[SPI Test] Test @_implementationOnly compatibility with @_spi imports

Author: xymus

test/SPI/implementation_only_spi_import.swift

@@ -0,0 +1,23 @@
+/// @_implementationOnly imports should be compatible with @_spi imports
+
+// 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: rm %t/A.swiftmodule
+// RUN: %target-swift-frontend -typecheck -verify -DLIB_C %s -I %t
+
+#if LIB_A
+
+@_spi(A) public func foo() {}
+
+#elseif LIB_B
+
+@_spi(A) @_implementationOnly import A
+foo() // OK
+
+#elseif LIB_C
+
+import B
+foo() // expected-error{{use of unresolved identifier}}
+
+#endif