AST: Introduce SemanticDeclAttrsRequest.

This request will populate a decl's attrs list with any semantic attributes
that were not written in source.

Author: tshortli

include/swift/AST/Decl.h

@@ -351,7 +351,7 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl> {
   // for the inline bitfields.
   union { uint64_t OpaqueBits;
 
-  SWIFT_INLINE_BITFIELD_BASE(Decl, bitmax(NumDeclKindBits,8)+1+1+1+1+1,
+  SWIFT_INLINE_BITFIELD_BASE(Decl, bitmax(NumDeclKindBits,8)+1+1+1+1+1+1,
     Kind : bitmax(NumDeclKindBits,8),
 
     /// Whether this declaration is invalid.
@@ -374,7 +374,10 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl> {
     /// a local context, but should behave like a top-level
     /// declaration for name lookup purposes. This is used by
     /// lldb.
-    Hoisted : 1
+    Hoisted : 1,
+
+    /// Whether the set of semantic attributes has been computed.
+    SemanticAttrsComputed : 1
   );
 
   SWIFT_INLINE_BITFIELD_FULL(PatternBindingDecl, Decl, 1+1+2+16,
@@ -1090,6 +1093,14 @@ class alignas(1 << DeclAlignInBits) Decl : public ASTAllocated<Decl> {
     Bits.Decl.EscapedFromIfConfig = Escaped;
   }
 
+  bool getSemanticAttrsComputed() const {
+    return Bits.Decl.SemanticAttrsComputed;
+  }
+
+  void setSemanticAttrsComputed(bool Computed) {
+    Bits.Decl.SemanticAttrsComputed = Computed;
+  }
+
   /// \returns the unparsed comment attached to this declaration.
   RawComment getRawComment() const;
 

include/swift/AST/TypeCheckRequests.h

@@ -4600,6 +4600,25 @@ class IsFunctionBodySkippedRequest
   void cacheResult(bool isSkipped) const;
 };
 
+class SemanticDeclAttrsRequest
+    : public SimpleRequest<SemanticDeclAttrsRequest,
+                           DeclAttributes(const Decl *),
+                           RequestFlags::SeparatelyCached> {
+public:
+  using SimpleRequest::SimpleRequest;
+
+private:
+  friend SimpleRequest;
+
+  DeclAttributes evaluate(Evaluator &evaluator, const Decl *) const;
+
+public:
+  // Separate caching.
+  bool isCached() const { return true; }
+  llvm::Optional<DeclAttributes> getCachedResult() const;
+  void cacheResult(DeclAttributes) const;
+};
+
 #define SWIFT_TYPEID_ZONE TypeChecker
 #define SWIFT_TYPEID_HEADER "swift/AST/TypeCheckerTypeIDZone.def"
 #include "swift/Basic/DefineTypeIDZone.h"

include/swift/AST/TypeCheckerTypeIDZone.def

@@ -523,3 +523,6 @@ SWIFT_REQUEST(TypeChecker, IsFunctionBodySkippedRequest,
 SWIFT_REQUEST(TypeChecker, IsCCompatibleFuncDeclRequest,
               bool(const FuncDecl *),
               Cached, NoLocationInfo)
+SWIFT_REQUEST(TypeChecker, SemanticDeclAttrsRequest,
+              DeclAttributes(const Decl *),
+              Cached, NoLocationInfo)

lib/AST/Decl.cpp

@@ -376,11 +376,8 @@ OrigDeclAttributes Decl::getOriginalAttrs() const {
 }
 
 DeclAttributes Decl::getSemanticAttrs() const {
-  auto mutableThis = const_cast<Decl *>(this);
   (void)evaluateOrDefault(getASTContext().evaluator,
-                          ExpandMemberAttributeMacros{mutableThis},
-                          { });
-
+                          SemanticDeclAttrsRequest{this}, {});
   return getAttrs();
 }
 

lib/AST/TypeCheckRequests.cpp

@@ -2062,3 +2062,28 @@ void ExpandPeerMacroRequest::noteCycleStep(DiagnosticEngine &diags) const {
                    "peer");
   }
 }
+
+//----------------------------------------------------------------------------//
+// SemanticDeclAttrsRequest computation.
+//----------------------------------------------------------------------------//
+
+DeclAttributes SemanticDeclAttrsRequest::evaluate(Evaluator &evaluator,
+                                                  const Decl *decl) const {
+  auto mutableDecl = const_cast<Decl *>(decl);
+  (void)evaluateOrDefault(evaluator, ExpandMemberAttributeMacros{mutableDecl},
+                          {});
+  return decl->getAttrs();
+}
+
+llvm::Optional<DeclAttributes>
+SemanticDeclAttrsRequest::getCachedResult() const {
+  auto decl = std::get<0>(getStorage());
+  if (decl->getSemanticAttrsComputed())
+    return decl->getAttrs();
+  return llvm::None;
+}
+
+void SemanticDeclAttrsRequest::cacheResult(DeclAttributes attrs) const {
+  auto decl = std::get<0>(getStorage());
+  const_cast<Decl *>(decl)->setSemanticAttrsComputed(true);
+}