[Sema] Reword the warning on @_spi import of a public module

Author: xymus

include/swift/AST/DiagnosticsSema.def

@@ -1785,8 +1785,8 @@ ERROR(spi_attribute_on_frozen_stored_properties,none,
       "stored property %0 cannot be declared '@_spi' in a '@frozen' struct",
       (DeclName))
 WARNING(spi_attribute_on_import_of_public_module,none,
-        "importation of %0 has an ineffective '@_spi' attribute; "
-        "it was built from the public interface at %1",
+        "'@_spi' import of %0 will not include any SPI symbols; "
+        "%0 was built from the public interface at %1",
         (DeclName, StringRef))
 
 // Opaque return types

test/SPI/warn_on_ineffective_spi_import.swift

@@ -16,4 +16,4 @@
 // RUN: rm %t/SPIHelper.private.swiftinterface
 // RUN: %target-typecheck-verify-swift -I %t
 
-@_spi(SPIHelper) import SPIHelper // expected-warning {{importation of 'SPIHelper' has an ineffective '@_spi' attribute; it was built from the public interface at}}
+@_spi(SPIHelper) import SPIHelper // expected-warning {{'@_spi' import of 'SPIHelper' will not include any SPI symbols; 'SPIHelper' was built from the public interface at}}