[Sema] Remove the IterativeTypeChecker.

Author: DougGregor

include/swift/AST/Decl.h

@@ -3167,7 +3167,6 @@ class EnumDecl final : public NominalTypeDecl {
     llvm::PointerIntPair<Type, 1, bool> RawType;
   } LazySemanticInfo;
 
-  friend class IterativeTypeChecker;
   friend class EnumRawTypeRequest;
   friend class TypeChecker;
 
@@ -3417,7 +3416,6 @@ class ClassDecl final : public NominalTypeDecl {
     llvm::PointerIntPair<Type, 1, bool> Superclass;
   } LazySemanticInfo;
 
-  friend class IterativeTypeChecker;
   friend class SuperclassTypeRequest;
   friend class TypeChecker;
 

include/swift/Basic/LangOptions.h

@@ -157,9 +157,6 @@ namespace swift {
     /// solver should be debugged.
     unsigned DebugConstraintSolverAttempt = 0;
 
-    /// \brief Enable the iterative type checker.
-    bool IterativeTypeChecker = false;
-
     /// \brief Enable named lazy member loading.
     bool NamedLazyMemberLoading = true;
 

include/swift/Option/FrontendOptions.td

@@ -157,9 +157,6 @@ def debug_constraints : Flag<["-"], "debug-constraints">,
 def debug_constraints_attempt : Separate<["-"], "debug-constraints-attempt">,
   HelpText<"Debug the constraint solver at a given attempt">;
 
-def iterative_type_checker : Flag<["-"], "iterative-type-checker">,
-  HelpText<"Enable the iterative type checker">;
-
 def disable_named_lazy_member_loading : Flag<["-"], "disable-named-lazy-member-loading">,
   HelpText<"Disable per-name lazy member loading">;