[SPI Test] Test how modules can expose imported SPI through their SPI

Author: xymus

test/SPI/client_reuse_spi.swift

@@ -0,0 +1,29 @@
+/// A module should be able to leak SPI types from an import through SPI decls
+
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -emit-module -DLIB_A %s -module-name A -emit-module-path %t/A.swiftmodule
+// RUN: %target-swift-frontend -emit-module -DLIB_B %s -module-name B -emit-module-path %t/B.swiftmodule -I %t
+// RUN: %target-swift-frontend -typecheck -verify -verify-ignore-unknown -DLIB_C %s -I %t
+
+#if LIB_A
+
+@_spi(A) public struct SecretStruct {
+  @_spi(A) public func bar() {}
+}
+
+#elseif LIB_B
+
+@_spi(A) import A
+
+@_spi(B) public func foo() -> SecretStruct { fatalError() }
+
+#elseif LIB_C
+
+@_spi(B) import B
+
+var a = foo() // OK
+a.bar() // expected-error{{'bar' is inaccessible due to '@_spi' protection level}}
+
+var b = SecretStruct() // expected-error{{use of unresolved identifier}}
+
+#endif