Sema: Allow SPI references from implicitly public layouts

Author: xymus

lib/Sema/TypeCheckAvailability.cpp

@@ -240,12 +240,14 @@ bool ExportContext::canReferenceOrigin(DisallowedOriginKind originKind) const {
   if (originKind == DisallowedOriginKind::None)
     return true;
 
-  // Implicitly always emit into client code in embedded mode can still
-  // access many restricted origins as more dependencies are loaded
-  // in non-library-evolution mode and there isn't an enforced separation of
-  // public vs SPI.
+  // Exportability checks for non-library-evolution mode have less restrictions
+  // than the library-evolution ones. Implicitly always emit into client code
+  // in embedded mode and implicitly exported layouts in non-library-evolution
+  // mode can reference SPIs and non-public dependencies.
   if (getFragileFunctionKind().kind ==
-        FragileFunctionKind::EmbeddedAlwaysEmitIntoClient) {
+        FragileFunctionKind::EmbeddedAlwaysEmitIntoClient ||
+      *getExportabilityReason() ==
+        ExportabilityReason::ImplicitlyPublicVarDecl) {
     switch (originKind) {
     case DisallowedOriginKind::None:
     case DisallowedOriginKind::NonPublicImport:

test/Sema/hidden-memory-layout.swift

@@ -413,6 +413,8 @@ public struct ExposedLayoutPublicUser: ProtocolFromDirect {
   // expected-embedded-opt-in-error @-1 {{struct 'HiddenLayout' cannot be used in an embedded function not marked '@export(interface)' because 'HiddenLayout' is marked '@_implementationOnly'}}
   private func privateFuncClass(h: HiddenClass) {}
   // expected-embedded-opt-in-error @-1 {{class 'HiddenClass' cannot be used in an embedded function not marked '@export(interface)' because 'HiddenClass' is marked '@_implementationOnly'}}
+
+  @_spi(S) public var s: SPIStruct
 }
 
 internal struct ExposedLayoutInternalUser: ProtocolFromDirect {
@@ -448,6 +450,8 @@ internal struct ExposedLayoutInternalUser: ProtocolFromDirect {
   // expected-embedded-opt-in-error @-1 {{struct 'HiddenLayout' cannot be used in an embedded function not marked '@export(interface)' because 'HiddenLayout' is marked '@_implementationOnly'}}
   private func privateFuncClass(h: HiddenClass) {}
   // expected-embedded-opt-in-error @-1 {{class 'HiddenClass' cannot be used in an embedded function not marked '@export(interface)' because 'HiddenClass' is marked '@_implementationOnly'}}
+
+  @_spi(S) public var s: SPIStruct
 }
 
 private struct ExposedLayoutPrivateUser: ProtocolFromDirect {
@@ -483,6 +487,8 @@ private struct ExposedLayoutPrivateUser: ProtocolFromDirect {
   // expected-embedded-opt-in-error @-1 {{struct 'HiddenLayout' cannot be used in an embedded function not marked '@export(interface)' because 'HiddenLayout' is marked '@_implementationOnly'}}
   private func privateFuncClass(h: HiddenClass) {}
   // expected-embedded-opt-in-error @-1 {{class 'HiddenClass' cannot be used in an embedded function not marked '@export(interface)' because 'HiddenClass' is marked '@_implementationOnly'}}
+
+  @_spi(S) public var s: SPIStruct
 }
 
 #if UseImplementationOnly