AST: Remove SourceFile::UsedConformances

Sema no longer adds conformances to a per-SourceFile list that it thinks
are going to be "used" by SILGen, IRGen and the runtime. Instead, previous
commits already ensure that SILGen determines the set of conformances to be
emitted, triggering conformance checking as needed.

Author: slavapestov

include/swift/AST/Module.h

@@ -983,10 +983,6 @@ class SourceFile final : public FileUnit {
   /// If not, we can fast-path module checks.
   bool HasImplementationOnlyImports = false;
 
-  /// The list of protocol conformances that were "used" within this
-  /// source file.
-  llvm::SetVector<NormalProtocolConformance *> UsedConformances;
-
   /// The scope map that describes this source file.
   ASTScope *Scope = nullptr;
 
@@ -1146,17 +1142,6 @@ class SourceFile final : public FileUnit {
 
   virtual bool walk(ASTWalker &walker) override;
 
-  /// Note that the given conformance was used by this source file.
-  void addUsedConformance(NormalProtocolConformance *conformance) {
-    UsedConformances.insert(conformance);
-  }
-
-  /// Retrieve the set of conformances that were used in this source
-  /// file.
-  ArrayRef<NormalProtocolConformance *> getUsedConformances() const {
-    return UsedConformances.getArrayRef();
-  }
-
   /// @{
 
   /// Look up the given operator in this file.

include/swift/Basic/Statistics.def

@@ -141,9 +141,6 @@ FRONTEND_STATISTIC(AST, NumPrefixOperators)
 /// Number of precedence groups in the AST context.
 FRONTEND_STATISTIC(AST, NumPrecedenceGroups)
 
-/// Number of conformances used by code processed by this frontend job.
-FRONTEND_STATISTIC(AST, NumUsedConformances)
-
 /// Number of full function bodies parsed.
 FRONTEND_STATISTIC(Parse, NumFunctionsParsed)
 

lib/FrontendTool/FrontendTool.cpp

@@ -478,7 +478,6 @@ static void countStatsOfSourceFile(UnifiedStatsReporter &Stats,
   C.NumPostfixOperators += SF->PostfixOperators.size();
   C.NumPrefixOperators += SF->PrefixOperators.size();
   C.NumPrecedenceGroups += SF->PrecedenceGroups.size();
-  C.NumUsedConformances += SF->getUsedConformances().size();
 
   auto bufID = SF->getBufferID();
   if (bufID.hasValue()) {

lib/SILGen/SILGen.cpp

@@ -1688,10 +1688,6 @@ void SILGenModule::emitSourceFile(SourceFile *sf) {
     FrontendStatsTracer StatsTracer(getASTContext().Stats, "SILgen-tydecl", D);
     visit(D);
   }
-
-  // Mark any conformances as "used".
-  for (auto conformance : sf->getUsedConformances())
-    useConformance(ProtocolConformanceRef(conformance));
 }
 
 //===----------------------------------------------------------------------===//

lib/Sema/TypeCheckProtocol.cpp

@@ -4289,12 +4289,6 @@ void TypeChecker::markConformanceUsed(ProtocolConformanceRef conformance,
     // Make sure that the type checker completes this conformance.
     if (normalConformance->isIncomplete())
       UsedConformances.insert(normalConformance);
-
-    // Record the usage of this conformance in the enclosing source
-    // file.
-    if (auto sf = dc->getParentSourceFile()) {
-      sf->addUsedConformance(normalConformance);
-    }
   }
 }