[AST] Serialize bit async let info on AnyPattern

Author: LucianoPAlmeida

include/swift/AST/Pattern.h

@@ -79,6 +79,10 @@ class alignas(8) Pattern : public ASTAllocated<Pattern> {
     IsLet : 1
   );
 
+  SWIFT_INLINE_BITFIELD(AnyPattern, Pattern, 1,
+                        /// True if this is an "async let _"  pattern.
+                        IsAsyncLet : 1);
+
   } Bits;
 
   Pattern(PatternKind kind) {
@@ -369,14 +373,12 @@ class NamedPattern : public Pattern {
 /// bind a name to it.  This is spelled "_".
 class AnyPattern : public Pattern {
   SourceLoc Loc;
-  /// Flag representing if this is an "async let _: Type" pattern since 
-  /// `async let _` is a subPattern of a \c TypedPattern represented 
-  /// as \c AnyPattern
-  bool IsAsyncLet;
 
 public:
   explicit AnyPattern(SourceLoc Loc, bool IsAsyncLet = false)
-      : Pattern(PatternKind::Any), Loc(Loc), IsAsyncLet(IsAsyncLet) {}
+      : Pattern(PatternKind::Any), Loc(Loc) {
+    Bits.AnyPattern.IsAsyncLet = static_cast<uint64_t>(IsAsyncLet);
+  }
 
   static AnyPattern *createImplicit(ASTContext &Context) {
     auto *AP = new (Context) AnyPattern(SourceLoc());
@@ -387,7 +389,15 @@ class AnyPattern : public Pattern {
   SourceLoc getLoc() const { return Loc; }
   SourceRange getSourceRange() const { return Loc; }
 
-  bool isAsyncLet() const { return IsAsyncLet; }
+  /// True if this is an "async let _ pattern since `async let _` could be a 
+  /// subPattern of a \c TypedPattern represented as \c AnyPattern e.g. 
+  /// "async let _: Type = <expr>" or simply just an \c AnyPattern in 
+  /// "async let _ = <expr>" case.
+  bool isAsyncLet() const { return bool(Bits.AnyPattern.IsAsyncLet); }
+  
+  void setIsAsyncLet() {
+    Bits.AnyPattern.IsAsyncLet = static_cast<uint64_t>(true);
+  }
 
   static bool classof(const Pattern *P) {
     return P->getKind() == PatternKind::Any;

lib/Serialization/Deserialization.cpp

@@ -347,9 +347,13 @@ Expected<Pattern *> ModuleFile::readPattern(DeclContext *owningDC) {
   }
   case decls_block::ANY_PATTERN: {
     TypeID typeID;
+    bool isAsyncLet;
 
-    AnyPatternLayout::readRecord(scratch, typeID);
+    AnyPatternLayout::readRecord(scratch, typeID, isAsyncLet);
     auto result = AnyPattern::createImplicit(getContext());
+    if (isAsyncLet) {
+      result->setIsAsyncLet();
+    }
     recordPatternType(result, getType(typeID));
     restoreOffset.reset();
     return result;

lib/Serialization/ModuleFormat.h

@@ -1608,7 +1608,8 @@ namespace decls_block {
 
   using AnyPatternLayout = BCRecordLayout<
     ANY_PATTERN,
-    TypeIDField  // type
+    TypeIDField, // type
+    BCFixed<1>   // isAsyncLet
     // FIXME: is the type necessary?
   >;
 

lib/Serialization/Serialization.cpp

@@ -3091,8 +3091,10 @@ class Serializer::DeclSerializer : public DeclVisitor<DeclSerializer> {
     }
     case PatternKind::Any: {
       unsigned abbrCode = S.DeclTypeAbbrCodes[AnyPatternLayout::Code];
+      auto anyPattern = cast<AnyPattern>(pattern);
       AnyPatternLayout::emitRecord(S.Out, S.ScratchRecord, abbrCode,
-                                   S.addTypeRef(getPatternType()));
+                                   S.addTypeRef(getPatternType()),
+                                   anyPattern->isAsyncLet());
       break;
     }
     case PatternKind::Typed: {