[GSB] Resolve dependent member types in same-type and superclass constraints.

Once we're finalizing same-type-to-concrete and superclass
constraints, replace any unresolved DependentMemberTypes with their
resolved counterpairs. This allows us to simplify
DependentGenericTypeResolver, which only builds unresolved
DependentMemberTypes now, and eliminates the penultimate use of
ArchetypeResolutionKind::AlwaysPartial.

Author: DougGregor

lib/AST/GenericSignatureBuilder.cpp

@@ -4759,6 +4759,27 @@ void GenericSignatureBuilder::checkSameTypeConstraints(
   }
 }
 
+/// Resolve any unresolved dependent member types using the given builder.
+static Type resolveDependentMemberTypes(GenericSignatureBuilder &builder,
+                                        Type type) {
+  if (!type->hasTypeParameter()) return type;
+
+  return type.transformRec([&builder](TypeBase *type) -> Optional<Type> {
+    if (auto depTy = dyn_cast<DependentMemberType>(type)) {
+      if (depTy->getAssocType()) return None;
+
+      auto pa = builder.resolveArchetype(
+                             type, ArchetypeResolutionKind::CompleteWellFormed);
+      if (!pa)
+        return ErrorType::get(depTy);
+
+      return pa->getDependentType({ }, /*allowUnresolved=*/false);
+    }
+
+    return None;
+  });
+}
+
 void GenericSignatureBuilder::checkConcreteTypeConstraints(
                                  ArrayRef<GenericTypeParamType *> genericParams,
                                  PotentialArchetype *representative) {
@@ -4783,6 +4804,10 @@ void GenericSignatureBuilder::checkConcreteTypeConstraints(
     None,
     diag::redundant_same_type_to_concrete,
     diag::same_type_redundancy_here);
+
+  // Resolve any this-far-unresolved dependent types.
+  equivClass->concreteType =
+    resolveDependentMemberTypes(*this, equivClass->concreteType);
 }
 
 void GenericSignatureBuilder::checkSuperclassConstraints(
@@ -4821,6 +4846,10 @@ void GenericSignatureBuilder::checkSuperclassConstraints(
       diag::redundant_superclass_constraint,
       diag::superclass_redundancy_here);
 
+  // Resolve any this-far-unresolved dependent types.
+  equivClass->superclass =
+    resolveDependentMemberTypes(*this, equivClass->superclass);
+
   // If we have a concrete type, check it.
   // FIXME: Substitute into the concrete type.
   if (equivClass->concreteType) {

lib/Sema/GenericTypeResolver.h

@@ -100,14 +100,7 @@ class GenericTypeResolver {
 /// This generic type resolver leaves generic type parameter types alone
 /// and only trivially resolves dependent member types.
 class DependentGenericTypeResolver : public GenericTypeResolver {
-  GenericSignatureBuilder &Builder;
-  ArrayRef<GenericTypeParamType *> GenericParams;
-
 public:
-  DependentGenericTypeResolver(GenericSignatureBuilder &builder,
-                               ArrayRef<GenericTypeParamType *> genericParams)
-    : Builder(builder), GenericParams(genericParams) { }
-
   virtual Type resolveGenericTypeParamType(GenericTypeParamType *gp);
 
   virtual Type resolveDependentMemberType(Type baseTy,

lib/Sema/TypeCheckGeneric.cpp

@@ -42,17 +42,7 @@ Type DependentGenericTypeResolver::resolveDependentMemberType(
                                      DeclContext *DC,
                                      SourceRange baseRange,
                                      ComponentIdentTypeRepr *ref) {
-#if true
-  auto archetype =
-    Builder.resolveArchetype(baseTy, ArchetypeResolutionKind::AlwaysPartial);
-  assert(archetype && "Bad generic context nesting?");
-
-  return archetype
-           ->getNestedType(ref->getIdentifier(), Builder)
-           ->getDependentType(GenericParams, /*allowUnresolved=*/true);
-#else
   return DependentMemberType::get(baseTy, ref->getIdentifier());
-#endif
 }
 
 Type DependentGenericTypeResolver::resolveSelfAssociatedType(
@@ -794,7 +784,7 @@ TypeChecker::validateGenericFuncSignature(AbstractFunctionDecl *func) {
 
   // Type check the function declaration, treating all generic type
   // parameters as dependent, unresolved.
-  DependentGenericTypeResolver dependentResolver(builder, allGenericParams);
+  DependentGenericTypeResolver dependentResolver;
   if (checkGenericFuncSignature(*this, &builder, func, dependentResolver))
     invalid = true;
 
@@ -1025,7 +1015,7 @@ TypeChecker::validateGenericSubscriptSignature(SubscriptDecl *subscript) {
 
   // Type check the function declaration, treating all generic type
   // parameters as dependent, unresolved.
-  DependentGenericTypeResolver dependentResolver(builder, allGenericParams);
+  DependentGenericTypeResolver dependentResolver;
   if (checkGenericSubscriptSignature(*this, &builder, subscript,
                                      dependentResolver))
     invalid = true;
@@ -1144,7 +1134,7 @@ GenericEnvironment *TypeChecker::checkGenericEnvironment(
 
   // Type check the generic parameters, treating all generic type
   // parameters as dependent, unresolved.
-  DependentGenericTypeResolver dependentResolver(builder, allGenericParams);
+  DependentGenericTypeResolver dependentResolver;
   if (recursivelyVisitGenericParams) {
     visitOuterToInner(genericParams,
                       [&](GenericParamList *gpList) {

test/Generics/associated_type_typo.swift

@@ -14,7 +14,7 @@ protocol P2 {
 protocol P3 { }
 protocol P4 { }
 
-// expected-error@+1{{'T' does not have a member type named 'assoc'; did you mean 'Assoc'?}}{{30-35=Assoc}}
+// expected-error@+1{{'assoc' is not a member type of 'T'}}
 func typoAssoc1<T : P1>(x: T.assoc, _: T) { } 
 
 // expected-error@+2{{'T' does not have a member type named 'assoc'; did you mean 'Assoc'?}}{{53-58=Assoc}}

validation-test/compiler_crashers_2_fixed/0084-rdar31093854.swift

@@ -1,4 +1,4 @@
-// RUN: not %target-swift-frontend -swift-version 4 %s -typecheck -o /dev/null
+// RUN: %target-swift-frontend -swift-version 4 %s -typecheck -o /dev/null
 
 // This should actually type check successfully.
 

validation-test/compiler_crashers/28760-dist-0-nested-type-should-have-matched-associated-type.swift renamed to validation-test/compiler_crashers_fixed/28760-dist-0-nested-type-should-have-matched-associated-type.swift

@@ -6,5 +6,5 @@
 // See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
 
 // REQUIRES: asserts
-// RUN: not --crash %target-swift-frontend %s -emit-ir
+// RUN: not %target-swift-frontend %s -emit-ir
 protocol P{typealias e:P{}class a{{}func a:Self.a.e