Disable and rewrite Metadata and Token type inits

These initializers do not have corresponding create
calls in LLVM yet and so cannot possibly be used from
user code.  Disable them with a message.

Author: CodaFi

Sources/LLVM/IRType.swift

@@ -78,11 +78,11 @@ internal func convertType(_ type: LLVMTypeRef) -> IRType {
     let count = Int(LLVMGetVectorSize(type))
     return VectorType(elementType: elementType, count: count)
   case LLVMMetadataTypeKind:
-    return MetadataType(llvm: type)
+    return MetadataType(in: context)
   case LLVMX86_MMXTypeKind:
     return X86MMXType(in: context)
   case LLVMTokenTypeKind:
-    return TokenType(llvm: type)
+    return TokenType(in: context)
   default: fatalError("unknown type kind for type \(type)")
   }
 }

Sources/LLVM/MetadataType.swift

@@ -5,15 +5,19 @@ import cllvm
 /// The `MetadataType` type represents embedded metadata. No derived types may
 /// be created from metadata except for function arguments.
 public struct MetadataType: IRType {
-  internal let llvm: LLVMTypeRef
+  /// Returns the context associated with this type.
+  public let context: Context
 
   /// Creates an embedded metadata type for the given LLVM type object.
-  public init(llvm: LLVMTypeRef) {
-    self.llvm = llvm
+  ///
+  /// - parameter context: The context to create this type in
+  /// - SeeAlso: http://llvm.org/docs/ProgrammersManual.html#achieving-isolation-with-llvmcontext
+  public init(in context: Context = Context.global) {
+    self.context = context
   }
 
   /// Retrieves the underlying LLVM type object.
   public func asLLVM() -> LLVMTypeRef {
-    return llvm
+    fatalError("This version of LLVM does not support the creation of MetadataType objects")
   }
 }

Sources/LLVM/TokenType.swift

@@ -6,13 +6,19 @@ import cllvm
 /// uses of the value must not attempt to introspect or obscure it. As such, it
 /// is not appropriate to have a `PHI` or `select` of type `TokenType`.
 public struct TokenType: IRType {
-  internal let llvm: LLVMTypeRef
+  /// Returns the context associated with this type.
+  public let context: Context
 
   /// Initializes a token type from the given LLVM type object.
-  public init(llvm: LLVMTypeRef) { self.llvm = llvm }
+  ///
+  /// - parameter context: The context to create this type in
+  /// - SeeAlso: http://llvm.org/docs/ProgrammersManual.html#achieving-isolation-with-llvmcontext
+  public init(in context: Context = Context.global) {
+    self.context = context
+  }
 
   /// Retrieves the underlying LLVM type object.
   public func asLLVM() -> LLVMTypeRef {
-    return llvm
+    fatalError("This version of LLVM does not support the creation of TokenType objects")
   }
 }