SIL: Stored property initializers get the linkage of their containing type

This allows inlineble initializers to be defined on types that
have stored property initializers.

This is not the final behavior we want; in Swift 4 mode, we want
to give these shared linkage and make them fragile, and enforce
that stored property initializer expressions only reference other
public and versioned symbols.

This will match the behavior of default argument expressions in
Swift 4 mode, and I'll implement it when I do those.

Author: slavapestov

lib/SIL/SILDeclRef.cpp

@@ -438,11 +438,6 @@ SILLinkage SILDeclRef::getLinkage(ForDefinition_t forDefinition) const {
   if (isEnumElement())
     return SILLinkage::Shared;
 
-  // Stored property initializers have hidden linkage, since they are
-  // not meant to be used from outside of their module.
-  if (isStoredPropertyInitializer())
-    return (forDefinition ? SILLinkage::Hidden : SILLinkage::HiddenExternal);
-
   // Declarations imported from Clang modules have shared linkage.
   const SILLinkage ClangLinkage = SILLinkage::Shared;
 

test/SILGen/inlineable_attribute.swift

@@ -36,3 +36,11 @@ public class MyCls {
 @_inlineable public func referencesMyEnum() {
   _ = MyEnum.c
 }
+
+// CHECK-LABEL: sil [transparent] @_T020inlineable_attribute15HasInitializersV1xSivfi : $@convention(thin) () -> Int
+
+public struct HasInitializers {
+  public let x = 1234
+
+  @_inlineable public init() {}
+}