IRGen: Small cleanup

Author: slavapestov

lib/IRGen/GenProto.cpp

@@ -157,8 +157,6 @@ class PolymorphicConvention {
   }
 
 private:
-  void initGenerics();
-
   template <typename ...Args>
   void considerNewTypeSource(IsExact_t isExact, MetadataSource::Kind kind,
                              CanType type, Args... args);
@@ -213,9 +211,8 @@ class PolymorphicConvention {
 PolymorphicConvention::PolymorphicConvention(IRGenModule &IGM,
                                              CanSILFunctionType fnType,
                                              bool considerParameterSources = true)
-  : IGM(IGM), M(*IGM.getSwiftModule()), FnType(fnType){
-  initGenerics();
-
+  : IGM(IGM), M(*IGM.getSwiftModule()), FnType(fnType),
+    Generics(fnType->getInvocationGenericSignature()) {
   auto rep = fnType->getRepresentation();
 
   if (fnType->isPseudogeneric()) {
@@ -263,11 +260,8 @@ PolymorphicConvention::PolymorphicConvention(IRGenModule &IGM,
 
 void PolymorphicConvention::addPseudogenericFulfillments() {
   enumerateRequirements([&](GenericRequirement reqt) {
-    auto archetype = Generics.getGenericEnvironment()
-                        ->mapTypeIntoContext(reqt.getTypeParameter())
-                        ->getAs<ArchetypeType>();
-    assert(archetype && "did not get an archetype by mapping param?");
-    auto erasedTypeParam = archetype->getExistentialType()->getCanonicalType();
+    auto erasedTypeParam = Generics->getExistentialType(reqt.getTypeParameter())
+                              ->getCanonicalType();
     Sources.emplace_back(MetadataSource::Kind::ErasedTypeMetadata,
                          reqt.getTypeParameter(), erasedTypeParam);
 
@@ -333,10 +327,6 @@ enumerateUnfulfilledRequirements(const RequirementCallback &callback) {
   });
 }
 
-void PolymorphicConvention::initGenerics() {
-  Generics = FnType->getInvocationGenericSignature();
-}
-
 template <typename ...Args>
 void PolymorphicConvention::considerNewTypeSource(IsExact_t isExact,
                                                   MetadataSource::Kind kind,