[5.1] [ModuleInterfaces] Warn when emitting an interface in unsupported scenarios

include/swift/AST/DiagnosticsFrontend.def

@@ -261,6 +261,13 @@ ERROR(invalid_vfs_overlay_file,none,
 WARNING(module_interface_scoped_import_unsupported,none,
         "scoped imports are not yet supported in module interfaces",
         ())
+WARNING(warn_unsupported_module_interface_swift_version,none,
+        "module interfaces are only supported with Swift language version 5 "
+        "or later (currently using -swift-version %0)",
+        (StringRef))
+WARNING(warn_unsupported_module_interface_library_evolution,none,
+        "module interfaces are only supported with -enable-library-evolution",
+        ())
 ERROR(error_extracting_version_from_module_interface,none,
       "error extracting version from module interface", ())
 ERROR(unsupported_version_of_module_interface,none,

lib/FrontendTool/FrontendTool.cpp

@@ -358,12 +358,26 @@ static bool printAsObjCIfNeeded(StringRef outputPath, ModuleDecl *M,
 /// \returns true if there were any errors
 ///
 /// \see swift::emitParseableInterface
-static bool printParseableInterfaceIfNeeded(StringRef outputPath,
-                                            ParseableInterfaceOptions const &Opts,
-                                            ModuleDecl *M) {
+static bool
+printParseableInterfaceIfNeeded(StringRef outputPath,
+                                ParseableInterfaceOptions const &Opts,
+                                LangOptions const &LangOpts,
+                                ModuleDecl *M) {
   if (outputPath.empty())
     return false;
-  return withOutputFile(M->getDiags(), outputPath,
+
+  DiagnosticEngine &diags = M->getDiags();
+  if (!LangOpts.isSwiftVersionAtLeast(5)) {
+    assert(LangOpts.isSwiftVersionAtLeast(4));
+    diags.diagnose(SourceLoc(),
+                   diag::warn_unsupported_module_interface_swift_version,
+                   LangOpts.isSwiftVersionAtLeast(4, 2) ? "4.2" : "4");
+  }
+  if (M->getResilienceStrategy() != ResilienceStrategy::Resilient) {
+    diags.diagnose(SourceLoc(),
+                   diag::warn_unsupported_module_interface_library_evolution);
+  }
+  return withOutputFile(diags, outputPath,
                         [M, Opts](raw_ostream &out) -> bool {
     return swift::emitParseableInterface(out, Opts, M);
   });
@@ -922,6 +936,7 @@ static bool emitAnyWholeModulePostTypeCheckSupplementaryOutputs(
     hadAnyError |= printParseableInterfaceIfNeeded(
         Invocation.getParseableInterfaceOutputPathForWholeModule(),
         Invocation.getParseableInterfaceOptions(),
+        Invocation.getLangOptions(),
         Instance.getMainModule());
   }
 

test/ParseableInterface/imports.swift

@@ -1,6 +1,6 @@
 // RUN: %empty-directory(%t)
 // RUN: %target-swift-frontend -emit-module -o %t/empty.swiftmodule %S/../Inputs/empty.swift
-// RUN: %target-swift-frontend -typecheck -emit-parseable-module-interface-path - %s %S/Inputs/imports-other.swift -I %S/Inputs/imports-clang-modules/ -I %t -verify | %FileCheck -implicit-check-not BAD %s
+// RUN: %target-swift-frontend -typecheck -emit-parseable-module-interface-path - %s %S/Inputs/imports-other.swift -I %S/Inputs/imports-clang-modules/ -I %t -verify -swift-version 5 -enable-library-evolution | %FileCheck -implicit-check-not BAD %s
 
 
 @_exported import empty

test/ParseableInterface/unsupported-configurations.swift

@@ -0,0 +1,33 @@
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -typecheck -emit-parseable-module-interface-path %t/empty.swiftinterface %s -swift-version 4 2>&1 | %FileCheck -DVERSION=4 %s
+// RUN: ls %t/empty.swiftinterface
+
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -typecheck -emit-parseable-module-interface-path %t/empty.swiftinterface %s -swift-version 4.2 2>&1 | %FileCheck -DVERSION=4.2 %s
+// RUN: ls %t/empty.swiftinterface
+
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -typecheck -emit-parseable-module-interface-path %t/empty.swiftinterface %s -swift-version 4.2 -enable-library-evolution 2>&1 | %FileCheck -check-prefix=CHECK-VERSION-ONLY -DVERSION=4.2 %s
+// RUN: ls %t/empty.swiftinterface
+
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -typecheck -emit-parseable-module-interface-path %t/empty.swiftinterface %s -swift-version 5 2>&1 | %FileCheck -check-prefix=CHECK-EVOLUTION-ONLY %s
+// RUN: ls %t/empty.swiftinterface
+
+// RUN: %empty-directory(%t)
+// RUN: %target-swift-frontend -typecheck -emit-parseable-module-interface-path %t/empty.swiftinterface %s -swift-version 5 -enable-library-evolution 2>&1 | %FileCheck -check-prefix=NEGATIVE -allow-empty %s
+// RUN: ls %t/empty.swiftinterface
+
+// CHECK-DAG: warning: module interfaces are only supported with Swift language version 5 or later (currently using -swift-version [[VERSION]])
+// CHECK-DAG: warning: module interfaces are only supported with -enable-library-evolution
+
+// CHECK-VERSION-ONLY-NOT: warning:
+// CHECK-VERSION-ONLY: warning: module interfaces are only supported with Swift language version 5 or later (currently using -swift-version [[VERSION]])
+// CHECK-VERSION-ONLY-NOT: warning:
+
+// CHECK-EVOLUTION-ONLY-NOT: warning:
+// CHECK-EVOLUTION-ONLY: warning: module interfaces are only supported with -enable-library-evolution
+// CHECK-EVOLUTION-ONLY-NOT: warning:
+
+// NEGATIVE-NOT: warning:
+// NEGATIVE-NOT: error: