xref: /llvm-project/llvm/include/llvm/Support/YAMLTraits.h (revision 4f26edd5e9eb3b6cea19e15ca8fb2c8416b82fa8)
1 //===- llvm/Support/YAMLTraits.h --------------------------------*- C++ -*-===//
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 #ifndef LLVM_SUPPORT_YAMLTRAITS_H
10 #define LLVM_SUPPORT_YAMLTRAITS_H
11 
12 #include "llvm/ADT/ArrayRef.h"
13 #include "llvm/ADT/BitVector.h"
14 #include "llvm/ADT/SmallVector.h"
15 #include "llvm/ADT/StringExtras.h"
16 #include "llvm/ADT/StringMap.h"
17 #include "llvm/ADT/StringRef.h"
18 #include "llvm/ADT/Twine.h"
19 #include "llvm/Support/AlignOf.h"
20 #include "llvm/Support/Allocator.h"
21 #include "llvm/Support/Endian.h"
22 #include "llvm/Support/SMLoc.h"
23 #include "llvm/Support/SourceMgr.h"
24 #include "llvm/Support/YAMLParser.h"
25 #include "llvm/Support/raw_ostream.h"
26 #include <array>
27 #include <cassert>
28 #include <map>
29 #include <memory>
30 #include <new>
31 #include <optional>
32 #include <string>
33 #include <system_error>
34 #include <type_traits>
35 #include <vector>
36 
37 namespace llvm {
38 
39 class VersionTuple;
40 
41 namespace yaml {
42 
43 enum class NodeKind : uint8_t {
44   Scalar,
45   Map,
46   Sequence,
47 };
48 
49 struct EmptyContext {};
50 
51 /// This class should be specialized by any type that needs to be converted
52 /// to/from a YAML mapping.  For example:
53 ///
54 ///     struct MappingTraits<MyStruct> {
55 ///       static void mapping(IO &io, MyStruct &s) {
56 ///         io.mapRequired("name", s.name);
57 ///         io.mapRequired("size", s.size);
58 ///         io.mapOptional("age",  s.age);
59 ///       }
60 ///     };
61 template<class T>
62 struct MappingTraits {
63   // Must provide:
64   // static void mapping(IO &io, T &fields);
65   // Optionally may provide:
66   // static std::string validate(IO &io, T &fields);
67   // static void enumInput(IO &io, T &value);
68   //
69   // The optional flow flag will cause generated YAML to use a flow mapping
70   // (e.g. { a: 0, b: 1 }):
71   // static const bool flow = true;
72 };
73 
74 /// This class is similar to MappingTraits<T> but allows you to pass in
75 /// additional context for each map operation.  For example:
76 ///
77 ///     struct MappingContextTraits<MyStruct, MyContext> {
78 ///       static void mapping(IO &io, MyStruct &s, MyContext &c) {
79 ///         io.mapRequired("name", s.name);
80 ///         io.mapRequired("size", s.size);
81 ///         io.mapOptional("age",  s.age);
82 ///         ++c.TimesMapped;
83 ///       }
84 ///     };
85 template <class T, class Context> struct MappingContextTraits {
86   // Must provide:
87   // static void mapping(IO &io, T &fields, Context &Ctx);
88   // Optionally may provide:
89   // static std::string validate(IO &io, T &fields, Context &Ctx);
90   //
91   // The optional flow flag will cause generated YAML to use a flow mapping
92   // (e.g. { a: 0, b: 1 }):
93   // static const bool flow = true;
94 };
95 
96 /// This class should be specialized by any integral type that converts
97 /// to/from a YAML scalar where there is a one-to-one mapping between
98 /// in-memory values and a string in YAML.  For example:
99 ///
100 ///     struct ScalarEnumerationTraits<Colors> {
101 ///         static void enumeration(IO &io, Colors &value) {
102 ///           io.enumCase(value, "red",   cRed);
103 ///           io.enumCase(value, "blue",  cBlue);
104 ///           io.enumCase(value, "green", cGreen);
105 ///         }
106 ///       };
107 template <typename T, typename Enable = void> struct ScalarEnumerationTraits {
108   // Must provide:
109   // static void enumeration(IO &io, T &value);
110 };
111 
112 /// This class should be specialized by any integer type that is a union
113 /// of bit values and the YAML representation is a flow sequence of
114 /// strings.  For example:
115 ///
116 ///      struct ScalarBitSetTraits<MyFlags> {
117 ///        static void bitset(IO &io, MyFlags &value) {
118 ///          io.bitSetCase(value, "big",   flagBig);
119 ///          io.bitSetCase(value, "flat",  flagFlat);
120 ///          io.bitSetCase(value, "round", flagRound);
121 ///        }
122 ///      };
123 template <typename T, typename Enable = void> struct ScalarBitSetTraits {
124   // Must provide:
125   // static void bitset(IO &io, T &value);
126 };
127 
128 /// Describe which type of quotes should be used when quoting is necessary.
129 /// Some non-printable characters need to be double-quoted, while some others
130 /// are fine with simple-quoting, and some don't need any quoting.
131 enum class QuotingType { None, Single, Double };
132 
133 /// This class should be specialized by type that requires custom conversion
134 /// to/from a yaml scalar.  For example:
135 ///
136 ///    template<>
137 ///    struct ScalarTraits<MyType> {
138 ///      static void output(const MyType &val, void*, llvm::raw_ostream &out) {
139 ///        // stream out custom formatting
140 ///        out << llvm::format("%x", val);
141 ///      }
142 ///      static StringRef input(StringRef scalar, void*, MyType &value) {
143 ///        // parse scalar and set `value`
144 ///        // return empty string on success, or error string
145 ///        return StringRef();
146 ///      }
147 ///      static QuotingType mustQuote(StringRef) { return QuotingType::Single; }
148 ///    };
149 template <typename T, typename Enable = void> struct ScalarTraits {
150   // Must provide:
151   //
152   // Function to write the value as a string:
153   // static void output(const T &value, void *ctxt, llvm::raw_ostream &out);
154   //
155   // Function to convert a string to a value.  Returns the empty
156   // StringRef on success or an error string if string is malformed:
157   // static StringRef input(StringRef scalar, void *ctxt, T &value);
158   //
159   // Function to determine if the value should be quoted.
160   // static QuotingType mustQuote(StringRef);
161 };
162 
163 /// This class should be specialized by type that requires custom conversion
164 /// to/from a YAML literal block scalar. For example:
165 ///
166 ///    template <>
167 ///    struct BlockScalarTraits<MyType> {
168 ///      static void output(const MyType &Value, void*, llvm::raw_ostream &Out)
169 ///      {
170 ///        // stream out custom formatting
171 ///        Out << Value;
172 ///      }
173 ///      static StringRef input(StringRef Scalar, void*, MyType &Value) {
174 ///        // parse scalar and set `value`
175 ///        // return empty string on success, or error string
176 ///        return StringRef();
177 ///      }
178 ///    };
179 template <typename T>
180 struct BlockScalarTraits {
181   // Must provide:
182   //
183   // Function to write the value as a string:
184   // static void output(const T &Value, void *ctx, llvm::raw_ostream &Out);
185   //
186   // Function to convert a string to a value.  Returns the empty
187   // StringRef on success or an error string if string is malformed:
188   // static StringRef input(StringRef Scalar, void *ctxt, T &Value);
189   //
190   // Optional:
191   // static StringRef inputTag(T &Val, std::string Tag)
192   // static void outputTag(const T &Val, raw_ostream &Out)
193 };
194 
195 /// This class should be specialized by type that requires custom conversion
196 /// to/from a YAML scalar with optional tags. For example:
197 ///
198 ///    template <>
199 ///    struct TaggedScalarTraits<MyType> {
200 ///      static void output(const MyType &Value, void*, llvm::raw_ostream
201 ///      &ScalarOut, llvm::raw_ostream &TagOut)
202 ///      {
203 ///        // stream out custom formatting including optional Tag
204 ///        Out << Value;
205 ///      }
206 ///      static StringRef input(StringRef Scalar, StringRef Tag, void*, MyType
207 ///      &Value) {
208 ///        // parse scalar and set `value`
209 ///        // return empty string on success, or error string
210 ///        return StringRef();
211 ///      }
212 ///      static QuotingType mustQuote(const MyType &Value, StringRef) {
213 ///        return QuotingType::Single;
214 ///      }
215 ///    };
216 template <typename T> struct TaggedScalarTraits {
217   // Must provide:
218   //
219   // Function to write the value and tag as strings:
220   // static void output(const T &Value, void *ctx, llvm::raw_ostream &ScalarOut,
221   // llvm::raw_ostream &TagOut);
222   //
223   // Function to convert a string to a value.  Returns the empty
224   // StringRef on success or an error string if string is malformed:
225   // static StringRef input(StringRef Scalar, StringRef Tag, void *ctxt, T
226   // &Value);
227   //
228   // Function to determine if the value should be quoted.
229   // static QuotingType mustQuote(const T &Value, StringRef Scalar);
230 };
231 
232 /// This class should be specialized by any type that needs to be converted
233 /// to/from a YAML sequence.  For example:
234 ///
235 ///    template<>
236 ///    struct SequenceTraits<MyContainer> {
237 ///      static size_t size(IO &io, MyContainer &seq) {
238 ///        return seq.size();
239 ///      }
240 ///      static MyType& element(IO &, MyContainer &seq, size_t index) {
241 ///        if ( index >= seq.size() )
242 ///          seq.resize(index+1);
243 ///        return seq[index];
244 ///      }
245 ///    };
246 template<typename T, typename EnableIf = void>
247 struct SequenceTraits {
248   // Must provide:
249   // static size_t size(IO &io, T &seq);
250   // static T::value_type& element(IO &io, T &seq, size_t index);
251   //
252   // The following is option and will cause generated YAML to use
253   // a flow sequence (e.g. [a,b,c]).
254   // static const bool flow = true;
255 };
256 
257 /// This class should be specialized by any type for which vectors of that
258 /// type need to be converted to/from a YAML sequence.
259 template<typename T, typename EnableIf = void>
260 struct SequenceElementTraits {
261   // Must provide:
262   // static const bool flow;
263 };
264 
265 /// This class should be specialized by any type that needs to be converted
266 /// to/from a list of YAML documents.
267 template<typename T>
268 struct DocumentListTraits {
269   // Must provide:
270   // static size_t size(IO &io, T &seq);
271   // static T::value_type& element(IO &io, T &seq, size_t index);
272 };
273 
274 /// This class should be specialized by any type that needs to be converted
275 /// to/from a YAML mapping in the case where the names of the keys are not known
276 /// in advance, e.g. a string map.
277 template <typename T>
278 struct CustomMappingTraits {
279   // static void inputOne(IO &io, StringRef key, T &elem);
280   // static void output(IO &io, T &elem);
281 };
282 
283 /// This class should be specialized by any type that can be represented as
284 /// a scalar, map, or sequence, decided dynamically. For example:
285 ///
286 ///    typedef std::unique_ptr<MyBase> MyPoly;
287 ///
288 ///    template<>
289 ///    struct PolymorphicTraits<MyPoly> {
290 ///      static NodeKind getKind(const MyPoly &poly) {
291 ///        return poly->getKind();
292 ///      }
293 ///      static MyScalar& getAsScalar(MyPoly &poly) {
294 ///        if (!poly || !isa<MyScalar>(poly))
295 ///          poly.reset(new MyScalar());
296 ///        return *cast<MyScalar>(poly.get());
297 ///      }
298 ///      // ...
299 ///    };
300 template <typename T> struct PolymorphicTraits {
301   // Must provide:
302   // static NodeKind getKind(const T &poly);
303   // static scalar_type &getAsScalar(T &poly);
304   // static map_type &getAsMap(T &poly);
305   // static sequence_type &getAsSequence(T &poly);
306 };
307 
308 // Only used for better diagnostics of missing traits
309 template <typename T>
310 struct MissingTrait;
311 
312 // Test if ScalarEnumerationTraits<T> is defined on type T.
313 template <class T>
314 struct has_ScalarEnumerationTraits
315 {
316   using Signature_enumeration = void (*)(class IO&, T&);
317 
318   template <typename U>
319   static char test(SameType<Signature_enumeration, &U::enumeration>*);
320 
321   template <typename U>
322   static double test(...);
323 
324   static bool const value =
325     (sizeof(test<ScalarEnumerationTraits<T>>(nullptr)) == 1);
326 };
327 
328 // Test if ScalarBitSetTraits<T> is defined on type T.
329 template <class T>
330 struct has_ScalarBitSetTraits
331 {
332   using Signature_bitset = void (*)(class IO&, T&);
333 
334   template <typename U>
335   static char test(SameType<Signature_bitset, &U::bitset>*);
336 
337   template <typename U>
338   static double test(...);
339 
340   static bool const value = (sizeof(test<ScalarBitSetTraits<T>>(nullptr)) == 1);
341 };
342 
343 // Test if ScalarTraits<T> is defined on type T.
344 template <class T>
345 struct has_ScalarTraits
346 {
347   using Signature_input = StringRef (*)(StringRef, void*, T&);
348   using Signature_output = void (*)(const T&, void*, raw_ostream&);
349   using Signature_mustQuote = QuotingType (*)(StringRef);
350 
351   template <typename U>
352   static char test(SameType<Signature_input, &U::input> *,
353                    SameType<Signature_output, &U::output> *,
354                    SameType<Signature_mustQuote, &U::mustQuote> *);
355 
356   template <typename U>
357   static double test(...);
358 
359   static bool const value =
360       (sizeof(test<ScalarTraits<T>>(nullptr, nullptr, nullptr)) == 1);
361 };
362 
363 // Test if BlockScalarTraits<T> is defined on type T.
364 template <class T>
365 struct has_BlockScalarTraits
366 {
367   using Signature_input = StringRef (*)(StringRef, void *, T &);
368   using Signature_output = void (*)(const T &, void *, raw_ostream &);
369 
370   template <typename U>
371   static char test(SameType<Signature_input, &U::input> *,
372                    SameType<Signature_output, &U::output> *);
373 
374   template <typename U>
375   static double test(...);
376 
377   static bool const value =
378       (sizeof(test<BlockScalarTraits<T>>(nullptr, nullptr)) == 1);
379 };
380 
381 // Test if TaggedScalarTraits<T> is defined on type T.
382 template <class T> struct has_TaggedScalarTraits {
383   using Signature_input = StringRef (*)(StringRef, StringRef, void *, T &);
384   using Signature_output = void (*)(const T &, void *, raw_ostream &,
385                                     raw_ostream &);
386   using Signature_mustQuote = QuotingType (*)(const T &, StringRef);
387 
388   template <typename U>
389   static char test(SameType<Signature_input, &U::input> *,
390                    SameType<Signature_output, &U::output> *,
391                    SameType<Signature_mustQuote, &U::mustQuote> *);
392 
393   template <typename U> static double test(...);
394 
395   static bool const value =
396       (sizeof(test<TaggedScalarTraits<T>>(nullptr, nullptr, nullptr)) == 1);
397 };
398 
399 // Test if MappingContextTraits<T> is defined on type T.
400 template <class T, class Context> struct has_MappingTraits {
401   using Signature_mapping = void (*)(class IO &, T &, Context &);
402 
403   template <typename U>
404   static char test(SameType<Signature_mapping, &U::mapping>*);
405 
406   template <typename U>
407   static double test(...);
408 
409   static bool const value =
410       (sizeof(test<MappingContextTraits<T, Context>>(nullptr)) == 1);
411 };
412 
413 // Test if MappingTraits<T> is defined on type T.
414 template <class T> struct has_MappingTraits<T, EmptyContext> {
415   using Signature_mapping = void (*)(class IO &, T &);
416 
417   template <typename U>
418   static char test(SameType<Signature_mapping, &U::mapping> *);
419 
420   template <typename U> static double test(...);
421 
422   static bool const value = (sizeof(test<MappingTraits<T>>(nullptr)) == 1);
423 };
424 
425 // Test if MappingContextTraits<T>::validate() is defined on type T.
426 template <class T, class Context> struct has_MappingValidateTraits {
427   using Signature_validate = std::string (*)(class IO &, T &, Context &);
428 
429   template <typename U>
430   static char test(SameType<Signature_validate, &U::validate>*);
431 
432   template <typename U>
433   static double test(...);
434 
435   static bool const value =
436       (sizeof(test<MappingContextTraits<T, Context>>(nullptr)) == 1);
437 };
438 
439 // Test if MappingTraits<T>::validate() is defined on type T.
440 template <class T> struct has_MappingValidateTraits<T, EmptyContext> {
441   using Signature_validate = std::string (*)(class IO &, T &);
442 
443   template <typename U>
444   static char test(SameType<Signature_validate, &U::validate> *);
445 
446   template <typename U> static double test(...);
447 
448   static bool const value = (sizeof(test<MappingTraits<T>>(nullptr)) == 1);
449 };
450 
451 // Test if MappingContextTraits<T>::enumInput() is defined on type T.
452 template <class T, class Context> struct has_MappingEnumInputTraits {
453   using Signature_validate = void (*)(class IO &, T &);
454 
455   template <typename U>
456   static char test(SameType<Signature_validate, &U::enumInput> *);
457 
458   template <typename U> static double test(...);
459 
460   static bool const value =
461       (sizeof(test<MappingContextTraits<T, Context>>(nullptr)) == 1);
462 };
463 
464 // Test if MappingTraits<T>::enumInput() is defined on type T.
465 template <class T> struct has_MappingEnumInputTraits<T, EmptyContext> {
466   using Signature_validate = void (*)(class IO &, T &);
467 
468   template <typename U>
469   static char test(SameType<Signature_validate, &U::enumInput> *);
470 
471   template <typename U> static double test(...);
472 
473   static bool const value = (sizeof(test<MappingTraits<T>>(nullptr)) == 1);
474 };
475 
476 // Test if SequenceTraits<T> is defined on type T.
477 template <class T>
478 struct has_SequenceMethodTraits
479 {
480   using Signature_size = size_t (*)(class IO&, T&);
481 
482   template <typename U>
483   static char test(SameType<Signature_size, &U::size>*);
484 
485   template <typename U>
486   static double test(...);
487 
488   static bool const value =  (sizeof(test<SequenceTraits<T>>(nullptr)) == 1);
489 };
490 
491 // Test if CustomMappingTraits<T> is defined on type T.
492 template <class T>
493 struct has_CustomMappingTraits
494 {
495   using Signature_input = void (*)(IO &io, StringRef key, T &v);
496 
497   template <typename U>
498   static char test(SameType<Signature_input, &U::inputOne>*);
499 
500   template <typename U>
501   static double test(...);
502 
503   static bool const value =
504       (sizeof(test<CustomMappingTraits<T>>(nullptr)) == 1);
505 };
506 
507 // has_FlowTraits<int> will cause an error with some compilers because
508 // it subclasses int.  Using this wrapper only instantiates the
509 // real has_FlowTraits only if the template type is a class.
510 template <typename T, bool Enabled = std::is_class_v<T>> class has_FlowTraits {
511 public:
512    static const bool value = false;
513 };
514 
515 // Some older gcc compilers don't support straight forward tests
516 // for members, so test for ambiguity cause by the base and derived
517 // classes both defining the member.
518 template <class T>
519 struct has_FlowTraits<T, true>
520 {
521   struct Fallback { bool flow; };
522   struct Derived : T, Fallback { };
523 
524   template<typename C>
525   static char (&f(SameType<bool Fallback::*, &C::flow>*))[1];
526 
527   template<typename C>
528   static char (&f(...))[2];
529 
530   static bool const value = sizeof(f<Derived>(nullptr)) == 2;
531 };
532 
533 // Test if SequenceTraits<T> is defined on type T
534 template<typename T>
535 struct has_SequenceTraits : public std::integral_constant<bool,
536                                       has_SequenceMethodTraits<T>::value > { };
537 
538 // Test if DocumentListTraits<T> is defined on type T
539 template <class T>
540 struct has_DocumentListTraits
541 {
542   using Signature_size = size_t (*)(class IO &, T &);
543 
544   template <typename U>
545   static char test(SameType<Signature_size, &U::size>*);
546 
547   template <typename U>
548   static double test(...);
549 
550   static bool const value = (sizeof(test<DocumentListTraits<T>>(nullptr))==1);
551 };
552 
553 template <class T> struct has_PolymorphicTraits {
554   using Signature_getKind = NodeKind (*)(const T &);
555 
556   template <typename U>
557   static char test(SameType<Signature_getKind, &U::getKind> *);
558 
559   template <typename U> static double test(...);
560 
561   static bool const value = (sizeof(test<PolymorphicTraits<T>>(nullptr)) == 1);
562 };
563 
564 inline bool isNumeric(StringRef S) {
565   const auto skipDigits = [](StringRef Input) {
566     return Input.ltrim("0123456789");
567   };
568 
569   // Make S.front() and S.drop_front().front() (if S.front() is [+-]) calls
570   // safe.
571   if (S.empty() || S == "+" || S == "-")
572     return false;
573 
574   if (S == ".nan" || S == ".NaN" || S == ".NAN")
575     return true;
576 
577   // Infinity and decimal numbers can be prefixed with sign.
578   StringRef Tail = (S.front() == '-' || S.front() == '+') ? S.drop_front() : S;
579 
580   // Check for infinity first, because checking for hex and oct numbers is more
581   // expensive.
582   if (Tail == ".inf" || Tail == ".Inf" || Tail == ".INF")
583     return true;
584 
585   // Section 10.3.2 Tag Resolution
586   // YAML 1.2 Specification prohibits Base 8 and Base 16 numbers prefixed with
587   // [-+], so S should be used instead of Tail.
588   if (S.starts_with("0o"))
589     return S.size() > 2 &&
590            S.drop_front(2).find_first_not_of("01234567") == StringRef::npos;
591 
592   if (S.starts_with("0x"))
593     return S.size() > 2 && S.drop_front(2).find_first_not_of(
594                                "0123456789abcdefABCDEF") == StringRef::npos;
595 
596   // Parse float: [-+]? (\. [0-9]+ | [0-9]+ (\. [0-9]* )?) ([eE] [-+]? [0-9]+)?
597   S = Tail;
598 
599   // Handle cases when the number starts with '.' and hence needs at least one
600   // digit after dot (as opposed by number which has digits before the dot), but
601   // doesn't have one.
602   if (S.starts_with(".") &&
603       (S == "." ||
604        (S.size() > 1 && std::strchr("0123456789", S[1]) == nullptr)))
605     return false;
606 
607   if (S.starts_with("E") || S.starts_with("e"))
608     return false;
609 
610   enum ParseState {
611     Default,
612     FoundDot,
613     FoundExponent,
614   };
615   ParseState State = Default;
616 
617   S = skipDigits(S);
618 
619   // Accept decimal integer.
620   if (S.empty())
621     return true;
622 
623   if (S.front() == '.') {
624     State = FoundDot;
625     S = S.drop_front();
626   } else if (S.front() == 'e' || S.front() == 'E') {
627     State = FoundExponent;
628     S = S.drop_front();
629   } else {
630     return false;
631   }
632 
633   if (State == FoundDot) {
634     S = skipDigits(S);
635     if (S.empty())
636       return true;
637 
638     if (S.front() == 'e' || S.front() == 'E') {
639       State = FoundExponent;
640       S = S.drop_front();
641     } else {
642       return false;
643     }
644   }
645 
646   assert(State == FoundExponent && "Should have found exponent at this point.");
647   if (S.empty())
648     return false;
649 
650   if (S.front() == '+' || S.front() == '-') {
651     S = S.drop_front();
652     if (S.empty())
653       return false;
654   }
655 
656   return skipDigits(S).empty();
657 }
658 
659 inline bool isNull(StringRef S) {
660   return S == "null" || S == "Null" || S == "NULL" || S == "~";
661 }
662 
663 inline bool isBool(StringRef S) {
664   // FIXME: using parseBool is causing multiple tests to fail.
665   return S == "true" || S == "True" || S == "TRUE" || S == "false" ||
666          S == "False" || S == "FALSE";
667 }
668 
669 // 5.1. Character Set
670 // The allowed character range explicitly excludes the C0 control block #x0-#x1F
671 // (except for TAB #x9, LF #xA, and CR #xD which are allowed), DEL #x7F, the C1
672 // control block #x80-#x9F (except for NEL #x85 which is allowed), the surrogate
673 // block #xD800-#xDFFF, #xFFFE, and #xFFFF.
674 //
675 // Some strings are valid YAML values even unquoted, but without quotes are
676 // interpreted as non-string type, for instance null, boolean or numeric values.
677 // If ForcePreserveAsString is set, such strings are quoted.
678 inline QuotingType needsQuotes(StringRef S, bool ForcePreserveAsString = true) {
679   if (S.empty())
680     return QuotingType::Single;
681 
682   QuotingType MaxQuotingNeeded = QuotingType::None;
683   if (isSpace(static_cast<unsigned char>(S.front())) ||
684       isSpace(static_cast<unsigned char>(S.back())))
685     MaxQuotingNeeded = QuotingType::Single;
686   if (ForcePreserveAsString) {
687     if (isNull(S))
688       MaxQuotingNeeded = QuotingType::Single;
689     if (isBool(S))
690       MaxQuotingNeeded = QuotingType::Single;
691     if (isNumeric(S))
692       MaxQuotingNeeded = QuotingType::Single;
693   }
694 
695   // 7.3.3 Plain Style
696   // Plain scalars must not begin with most indicators, as this would cause
697   // ambiguity with other YAML constructs.
698   if (std::strchr(R"(-?:\,[]{}#&*!|>'"%@`)", S[0]) != nullptr)
699     MaxQuotingNeeded = QuotingType::Single;
700 
701   for (unsigned char C : S) {
702     // Alphanum is safe.
703     if (isAlnum(C))
704       continue;
705 
706     switch (C) {
707     // Safe scalar characters.
708     case '_':
709     case '-':
710     case '^':
711     case '.':
712     case ',':
713     case ' ':
714     // TAB (0x9) is allowed in unquoted strings.
715     case 0x9:
716       continue;
717     // LF(0xA) and CR(0xD) may delimit values and so require at least single
718     // quotes. LLVM YAML parser cannot handle single quoted multiline so use
719     // double quoting to produce valid YAML.
720     case 0xA:
721     case 0xD:
722       return QuotingType::Double;
723     // DEL (0x7F) are excluded from the allowed character range.
724     case 0x7F:
725       return QuotingType::Double;
726     // Forward slash is allowed to be unquoted, but we quote it anyway.  We have
727     // many tests that use FileCheck against YAML output, and this output often
728     // contains paths.  If we quote backslashes but not forward slashes then
729     // paths will come out either quoted or unquoted depending on which platform
730     // the test is run on, making FileCheck comparisons difficult.
731     case '/':
732     default: {
733       // C0 control block (0x0 - 0x1F) is excluded from the allowed character
734       // range.
735       if (C <= 0x1F)
736         return QuotingType::Double;
737 
738       // Always double quote UTF-8.
739       if ((C & 0x80) != 0)
740         return QuotingType::Double;
741 
742       // The character is not safe, at least simple quoting needed.
743       MaxQuotingNeeded = QuotingType::Single;
744     }
745     }
746   }
747 
748   return MaxQuotingNeeded;
749 }
750 
751 template <typename T, typename Context>
752 struct missingTraits
753     : public std::integral_constant<bool,
754                                     !has_ScalarEnumerationTraits<T>::value &&
755                                         !has_ScalarBitSetTraits<T>::value &&
756                                         !has_ScalarTraits<T>::value &&
757                                         !has_BlockScalarTraits<T>::value &&
758                                         !has_TaggedScalarTraits<T>::value &&
759                                         !has_MappingTraits<T, Context>::value &&
760                                         !has_SequenceTraits<T>::value &&
761                                         !has_CustomMappingTraits<T>::value &&
762                                         !has_DocumentListTraits<T>::value &&
763                                         !has_PolymorphicTraits<T>::value> {};
764 
765 template <typename T, typename Context>
766 struct validatedMappingTraits
767     : public std::integral_constant<
768           bool, has_MappingTraits<T, Context>::value &&
769                     has_MappingValidateTraits<T, Context>::value> {};
770 
771 template <typename T, typename Context>
772 struct unvalidatedMappingTraits
773     : public std::integral_constant<
774           bool, has_MappingTraits<T, Context>::value &&
775                     !has_MappingValidateTraits<T, Context>::value> {};
776 
777 // Base class for Input and Output.
778 class IO {
779 public:
780   IO(void *Ctxt = nullptr);
781   virtual ~IO();
782 
783   virtual bool outputting() const = 0;
784 
785   virtual unsigned beginSequence() = 0;
786   virtual bool preflightElement(unsigned, void *&) = 0;
787   virtual void postflightElement(void*) = 0;
788   virtual void endSequence() = 0;
789   virtual bool canElideEmptySequence() = 0;
790 
791   virtual unsigned beginFlowSequence() = 0;
792   virtual bool preflightFlowElement(unsigned, void *&) = 0;
793   virtual void postflightFlowElement(void*) = 0;
794   virtual void endFlowSequence() = 0;
795 
796   virtual bool mapTag(StringRef Tag, bool Default=false) = 0;
797   virtual void beginMapping() = 0;
798   virtual void endMapping() = 0;
799   virtual bool preflightKey(const char*, bool, bool, bool &, void *&) = 0;
800   virtual void postflightKey(void*) = 0;
801   virtual std::vector<StringRef> keys() = 0;
802 
803   virtual void beginFlowMapping() = 0;
804   virtual void endFlowMapping() = 0;
805 
806   virtual void beginEnumScalar() = 0;
807   virtual bool matchEnumScalar(const char*, bool) = 0;
808   virtual bool matchEnumFallback() = 0;
809   virtual void endEnumScalar() = 0;
810 
811   virtual bool beginBitSetScalar(bool &) = 0;
812   virtual bool bitSetMatch(const char*, bool) = 0;
813   virtual void endBitSetScalar() = 0;
814 
815   virtual void scalarString(StringRef &, QuotingType) = 0;
816   virtual void blockScalarString(StringRef &) = 0;
817   virtual void scalarTag(std::string &) = 0;
818 
819   virtual NodeKind getNodeKind() = 0;
820 
821   virtual void setError(const Twine &) = 0;
822   virtual std::error_code error() = 0;
823   virtual void setAllowUnknownKeys(bool Allow);
824 
825   template <typename T>
826   void enumCase(T &Val, const char* Str, const T ConstVal) {
827     if ( matchEnumScalar(Str, outputting() && Val == ConstVal) ) {
828       Val = ConstVal;
829     }
830   }
831 
832   // allow anonymous enum values to be used with LLVM_YAML_STRONG_TYPEDEF
833   template <typename T>
834   void enumCase(T &Val, const char* Str, const uint32_t ConstVal) {
835     if ( matchEnumScalar(Str, outputting() && Val == static_cast<T>(ConstVal)) ) {
836       Val = ConstVal;
837     }
838   }
839 
840   template <typename FBT, typename T>
841   void enumFallback(T &Val) {
842     if (matchEnumFallback()) {
843       EmptyContext Context;
844       // FIXME: Force integral conversion to allow strong typedefs to convert.
845       FBT Res = static_cast<typename FBT::BaseType>(Val);
846       yamlize(*this, Res, true, Context);
847       Val = static_cast<T>(static_cast<typename FBT::BaseType>(Res));
848     }
849   }
850 
851   template <typename T>
852   void bitSetCase(T &Val, const char* Str, const T ConstVal) {
853     if ( bitSetMatch(Str, outputting() && (Val & ConstVal) == ConstVal) ) {
854       Val = static_cast<T>(Val | ConstVal);
855     }
856   }
857 
858   // allow anonymous enum values to be used with LLVM_YAML_STRONG_TYPEDEF
859   template <typename T>
860   void bitSetCase(T &Val, const char* Str, const uint32_t ConstVal) {
861     if ( bitSetMatch(Str, outputting() && (Val & ConstVal) == ConstVal) ) {
862       Val = static_cast<T>(Val | ConstVal);
863     }
864   }
865 
866   template <typename T>
867   void maskedBitSetCase(T &Val, const char *Str, T ConstVal, T Mask) {
868     if (bitSetMatch(Str, outputting() && (Val & Mask) == ConstVal))
869       Val = Val | ConstVal;
870   }
871 
872   template <typename T>
873   void maskedBitSetCase(T &Val, const char *Str, uint32_t ConstVal,
874                         uint32_t Mask) {
875     if (bitSetMatch(Str, outputting() && (Val & Mask) == ConstVal))
876       Val = Val | ConstVal;
877   }
878 
879   void *getContext() const;
880   void setContext(void *);
881 
882   template <typename T> void mapRequired(const char *Key, T &Val) {
883     EmptyContext Ctx;
884     this->processKey(Key, Val, true, Ctx);
885   }
886 
887   template <typename T, typename Context>
888   void mapRequired(const char *Key, T &Val, Context &Ctx) {
889     this->processKey(Key, Val, true, Ctx);
890   }
891 
892   template <typename T> void mapOptional(const char *Key, T &Val) {
893     EmptyContext Ctx;
894     mapOptionalWithContext(Key, Val, Ctx);
895   }
896 
897   template <typename T, typename DefaultT>
898   void mapOptional(const char *Key, T &Val, const DefaultT &Default) {
899     EmptyContext Ctx;
900     mapOptionalWithContext(Key, Val, Default, Ctx);
901   }
902 
903   template <typename T, typename Context>
904   std::enable_if_t<has_SequenceTraits<T>::value, void>
905   mapOptionalWithContext(const char *Key, T &Val, Context &Ctx) {
906     // omit key/value instead of outputting empty sequence
907     if (this->canElideEmptySequence() && !(Val.begin() != Val.end()))
908       return;
909     this->processKey(Key, Val, false, Ctx);
910   }
911 
912   template <typename T, typename Context>
913   void mapOptionalWithContext(const char *Key, std::optional<T> &Val,
914                               Context &Ctx) {
915     this->processKeyWithDefault(Key, Val, std::optional<T>(),
916                                 /*Required=*/false, Ctx);
917   }
918 
919   template <typename T, typename Context>
920   std::enable_if_t<!has_SequenceTraits<T>::value, void>
921   mapOptionalWithContext(const char *Key, T &Val, Context &Ctx) {
922     this->processKey(Key, Val, false, Ctx);
923   }
924 
925   template <typename T, typename Context, typename DefaultT>
926   void mapOptionalWithContext(const char *Key, T &Val, const DefaultT &Default,
927                               Context &Ctx) {
928     static_assert(std::is_convertible<DefaultT, T>::value,
929                   "Default type must be implicitly convertible to value type!");
930     this->processKeyWithDefault(Key, Val, static_cast<const T &>(Default),
931                                 false, Ctx);
932   }
933 
934 private:
935   template <typename T, typename Context>
936   void processKeyWithDefault(const char *Key, std::optional<T> &Val,
937                              const std::optional<T> &DefaultValue,
938                              bool Required, Context &Ctx);
939 
940   template <typename T, typename Context>
941   void processKeyWithDefault(const char *Key, T &Val, const T &DefaultValue,
942                              bool Required, Context &Ctx) {
943     void *SaveInfo;
944     bool UseDefault;
945     const bool sameAsDefault = outputting() && Val == DefaultValue;
946     if ( this->preflightKey(Key, Required, sameAsDefault, UseDefault,
947                                                                   SaveInfo) ) {
948       yamlize(*this, Val, Required, Ctx);
949       this->postflightKey(SaveInfo);
950     }
951     else {
952       if ( UseDefault )
953         Val = DefaultValue;
954     }
955   }
956 
957   template <typename T, typename Context>
958   void processKey(const char *Key, T &Val, bool Required, Context &Ctx) {
959     void *SaveInfo;
960     bool UseDefault;
961     if ( this->preflightKey(Key, Required, false, UseDefault, SaveInfo) ) {
962       yamlize(*this, Val, Required, Ctx);
963       this->postflightKey(SaveInfo);
964     }
965   }
966 
967 private:
968   void *Ctxt;
969 };
970 
971 namespace detail {
972 
973 template <typename T, typename Context>
974 void doMapping(IO &io, T &Val, Context &Ctx) {
975   MappingContextTraits<T, Context>::mapping(io, Val, Ctx);
976 }
977 
978 template <typename T> void doMapping(IO &io, T &Val, EmptyContext &Ctx) {
979   MappingTraits<T>::mapping(io, Val);
980 }
981 
982 } // end namespace detail
983 
984 template <typename T>
985 std::enable_if_t<has_ScalarEnumerationTraits<T>::value, void>
986 yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
987   io.beginEnumScalar();
988   ScalarEnumerationTraits<T>::enumeration(io, Val);
989   io.endEnumScalar();
990 }
991 
992 template <typename T>
993 std::enable_if_t<has_ScalarBitSetTraits<T>::value, void>
994 yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
995   bool DoClear;
996   if ( io.beginBitSetScalar(DoClear) ) {
997     if ( DoClear )
998       Val = T();
999     ScalarBitSetTraits<T>::bitset(io, Val);
1000     io.endBitSetScalar();
1001   }
1002 }
1003 
1004 template <typename T>
1005 std::enable_if_t<has_ScalarTraits<T>::value, void> yamlize(IO &io, T &Val, bool,
1006                                                            EmptyContext &Ctx) {
1007   if ( io.outputting() ) {
1008     SmallString<128> Storage;
1009     raw_svector_ostream Buffer(Storage);
1010     ScalarTraits<T>::output(Val, io.getContext(), Buffer);
1011     StringRef Str = Buffer.str();
1012     io.scalarString(Str, ScalarTraits<T>::mustQuote(Str));
1013   }
1014   else {
1015     StringRef Str;
1016     io.scalarString(Str, ScalarTraits<T>::mustQuote(Str));
1017     StringRef Result = ScalarTraits<T>::input(Str, io.getContext(), Val);
1018     if ( !Result.empty() ) {
1019       io.setError(Twine(Result));
1020     }
1021   }
1022 }
1023 
1024 template <typename T>
1025 std::enable_if_t<has_BlockScalarTraits<T>::value, void>
1026 yamlize(IO &YamlIO, T &Val, bool, EmptyContext &Ctx) {
1027   if (YamlIO.outputting()) {
1028     std::string Storage;
1029     raw_string_ostream Buffer(Storage);
1030     BlockScalarTraits<T>::output(Val, YamlIO.getContext(), Buffer);
1031     StringRef Str(Storage);
1032     YamlIO.blockScalarString(Str);
1033   } else {
1034     StringRef Str;
1035     YamlIO.blockScalarString(Str);
1036     StringRef Result =
1037         BlockScalarTraits<T>::input(Str, YamlIO.getContext(), Val);
1038     if (!Result.empty())
1039       YamlIO.setError(Twine(Result));
1040   }
1041 }
1042 
1043 template <typename T>
1044 std::enable_if_t<has_TaggedScalarTraits<T>::value, void>
1045 yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
1046   if (io.outputting()) {
1047     std::string ScalarStorage, TagStorage;
1048     raw_string_ostream ScalarBuffer(ScalarStorage), TagBuffer(TagStorage);
1049     TaggedScalarTraits<T>::output(Val, io.getContext(), ScalarBuffer,
1050                                   TagBuffer);
1051     io.scalarTag(TagStorage);
1052     StringRef ScalarStr(ScalarStorage);
1053     io.scalarString(ScalarStr,
1054                     TaggedScalarTraits<T>::mustQuote(Val, ScalarStr));
1055   } else {
1056     std::string Tag;
1057     io.scalarTag(Tag);
1058     StringRef Str;
1059     io.scalarString(Str, QuotingType::None);
1060     StringRef Result =
1061         TaggedScalarTraits<T>::input(Str, Tag, io.getContext(), Val);
1062     if (!Result.empty()) {
1063       io.setError(Twine(Result));
1064     }
1065   }
1066 }
1067 
1068 namespace detail {
1069 
1070 template <typename T, typename Context>
1071 std::string doValidate(IO &io, T &Val, Context &Ctx) {
1072   return MappingContextTraits<T, Context>::validate(io, Val, Ctx);
1073 }
1074 
1075 template <typename T> std::string doValidate(IO &io, T &Val, EmptyContext &) {
1076   return MappingTraits<T>::validate(io, Val);
1077 }
1078 
1079 } // namespace detail
1080 
1081 template <typename T, typename Context>
1082 std::enable_if_t<validatedMappingTraits<T, Context>::value, void>
1083 yamlize(IO &io, T &Val, bool, Context &Ctx) {
1084   if (has_FlowTraits<MappingTraits<T>>::value)
1085     io.beginFlowMapping();
1086   else
1087     io.beginMapping();
1088   if (io.outputting()) {
1089     std::string Err = detail::doValidate(io, Val, Ctx);
1090     if (!Err.empty()) {
1091       errs() << Err << "\n";
1092       assert(Err.empty() && "invalid struct trying to be written as yaml");
1093     }
1094   }
1095   detail::doMapping(io, Val, Ctx);
1096   if (!io.outputting()) {
1097     std::string Err = detail::doValidate(io, Val, Ctx);
1098     if (!Err.empty())
1099       io.setError(Err);
1100   }
1101   if (has_FlowTraits<MappingTraits<T>>::value)
1102     io.endFlowMapping();
1103   else
1104     io.endMapping();
1105 }
1106 
1107 template <typename T, typename Context>
1108 std::enable_if_t<!has_MappingEnumInputTraits<T, Context>::value, bool>
1109 yamlizeMappingEnumInput(IO &io, T &Val) {
1110   return false;
1111 }
1112 
1113 template <typename T, typename Context>
1114 std::enable_if_t<has_MappingEnumInputTraits<T, Context>::value, bool>
1115 yamlizeMappingEnumInput(IO &io, T &Val) {
1116   if (io.outputting())
1117     return false;
1118 
1119   io.beginEnumScalar();
1120   MappingTraits<T>::enumInput(io, Val);
1121   bool Matched = !io.matchEnumFallback();
1122   io.endEnumScalar();
1123   return Matched;
1124 }
1125 
1126 template <typename T, typename Context>
1127 std::enable_if_t<unvalidatedMappingTraits<T, Context>::value, void>
1128 yamlize(IO &io, T &Val, bool, Context &Ctx) {
1129   if (yamlizeMappingEnumInput<T, Context>(io, Val))
1130     return;
1131   if (has_FlowTraits<MappingTraits<T>>::value) {
1132     io.beginFlowMapping();
1133     detail::doMapping(io, Val, Ctx);
1134     io.endFlowMapping();
1135   } else {
1136     io.beginMapping();
1137     detail::doMapping(io, Val, Ctx);
1138     io.endMapping();
1139   }
1140 }
1141 
1142 template <typename T>
1143 std::enable_if_t<has_CustomMappingTraits<T>::value, void>
1144 yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
1145   if ( io.outputting() ) {
1146     io.beginMapping();
1147     CustomMappingTraits<T>::output(io, Val);
1148     io.endMapping();
1149   } else {
1150     io.beginMapping();
1151     for (StringRef key : io.keys())
1152       CustomMappingTraits<T>::inputOne(io, key, Val);
1153     io.endMapping();
1154   }
1155 }
1156 
1157 template <typename T>
1158 std::enable_if_t<has_PolymorphicTraits<T>::value, void>
1159 yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
1160   switch (io.outputting() ? PolymorphicTraits<T>::getKind(Val)
1161                           : io.getNodeKind()) {
1162   case NodeKind::Scalar:
1163     return yamlize(io, PolymorphicTraits<T>::getAsScalar(Val), true, Ctx);
1164   case NodeKind::Map:
1165     return yamlize(io, PolymorphicTraits<T>::getAsMap(Val), true, Ctx);
1166   case NodeKind::Sequence:
1167     return yamlize(io, PolymorphicTraits<T>::getAsSequence(Val), true, Ctx);
1168   }
1169 }
1170 
1171 template <typename T>
1172 std::enable_if_t<missingTraits<T, EmptyContext>::value, void>
1173 yamlize(IO &io, T &Val, bool, EmptyContext &Ctx) {
1174   char missing_yaml_trait_for_type[sizeof(MissingTrait<T>)];
1175 }
1176 
1177 template <typename T, typename Context>
1178 std::enable_if_t<has_SequenceTraits<T>::value, void>
1179 yamlize(IO &io, T &Seq, bool, Context &Ctx) {
1180   if ( has_FlowTraits< SequenceTraits<T>>::value ) {
1181     unsigned incnt = io.beginFlowSequence();
1182     unsigned count = io.outputting() ? SequenceTraits<T>::size(io, Seq) : incnt;
1183     for(unsigned i=0; i < count; ++i) {
1184       void *SaveInfo;
1185       if ( io.preflightFlowElement(i, SaveInfo) ) {
1186         yamlize(io, SequenceTraits<T>::element(io, Seq, i), true, Ctx);
1187         io.postflightFlowElement(SaveInfo);
1188       }
1189     }
1190     io.endFlowSequence();
1191   }
1192   else {
1193     unsigned incnt = io.beginSequence();
1194     unsigned count = io.outputting() ? SequenceTraits<T>::size(io, Seq) : incnt;
1195     for(unsigned i=0; i < count; ++i) {
1196       void *SaveInfo;
1197       if ( io.preflightElement(i, SaveInfo) ) {
1198         yamlize(io, SequenceTraits<T>::element(io, Seq, i), true, Ctx);
1199         io.postflightElement(SaveInfo);
1200       }
1201     }
1202     io.endSequence();
1203   }
1204 }
1205 
1206 template<>
1207 struct ScalarTraits<bool> {
1208   static void output(const bool &, void* , raw_ostream &);
1209   static StringRef input(StringRef, void *, bool &);
1210   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
1211 };
1212 
1213 template<>
1214 struct ScalarTraits<StringRef> {
1215   static void output(const StringRef &, void *, raw_ostream &);
1216   static StringRef input(StringRef, void *, StringRef &);
1217   static QuotingType mustQuote(StringRef S) { return needsQuotes(S); }
1218 };
1219 
1220 template<>
1221 struct ScalarTraits<std::string> {
1222   static void output(const std::string &, void *, raw_ostream &);
1223   static StringRef input(StringRef, void *, std::string &);
1224   static QuotingType mustQuote(StringRef S) { return needsQuotes(S); }
1225 };
1226 
1227 template<>
1228 struct ScalarTraits<uint8_t> {
1229   static void output(const uint8_t &, void *, raw_ostream &);
1230   static StringRef input(StringRef, void *, uint8_t &);
1231   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
1232 };
1233 
1234 template<>
1235 struct ScalarTraits<uint16_t> {
1236   static void output(const uint16_t &, void *, raw_ostream &);
1237   static StringRef input(StringRef, void *, uint16_t &);
1238   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
1239 };
1240 
1241 template<>
1242 struct ScalarTraits<uint32_t> {
1243   static void output(const uint32_t &, void *, raw_ostream &);
1244   static StringRef input(StringRef, void *, uint32_t &);
1245   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
1246 };
1247 
1248 template<>
1249 struct ScalarTraits<uint64_t> {
1250   static void output(const uint64_t &, void *, raw_ostream &);
1251   static StringRef input(StringRef, void *, uint64_t &);
1252   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
1253 };
1254 
1255 template<>
1256 struct ScalarTraits<int8_t> {
1257   static void output(const int8_t &, void *, raw_ostream &);
1258   static StringRef input(StringRef, void *, int8_t &);
1259   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
1260 };
1261 
1262 template<>
1263 struct ScalarTraits<int16_t> {
1264   static void output(const int16_t &, void *, raw_ostream &);
1265   static StringRef input(StringRef, void *, int16_t &);
1266   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
1267 };
1268 
1269 template<>
1270 struct ScalarTraits<int32_t> {
1271   static void output(const int32_t &, void *, raw_ostream &);
1272   static StringRef input(StringRef, void *, int32_t &);
1273   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
1274 };
1275 
1276 template<>
1277 struct ScalarTraits<int64_t> {
1278   static void output(const int64_t &, void *, raw_ostream &);
1279   static StringRef input(StringRef, void *, int64_t &);
1280   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
1281 };
1282 
1283 template<>
1284 struct ScalarTraits<float> {
1285   static void output(const float &, void *, raw_ostream &);
1286   static StringRef input(StringRef, void *, float &);
1287   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
1288 };
1289 
1290 template<>
1291 struct ScalarTraits<double> {
1292   static void output(const double &, void *, raw_ostream &);
1293   static StringRef input(StringRef, void *, double &);
1294   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
1295 };
1296 
1297 // For endian types, we use existing scalar Traits class for the underlying
1298 // type.  This way endian aware types are supported whenever the traits are
1299 // defined for the underlying type.
1300 template <typename value_type, llvm::endianness endian, size_t alignment>
1301 struct ScalarTraits<support::detail::packed_endian_specific_integral<
1302                         value_type, endian, alignment>,
1303                     std::enable_if_t<has_ScalarTraits<value_type>::value>> {
1304   using endian_type =
1305       support::detail::packed_endian_specific_integral<value_type, endian,
1306                                                        alignment>;
1307 
1308   static void output(const endian_type &E, void *Ctx, raw_ostream &Stream) {
1309     ScalarTraits<value_type>::output(static_cast<value_type>(E), Ctx, Stream);
1310   }
1311 
1312   static StringRef input(StringRef Str, void *Ctx, endian_type &E) {
1313     value_type V;
1314     auto R = ScalarTraits<value_type>::input(Str, Ctx, V);
1315     E = static_cast<endian_type>(V);
1316     return R;
1317   }
1318 
1319   static QuotingType mustQuote(StringRef Str) {
1320     return ScalarTraits<value_type>::mustQuote(Str);
1321   }
1322 };
1323 
1324 template <typename value_type, llvm::endianness endian, size_t alignment>
1325 struct ScalarEnumerationTraits<
1326     support::detail::packed_endian_specific_integral<value_type, endian,
1327                                                      alignment>,
1328     std::enable_if_t<has_ScalarEnumerationTraits<value_type>::value>> {
1329   using endian_type =
1330       support::detail::packed_endian_specific_integral<value_type, endian,
1331                                                        alignment>;
1332 
1333   static void enumeration(IO &io, endian_type &E) {
1334     value_type V = E;
1335     ScalarEnumerationTraits<value_type>::enumeration(io, V);
1336     E = V;
1337   }
1338 };
1339 
1340 template <typename value_type, llvm::endianness endian, size_t alignment>
1341 struct ScalarBitSetTraits<
1342     support::detail::packed_endian_specific_integral<value_type, endian,
1343                                                      alignment>,
1344     std::enable_if_t<has_ScalarBitSetTraits<value_type>::value>> {
1345   using endian_type =
1346       support::detail::packed_endian_specific_integral<value_type, endian,
1347                                                        alignment>;
1348   static void bitset(IO &io, endian_type &E) {
1349     value_type V = E;
1350     ScalarBitSetTraits<value_type>::bitset(io, V);
1351     E = V;
1352   }
1353 };
1354 
1355 // Utility for use within MappingTraits<>::mapping() method
1356 // to [de]normalize an object for use with YAML conversion.
1357 template <typename TNorm, typename TFinal>
1358 struct MappingNormalization {
1359   MappingNormalization(IO &i_o, TFinal &Obj)
1360       : io(i_o), BufPtr(nullptr), Result(Obj) {
1361     if ( io.outputting() ) {
1362       BufPtr = new (&Buffer) TNorm(io, Obj);
1363     }
1364     else {
1365       BufPtr = new (&Buffer) TNorm(io);
1366     }
1367   }
1368 
1369   ~MappingNormalization() {
1370     if ( ! io.outputting() ) {
1371       Result = BufPtr->denormalize(io);
1372     }
1373     BufPtr->~TNorm();
1374   }
1375 
1376   TNorm* operator->() { return BufPtr; }
1377 
1378 private:
1379   using Storage = AlignedCharArrayUnion<TNorm>;
1380 
1381   Storage       Buffer;
1382   IO           &io;
1383   TNorm        *BufPtr;
1384   TFinal       &Result;
1385 };
1386 
1387 // Utility for use within MappingTraits<>::mapping() method
1388 // to [de]normalize an object for use with YAML conversion.
1389 template <typename TNorm, typename TFinal>
1390 struct MappingNormalizationHeap {
1391   MappingNormalizationHeap(IO &i_o, TFinal &Obj, BumpPtrAllocator *allocator)
1392     : io(i_o), Result(Obj) {
1393     if ( io.outputting() ) {
1394       BufPtr = new (&Buffer) TNorm(io, Obj);
1395     }
1396     else if (allocator) {
1397       BufPtr = allocator->Allocate<TNorm>();
1398       new (BufPtr) TNorm(io);
1399     } else {
1400       BufPtr = new TNorm(io);
1401     }
1402   }
1403 
1404   ~MappingNormalizationHeap() {
1405     if ( io.outputting() ) {
1406       BufPtr->~TNorm();
1407     }
1408     else {
1409       Result = BufPtr->denormalize(io);
1410     }
1411   }
1412 
1413   TNorm* operator->() { return BufPtr; }
1414 
1415 private:
1416   using Storage = AlignedCharArrayUnion<TNorm>;
1417 
1418   Storage       Buffer;
1419   IO           &io;
1420   TNorm        *BufPtr = nullptr;
1421   TFinal       &Result;
1422 };
1423 
1424 ///
1425 /// The Input class is used to parse a yaml document into in-memory structs
1426 /// and vectors.
1427 ///
1428 /// It works by using YAMLParser to do a syntax parse of the entire yaml
1429 /// document, then the Input class builds a graph of HNodes which wraps
1430 /// each yaml Node.  The extra layer is buffering.  The low level yaml
1431 /// parser only lets you look at each node once.  The buffering layer lets
1432 /// you search and interate multiple times.  This is necessary because
1433 /// the mapRequired() method calls may not be in the same order
1434 /// as the keys in the document.
1435 ///
1436 class Input : public IO {
1437 public:
1438   // Construct a yaml Input object from a StringRef and optional
1439   // user-data. The DiagHandler can be specified to provide
1440   // alternative error reporting.
1441   Input(StringRef InputContent,
1442         void *Ctxt = nullptr,
1443         SourceMgr::DiagHandlerTy DiagHandler = nullptr,
1444         void *DiagHandlerCtxt = nullptr);
1445   Input(MemoryBufferRef Input,
1446         void *Ctxt = nullptr,
1447         SourceMgr::DiagHandlerTy DiagHandler = nullptr,
1448         void *DiagHandlerCtxt = nullptr);
1449   ~Input() override;
1450 
1451   // Check if there was an syntax or semantic error during parsing.
1452   std::error_code error() override;
1453 
1454 private:
1455   bool outputting() const override;
1456   bool mapTag(StringRef, bool) override;
1457   void beginMapping() override;
1458   void endMapping() override;
1459   bool preflightKey(const char *, bool, bool, bool &, void *&) override;
1460   void postflightKey(void *) override;
1461   std::vector<StringRef> keys() override;
1462   void beginFlowMapping() override;
1463   void endFlowMapping() override;
1464   unsigned beginSequence() override;
1465   void endSequence() override;
1466   bool preflightElement(unsigned index, void *&) override;
1467   void postflightElement(void *) override;
1468   unsigned beginFlowSequence() override;
1469   bool preflightFlowElement(unsigned , void *&) override;
1470   void postflightFlowElement(void *) override;
1471   void endFlowSequence() override;
1472   void beginEnumScalar() override;
1473   bool matchEnumScalar(const char*, bool) override;
1474   bool matchEnumFallback() override;
1475   void endEnumScalar() override;
1476   bool beginBitSetScalar(bool &) override;
1477   bool bitSetMatch(const char *, bool ) override;
1478   void endBitSetScalar() override;
1479   void scalarString(StringRef &, QuotingType) override;
1480   void blockScalarString(StringRef &) override;
1481   void scalarTag(std::string &) override;
1482   NodeKind getNodeKind() override;
1483   void setError(const Twine &message) override;
1484   bool canElideEmptySequence() override;
1485 
1486   class HNode {
1487   public:
1488     HNode(Node *n) : _node(n) {}
1489 
1490     static bool classof(const HNode *) { return true; }
1491 
1492     Node *_node;
1493   };
1494 
1495   class EmptyHNode : public HNode {
1496   public:
1497     EmptyHNode(Node *n) : HNode(n) { }
1498 
1499     static bool classof(const HNode *n) { return NullNode::classof(n->_node); }
1500 
1501     static bool classof(const EmptyHNode *) { return true; }
1502   };
1503 
1504   class ScalarHNode : public HNode {
1505   public:
1506     ScalarHNode(Node *n, StringRef s) : HNode(n), _value(s) { }
1507 
1508     StringRef value() const { return _value; }
1509 
1510     static bool classof(const HNode *n) {
1511       return ScalarNode::classof(n->_node) ||
1512              BlockScalarNode::classof(n->_node);
1513     }
1514 
1515     static bool classof(const ScalarHNode *) { return true; }
1516 
1517   protected:
1518     StringRef _value;
1519   };
1520 
1521   class MapHNode : public HNode {
1522   public:
1523     MapHNode(Node *n) : HNode(n) { }
1524 
1525     static bool classof(const HNode *n) {
1526       return MappingNode::classof(n->_node);
1527     }
1528 
1529     static bool classof(const MapHNode *) { return true; }
1530 
1531     using NameToNodeAndLoc = StringMap<std::pair<HNode *, SMRange>>;
1532 
1533     NameToNodeAndLoc Mapping;
1534     SmallVector<std::string, 6> ValidKeys;
1535   };
1536 
1537   class SequenceHNode : public HNode {
1538   public:
1539     SequenceHNode(Node *n) : HNode(n) { }
1540 
1541     static bool classof(const HNode *n) {
1542       return SequenceNode::classof(n->_node);
1543     }
1544 
1545     static bool classof(const SequenceHNode *) { return true; }
1546 
1547     std::vector<HNode *> Entries;
1548   };
1549 
1550   Input::HNode *createHNodes(Node *node);
1551   void setError(HNode *hnode, const Twine &message);
1552   void setError(Node *node, const Twine &message);
1553   void setError(const SMRange &Range, const Twine &message);
1554 
1555   void reportWarning(HNode *hnode, const Twine &message);
1556   void reportWarning(Node *hnode, const Twine &message);
1557   void reportWarning(const SMRange &Range, const Twine &message);
1558 
1559   /// Release memory used by HNodes.
1560   void releaseHNodeBuffers();
1561 
1562 public:
1563   // These are only used by operator>>. They could be private
1564   // if those templated things could be made friends.
1565   bool setCurrentDocument();
1566   bool nextDocument();
1567 
1568   /// Returns the current node that's being parsed by the YAML Parser.
1569   const Node *getCurrentNode() const;
1570 
1571   void setAllowUnknownKeys(bool Allow) override;
1572 
1573 private:
1574   SourceMgr                           SrcMgr; // must be before Strm
1575   std::unique_ptr<llvm::yaml::Stream> Strm;
1576   HNode *TopNode = nullptr;
1577   std::error_code                     EC;
1578   BumpPtrAllocator                    StringAllocator;
1579   SpecificBumpPtrAllocator<EmptyHNode> EmptyHNodeAllocator;
1580   SpecificBumpPtrAllocator<ScalarHNode> ScalarHNodeAllocator;
1581   SpecificBumpPtrAllocator<MapHNode> MapHNodeAllocator;
1582   SpecificBumpPtrAllocator<SequenceHNode> SequenceHNodeAllocator;
1583   document_iterator                   DocIterator;
1584   llvm::BitVector                     BitValuesUsed;
1585   HNode *CurrentNode = nullptr;
1586   bool                                ScalarMatchFound = false;
1587   bool AllowUnknownKeys = false;
1588 };
1589 
1590 ///
1591 /// The Output class is used to generate a yaml document from in-memory structs
1592 /// and vectors.
1593 ///
1594 class Output : public IO {
1595 public:
1596   Output(raw_ostream &, void *Ctxt = nullptr, int WrapColumn = 70);
1597   ~Output() override;
1598 
1599   /// Set whether or not to output optional values which are equal
1600   /// to the default value.  By default, when outputting if you attempt
1601   /// to write a value that is equal to the default, the value gets ignored.
1602   /// Sometimes, it is useful to be able to see these in the resulting YAML
1603   /// anyway.
1604   void setWriteDefaultValues(bool Write) { WriteDefaultValues = Write; }
1605 
1606   bool outputting() const override;
1607   bool mapTag(StringRef, bool) override;
1608   void beginMapping() override;
1609   void endMapping() override;
1610   bool preflightKey(const char *key, bool, bool, bool &, void *&) override;
1611   void postflightKey(void *) override;
1612   std::vector<StringRef> keys() override;
1613   void beginFlowMapping() override;
1614   void endFlowMapping() override;
1615   unsigned beginSequence() override;
1616   void endSequence() override;
1617   bool preflightElement(unsigned, void *&) override;
1618   void postflightElement(void *) override;
1619   unsigned beginFlowSequence() override;
1620   bool preflightFlowElement(unsigned, void *&) override;
1621   void postflightFlowElement(void *) override;
1622   void endFlowSequence() override;
1623   void beginEnumScalar() override;
1624   bool matchEnumScalar(const char*, bool) override;
1625   bool matchEnumFallback() override;
1626   void endEnumScalar() override;
1627   bool beginBitSetScalar(bool &) override;
1628   bool bitSetMatch(const char *, bool ) override;
1629   void endBitSetScalar() override;
1630   void scalarString(StringRef &, QuotingType) override;
1631   void blockScalarString(StringRef &) override;
1632   void scalarTag(std::string &) override;
1633   NodeKind getNodeKind() override;
1634   void setError(const Twine &message) override;
1635   std::error_code error() override;
1636   bool canElideEmptySequence() override;
1637 
1638   // These are only used by operator<<. They could be private
1639   // if that templated operator could be made a friend.
1640   void beginDocuments();
1641   bool preflightDocument(unsigned);
1642   void postflightDocument();
1643   void endDocuments();
1644 
1645 private:
1646   void output(StringRef s);
1647   void output(StringRef, QuotingType);
1648   void outputUpToEndOfLine(StringRef s);
1649   void newLineCheck(bool EmptySequence = false);
1650   void outputNewLine();
1651   void paddedKey(StringRef key);
1652   void flowKey(StringRef Key);
1653 
1654   enum InState {
1655     inSeqFirstElement,
1656     inSeqOtherElement,
1657     inFlowSeqFirstElement,
1658     inFlowSeqOtherElement,
1659     inMapFirstKey,
1660     inMapOtherKey,
1661     inFlowMapFirstKey,
1662     inFlowMapOtherKey
1663   };
1664 
1665   static bool inSeqAnyElement(InState State);
1666   static bool inFlowSeqAnyElement(InState State);
1667   static bool inMapAnyKey(InState State);
1668   static bool inFlowMapAnyKey(InState State);
1669 
1670   raw_ostream &Out;
1671   int WrapColumn;
1672   SmallVector<InState, 8> StateStack;
1673   int Column = 0;
1674   int ColumnAtFlowStart = 0;
1675   int ColumnAtMapFlowStart = 0;
1676   bool NeedBitValueComma = false;
1677   bool NeedFlowSequenceComma = false;
1678   bool EnumerationMatchFound = false;
1679   bool WriteDefaultValues = false;
1680   StringRef Padding;
1681   StringRef PaddingBeforeContainer;
1682 };
1683 
1684 template <typename T, typename Context>
1685 void IO::processKeyWithDefault(const char *Key, std::optional<T> &Val,
1686                                const std::optional<T> &DefaultValue,
1687                                bool Required, Context &Ctx) {
1688   assert(!DefaultValue && "std::optional<T> shouldn't have a value!");
1689   void *SaveInfo;
1690   bool UseDefault = true;
1691   const bool sameAsDefault = outputting() && !Val;
1692   if (!outputting() && !Val)
1693     Val = T();
1694   if (Val &&
1695       this->preflightKey(Key, Required, sameAsDefault, UseDefault, SaveInfo)) {
1696 
1697     // When reading an std::optional<X> key from a YAML description, we allow
1698     // the special "<none>" value, which can be used to specify that no value
1699     // was requested, i.e. the DefaultValue will be assigned. The DefaultValue
1700     // is usually None.
1701     bool IsNone = false;
1702     if (!outputting())
1703       if (const auto *Node =
1704               dyn_cast<ScalarNode>(((Input *)this)->getCurrentNode()))
1705         // We use rtrim to ignore possible white spaces that might exist when a
1706         // comment is present on the same line.
1707         IsNone = Node->getRawValue().rtrim(' ') == "<none>";
1708 
1709     if (IsNone)
1710       Val = DefaultValue;
1711     else
1712       yamlize(*this, *Val, Required, Ctx);
1713     this->postflightKey(SaveInfo);
1714   } else {
1715     if (UseDefault)
1716       Val = DefaultValue;
1717   }
1718 }
1719 
1720 /// YAML I/O does conversion based on types. But often native data types
1721 /// are just a typedef of built in intergral types (e.g. int).  But the C++
1722 /// type matching system sees through the typedef and all the typedefed types
1723 /// look like a built in type. This will cause the generic YAML I/O conversion
1724 /// to be used. To provide better control over the YAML conversion, you can
1725 /// use this macro instead of typedef.  It will create a class with one field
1726 /// and automatic conversion operators to and from the base type.
1727 /// Based on BOOST_STRONG_TYPEDEF
1728 #define LLVM_YAML_STRONG_TYPEDEF(_base, _type)                                 \
1729     struct _type {                                                             \
1730         _type() = default;                                                     \
1731         _type(const _base v) : value(v) {}                                     \
1732         _type(const _type &v) = default;                                       \
1733         _type &operator=(const _type &rhs) = default;                          \
1734         _type &operator=(const _base &rhs) { value = rhs; return *this; }      \
1735         operator const _base & () const { return value; }                      \
1736         bool operator==(const _type &rhs) const { return value == rhs.value; } \
1737         bool operator==(const _base &rhs) const { return value == rhs; }       \
1738         bool operator<(const _type &rhs) const { return value < rhs.value; }   \
1739         _base value;                                                           \
1740         using BaseType = _base;                                                \
1741     };
1742 
1743 ///
1744 /// Use these types instead of uintXX_t in any mapping to have
1745 /// its yaml output formatted as hexadecimal.
1746 ///
1747 LLVM_YAML_STRONG_TYPEDEF(uint8_t, Hex8)
1748 LLVM_YAML_STRONG_TYPEDEF(uint16_t, Hex16)
1749 LLVM_YAML_STRONG_TYPEDEF(uint32_t, Hex32)
1750 LLVM_YAML_STRONG_TYPEDEF(uint64_t, Hex64)
1751 
1752 template<>
1753 struct ScalarTraits<Hex8> {
1754   static void output(const Hex8 &, void *, raw_ostream &);
1755   static StringRef input(StringRef, void *, Hex8 &);
1756   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
1757 };
1758 
1759 template<>
1760 struct ScalarTraits<Hex16> {
1761   static void output(const Hex16 &, void *, raw_ostream &);
1762   static StringRef input(StringRef, void *, Hex16 &);
1763   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
1764 };
1765 
1766 template<>
1767 struct ScalarTraits<Hex32> {
1768   static void output(const Hex32 &, void *, raw_ostream &);
1769   static StringRef input(StringRef, void *, Hex32 &);
1770   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
1771 };
1772 
1773 template<>
1774 struct ScalarTraits<Hex64> {
1775   static void output(const Hex64 &, void *, raw_ostream &);
1776   static StringRef input(StringRef, void *, Hex64 &);
1777   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
1778 };
1779 
1780 template <> struct ScalarTraits<VersionTuple> {
1781   static void output(const VersionTuple &Value, void *, llvm::raw_ostream &Out);
1782   static StringRef input(StringRef, void *, VersionTuple &);
1783   static QuotingType mustQuote(StringRef) { return QuotingType::None; }
1784 };
1785 
1786 // Define non-member operator>> so that Input can stream in a document list.
1787 template <typename T>
1788 inline std::enable_if_t<has_DocumentListTraits<T>::value, Input &>
1789 operator>>(Input &yin, T &docList) {
1790   int i = 0;
1791   EmptyContext Ctx;
1792   while ( yin.setCurrentDocument() ) {
1793     yamlize(yin, DocumentListTraits<T>::element(yin, docList, i), true, Ctx);
1794     if ( yin.error() )
1795       return yin;
1796     yin.nextDocument();
1797     ++i;
1798   }
1799   return yin;
1800 }
1801 
1802 // Define non-member operator>> so that Input can stream in a map as a document.
1803 template <typename T>
1804 inline std::enable_if_t<has_MappingTraits<T, EmptyContext>::value, Input &>
1805 operator>>(Input &yin, T &docMap) {
1806   EmptyContext Ctx;
1807   yin.setCurrentDocument();
1808   yamlize(yin, docMap, true, Ctx);
1809   return yin;
1810 }
1811 
1812 // Define non-member operator>> so that Input can stream in a sequence as
1813 // a document.
1814 template <typename T>
1815 inline std::enable_if_t<has_SequenceTraits<T>::value, Input &>
1816 operator>>(Input &yin, T &docSeq) {
1817   EmptyContext Ctx;
1818   if (yin.setCurrentDocument())
1819     yamlize(yin, docSeq, true, Ctx);
1820   return yin;
1821 }
1822 
1823 // Define non-member operator>> so that Input can stream in a block scalar.
1824 template <typename T>
1825 inline std::enable_if_t<has_BlockScalarTraits<T>::value, Input &>
1826 operator>>(Input &In, T &Val) {
1827   EmptyContext Ctx;
1828   if (In.setCurrentDocument())
1829     yamlize(In, Val, true, Ctx);
1830   return In;
1831 }
1832 
1833 // Define non-member operator>> so that Input can stream in a string map.
1834 template <typename T>
1835 inline std::enable_if_t<has_CustomMappingTraits<T>::value, Input &>
1836 operator>>(Input &In, T &Val) {
1837   EmptyContext Ctx;
1838   if (In.setCurrentDocument())
1839     yamlize(In, Val, true, Ctx);
1840   return In;
1841 }
1842 
1843 // Define non-member operator>> so that Input can stream in a polymorphic type.
1844 template <typename T>
1845 inline std::enable_if_t<has_PolymorphicTraits<T>::value, Input &>
1846 operator>>(Input &In, T &Val) {
1847   EmptyContext Ctx;
1848   if (In.setCurrentDocument())
1849     yamlize(In, Val, true, Ctx);
1850   return In;
1851 }
1852 
1853 // Provide better error message about types missing a trait specialization
1854 template <typename T>
1855 inline std::enable_if_t<missingTraits<T, EmptyContext>::value, Input &>
1856 operator>>(Input &yin, T &docSeq) {
1857   char missing_yaml_trait_for_type[sizeof(MissingTrait<T>)];
1858   return yin;
1859 }
1860 
1861 // Define non-member operator<< so that Output can stream out document list.
1862 template <typename T>
1863 inline std::enable_if_t<has_DocumentListTraits<T>::value, Output &>
1864 operator<<(Output &yout, T &docList) {
1865   EmptyContext Ctx;
1866   yout.beginDocuments();
1867   const size_t count = DocumentListTraits<T>::size(yout, docList);
1868   for(size_t i=0; i < count; ++i) {
1869     if ( yout.preflightDocument(i) ) {
1870       yamlize(yout, DocumentListTraits<T>::element(yout, docList, i), true,
1871               Ctx);
1872       yout.postflightDocument();
1873     }
1874   }
1875   yout.endDocuments();
1876   return yout;
1877 }
1878 
1879 // Define non-member operator<< so that Output can stream out a map.
1880 template <typename T>
1881 inline std::enable_if_t<has_MappingTraits<T, EmptyContext>::value, Output &>
1882 operator<<(Output &yout, T &map) {
1883   EmptyContext Ctx;
1884   yout.beginDocuments();
1885   if ( yout.preflightDocument(0) ) {
1886     yamlize(yout, map, true, Ctx);
1887     yout.postflightDocument();
1888   }
1889   yout.endDocuments();
1890   return yout;
1891 }
1892 
1893 // Define non-member operator<< so that Output can stream out a sequence.
1894 template <typename T>
1895 inline std::enable_if_t<has_SequenceTraits<T>::value, Output &>
1896 operator<<(Output &yout, T &seq) {
1897   EmptyContext Ctx;
1898   yout.beginDocuments();
1899   if ( yout.preflightDocument(0) ) {
1900     yamlize(yout, seq, true, Ctx);
1901     yout.postflightDocument();
1902   }
1903   yout.endDocuments();
1904   return yout;
1905 }
1906 
1907 // Define non-member operator<< so that Output can stream out a block scalar.
1908 template <typename T>
1909 inline std::enable_if_t<has_BlockScalarTraits<T>::value, Output &>
1910 operator<<(Output &Out, T &Val) {
1911   EmptyContext Ctx;
1912   Out.beginDocuments();
1913   if (Out.preflightDocument(0)) {
1914     yamlize(Out, Val, true, Ctx);
1915     Out.postflightDocument();
1916   }
1917   Out.endDocuments();
1918   return Out;
1919 }
1920 
1921 // Define non-member operator<< so that Output can stream out a string map.
1922 template <typename T>
1923 inline std::enable_if_t<has_CustomMappingTraits<T>::value, Output &>
1924 operator<<(Output &Out, T &Val) {
1925   EmptyContext Ctx;
1926   Out.beginDocuments();
1927   if (Out.preflightDocument(0)) {
1928     yamlize(Out, Val, true, Ctx);
1929     Out.postflightDocument();
1930   }
1931   Out.endDocuments();
1932   return Out;
1933 }
1934 
1935 // Define non-member operator<< so that Output can stream out a polymorphic
1936 // type.
1937 template <typename T>
1938 inline std::enable_if_t<has_PolymorphicTraits<T>::value, Output &>
1939 operator<<(Output &Out, T &Val) {
1940   EmptyContext Ctx;
1941   Out.beginDocuments();
1942   if (Out.preflightDocument(0)) {
1943     // FIXME: The parser does not support explicit documents terminated with a
1944     // plain scalar; the end-marker is included as part of the scalar token.
1945     assert(PolymorphicTraits<T>::getKind(Val) != NodeKind::Scalar && "plain scalar documents are not supported");
1946     yamlize(Out, Val, true, Ctx);
1947     Out.postflightDocument();
1948   }
1949   Out.endDocuments();
1950   return Out;
1951 }
1952 
1953 // Provide better error message about types missing a trait specialization
1954 template <typename T>
1955 inline std::enable_if_t<missingTraits<T, EmptyContext>::value, Output &>
1956 operator<<(Output &yout, T &seq) {
1957   char missing_yaml_trait_for_type[sizeof(MissingTrait<T>)];
1958   return yout;
1959 }
1960 
1961 template <bool B> struct IsFlowSequenceBase {};
1962 template <> struct IsFlowSequenceBase<true> { static const bool flow = true; };
1963 
1964 template <typename T, typename U = void>
1965 struct IsResizable : std::false_type {};
1966 
1967 template <typename T>
1968 struct IsResizable<T, std::void_t<decltype(std::declval<T>().resize(0))>>
1969     : public std::true_type {};
1970 
1971 template <typename T, bool B> struct IsResizableBase {
1972   using type = typename T::value_type;
1973 
1974   static type &element(IO &io, T &seq, size_t index) {
1975     if (index >= seq.size())
1976       seq.resize(index + 1);
1977     return seq[index];
1978   }
1979 };
1980 
1981 template <typename T> struct IsResizableBase<T, false> {
1982   using type = typename T::value_type;
1983 
1984   static type &element(IO &io, T &seq, size_t index) {
1985     if (index >= seq.size()) {
1986       io.setError(Twine("value sequence extends beyond static size (") +
1987                   Twine(seq.size()) + ")");
1988       return seq[0];
1989     }
1990     return seq[index];
1991   }
1992 };
1993 
1994 template <typename T, bool Flow>
1995 struct SequenceTraitsImpl
1996     : IsFlowSequenceBase<Flow>, IsResizableBase<T, IsResizable<T>::value> {
1997   static size_t size(IO &io, T &seq) { return seq.size(); }
1998 };
1999 
2000 // Simple helper to check an expression can be used as a bool-valued template
2001 // argument.
2002 template <bool> struct CheckIsBool { static const bool value = true; };
2003 
2004 // If T has SequenceElementTraits, then vector<T> and SmallVector<T, N> have
2005 // SequenceTraits that do the obvious thing.
2006 template <typename T>
2007 struct SequenceTraits<
2008     std::vector<T>,
2009     std::enable_if_t<CheckIsBool<SequenceElementTraits<T>::flow>::value>>
2010     : SequenceTraitsImpl<std::vector<T>, SequenceElementTraits<T>::flow> {};
2011 template <typename T, size_t N>
2012 struct SequenceTraits<
2013     std::array<T, N>,
2014     std::enable_if_t<CheckIsBool<SequenceElementTraits<T>::flow>::value>>
2015     : SequenceTraitsImpl<std::array<T, N>, SequenceElementTraits<T>::flow> {};
2016 template <typename T, unsigned N>
2017 struct SequenceTraits<
2018     SmallVector<T, N>,
2019     std::enable_if_t<CheckIsBool<SequenceElementTraits<T>::flow>::value>>
2020     : SequenceTraitsImpl<SmallVector<T, N>, SequenceElementTraits<T>::flow> {};
2021 template <typename T>
2022 struct SequenceTraits<
2023     SmallVectorImpl<T>,
2024     std::enable_if_t<CheckIsBool<SequenceElementTraits<T>::flow>::value>>
2025     : SequenceTraitsImpl<SmallVectorImpl<T>, SequenceElementTraits<T>::flow> {};
2026 template <typename T>
2027 struct SequenceTraits<
2028     MutableArrayRef<T>,
2029     std::enable_if_t<CheckIsBool<SequenceElementTraits<T>::flow>::value>>
2030     : SequenceTraitsImpl<MutableArrayRef<T>, SequenceElementTraits<T>::flow> {};
2031 
2032 // Sequences of fundamental types use flow formatting.
2033 template <typename T>
2034 struct SequenceElementTraits<T, std::enable_if_t<std::is_fundamental_v<T>>> {
2035   static const bool flow = true;
2036 };
2037 
2038 // Sequences of strings use block formatting.
2039 template<> struct SequenceElementTraits<std::string> {
2040   static const bool flow = false;
2041 };
2042 template<> struct SequenceElementTraits<StringRef> {
2043   static const bool flow = false;
2044 };
2045 template<> struct SequenceElementTraits<std::pair<std::string, std::string>> {
2046   static const bool flow = false;
2047 };
2048 
2049 /// Implementation of CustomMappingTraits for std::map<std::string, T>.
2050 template <typename T> struct StdMapStringCustomMappingTraitsImpl {
2051   using map_type = std::map<std::string, T>;
2052 
2053   static void inputOne(IO &io, StringRef key, map_type &v) {
2054     io.mapRequired(key.str().c_str(), v[std::string(key)]);
2055   }
2056 
2057   static void output(IO &io, map_type &v) {
2058     for (auto &p : v)
2059       io.mapRequired(p.first.c_str(), p.second);
2060   }
2061 };
2062 
2063 } // end namespace yaml
2064 } // end namespace llvm
2065 
2066 #define LLVM_YAML_IS_SEQUENCE_VECTOR_IMPL(TYPE, FLOW)                          \
2067   namespace llvm {                                                             \
2068   namespace yaml {                                                             \
2069   static_assert(                                                               \
2070       !std::is_fundamental_v<TYPE> && !std::is_same_v<TYPE, std::string> &&    \
2071           !std::is_same_v<TYPE, llvm::StringRef>,                              \
2072       "only use LLVM_YAML_IS_SEQUENCE_VECTOR for types you control");          \
2073   template <> struct SequenceElementTraits<TYPE> {                             \
2074     static const bool flow = FLOW;                                             \
2075   };                                                                           \
2076   }                                                                            \
2077   }
2078 
2079 /// Utility for declaring that a std::vector of a particular type
2080 /// should be considered a YAML sequence.
2081 #define LLVM_YAML_IS_SEQUENCE_VECTOR(type)                                     \
2082   LLVM_YAML_IS_SEQUENCE_VECTOR_IMPL(type, false)
2083 
2084 /// Utility for declaring that a std::vector of a particular type
2085 /// should be considered a YAML flow sequence.
2086 #define LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(type)                                \
2087   LLVM_YAML_IS_SEQUENCE_VECTOR_IMPL(type, true)
2088 
2089 #define LLVM_YAML_DECLARE_MAPPING_TRAITS(Type)                                 \
2090   namespace llvm {                                                             \
2091   namespace yaml {                                                             \
2092   template <> struct LLVM_ABI MappingTraits<Type> {                            \
2093     static void mapping(IO &IO, Type &Obj);                                    \
2094   };                                                                           \
2095   }                                                                            \
2096   }
2097 
2098 #define LLVM_YAML_DECLARE_MAPPING_TRAITS_PRIVATE(Type)                         \
2099   namespace llvm {                                                             \
2100   namespace yaml {                                                             \
2101   template <> struct MappingTraits<Type> {                                     \
2102     static void mapping(IO &IO, Type &Obj);                                    \
2103   };                                                                           \
2104   }                                                                            \
2105   }
2106 
2107 #define LLVM_YAML_DECLARE_ENUM_TRAITS(Type)                                    \
2108   namespace llvm {                                                             \
2109   namespace yaml {                                                             \
2110   template <> struct LLVM_ABI ScalarEnumerationTraits<Type> {                  \
2111     static void enumeration(IO &io, Type &Value);                              \
2112   };                                                                           \
2113   }                                                                            \
2114   }
2115 
2116 #define LLVM_YAML_DECLARE_BITSET_TRAITS(Type)                                  \
2117   namespace llvm {                                                             \
2118   namespace yaml {                                                             \
2119   template <> struct LLVM_ABI ScalarBitSetTraits<Type> {                       \
2120     static void bitset(IO &IO, Type &Options);                                 \
2121   };                                                                           \
2122   }                                                                            \
2123   }
2124 
2125 #define LLVM_YAML_DECLARE_SCALAR_TRAITS(Type, MustQuote)                       \
2126   namespace llvm {                                                             \
2127   namespace yaml {                                                             \
2128   template <> struct LLVM_ABI ScalarTraits<Type> {                             \
2129     static void output(const Type &Value, void *ctx, raw_ostream &Out);        \
2130     static StringRef input(StringRef Scalar, void *ctxt, Type &Value);         \
2131     static QuotingType mustQuote(StringRef) { return MustQuote; }              \
2132   };                                                                           \
2133   }                                                                            \
2134   }
2135 
2136 /// Utility for declaring that a std::vector of a particular type
2137 /// should be considered a YAML document list.
2138 #define LLVM_YAML_IS_DOCUMENT_LIST_VECTOR(_type)                               \
2139   namespace llvm {                                                             \
2140   namespace yaml {                                                             \
2141   template <unsigned N>                                                        \
2142   struct DocumentListTraits<SmallVector<_type, N>>                             \
2143       : public SequenceTraitsImpl<SmallVector<_type, N>, false> {};            \
2144   template <>                                                                  \
2145   struct DocumentListTraits<std::vector<_type>>                                \
2146       : public SequenceTraitsImpl<std::vector<_type>, false> {};               \
2147   }                                                                            \
2148   }
2149 
2150 /// Utility for declaring that std::map<std::string, _type> should be considered
2151 /// a YAML map.
2152 #define LLVM_YAML_IS_STRING_MAP(_type)                                         \
2153   namespace llvm {                                                             \
2154   namespace yaml {                                                             \
2155   template <>                                                                  \
2156   struct CustomMappingTraits<std::map<std::string, _type>>                     \
2157       : public StdMapStringCustomMappingTraitsImpl<_type> {};                  \
2158   }                                                                            \
2159   }
2160 
2161 LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(llvm::yaml::Hex64)
2162 LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(llvm::yaml::Hex32)
2163 LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(llvm::yaml::Hex16)
2164 LLVM_YAML_IS_FLOW_SEQUENCE_VECTOR(llvm::yaml::Hex8)
2165 
2166 #endif // LLVM_SUPPORT_YAMLTRAITS_H
2167