Sema: Fix call to SubstitutionMap::getProtocolSubstitutions()

The conforming type didn't match the conformance, which is going to
be flagged by SubstitutionMap::verify().

Author: slavapestov

lib/Sema/AssociatedTypeInference.cpp

@@ -38,6 +38,7 @@
 
 #include "swift/AST/ConformanceLookup.h"
 #include "swift/AST/Decl.h"
+#include "swift/AST/GenericEnvironment.h"
 #include "swift/AST/GenericSignature.h"
 #include "swift/AST/NameLookupRequests.h"
 #include "swift/AST/PrettyStackTrace.h"
@@ -2860,12 +2861,18 @@ bool AssociatedTypeInference::checkCurrentTypeWitnesses(
   // Check any same-type requirements in the protocol's requirement signature.
   SubstOptions options = getSubstOptionsWithCurrentTypeWitnesses();
 
-  auto typeInContext = dc->mapTypeIntoContext(adoptee);
+  auto typeInContext = adoptee;
+  ProtocolConformanceRef conformanceInContext(conformance);
+  if (auto *genericEnv = conformance->getGenericEnvironment()) {
+    typeInContext = genericEnv->mapTypeIntoContext(typeInContext);
+    conformanceInContext =
+      conformanceInContext.subst(conformance->getType(),
+                                 genericEnv->getForwardingSubstitutionMap());
+  }
 
   auto substitutions =
     SubstitutionMap::getProtocolSubstitutions(
-                                    proto, typeInContext,
-                                    ProtocolConformanceRef(conformance));
+      proto, typeInContext, conformanceInContext);
 
   SmallVector<Requirement, 4> sanitizedRequirements;
   auto requirements = proto->getRequirementSignature().getRequirements();