[NFC] Move ImportKind to a new Import.h header

Author: beccadax

include/swift/AST/Decl.h

@@ -1457,21 +1457,6 @@ class GenericContext : private _GenericContext, public DeclContext {
 static_assert(sizeof(_GenericContext) + sizeof(DeclContext) ==
               sizeof(GenericContext), "Please add fields to _GenericContext");
 
-/// Describes what kind of name is being imported.
-///
-/// If the enumerators here are changed, make sure to update all diagnostics
-/// using ImportKind as a select index.
-enum class ImportKind : uint8_t {
-  Module = 0,
-  Type,
-  Struct,
-  Class,
-  Enum,
-  Protocol,
-  Var,
-  Func
-};
-
 /// ImportDecl - This represents a single import declaration, e.g.:
 ///   import Swift
 ///   import typealias Swift.Int

include/swift/AST/Import.h

@@ -0,0 +1,40 @@
+//===-- Import.h - Representation of imports --------------------*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file contains types used to represent information about imports
+/// throughout the AST.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_IMPORT_H
+#define SWIFT_IMPORT_H
+
+namespace swift {
+/// Describes what kind of name is being imported.
+///
+/// If the enumerators here are changed, make sure to update all diagnostics
+/// using ImportKind as a select index.
+enum class ImportKind : uint8_t {
+  Module = 0,
+  Type,
+  Struct,
+  Class,
+  Enum,
+  Protocol,
+  Var,
+  Func
+};
+
+}
+
+#endif

include/swift/AST/Module.h

@@ -20,6 +20,7 @@
 #include "swift/AST/Decl.h"
 #include "swift/AST/DeclContext.h"
 #include "swift/AST/Identifier.h"
+#include "swift/AST/Import.h"
 #include "swift/AST/LookupKinds.h"
 #include "swift/AST/RawComment.h"
 #include "swift/AST/Type.h"