[ast] Add a @moveOnly type attribute only available at the SIL level.

It currently is just removed when we type check types, so it doesn't do
anything. Eventually this is going to be the way at the SIL level one can
convert an AST type into its move only equivalent.

Author: gottesmm

include/swift/AST/Attr.def

@@ -85,6 +85,8 @@ TYPE_ATTR(yields)
 TYPE_ATTR(yield_once)
 TYPE_ATTR(yield_many)
 TYPE_ATTR(captures_generics)
+// Used at the SIL level to mark a type as moveOnly.
+TYPE_ATTR(moveOnly)
 
 // SIL metatype attributes.
 TYPE_ATTR(thin)

lib/Sema/TypeCheckType.cpp

@@ -2840,6 +2840,12 @@ TypeResolver::resolveAttributedType(TypeAttributes &attrs, TypeRepr *repr,
     attrs.clearAttribute(TAK_box);
   }
 
+  // In SIL *only*, allow @moveOnly to specify a moveOnly type.
+  if ((options & TypeResolutionFlags::SILType) && attrs.has(TAK_moveOnly)) {
+    //ty = ty->getCanonicalType()->getMoveOnlyType();
+    attrs.clearAttribute(TAK_moveOnly);
+  }
+
   // In SIL *only*, allow @dynamic_self to specify a dynamic Self type.
   if ((options & TypeResolutionFlags::SILMode) && attrs.has(TAK_dynamic_self)) {
     ty = rebuildWithDynamicSelf(getASTContext(), ty);

test/Sema/moveonly_type_attr.sil

@@ -0,0 +1,18 @@
+// RUN: %target-sil-opt -verify %s | %FileCheck %s
+
+sil_stage raw
+
+class Klass {}
+
+// Make sure that we just ignore this type attribute.
+
+// CHECK-LABEL: sil [ossa] @foo : $@convention(thin) (@owned @moveOnly Klass) -> () {
+// CHECK: bb0(%0 : @owned $@moveOnly Klass):
+// CHECK: destroy_value %0 : $@moveOnly Klass
+// CHECK: } // end sil function 'foo'
+sil [ossa] @foo : $@convention(thin) (@owned @moveOnly Klass) -> () {
+bb0(%0 : @owned $@moveOnly Klass):
+  destroy_value %0 : $@moveOnly Klass
+  %9999 = tuple()
+  return %9999 : $()
+}

test/Sema/moveonly_type_attr.swift

@@ -0,0 +1,9 @@
+// RUN: %target-typecheck-verify-swift -parse-stdlib -disable-availability-checking -verify-syntax-tree
+
+import Swift
+
+class Klass {}
+
+// Make sure we ignore this attribute and error in swift mode.
+
+let l: @moveOnly Klass = Klass() // expected-error {{attribute does not apply to type}}