AST: Allow non-canonical opaque archetypes

Author: slavapestov

include/swift/AST/TypeNodes.def

@@ -176,7 +176,7 @@ TYPE(DynamicSelf, Type)
 ABSTRACT_TYPE(Substitutable, Type)
   ABSTRACT_TYPE(Archetype, SubstitutableType)
     ALWAYS_CANONICAL_TYPE(PrimaryArchetype, ArchetypeType)
-    ALWAYS_CANONICAL_TYPE(OpaqueTypeArchetype, ArchetypeType)
+    TYPE(OpaqueTypeArchetype, ArchetypeType)
     ABSTRACT_TYPE(LocalArchetype, ArchetypeType)
       ALWAYS_CANONICAL_TYPE(ExistentialArchetype, LocalArchetypeType)
       ALWAYS_CANONICAL_TYPE(ElementArchetype, LocalArchetypeType)

lib/AST/ASTContext.cpp

@@ -6027,11 +6027,6 @@ GenericEnvironment *GenericEnvironment::forPrimary(GenericSignature signature) {
 /// outer substitutions.
 GenericEnvironment *GenericEnvironment::forOpaqueType(
     OpaqueTypeDecl *opaque, SubstitutionMap subs) {
-  // TODO: We could attempt to preserve type sugar in the substitution map.
-  // Currently archetypes are assumed to be always canonical in many places,
-  // though, so doing so would require fixing those places.
-  subs = subs.getCanonical();
-
   auto &ctx = opaque->getASTContext();
 
   auto properties = ArchetypeType::archetypeProperties(

lib/AST/GenericEnvironment.cpp

@@ -227,7 +227,6 @@ GenericEnvironment::GenericEnvironment(
 GenericEnvironment::GenericEnvironment(
       GenericSignature sig, OpaqueTypeDecl *opaque, SubstitutionMap subs)
   : sig(sig), kind(Kind::Opaque), canonical(subs.isCanonical()) {
-  ASSERT(canonical);
   *getTrailingObjects<SubstitutionMap>() = subs;
   new (getTrailingObjects<OpaqueEnvironmentData>())
     OpaqueEnvironmentData{opaque};

lib/AST/Type.cpp

@@ -2023,6 +2023,14 @@ CanType TypeBase::computeCanonicalType() {
     Result = ErrorUnionType::get(ctx, newTerms).getPointer();
     break;
   }
+  case TypeKind::OpaqueTypeArchetype: {
+    auto *AT = cast<OpaqueTypeArchetypeType>(this);
+    Result = OpaqueTypeArchetypeType::get(
+        AT->getDecl(), AT->getInterfaceType(),
+        AT->getSubstitutions().getCanonical())
+          ->castTo<OpaqueTypeArchetypeType>();
+    break;
+  }
   case TypeKind::Integer: {
     auto intTy = cast<IntegerType>(this);
     APInt value = intTy->getValue();