Cache LookupAllConformancesInContextRequest.

Now that this request will be triggered more often, due to inference
of function builders, cache the result.

Author: DougGregor

include/swift/AST/ASTTypeIDZone.def

@@ -56,6 +56,7 @@ SWIFT_TYPEID_NAMED(PatternBindingEntry *, PatternBindingEntry)
 SWIFT_TYPEID_NAMED(PostfixOperatorDecl *, PostfixOperatorDecl)
 SWIFT_TYPEID_NAMED(PrecedenceGroupDecl *, PrecedenceGroupDecl)
 SWIFT_TYPEID_NAMED(PrefixOperatorDecl *, PrefixOperatorDecl)
+SWIFT_TYPEID_NAMED(ProtocolConformance *, ProtocolConformance)
 SWIFT_TYPEID_NAMED(ProtocolDecl *, ProtocolDecl)
 SWIFT_TYPEID_NAMED(SourceFile *, SourceFile)
 SWIFT_TYPEID_NAMED(TypeAliasDecl *, TypeAliasDecl)

include/swift/AST/ASTTypeIDs.h

@@ -51,6 +51,7 @@ struct PropertyWrapperTypeInfo;
 enum class CtorInitializerKind;
 struct PropertyWrapperLValueness;
 struct PropertyWrapperMutability;
+class ProtocolConformance;
 class ProtocolDecl;
 class Requirement;
 enum class ResilienceExpansion : unsigned;

include/swift/AST/TypeCheckRequests.h

@@ -2234,7 +2234,7 @@ class ClosureHasExplicitResultRequest
   bool isCached() const { return true; }
 };
 
-using ProtocolConformanceLookupResult = SmallVector<ProtocolConformance *, 2>;
+using ProtocolConformanceLookupResult = std::vector<ProtocolConformance *>;
 void simple_display(llvm::raw_ostream &out, ConformanceLookupKind kind);
 
 /// Lookup and expand all conformances in the given context.
@@ -2255,7 +2255,7 @@ void simple_display(llvm::raw_ostream &out, ConformanceLookupKind kind);
 class LookupAllConformancesInContextRequest
     : public SimpleRequest<LookupAllConformancesInContextRequest,
                            ProtocolConformanceLookupResult(const DeclContext *),
-                           RequestFlags::Uncached |
+                           RequestFlags::Cached |
                                RequestFlags::DependencySink |
                                RequestFlags::DependencySource> {
 public:
@@ -2269,6 +2269,8 @@ class LookupAllConformancesInContextRequest
   evaluate(Evaluator &evaluator, const DeclContext *DC) const;
 
 public:
+  bool isCached() const { return true; }
+
   // Incremental dependencies
   evaluator::DependencySource readDependencySource(Evaluator &eval) const;
   void writeDependencySink(Evaluator &eval, ReferencedNameTracker &tracker,

include/swift/Basic/SimpleDisplay.h

@@ -136,6 +136,20 @@ namespace swift {
     out << "}";
   }
 
+  template<typename T>
+  void simple_display(llvm::raw_ostream &out,
+                      const std::vector<T> &vec) {
+    out << "{";
+    bool first = true;
+    for (const T &value : vec) {
+      if (first) first = false;
+      else out << ", ";
+
+      simple_display(out, value);
+    }
+    out << "}";
+  }
+
   template<typename T, typename U>
   void simple_display(llvm::raw_ostream &out,
                       const llvm::PointerUnion<T, U> &ptrUnion) {

lib/Sema/TypeCheckProtocol.cpp

@@ -5100,10 +5100,11 @@ diagnoseMissingAppendInterpolationMethod(NominalTypeDecl *typeDecl) {
   }
 }
 
-SmallVector<ProtocolConformance *, 2>
+std::vector<ProtocolConformance *>
 LookupAllConformancesInContextRequest::evaluate(
-    Evaluator &eval, const DeclContext *DC) const {
-  return DC->getLocalConformances(ConformanceLookupKind::All);
+    Evaluator &eval, const IterableDeclContext *IDC) const {
+  auto result = IDC->getLocalConformances(ConformanceLookupKind::All);
+  return std::vector<ProtocolConformance *>(result.begin(), result.end());
 }
 
 void TypeChecker::checkConformancesInContext(DeclContext *dc,

lib/Sema/TypeCheckRequestFunctions.cpp

@@ -207,10 +207,9 @@ static Type inferFunctionBuilderType(ValueDecl *decl)  {
   // this declaration. If this declaration is a witness to any
   // requirement within one of those protocols that has a function builder
   // attached, use that function builder type.
-  auto idc = cast<IterableDeclContext>(dc->getAsDecl());
   auto conformances = evaluateOrDefault(
       dc->getASTContext().evaluator,
-      LookupAllConformancesInContextRequest{idc}, { });
+      LookupAllConformancesInContextRequest{dc}, { });
 
   // Find all of the potentially inferred function builder types.
   struct Match {