[AST] Add attributes for hasMissingDesignatedInitializers and inheritsConvenienceInitializers

We're planning to emit these attributes in module interfaces, but until
we land that patch, we want to parse these attributes and ignore them.

Part of rdar://51249311

Author: Harlan Haskins

include/swift/AST/Attr.def

@@ -508,6 +508,16 @@ DECL_ATTR(differentiable, Differentiable,
   ABIStableToAdd | ABIBreakingToRemove | APIStableToAdd | APIBreakingToRemove,
   91)
 
+SIMPLE_DECL_ATTR(_hasMissingDesignatedInitializers,
+  HasMissingDesignatedInitializers, OnClass | UserInaccessible | NotSerialized |
+  APIBreakingToAdd | ABIBreakingToAdd | APIStableToRemove | ABIStableToRemove,
+  92)
+
+SIMPLE_DECL_ATTR(_inheritsConvenienceInitializers,
+  InheritsConvenienceInitializers, OnClass | UserInaccessible | NotSerialized |
+  APIStableToAdd | ABIStableToAdd | APIBreakingToRemove | ABIBreakingToRemove,
+  93)
+
 SIMPLE_DECL_ATTR(IBSegueAction, IBSegueAction,
   OnFunc |
   ABIStableToAdd | ABIStableToRemove | APIStableToAdd | APIStableToRemove,

lib/Sema/TypeCheckAttr.cpp

@@ -93,6 +93,8 @@ class AttributeChecker : public AttributeVisitor<AttributeChecker> {
   IGNORED_ATTR(Exported)
   IGNORED_ATTR(ForbidSerializingReference)
   IGNORED_ATTR(HasStorage)
+  IGNORED_ATTR(HasMissingDesignatedInitializers)
+  IGNORED_ATTR(InheritsConvenienceInitializers)
   IGNORED_ATTR(Inline)
   IGNORED_ATTR(ObjCBridged)
   IGNORED_ATTR(ObjCNonLazyRealization)

lib/Sema/TypeCheckDeclOverride.cpp

@@ -1286,12 +1286,14 @@ namespace  {
     UNINTERESTING_ATTR(Exported)
     UNINTERESTING_ATTR(ForbidSerializingReference)
     UNINTERESTING_ATTR(GKInspectable)
+    UNINTERESTING_ATTR(HasMissingDesignatedInitializers)
     UNINTERESTING_ATTR(IBAction)
     UNINTERESTING_ATTR(IBDesignable)
     UNINTERESTING_ATTR(IBInspectable)
     UNINTERESTING_ATTR(IBOutlet)
     UNINTERESTING_ATTR(IBSegueAction)
     UNINTERESTING_ATTR(Indirect)
+    UNINTERESTING_ATTR(InheritsConvenienceInitializers)
     UNINTERESTING_ATTR(Inline)
     UNINTERESTING_ATTR(Optimize)
     UNINTERESTING_ATTR(Inlinable)

test/attr/attr_hasMissingDesignatedInits.swift

@@ -0,0 +1,9 @@
+// RUN: %target-swift-frontend -typecheck %s -verify
+
+// This test just makes sure we don't error if we see either of these attributes.
+
+@_hasMissingDesignatedInitializers // no-error
+class MyClass {}
+
+@_inheritsConvenienceInitializers // no-error
+class MyOtherClass {}