Add a -disable-invalid-ephemeralness-as-error flag

Currently this does nothing, as we're warning by
default, but once we error by default, this will
downgrade the diagnostic to a warning.

Author: hamishknight

include/swift/Option/FrontendOptions.td

@@ -431,10 +431,14 @@ def solver_enable_operator_designated_types :
   Flag<["-"], "solver-enable-operator-designated-types">,
   HelpText<"Enable operator designated types in constraint solver">;
 
-def diagnose_invalid_ephemeralness_as_error :
-  Flag<["-"], "diagnose-invalid-ephemeralness-as-error">,
+def enable_invalid_ephemeralness_as_error :
+  Flag<["-"], "enable-invalid-ephemeralness-as-error">,
   HelpText<"Diagnose invalid ephemeral to non-ephemeral conversions as errors">;
 
+def disable_invalid_ephemeralness_as_error :
+  Flag<["-"], "disable-invalid-ephemeralness-as-error">,
+  HelpText<"Diagnose invalid ephemeral to non-ephemeral conversions as warnings">;
+
 def switch_checking_invocation_threshold_EQ : Joined<["-"],
     "switch-checking-invocation-threshold=">;
 

lib/Frontend/CompilerInvocation.cpp

@@ -278,7 +278,7 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
       Args.hasArg(OPT_enable_operator_designated_types);
 
   Opts.DiagnoseInvalidEphemeralnessAsError |=
-      Args.hasArg(OPT_diagnose_invalid_ephemeralness_as_error);
+      Args.hasArg(OPT_enable_invalid_ephemeralness_as_error);
 
   // Always enable operator designated types for the standard library.
   Opts.EnableOperatorDesignatedTypes |= FrontendOpts.ParseStdlib;

test/IDE/infer_import_as_member.swift

@@ -1,5 +1,5 @@
 // RUN: %target-swift-ide-test(mock-sdk: %clang-importer-sdk) -import-objc-header %S/Inputs/custom-modules/CollisionImportAsMember.h -I %t -I %S/Inputs/custom-modules -print-module -source-filename %s -module-to-print=InferImportAsMember -always-argument-labels -enable-infer-import-as-member -skip-unavailable > %t.printed.A.txt
-// RUN: %target-swift-frontend -typecheck -import-objc-header %S/Inputs/custom-modules/CollisionImportAsMember.h -I %t -I %S/Inputs/custom-modules %s -enable-infer-import-as-member -verify -diagnose-invalid-ephemeralness-as-error
+// RUN: %target-swift-frontend -typecheck -import-objc-header %S/Inputs/custom-modules/CollisionImportAsMember.h -I %t -I %S/Inputs/custom-modules %s -enable-infer-import-as-member -verify -enable-invalid-ephemeralness-as-error
 // RUN: %FileCheck %s -check-prefix=PRINT -strict-whitespace < %t.printed.A.txt
 
 // REQUIRES: objc_interop

test/Sema/diag_non_ephemeral.swift

@@ -2,7 +2,7 @@
 // RUN: %target-swift-frontend -emit-module -enable-library-evolution -parse-as-library -o %t -module-name=ModuleA %S/Inputs/diag_non_ephemeral_module1.swift
 // RUN: %target-swift-frontend -emit-module -enable-library-evolution -parse-as-library -o %t -module-name=ModuleB %S/Inputs/diag_non_ephemeral_module2.swift
 // RUN: cp %s %t/main.swift
-// RUN: %target-swift-frontend -typecheck -verify -diagnose-invalid-ephemeralness-as-error -I %t %t/main.swift %S/Inputs/diag_non_ephemeral_globals.swift
+// RUN: %target-swift-frontend -typecheck -verify -enable-invalid-ephemeralness-as-error -I %t %t/main.swift %S/Inputs/diag_non_ephemeral_globals.swift
 
 import ModuleA
 import ModuleB

test/stdlib/AutoreleasingUnsafeMutablePointerDiagnostics.swift

@@ -1,4 +1,4 @@
-// RUN: %target-typecheck-verify-swift -diagnose-invalid-ephemeralness-as-error
+// RUN: %target-typecheck-verify-swift -enable-invalid-ephemeralness-as-error
 // REQUIRES: objc_interop
 
 func unsafePointerInitEphemeralConversions() {

test/stdlib/UnsafePointerDiagnostics.swift

@@ -1,4 +1,4 @@
-// RUN: %target-typecheck-verify-swift -diagnose-invalid-ephemeralness-as-error
+// RUN: %target-typecheck-verify-swift -enable-invalid-ephemeralness-as-error
 
 // Test availability attributes on UnsafePointer initializers.
 // Assume the original source contains no UnsafeRawPointer types.