct &criticalConstruct) {
358     PopConstructName(criticalConstruct);
359   }
360   void Post(const parser::IfConstruct &ifConstruct) {
361     PopConstructName(ifConstruct);
362   }
363   void Post(const parser::CaseConstruct &caseConstruct) {
364     PopConstructName(caseConstruct);
365   }
366   void Post(const parser::SelectRankConstruct &selectRankConstruct) {
367     PopConstructName(selectRankConstruct);
368   }
369   void Post(const parser::SelectTypeConstruct &selectTypeConstruct) {
370     PopConstructName(selectTypeConstruct);
371   }
372   void Post(const parser::WhereConstruct &whereConstruct) {
373     PopConstructName(whereConstruct);
374   }
375   void Post(const parser::ForallConstruct &forallConstruct) {
376     PopConstructName(forallConstruct);
377   }
378 
379   // Checks for missing or mismatching names on various constructs (e.g., IF)
380   // and their intermediate or terminal statements that allow optional
381   // construct names(e.g., ELSE).  When an optional construct name is present,
382   // the construct as a whole must have a name that matches.
383   template <typename FIRST, typename CONSTRUCT, typename STMT>
384   void CheckOptionalName(const char *constructTag, const CONSTRUCT &a,
385       const parser::Statement<STMT> &stmt) {
386     if (const parser::CharBlock * name{GetStmtName(stmt)}) {
387       const auto &firstStmt{std::get<parser::Statement<FIRST>>(a.t)};
388       if (const parser::CharBlock * firstName{GetStmtName(firstStmt)}) {
389         if (*firstName != *name) {
390           context_.Say(*name, "%s name mismatch"_err_en_US, constructTag)
391               .Attach(*firstName, "should be"_en_US);
392         }
393       } else {
394         context_.Say(*name, "%s name not allowed"_err_en_US, constructTag)
395             .Attach(firstStmt.source, "in unnamed %s"_en_US, constructTag);
396       }
397     }
398   }
399 
400   // C1414
401   void Post(const parser::BlockData &blockData) {
402     CheckOptionalName<parser::BlockDataStmt>("BLOCK DATA subprogram", blockData,
403         std::get<parser::Statement<parser::EndBlockDataStmt>>(blockData.t));
404   }
405 
406   bool Pre(const parser::InterfaceBody &) {
407     PushDisposableMap();
408     return true;
409   }
410   void Post(const parser::InterfaceBody &) { PopDisposableMap(); }
411 
412   // C1564
413   void Post(const parser::InterfaceBody::Function &func) {
414     CheckOptionalName<parser::FunctionStmt>("FUNCTION", func,
415         std::get<parser::Statement<parser::EndFunctionStmt>>(func.t));
416   }
417 
418   // C1564
419   void Post(const parser::FunctionSubprogram &functionSubprogram) {
420     CheckOptionalName<parser::FunctionStmt>("FUNCTION", functionSubprogram,
421         std::get<parser::Statement<parser::EndFunctionStmt>>(
422             functionSubprogram.t));
423   }
424 
425   // C1502
426   void Post(const parser::InterfaceBlock &interfaceBlock) {
427     if (const auto &endGenericSpec{
428             std::get<parser::Statement<parser::EndInterfaceStmt>>(
429                 interfaceBlock.t)
430                 .statement.v}) {
431       const auto &interfaceStmt{
432           std::get<parser::Statement<parser::InterfaceStmt>>(interfaceBlock.t)};
433       if (std::holds_alternative<parser::Abstract>(interfaceStmt.statement.u)) {
434         context_
435             .Say(endGenericSpec->source,
436                 "END INTERFACE generic name (%s) may not appear for ABSTRACT INTERFACE"_err_en_US,
437                 endGenericSpec->source)
438             .Attach(
439                 interfaceStmt.source, "corresponding ABSTRACT INTERFACE"_en_US);
440       } else if (const auto &genericSpec{
441                      std::get<std::optional<parser::GenericSpec>>(
442                          interfaceStmt.statement.u)}) {
443         bool ok{genericSpec->source == endGenericSpec->source};
444         if (!ok) {
445           // Accept variant spellings of .LT. &c.
446           const auto *endOp{
447               std::get_if<parser::DefinedOperator>(&endGenericSpec->u)};
448           const auto *op{std::get_if<parser::DefinedOperator>(&genericSpec->u)};
449           if (endOp && op) {
450             const auto *endIntrin{
451                 std::get_if<parser::DefinedOperator::IntrinsicOperator>(
452                     &endOp->u)};
453             const auto *intrin{
454                 std::get_if<parser::DefinedOperator::IntrinsicOperator>(
455                     &op->u)};
456             ok = endIntrin && intrin && *endIntrin == *intrin;
457           }
458         }
459         if (!ok) {
460           context_
461               .Say(endGenericSpec->source,
462                   "END INTERFACE generic name (%s) does not match generic INTERFACE (%s)"_err_en_US,
463                   endGenericSpec->source, genericSpec->source)
464               .Attach(genericSpec->source, "corresponding INTERFACE"_en_US);
465         }
466       } else {
467         context_
468             .Say(endGenericSpec->source,
469                 "END INTERFACE generic name (%s) may not appear for non-generic INTERFACE"_err_en_US,
470                 endGenericSpec->source)
471             .Attach(interfaceStmt.source, "corresponding INTERFACE"_en_US);
472       }
473     }
474   }
475 
476   // C1402
477   void Post(const parser::Module &module) {
478     CheckOptionalName<parser::ModuleStmt>("MODULE", module,
479         std::get<parser::Statement<parser::EndModuleStmt>>(module.t));
480   }
481 
482   // C1569
483   void Post(const parser::SeparateModuleSubprogram &separateModuleSubprogram) {
484     CheckOptionalName<parser::MpSubprogramStmt>("MODULE PROCEDURE",
485         separateModuleSubprogram,
486         std::get<parser::Statement<parser::EndMpSubprogramStmt>>(
487             separateModuleSubprogram.t));
488   }
489 
490   // C1401
491   void Post(const parser::MainProgram &mainProgram) {
492     if (const parser::CharBlock *
493         endName{GetStmtName(std::get<parser::Statement<parser::EndProgramStmt>>(
494             mainProgram.t))}) {
495       if (const auto &program{
496               std::get<std::optional<parser::Statement<parser::ProgramStmt>>>(
497                   mainProgram.t)}) {
498         if (*endName != program->statement.v.source) {
499           context_.Say(*endName, "END PROGRAM name mismatch"_err_en_US)
500               .Attach(program->statement.v.source, "should be"_en_US);
501         }
502       } else {
503         context_.Say(*endName,
504             "END PROGRAM has name without PROGRAM statement"_err_en_US);
505       }
506     }
507   }
508 
509   // C1413
510   void Post(const parser::Submodule &submodule) {
511     CheckOptionalName<parser::SubmoduleStmt>("SUBMODULE", submodule,
512         std::get<parser::Statement<parser::EndSubmoduleStmt>>(submodule.t));
513   }
514 
515   // C1567
516   void Post(const parser::InterfaceBody::Subroutine &sub) {
517     CheckOptionalName<parser::SubroutineStmt>("SUBROUTINE", sub,
518         std::get<parser::Statement<parser::EndSubroutineStmt>>(sub.t));
519   }
520 
521   // C1567
522   void Post(const parser::SubroutineSubprogram &subroutineSubprogram) {
523     CheckOptionalName<parser::SubroutineStmt>("SUBROUTINE",
524         subroutineSubprogram,
525         std::get<parser::Statement<parser::EndSubroutineStmt>>(
526             subroutineSubprogram.t));
527   }
528 
529   // C739
530   bool Pre(const parser::DerivedTypeDef &) {
531     PushDisposableMap();
532     return true;
533   }
534   void Post(const parser::DerivedTypeDef &derivedTypeDef) {
535     CheckOptionalName<parser::DerivedTypeStmt>("derived type definition",
536         derivedTypeDef,
537         std::get<parser::Statement<parser::EndTypeStmt>>(derivedTypeDef.t));
538     PopDisposableMap();
539   }
540 
541   void Post(const parser::LabelDoStmt &labelDoStmt) {
542     AddLabelReferenceFromDoStmt(std::get<parser::Label>(labelDoStmt.t));
543   }
544   void Post(const parser::GotoStmt &gotoStmt) { AddLabelReference(gotoStmt.v); }
545   void Post(const parser::ComputedGotoStmt &computedGotoStmt) {
546     AddLabelReference(std::get<std::list<parser::Label>>(computedGotoStmt.t));
547   }
548   void Post(const parser::ArithmeticIfStmt &arithmeticIfStmt) {
549     AddLabelReference(std::get<1>(arithmeticIfStmt.t));
550     AddLabelReference(std::get<2>(arithmeticIfStmt.t));
551     AddLabelReference(std::get<3>(arithmeticIfStmt.t));
552   }
553   void Post(const parser::AssignStmt &assignStmt) {
554     AddLabelReferenceFromAssignStmt(std::get<parser::Label>(assignStmt.t));
555   }
556   void Post(const parser::AssignedGotoStmt &assignedGotoStmt) {
557     AddLabelReference(std::get<std::list<parser::Label>>(assignedGotoStmt.t));
558   }
559   void Post(const parser::AltReturnSpec &altReturnSpec) {
560     AddLabelReference(altReturnSpec.v);
561   }
562 
563   void Post(const parser::ErrLabel &errLabel) { AddLabelReference(errLabel.v); }
564   void Post(const parser::EndLabel &endLabel) { AddLabelReference(endLabel.v); }
565   void Post(const parser::EorLabel &eorLabel) { AddLabelReference(eorLabel.v); }
566   void Post(const parser::Format &format) {
567     if (const auto *labelPointer{std::get_if<parser::Label>(&format.u)}) {
568       AddLabelReferenceToFormatStmt(*labelPointer);
569     }
570   }
571   void Post(const parser::CycleStmt &cycleStmt) {
572     if (cycleStmt.v) {
573       CheckLabelContext("CYCLE", cycleStmt.v->source);
574     }
575   }
576   void Post(const parser::ExitStmt &exitStmt) {
577     if (exitStmt.v) {
578       CheckLabelContext("EXIT", exitStmt.v->source);
579     }
580   }
581 
582   const std::vector<UnitAnalysis> &ProgramUnits() const {
583     return programUnits_;
584   }
585   SemanticsContext &ErrorHandler() { return context_; }
586 
587 private:
588   ScopeInfo &PushScope(bool isExteriorGotoFatal) {
589     auto &model{programUnits_.back().scopeModel};
590     int newDepth{model.empty() ? 1 : model[currentScope_].depth + 1};
591     ScopeInfo &result{model.emplace_back()};
592     result.parent = currentScope_;
593     result.depth = newDepth;
594     result.isExteriorGotoFatal = isExteriorGotoFatal;
595     currentScope_ = model.size() - 1;
596     return result;
597   }
598   bool InitializeNewScopeContext() {
599     programUnits_.emplace_back(UnitAnalysis{});
600     currentScope_ = 0u;
601     PushScope(false);
602     return true;
603   }
604   ScopeInfo &PopScope() {
605     ScopeInfo &result{programUnits_.back().scopeModel[currentScope_]};
606     currentScope_ = result.parent;
607     return result;
608   }
609   ProxyForScope ParentScope() {
610     return programUnits_.back().scopeModel[currentScope_].parent;
611   }
612   bool SwitchToNewScope() {
613     PushScope(PopScope().isExteriorGotoFatal);
614     return true;
615   }
616 
617   template <typename A> bool PushConstructName(const A &a) {
618     const auto &optionalName{std::get<0>(std::get<0>(a.t).statement.t)};
619     if (optionalName) {
620       constructNames_.emplace_back(optionalName->ToString());
621     }
622     // Gotos into this construct from outside it are diagnosed, and
623     // are fatal unless the construct is a DO, IF, or SELECT CASE.
624     PushScope(!(std::is_same_v<A, parser::DoConstruct> ||
625         std::is_same_v<A, parser::IfConstruct> ||
626         std::is_same_v<A, parser::CaseConstruct>));
627     return true;
628   }
629   bool PushConstructName(const parser::BlockConstruct &blockConstruct) {
630     const auto &optionalName{
631         std::get<parser::Statement<parser::BlockStmt>>(blockConstruct.t)
632             .statement.v};
633     if (optionalName) {
634       constructNames_.emplace_back(optionalName->ToString());
635     }
636     PushScope(true);
637     return true;
638   }
639   template <typename A> void PopConstructNameIfPresent(const A &a) {
640     const auto &optionalName{std::get<0>(std::get<0>(a.t).statement.t)};
641     if (optionalName) {
642       constructNames_.pop_back();
643     }
644   }
645   void PopConstructNameIfPresent(const parser::BlockConstruct &blockConstruct) {
646     const auto &optionalName{
647         std::get<parser::Statement<parser::BlockStmt>>(blockConstruct.t)
648             .statement.v};
649     if (optionalName) {
650       constructNames_.pop_back();
651     }
652   }
653 
654   template <typename A> void PopConstructName(const A &a) {
655     CheckName(a);
656     PopScope();
657     PopConstructNameIfPresent(a);
658   }
659 
660   template <typename FIRST, typename CASEBLOCK, typename CASE,
661       typename CONSTRUCT>
662   void CheckSelectNames(const char *tag, const CONSTRUCT &construct) {
663     CheckEndName<FIRST, parser::EndSelectStmt>(tag, construct);
664     for (const auto &inner : std::get<std::list<CASEBLOCK>>(construct.t)) {
665       CheckOptionalName<FIRST>(
666           tag, construct, std::get<parser::Statement<CASE>>(inner.t));
667     }
668   }
669 
670   // C1144
671   void PopConstructName(const parser::CaseConstruct &caseConstruct) {
672     CheckSelectNames<parser::SelectCaseStmt, parser::CaseConstruct::Case,
673         parser::CaseStmt>("SELECT CASE", caseConstruct);
674     PopScope();
675     PopConstructNameIfPresent(caseConstruct);
676   }
677 
678   // C1154, C1156
679   void PopConstructName(
680       const parser::SelectRankConstruct &selectRankConstruct) {
681     CheckSelectNames<parser::SelectRankStmt,
682         parser::SelectRankConstruct::RankCase, parser::SelectRankCaseStmt>(
683         "SELECT RANK", selectRankConstruct);
684     PopScope();
685     PopConstructNameIfPresent(selectRankConstruct);
686   }
687 
688   // C1165
689   void PopConstructName(
690       const parser::SelectTypeConstruct &selectTypeConstruct) {
691     CheckSelectNames<parser::SelectTypeStmt,
692         parser::SelectTypeConstruct::TypeCase, parser::TypeGuardStmt>(
693         "SELECT TYPE", selectTypeConstruct);
694     PopScope();
695     PopConstructNameIfPresent(selectTypeConstruct);
696   }
697 
698   // Checks for missing or mismatching names on various constructs (e.g., BLOCK)
699   // and their END statements.  Both names must be present if either one is.
700   template <typename FIRST, typename END, typename CONSTRUCT>
701   void CheckEndName(const char *constructTag, const CONSTRUCT &a) {
702     const auto &constructStmt{std::get<parser::Statement<FIRST>>(a.t)};
703     const auto &endStmt{std::get<parser::Statement<END>>(a.t)};
704     const parser::CharBlock *endName{GetStmtName(endStmt)};
705     if (const parser::CharBlock * constructName{GetStmtName(constructStmt)}) {
706       if (endName) {
707         if (*constructName != *endName) {
708           context_
709               .Say(*endName, "%s construct name mismatch"_err_en_US,
710                   constructTag)
711               .Attach(*constructName, "should be"_en_US);
712         }
713       } else {
714         context_
715             .Say(endStmt.source,
716                 "%s construct name required but missing"_err_en_US,
717                 constructTag)
718             .Attach(*constructName, "should be"_en_US);
719       }
720     } else if (endName) {
721       context_
722           .Say(*endName, "%s construct name unexpected"_err_en_US, constructTag)
723           .Attach(
724               constructStmt.source, "unnamed %s statement"_en_US, constructTag);
725     }
726   }
727 
728   // C1106
729   void CheckName(const parser::AssociateConstruct &associateConstruct) {
730     CheckEndName<parser::AssociateStmt, parser::EndAssociateStmt>(
731         "ASSOCIATE", associateConstruct);
732   }
733   // C1117
734   void CheckName(const parser::CriticalConstruct &criticalConstruct) {
735     CheckEndName<parser::CriticalStmt, parser::EndCriticalStmt>(
736         "CRITICAL", criticalConstruct);
737   }
738   // C1131
739   void CheckName(const parser::DoConstruct &doConstruct) {
740     CheckEndName<parser::NonLabelDoStmt, parser::EndDoStmt>("DO", doConstruct);
741     if (auto label{std::get<std::optional<parser::Label>>(
742             std::get<parser::Statement<parser::NonLabelDoStmt>>(doConstruct.t)
743                 .statement.t)}) {
744       const auto &endDoStmt{
745           std::get<parser::Statement<parser::EndDoStmt>>(doConstruct.t)};
746       if (!endDoStmt.label || *endDoStmt.label != *label) {
747         context_
748             .Say(endDoStmt.source,
749                 "END DO statement must have the label '%d' matching its DO statement"_err_en_US,
750                 *label)
751             .Attach(std::get<parser::Statement<parser::NonLabelDoStmt>>(
752                         doConstruct.t)
753                         .source,
754                 "corresponding DO statement"_en_US);
755       }
756     }
757   }
758   // C1035
759   void CheckName(const parser::ForallConstruct &forallConstruct) {
760     CheckEndName<parser::ForallConstructStmt, parser::EndForallStmt>(
761         "FORALL", forallConstruct);
762   }
763 
764   // C1109
765   void CheckName(const parser::BlockConstruct &blockConstruct) {
766     CheckEndName<parser::BlockStmt, parser::EndBlockStmt>(
767         "BLOCK", blockConstruct);
768   }
769   // C1112
770   void CheckName(const parser::ChangeTeamConstruct &changeTeamConstruct) {
771     CheckEndName<parser::ChangeTeamStmt, parser::EndChangeTeamStmt>(
772         "CHANGE TEAM", changeTeamConstruct);
773   }
774 
775   // C1142
776   void CheckName(const parser::IfConstruct &ifConstruct) {
777     CheckEndName<parser::IfThenStmt, parser::EndIfStmt>("IF", ifConstruct);
778     for (const auto &elseIfBlock :
779         std::get<std::list<parser::IfConstruct::ElseIfBlock>>(ifConstruct.t)) {
780       CheckOptionalName<parser::IfThenStmt>("IF construct", ifConstruct,
781           std::get<parser::Statement<parser::ElseIfStmt>>(elseIfBlock.t));
782     }
783     if (const auto &elseBlock{
784             std::get<std::optional<parser::IfConstruct::ElseBlock>>(
785                 ifConstruct.t)}) {
786       CheckOptionalName<parser::IfThenStmt>("IF construct", ifConstruct,
787           std::get<parser::Statement<parser::ElseStmt>>(elseBlock->t));
788     }
789   }
790 
791   // C1033
792   void CheckName(const parser::WhereConstruct &whereConstruct) {
793     CheckEndName<parser::WhereConstructStmt, parser::EndWhereStmt>(
794         "WHERE", whereConstruct);
795     for (const auto &maskedElsewhere :
796         std::get<std::list<parser::WhereConstruct::MaskedElsewhere>>(
797             whereConstruct.t)) {
798       CheckOptionalName<parser::WhereConstructStmt>("WHERE construct",
799           whereConstruct,
800           std::get<parser::Statement<parser::MaskedElsewhereStmt>>(
801               maskedElsewhere.t));
802     }
803     if (const auto &elsewhere{
804             std::get<std::optional<parser::WhereConstruct::Elsewhere>>(
805                 whereConstruct.t)}) {
806       CheckOptionalName<parser::WhereConstructStmt>("WHERE construct",
807           whereConstruct,
808           std::get<parser::Statement<parser::ElsewhereStmt>>(elsewhere->t));
809     }
810   }
811 
812   // C1134, C1166
813   void CheckLabelContext(
814       const char *const stmtString, const parser::CharBlock &constructName) {
815     const auto iter{std::find(constructNames_.crbegin(),
816         constructNames_.crend(), constructName.ToString())};
817     if (iter == constructNames_.crend()) {
818       context_.Say(constructName, "%s construct-name is not in scope"_err_en_US,
819           stmtString);
820     }
821   }
822 
823   // 6.2.5, paragraph 2
824   void CheckLabelInRange(parser::Label label) {
825     if (label < 1 || label > 99999) {
826       context_.Say(currentPosition_, "Label '%u' is out of range"_err_en_US,
827           SayLabel(label));
828     }
829   }
830 
831   // 6.2.5., paragraph 2
832   void AddTargetLabelDefinition(parser::Label label,
833       LabeledStmtClassificationSet labeledStmtClassificationSet,
834       ProxyForScope scope, bool isExecutableConstructEndStmt) {
835     CheckLabelInRange(label);
836     TargetStmtMap &targetStmtMap{disposableMaps_.empty()
837             ? programUnits_.back().targetStmts
838             : disposableMaps_.back()};
839     const auto pair{targetStmtMap.emplace(label,
840         LabeledStatementInfoTuplePOD{scope, currentPosition_,
841             labeledStmtClassificationSet, isExecutableConstructEndStmt})};
842     if (!pair.second) {
843       context_.Say(currentPosition_, "Label '%u' is not distinct"_err_en_US,
844           SayLabel(label));
845     }
846   }
847 
848   void AddLabelReferenceFromDoStmt(parser::Label label) {
849     CheckLabelInRange(label);
850     programUnits_.back().doStmtSources.emplace_back(
851         label, currentScope_, currentPosition_);
852   }
853 
854   void AddLabelReferenceToFormatStmt(parser::Label label) {
855     CheckLabelInRange(label);
856     programUnits_.back().formatStmtSources.emplace_back(
857         label, currentScope_, currentPosition_);
858   }
859 
860   void AddLabelReferenceFromAssignStmt(parser::Label label) {
861     CheckLabelInRange(label);
862     programUnits_.back().assignStmtSources.emplace_back(
863         label, currentScope_, currentPosition_);
864   }
865 
866   void AddLabelReference(parser::Label label) {
867     CheckLabelInRange(label);
868     programUnits_.back().otherStmtSources.emplace_back(
869         label, currentScope_, currentPosition_);
870   }
871 
872   void AddLabelReference(const std::list<parser::Label> &labels) {
873     for (const parser::Label &label : labels) {
874       AddLabelReference(label);
875     }
876   }
877 
878   void PushDisposableMap() { disposableMaps_.emplace_back(); }
879   void PopDisposableMap() { disposableMaps_.pop_back(); }
880 
881   std::vector<UnitAnalysis> programUnits_;
882   SemanticsContext &context_;
883   parser::CharBlock currentPosition_;
884   ProxyForScope currentScope_;
885   std::vector<std::string> constructNames_;
886   // For labels in derived type definitions and procedure
887   // interfaces, which are their own inclusive scopes.  None
888   // of these labels can be used as a branch target, but they
889   // should be pairwise distinct.
890   std::vector<TargetStmtMap> disposableMaps_;
891 };
892 
893 bool InInclusiveScope(const std::vector<ScopeInfo> &scopes, ProxyForScope tail,
894     ProxyForScope head) {
895   for (; tail != head; tail = scopes[tail].parent) {
896     if (!HasScope(tail)) {
897       return false;
898     }
899   }
900   return true;
901 }
902 
903 ParseTreeAnalyzer LabelAnalysis(
904     SemanticsContext &context, const parser::Program &program) {
905   ParseTreeAnalyzer analysis{context};
906   Walk(program, analysis);
907   return analysis;
908 }
909 
910 bool InBody(const parser::CharBlock &position,
911     const std::pair<parser::CharBlock, parser::CharBlock> &pair) {
912   if (position.begin() >= pair.first.begin()) {
913     if (position.begin() < pair.second.end()) {
914       return true;
915     }
916   }
917   return false;
918 }
919 
920 static LabeledStatementInfoTuplePOD GetLabel(
921     const TargetStmtMap &labels, const parser::Label &label) {
922   const auto iter{labels.find(label)};
923   if (iter == labels.cend()) {
924     return {0u, nullptr, LabeledStmtClassificationSet{}, false};
925   } else {
926     return iter->second;
927   }
928 }
929 
930 // 11.1.7.3
931 void CheckBranchesIntoDoBody(const SourceStmtList &branches,
932     const TargetStmtMap &labels, const IndexList &loopBodies,
933     SemanticsContext &context) {
934   for (const auto &branch : branches) {
935     const auto &label{branch.parserLabel};
936     auto branchTarget{GetLabel(labels, label)};
937     if (HasScope(branchTarget.proxyForScope)) {
938       const auto &fromPosition{branch.parserCharBlock};
939       const auto &toPosition{branchTarget.parserCharBlock};
940       for (const auto &body : loopBodies) {
941         if (!InBody(fromPosition, body) && InBody(toPosition, body) &&
942             context.ShouldWarn(common::LanguageFeature::BranchIntoConstruct)) {
943           context
944               .Say(
945                   fromPosition, "branch into loop body from outside"_warn_en_US)
946               .Attach(body.first, "the loop branched into"_en_US)
947               .set_languageFeature(
948                   common::LanguageFeature::BranchIntoConstruct);
949         }
950       }
951     }
952   }
953 }
954 
955 void CheckDoNesting(const IndexList &loopBodies, SemanticsContext &context) {
956   for (auto i1{loopBodies.cbegin()}; i1 != loopBodies.cend(); ++i1) {
957     const auto &v1{*i1};
958     for (auto i2{i1 + 1}; i2 != loopBodies.cend(); ++i2) {
959       const auto &v2{*i2};
960       if (v2.first.begin() < v1.second.end() &&
961           v1.second.begin() < v2.second.begin()) {
962         context.Say(v1.first, "DO loop doesn't properly nest"_err_en_US)
963             .Attach(v2.first, "DO loop conflicts"_en_US);
964       }
965     }
966   }
967 }
968 
969 parser::CharBlock SkipLabel(const parser::CharBlock &position) {
970   const std::size_t maxPosition{position.size()};
971   if (maxPosition && parser::IsDecimalDigit(position[0])) {
972     std::size_t i{1l};
973     for (; (i < maxPosition) && parser::IsDecimalDigit(position[i]); ++i) {
974     }
975     for (; (i < maxPosition) && parser::IsWhiteSpace(position[i]); ++i) {
976     }
977     return parser::CharBlock{position.begin() + i, position.end()};
978   }
979   return position;
980 }
981 
982 ProxyForScope ParentScope(
983     const std::vector<ScopeInfo> &scopes, ProxyForScope scope) {
984   return scopes[scope].parent;
985 }
986 
987 void CheckLabelDoConstraints(const SourceStmtList &dos,
988     const SourceStmtList &branches, const TargetStmtMap &labels,
989     const std::vector<ScopeInfo> &scopes, SemanticsContext &context) {
990   IndexList loopBodies;
991   for (const auto &stmt : dos) {
992     const auto &label{stmt.parserLabel};
993     const auto &scope{stmt.proxyForScope};
994     const auto &position{stmt.parserCharBlock};
995     auto doTarget{GetLabel(labels, label)};
996     if (!HasScope(doTarget.proxyForScope)) {
997       // C1133
998       context.Say(
999           position, "Label '%u' cannot be found"_err_en_US, SayLabel(label));
1000     } else if (doTarget.parserCharBlock.begin() < position.begin()) {
1001       // R1119
1002       context.Say(position,
1003           "Label '%u' doesn't lexically follow DO stmt"_err_en_US,
1004           SayLabel(label));
1005 
1006     } else if ((InInclusiveScope(scopes, scope, doTarget.proxyForScope) &&
1007                    doTarget.labeledStmtClassificationSet.test(
1008                        TargetStatementEnum::CompatibleDo)) ||
1009         (doTarget.isExecutableConstructEndStmt &&
1010             ParentScope(scopes, doTarget.proxyForScope) == scope)) {
1011       if (context.ShouldWarn(
1012               common::LanguageFeature::OldLabelDoEndStatements)) {
1013         context
1014             .Say(position,
1015                 "A DO loop should terminate with an END DO or CONTINUE"_port_en_US)
1016             .Attach(doTarget.parserCharBlock,
1017                 "DO loop currently ends at statement:"_en_US)
1018             .set_languageFeature(
1019                 common::LanguageFeature::OldLabelDoEndStatements);
1020       }
1021     } else if (!InInclusiveScope(scopes, scope, doTarget.proxyForScope)) {
1022       context.Say(position, "Label '%u' is not in DO loop scope"_err_en_US,
1023           SayLabel(label));
1024     } else if (!doTarget.labeledStmtClassificationSet.test(
1025                    TargetStatementEnum::Do)) {
1026       context.Say(doTarget.parserCharBlock,
1027           "A DO loop should terminate with an END DO or CONTINUE"_err_en_US);
1028     } else {
1029       loopBodies.emplace_back(SkipLabel(position), doTarget.parserCharBlock);
1030     }
1031   }
1032 
1033   CheckBranchesIntoDoBody(branches, labels, loopBodies, context);
1034   CheckDoNesting(loopBodies, context);
1035 }
1036 
1037 // 6.2.5
1038 void CheckScopeConstraints(const SourceStmtList &stmts,
1039     const TargetStmtMap &labels, const std::vector<ScopeInfo> &scopes,
1040     SemanticsContext &context) {
1041   for (const auto &stmt : stmts) {
1042     const auto &label{stmt.parserLabel};
1043     const auto &scope{stmt.proxyForScope};
1044     const auto &position{stmt.parserCharBlock};
1045     auto target{GetLabel(labels, label)};
1046     if (!HasScope(target.proxyForScope)) {
1047       context.Say(
1048           position, "Label '%u' was not found"_err_en_US, SayLabel(label));
1049     } else if (!InInclusiveScope(scopes, scope, target.proxyForScope)) {
1050       // Clause 11.1.2.1 prohibits transfer of control to the interior of a
1051       // block from outside the block, but this does not apply to formats.
1052       // C1038 and C1034 forbid statements in FORALL and WHERE constructs
1053       // (resp.) from being branch targets.
1054       if (target.labeledStmtClassificationSet.test(
1055               TargetStatementEnum::Format)) {
1056         continue;
1057       }
1058       bool isFatal{false};
1059       ProxyForScope fromScope{scope};
1060       for (ProxyForScope toScope{target.proxyForScope}; HasScope(toScope);
1061            toScope = scopes[toScope].parent) {
1062         while (scopes[fromScope].depth > scopes[toScope].depth) {
1063           fromScope = scopes[fromScope].parent;
1064         }
1065         if (toScope == fromScope) {
1066           break;
1067         }
1068         if (scopes[toScope].isExteriorGotoFatal) {
1069           isFatal = true;
1070           break;
1071         }
1072       }
1073       if (isFatal) {
1074         context.Say(position,
1075             "Label '%u' is in a construct that prevents its use as a branch target here"_err_en_US,
1076             SayLabel(label));
1077       } else if (context.ShouldWarn(
1078                      common::LanguageFeature::BranchIntoConstruct)) {
1079         context
1080             .Say(position,
1081                 "Label '%u' is in a construct that should not be used as a branch target here"_warn_en_US,
1082                 SayLabel(label))
1083             .set_languageFeature(common::LanguageFeature::BranchIntoConstruct);
1084       }
1085     }
1086   }
1087 }
1088 
1089 void CheckBranchTargetConstraints(const SourceStmtList &stmts,
1090     const TargetStmtMap &labels, SemanticsContext &context) {
1091   for (const auto &stmt : stmts) {
1092     const auto &label{stmt.parserLabel};
1093     auto branchTarget{GetLabel(labels, label)};
1094     if (HasScope(branchTarget.proxyForScope)) {
1095       if (!branchTarget.labeledStmtClassificationSet.test(
1096               TargetStatementEnum::Branch) &&
1097           !branchTarget.labeledStmtClassificationSet.test(
1098               TargetStatementEnum::CompatibleBranch)) { // error
1099         context
1100             .Say(branchTarget.parserCharBlock,
1101                 "Label '%u' is not a branch target"_err_en_US, SayLabel(label))
1102             .Attach(stmt.parserCharBlock, "Control flow use of '%u'"_en_US,
1103                 SayLabel(label));
1104       } else if (!branchTarget.labeledStmtClassificationSet.test(
1105                      TargetStatementEnum::Branch) &&
1106           context.ShouldWarn(common::LanguageFeature::BadBranchTarget)) {
1107         context
1108             .Say(branchTarget.parserCharBlock,
1109                 "Label '%u' is not a branch target"_warn_en_US, SayLabel(label))
1110             .Attach(stmt.parserCharBlock, "Control flow use of '%u'"_en_US,
1111                 SayLabel(label))
1112             .set_languageFeature(common::LanguageFeature::BadBranchTarget);
1113       }
1114     }
1115   }
1116 }
1117 
1118 void CheckBranchConstraints(const SourceStmtList &branches,
1119     const TargetStmtMap &labels, const std::vector<ScopeInfo> &scopes,
1120     SemanticsContext &context) {
1121   CheckScopeConstraints(branches, labels, scopes, context);
1122   CheckBranchTargetConstraints(branches, labels, context);
1123 }
1124 
1125 void CheckDataXferTargetConstraints(const SourceStmtList &stmts,
1126     const TargetStmtMap &labels, SemanticsContext &context) {
1127   for (const auto &stmt : stmts) {
1128     const auto &label{stmt.parserLabel};
1129     auto ioTarget{GetLabel(labels, label)};
1130     if (HasScope(ioTarget.proxyForScope)) {
1131       if (!ioTarget.labeledStmtClassificationSet.test(
1132               TargetStatementEnum::Format)) {
1133         context
1134             .Say(ioTarget.parserCharBlock, "'%u' not a FORMAT"_err_en_US,
1135                 SayLabel(label))
1136             .Attach(stmt.parserCharBlock, "data transfer use of '%u'"_en_US,
1137                 SayLabel(label));
1138       }
1139     }
1140   }
1141 }
1142 
1143 void CheckDataTransferConstraints(const SourceStmtList &dataTransfers,
1144     const TargetStmtMap &labels, const std::vector<ScopeInfo> &scopes,
1145     SemanticsContext &context) {
1146   CheckScopeConstraints(dataTransfers, labels, scopes, context);
1147   CheckDataXferTargetConstraints(dataTransfers, labels, context);
1148 }
1149 
1150 void CheckAssignTargetConstraints(const SourceStmtList &stmts,
1151     const TargetStmtMap &labels, SemanticsContext &context) {
1152   for (const auto &stmt : stmts) {
1153     const auto &label{stmt.parserLabel};
1154     auto target{GetLabel(labels, label)};
1155     if (HasScope(target.proxyForScope) &&
1156         !target.labeledStmtClassificationSet.test(
1157             TargetStatementEnum::Branch) &&
1158         !target.labeledStmtClassificationSet.test(
1159             TargetStatementEnum::Format)) {
1160       parser::Message *msg{nullptr};
1161       if (!target.labeledStmtClassificationSet.test(
1162               TargetStatementEnum::CompatibleBranch)) {
1163         msg = &context.Say(target.parserCharBlock,
1164             "Label '%u' is not a branch target or FORMAT"_err_en_US,
1165             SayLabel(label));
1166       } else if (context.ShouldWarn(common::LanguageFeature::BadBranchTarget)) {
1167         msg =
1168             &context
1169                  .Say(target.parserCharBlock,
1170                      "Label '%u' is not a branch target or FORMAT"_warn_en_US,
1171                      SayLabel(label))
1172                  .set_languageFeature(common::LanguageFeature::BadBranchTarget);
1173       }
1174       if (msg) {
1175         msg->Attach(stmt.parserCharBlock, "ASSIGN statement use of '%u'"_en_US,
1176             SayLabel(label));
1177       }
1178     }
1179   }
1180 }
1181 
1182 void CheckAssignConstraints(const SourceStmtList &assigns,
1183     const TargetStmtMap &labels, const std::vector<ScopeInfo> &scopes,
1184     SemanticsContext &context) {
1185   CheckScopeConstraints(assigns, labels, scopes, context);
1186   CheckAssignTargetConstraints(assigns, labels, context);
1187 }
1188 
1189 bool CheckConstraints(ParseTreeAnalyzer &&parseTreeAnalysis) {
1190   auto &context{parseTreeAnalysis.ErrorHandler()};
1191   for (const auto &programUnit : parseTreeAnalysis.ProgramUnits()) {
1192     const auto &dos{programUnit.doStmtSources};
1193     const auto &branches{programUnit.otherStmtSources};
1194     const auto &labels{programUnit.targetStmts};
1195     const auto &scopes{programUnit.scopeModel};
1196     CheckLabelDoConstraints(dos, branches, labels, scopes, context);
1197     CheckBranchConstraints(branches, labels, scopes, context);
1198     const auto &dataTransfers{programUnit.formatStmtSources};
1199     CheckDataTransferConstraints(dataTransfers, labels, scopes, context);
1200     const auto &assigns{programUnit.assignStmtSources};
1201     CheckAssignConstraints(assigns, labels, scopes, context);
1202   }
1203   return !context.AnyFatalError();
1204 }
1205 
1206 bool ValidateLabels(SemanticsContext &context, const parser::Program &program) {
1207   return CheckConstraints(LabelAnalysis(context, program));
1208 }
1209 } // namespace Fortran::semantics
1210