RequirementMachine: Fix lookupConcreteNestedType() to cope with opaque archetypes

Author: slavapestov

lib/AST/RequirementMachine/ConcreteContraction.cpp

@@ -235,19 +235,10 @@ Optional<Type> ConcreteContraction::substTypeParameter(
                     ->substBaseType(module, *substBaseType);
   }
 
-  auto *decl = (*substBaseType)->getAnyNominal();
-  if (decl == nullptr) {
-    if (Debug) {
-      llvm::dbgs() << "@@@ Not a nominal type: " << *substBaseType << "\n";
-    }
-
-    return None;
-  }
-
   // An unresolved DependentMemberType stores an identifier. Handle this
   // by performing a name lookup into the base type.
   SmallVector<TypeDecl *> concreteDecls;
-  lookupConcreteNestedType(decl, memberType->getName(), concreteDecls);
+  lookupConcreteNestedType(*substBaseType, memberType->getName(), concreteDecls);
 
   auto *typeDecl = findBestConcreteNestedType(concreteDecls);
   if (typeDecl == nullptr) {
@@ -261,8 +252,9 @@ Optional<Type> ConcreteContraction::substTypeParameter(
   }
 
   // Substitute the base type into the member type.
+  auto *dc = typeDecl->getDeclContext();
   auto subMap = (*substBaseType)->getContextSubstitutionMap(
-      decl->getParentModule(), typeDecl->getDeclContext());
+      dc->getParentModule(), dc);
   return typeDecl->getDeclaredInterfaceType().subst(subMap);
 }
 

lib/AST/RequirementMachine/GenericSignatureQueries.cpp

@@ -17,6 +17,7 @@
 
 #include "swift/AST/ASTContext.h"
 #include "swift/AST/Decl.h"
+#include "swift/AST/GenericEnvironment.h"
 #include "swift/AST/GenericSignature.h"
 #include "swift/AST/Module.h"
 #include <vector>
@@ -659,8 +660,7 @@ RequirementMachine::lookupNestedType(Type depType, Identifier name) const {
       typeToSearch = props->getSuperclassBound();
 
     if (typeToSearch)
-      if (auto *decl = typeToSearch->getAnyNominal())
-        lookupConcreteNestedType(decl, name, concreteDecls);
+      lookupConcreteNestedType(typeToSearch, name, concreteDecls);
   }
 
   if (bestAssocType) {

lib/AST/RequirementMachine/NameLookup.cpp

@@ -12,13 +12,33 @@
 
 #include "NameLookup.h"
 #include "swift/AST/Decl.h"
+#include "swift/AST/GenericEnvironment.h"
 #include "swift/AST/Module.h"
+#include "swift/AST/Types.h"
 #include "llvm/ADT/SmallVector.h"
 #include <algorithm>
 
 using namespace swift;
 using namespace rewriting;
 
+void
+swift::rewriting::lookupConcreteNestedType(
+    Type baseType,
+    Identifier name,
+    SmallVectorImpl<TypeDecl *> &concreteDecls) {
+  if (auto *decl = baseType->getAnyNominal())
+    lookupConcreteNestedType(decl, name, concreteDecls);
+  else if (auto *archetype = baseType->getAs<OpaqueTypeArchetypeType>()) {
+    // If our concrete type is an opaque result archetype, look into its
+    // generic environment recursively.
+    auto *genericEnv = archetype->getGenericEnvironment();
+    auto genericSig = genericEnv->getGenericSignature();
+
+    concreteDecls.push_back(
+        genericSig->lookupNestedType(archetype->getInterfaceType(), name));
+  }
+}
+
 void
 swift::rewriting::lookupConcreteNestedType(
     NominalTypeDecl *decl,

lib/AST/RequirementMachine/NameLookup.h

@@ -19,10 +19,16 @@ namespace swift {
 
 class Identifier;
 class NominalTypeDecl;
+class Type;
 class TypeDecl;
 
 namespace rewriting {
 
+void lookupConcreteNestedType(
+    Type baseType,
+    Identifier name,
+    llvm::SmallVectorImpl<TypeDecl *> &concreteDecls);
+
 void lookupConcreteNestedType(
     NominalTypeDecl *decl,
     Identifier name,