GSB: Simplify maybeResolveEquivalenceClass()

When passing in wantExactPotentialArchetype=false, we don't actually ever
call getDependentType() on the result. So the Type + EquivalenceClass form
of ResolvedType can be removed.

Author: slavapestov

lib/AST/GenericSignatureBuilder.cpp

@@ -3677,19 +3677,7 @@ ResolvedType GenericSignatureBuilder::maybeResolveEquivalenceClass(
       if (!nestedPA)
         return ResolvedType::forUnresolved(baseEquivClass);
 
-      // If base resolved to the anchor, then the nested potential archetype
-      // we found is the resolved potential archetype. Return it directly,
-      // so it doesn't need to be resolved again.
-      if (basePA == resolvedBase.getPotentialArchetypeIfKnown())
-        return ResolvedType(nestedPA);
-
-      // Compute the resolved dependent type to return.
-      Type resolvedBaseType = resolvedBase.getDependentType(*this);
-      Type resolvedMemberType =
-          DependentMemberType::get(resolvedBaseType, assocType);
-
-      return ResolvedType(resolvedMemberType,
-                          nestedPA->getOrCreateEquivalenceClass(*this));
+      return ResolvedType(nestedPA);
     } else {
       auto *concreteDecl =
           baseEquivClass->lookupNestedType(*this, depMemTy->getName());

lib/AST/GenericSignatureBuilderImpl.h

@@ -21,17 +21,16 @@ class GenericSignatureBuilder::ResolvedType {
   ResolvedType(EquivalenceClass *equivClass)
     : type(), equivClass(equivClass) { }
 
+  /// A concrete resolved type .
+  ResolvedType(Type type) : type(type), equivClass(nullptr) {
+    assert(!type->isTypeParameter());
+  }
+
 public:
   /// A specific resolved potential archetype.
   ResolvedType(PotentialArchetype *pa)
     : type(pa), equivClass(nullptr) { }
 
-  /// A resolved type within the given equivalence class.
-  ResolvedType(Type type, EquivalenceClass *equivClass)
-      : type(type), equivClass(equivClass) {
-    assert(type->isTypeParameter() == static_cast<bool>(equivClass) &&
-           "type parameters must have equivalence classes");
-  }
 
   /// Return an unresolved result, which could be resolved when we
   /// learn more information about the given equivalence class.
@@ -41,7 +40,7 @@ class GenericSignatureBuilder::ResolvedType {
 
   /// Return a result for a concrete type.
   static ResolvedType forConcrete(Type concreteType) {
-    return ResolvedType(concreteType, nullptr);
+    return ResolvedType(concreteType);
   }
 
   /// Determine whether this result was resolved.