[GenericEnvironment] Don't apply outer context substitutions before

type.subst in mapTypeIntoContext.

The outer context substitutions are already applied when invoking
QueryInterfaceTypeSubstitutions. Applying the context substitutions
before subst also causes problems because QueryInterfaceTypeSubstitutions
will return a null type if given an archetype, which manifested with
opened pack element environments.

Author: hborla

lib/AST/GenericEnvironment.cpp

@@ -635,7 +635,6 @@ Type GenericEnvironment::mapTypeIntoContext(
   assert((!type->hasArchetype() || type->hasLocalArchetype()) &&
          "already have a contextual type");
 
-  type = maybeApplyOuterContextSubstitutions(type);
   Type result = type.subst(QueryInterfaceTypeSubstitutions(this),
                            lookupConformance,
                            SubstFlags::AllowLoweredTypes |

test/Constraints/pack-expansion-expressions.swift

@@ -553,3 +553,11 @@ do {
     _ = (repeat overloaded(1, each a))
   }
 }
+
+func configure<T, each Element>(
+  _ item: T,
+  with configuration: repeat (ReferenceWritableKeyPath<T, each Element>, each Element)
+) -> T {
+  repeat item[keyPath: (each configuration).0] = (each configuration).1
+  return item
+}