Revert "[Tests] Add a test to round-trip types through mangled names."

Author: shahmishal

docs/Testing.md

@@ -384,16 +384,6 @@ code for the target that is not the build machine:
 
   Add ``REQUIRES: static_stdlib`` to the test.
 
-* ``%target-rtti-opt``: the ``-frtti`` or ``-fno-rtti`` option required to
-  link with the Swift libraries on the target platform.
-
-* ``%target-cxx-lib``: the argument to add to the command line when using
-  ``swiftc`` and linking in a C++ object file.  Typically ``-lc++`` or
-  ``-lstdc++`` depending on platform.
-
-* ``%target-msvc-runtime-opt``: for Windows, the MSVC runtime option, e.g.
-  ``-MD``, to use when building C/C++ code to link with Swift.
-
 Always use ``%target-*`` substitutions unless you have a good reason.  For
 example, an exception would be a test that checks how the compiler handles
 mixing module files for incompatible platforms (that test would need to compile

stdlib/public/runtime/Private.h

@@ -268,9 +268,8 @@ class TypeInfo {
   const ContextDescriptor *
   _searchConformancesByMangledTypeName(Demangle::NodePointer node);
 
-  SWIFT_RUNTIME_EXPORT
   Demangle::NodePointer _swift_buildDemanglingForMetadata(const Metadata *type,
-                                                          Demangle::Demangler &Dem);
+                                                      Demangle::Demangler &Dem);
 
   /// Callback used to provide the substitution of a generic parameter
   /// (described by depth/index) to its metadata.
@@ -368,15 +367,13 @@ class TypeInfo {
                                         unsigned index) const;
   };
 
-#pragma clang diagnostic push
-#pragma clang diagnostic ignored "-Wreturn-type-c-linkage" 
   /// Retrieve the type metadata described by the given demangled type name.
   ///
   /// \p substGenericParam Function that provides generic argument metadata
   /// given a particular generic parameter specified by depth/index.
   /// \p substWitnessTable Function that provides witness tables given a
   /// particular dependent conformance index.
-  SWIFT_RUNTIME_EXPORT SWIFT_CC(swift)
+  SWIFT_CC(swift)
   TypeLookupErrorOr<TypeInfo> swift_getTypeByMangledNode(
                                MetadataRequest request,
                                Demangler &demangler,
@@ -391,14 +388,13 @@ class TypeInfo {
   /// given a particular generic parameter specified by depth/index.
   /// \p substWitnessTable Function that provides witness tables given a
   /// particular dependent conformance index.
-  SWIFT_RUNTIME_EXPORT SWIFT_CC(swift)
+  SWIFT_CC(swift)
   TypeLookupErrorOr<TypeInfo> swift_getTypeByMangledName(
                                MetadataRequest request,
                                StringRef typeName,
                                const void * const *arguments,
                                SubstGenericParameterFn substGenericParam,
                                SubstDependentWitnessTableFn substWitnessTable);
-#pragma clang diagnostic pop
 
   /// Function object that produces substitutions for the generic parameters
   /// that occur within a mangled name, using the complete set of generic