Fix IRGen for associated type witness accessor functions in generic contexts with

same type requirements.

rdar://27718494
SR-1951

Author: aschwaighofer

lib/IRGen/GenProto.cpp

@@ -995,6 +995,10 @@ getWitnessTableLazyAccessFunction(IRGenModule &IGM,
   return accessor;
 }
 
+static void bindArchetypeAccessPaths(IRGenFunction &IGF,
+                                     GenericSignature *Generics,
+                                     GetTypeParameterInContextFn getInContext);
+
 namespace {
 
 /// Conformance info for a witness table that can be directly generated.
@@ -1276,6 +1280,17 @@ class AccessorConformanceInfo : public ConformanceInfo {
       }
       return *Fulfillments;
     }
+
+    void bindArchetypeAccessPathsInConformance(IRGenFunction &IGF) {
+      auto declCtx = Conformance.getDeclContext();
+      if (auto generics = declCtx->getGenericSignatureOfContext()) {
+        auto getInContext = [&](CanType type) -> CanType {
+          return ArchetypeBuilder::mapTypeIntoContext(declCtx, type, nullptr)
+              ->getCanonicalType();
+        };
+        bindArchetypeAccessPaths(IGF, generics, getInContext);
+      }
+    }
   };
 }
 
@@ -1335,6 +1350,9 @@ getAssociatedTypeMetadataAccessFunction(AssociatedTypeDecl *requirement,
   // Bind local type data from the metadata argument.
   IGF.bindLocalTypeDataFromTypeMetadata(ConcreteType, IsExact, self);
 
+  // Bind archetype access paths.
+  bindArchetypeAccessPathsInConformance(IGF);
+
   // For now, assume that an associated type is cheap enough to access
   // that it doesn't need a new cache entry.
   if (auto archetype = dyn_cast<ArchetypeType>(associatedType)) {
@@ -1458,6 +1476,9 @@ getAssociatedTypeWitnessTableAccessFunction(AssociatedTypeDecl *requirement,
                                         associatedTypeMetadata);
   IGF.bindLocalTypeDataFromTypeMetadata(ConcreteType, IsExact, self);
 
+  // Bind archetype access paths.
+  bindArchetypeAccessPathsInConformance(IGF);
+
   // For now, assume that finding an abstract conformance is always
   // fast enough that it's not worth caching.
   // TODO: provide an API to find the best metadata path to the conformance

test/IRGen/same_type_constraints.swift

@@ -22,3 +22,14 @@ public class C1<T: Equatable> { }
 public class C2<T: Equatable, U: P where T == U.Foo>: C1<T> {}
 
 // CHECK: define{{( protected)?}} void @_TFC21same_type_constraints2C1D
+
+public protocol DataType {}
+
+public protocol E {
+  associatedtype Data: DataType
+}
+
+public class GenericKlazz<T: DataType, R: E> : E where R.Data == T
+{
+  public typealias Data = T
+}