Frontend: Allow -enable-experimental-feature to specify upcoming features

lib/Frontend/CompilerInvocation.cpp

@@ -1014,6 +1014,21 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
     Opts.EnableExperimentalStringProcessing = true;
   }
 
+  auto enableUpcomingFeature = [&Opts, &Diags](Feature feature) -> bool {
+    // Check if this feature was introduced already in this language version.
+    if (auto firstVersion = getFeatureLanguageVersion(feature)) {
+      if (Opts.isSwiftVersionAtLeast(*firstVersion)) {
+        Diags.diagnose(SourceLoc(), diag::error_upcoming_feature_on_by_default,
+                       getFeatureName(feature), *firstVersion);
+        return true;
+      }
+    }
+
+    Opts.enableFeature(feature);
+    return false;
+  };
+
+  // Enable experimental features.
   for (const Arg *A : Args.filtered(OPT_enable_experimental_feature)) {
     // Allow StrictConcurrency to have a value that corresponds to the
     // -strict-concurrency=<blah> settings.
@@ -1040,12 +1055,14 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
       } else {
         Opts.enableFeature(*feature);
       }
+    }
 
-      if (*feature == Feature::NoncopyableGenerics2)
-        Opts.enableFeature(Feature::NoncopyableGenerics);
-
-      if (*feature == Feature::IsolatedAny2)
-        Opts.enableFeature(Feature::IsolatedAny);
+    // For compatibility, upcoming features can be enabled with the
+    // -enable-experimental-feature flag too since the feature may have
+    // graduated from being experimental.
+    if (auto feature = getUpcomingFeature(value)) {
+      if (enableUpcomingFeature(*feature))
+        HadError = true;
     }
 
     // Hack: In order to support using availability macros in SPM packages, we
@@ -1062,24 +1079,15 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
     }
   }
 
-  // Map historical flags over to future features.
+  // Enable upcoming features.
   for (const Arg *A : Args.filtered(OPT_enable_upcoming_feature)) {
     // Ignore unknown features.
     auto feature = getUpcomingFeature(A->getValue());
     if (!feature)
       continue;
 
-    // Check if this feature was introduced already in this language version.
-    if (auto firstVersion = getFeatureLanguageVersion(*feature)) {
-      if (Opts.isSwiftVersionAtLeast(*firstVersion)) {
-        Diags.diagnose(SourceLoc(), diag::error_upcoming_feature_on_by_default,
-                       A->getValue(), *firstVersion);
-        continue;
-      }
-    }
-
-    // Add the feature.
-    Opts.enableFeature(*feature);
+    if (enableUpcomingFeature(*feature))
+      HadError = true;
   }
 
   // Map historical flags over to experimental features. We do this for all

test/Concurrency/isolated_default_arguments_serialized.swift

@@ -2,7 +2,7 @@
 // RUN: %target-swift-frontend -emit-module -swift-version 5 -emit-module-path %t/SerializedDefaultArguments.swiftmodule -module-name SerializedDefaultArguments -enable-upcoming-feature IsolatedDefaultValues %S/Inputs/serialized_default_arguments.swift
 
 // RUN: %target-swift-frontend %s -emit-sil -o /dev/null -verify -disable-availability-checking -swift-version 6 -I %t
-// RUN: %target-swift-frontend %s -emit-sil -o /dev/null -verify -disable-availability-checking -swift-version 6 -I %t -enable-upcoming-feature RegionBasedIsolation -enable-upcoming-feature IsolatedDefaultValues
+// RUN: %target-swift-frontend %s -emit-sil -o /dev/null -verify -disable-availability-checking -swift-version 5 -I %t -enable-upcoming-feature RegionBasedIsolation -enable-upcoming-feature IsolatedDefaultValues -enable-upcoming-feature StrictConcurrency
 
 // REQUIRES: concurrency
 

test/Concurrency/predates_concurrency_import_swift6.swift

@@ -3,7 +3,6 @@
 // RUN: %target-swift-frontend -emit-module -emit-module-path %t/NonStrictModule.swiftmodule -module-name NonStrictModule %S/Inputs/NonStrictModule.swift
 
 // RUN: %target-swift-frontend -swift-version 6 -I %t %s -emit-sil -o /dev/null -verify -parse-as-library
-// RUN: %target-swift-frontend -swift-version 6 -I %t %s -emit-sil -o /dev/null -verify -enable-upcoming-feature RegionBasedIsolation -parse-as-library
 
 @preconcurrency import NonStrictModule
 @preconcurrency import StrictModule

test/Concurrency/property_initializers_swift6.swift

@@ -1,5 +1,4 @@
 // RUN: %target-swift-frontend -swift-version 6 -disable-availability-checking -strict-concurrency=complete -emit-sil -o /dev/null -verify %s
-// RUN: %target-swift-frontend -swift-version 6 -disable-availability-checking -strict-concurrency=complete -emit-sil -o /dev/null -verify %s -enable-upcoming-feature RegionBasedIsolation
 
 // REQUIRES: concurrency
 

test/Frontend/upcoming_feature.swift

@@ -12,9 +12,13 @@
 // RUN: %target-swift-frontend -typecheck -enable-upcoming-feature ConciseMagicFile -enable-upcoming-feature UnknownFeature %s
 // RUN: %target-swift-frontend -typecheck -enable-upcoming-feature UnknownFeature -enable-upcoming-feature ConciseMagicFile %s
 
+// For compatibility when a feature graduates, it's fine to refer to an
+// upcoming feature as an experimental feature.
+// RUN: %target-swift-frontend -typecheck -enable-experimental-feature ConciseMagicFile %s
 
 // It's not fine to provide a feature that's in the specified language version.
 // RUN: not %target-swift-frontend -typecheck -enable-upcoming-feature ConciseMagicFile -swift-version 6 %s 2>&1 | %FileCheck %s
+// RUN: not %target-swift-frontend -typecheck -enable-experimental-feature ConciseMagicFile -swift-version 6 %s 2>&1 | %FileCheck %s
 
 // CHECK: error: upcoming feature 'ConciseMagicFile' is already enabled as of Swift version 6
 

test/Sema/access-level-import-flag-check.swift

@@ -19,7 +19,6 @@
 // RUN: %target-swift-frontend -typecheck %t/ClientWithoutTheFlag.swift -I %t \
 // RUN:   -enable-upcoming-feature InternalImportsByDefault \
 // RUN:   -package-name package -verify
-// REQUIRES: asserts
 
 /// swiftinterfaces don't need the flag.
 // RUN: %target-swift-typecheck-module-from-interface(%t/Client.swiftinterface) -I %t

test/type/explicit_existential.swift

@@ -1,6 +1,7 @@
 // RUN: %target-typecheck-verify-swift -verify-additional-prefix default-swift-mode-
 // RUN: %target-typecheck-verify-swift -swift-version 6 -verify-additional-prefix swift-6-
 // RUN: %target-typecheck-verify-swift -enable-upcoming-feature ExistentialAny -verify-additional-prefix explicit-any- -verify-additional-prefix default-swift-mode-
+// RUN: %target-typecheck-verify-swift -enable-experimental-feature ExistentialAny -verify-additional-prefix explicit-any- -verify-additional-prefix default-swift-mode-
 
 
 protocol HasSelfRequirements {