[SE-0458] Enable unsafe expressions / attributes / for..in effects by default

With the acceptance of SE-0458, allow the use of unsafe expressions, the
@safe and @unsafe attributes, and the `unsafe` effect on the for..in loop
in all Swift code.

Introduce the `-strict-memory-safety` flag detailed in the proposal to
enable strict memory safety checking. This enables a new class of
feature, an optional feature (that is *not* upcoming or experimental),
and which can be detected via `hasFeature(StrictMemorySafety)`.

test/Unsafe/interface_printing.swift

@@ -1,10 +1,8 @@
 // RUN: %empty-directory(%t)
 
-// RUN: %target-swift-frontend -swift-version 5 -enable-library-evolution -module-name unsafe -emit-module -o %t/unsafe.swiftmodule -emit-module-interface-path - %s -enable-experimental-feature AllowUnsafeAttribute | %FileCheck %s
+// RUN: %target-swift-frontend -swift-version 5 -enable-library-evolution -module-name unsafe -emit-module -o %t/unsafe.swiftmodule -emit-module-interface-path - %s | %FileCheck %s
 
-// REQUIRES: swift_feature_AllowUnsafeAttribute
-
-// CHECK: #if compiler(>=5.3) && $AllowUnsafeAttribute
+// CHECK: #if compiler(>=5.3) && $MemorySafetyAttributes
 // CHECK: @unsafe public func testFunction()
 // CHECK: #else
 // CHECK: public func testFunction()

test/Unsafe/module-interface.swift

@@ -1,11 +1,8 @@
-// RUN: %target-swift-emit-module-interface(%t.swiftinterface) %s -module-name UserModule -enable-experimental-feature AllowUnsafeAttribute  -enable-experimental-feature WarnUnsafe
+// RUN: %target-swift-emit-module-interface(%t.swiftinterface) %s -module-name UserModule -strict-memory-safety
 // RUN: %target-swift-typecheck-module-from-interface(%t.swiftinterface) -module-name UserModule
 // RUN: %FileCheck %s < %t.swiftinterface
 
-// REQUIRES: swift_feature_AllowUnsafeAttribute
-// REQUIRES: swift_feature_WarnUnsafe
-
-// CHECK: #if compiler(>=5.3) && $AllowUnsafeAttribute
+// CHECK: #if compiler(>=5.3) && $MemorySafetyAttributes
 // CHECK: @unsafe public func getIntUnsafely() -> Swift.Int
 // CHECK: #else
 // CHECK: public func getIntUnsafely() -> Swift.Int
@@ -25,7 +22,7 @@ public protocol P {
 
 // CHECK: public struct X : @unsafe UserModule.P
 public struct X: @unsafe P {
-// CHECK:  #if compiler(>=5.3) && $AllowUnsafeAttribute
+// CHECK:  #if compiler(>=5.3) && $MemorySafetyAttributes
 // CHECK:  @unsafe public func f()
 // CHECK:  #else
 // CHECK:  public func f()

test/Unsafe/module-trace.swift

@@ -1,14 +1,11 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-swift-frontend -emit-module-path %t/unsafe_swift_decls.swiftmodule %S/Inputs/unsafe_swift_decls.swift -enable-experimental-feature AllowUnsafeAttribute
-// RUN: %target-swift-frontend -emit-module-path %t/safe_swift_decls.swiftmodule %S/Inputs/safe_swift_decls.swift -enable-experimental-feature AllowUnsafeAttribute -enable-experimental-feature WarnUnsafe
+// RUN: %target-swift-frontend -emit-module-path %t/unsafe_swift_decls.swiftmodule %S/Inputs/unsafe_swift_decls.swift
+// RUN: %target-swift-frontend -emit-module-path %t/safe_swift_decls.swiftmodule %S/Inputs/safe_swift_decls.swift -strict-memory-safety
 
-// RUN: %target-typecheck-verify-swift -enable-experimental-feature AllowUnsafeAttribute -enable-experimental-feature WarnUnsafe -I %S/Inputs -I %t -emit-loaded-module-trace-path %t/unsafe.trace
+// RUN: %target-typecheck-verify-swift -strict-memory-safety -I %S/Inputs -I %t -emit-loaded-module-trace-path %t/unsafe.trace
 
 // RUN: %FileCheck -check-prefix TRACE %s < %t/unsafe.trace
 
-// REQUIRES: swift_feature_AllowUnsafeAttribute
-// REQUIRES: swift_feature_WarnUnsafe
-
 import unsafe_decls
 import unsafe_swift_decls
 import safe_swift_decls

test/Unsafe/safe.swift

@@ -1,7 +1,10 @@
-// RUN: %target-typecheck-verify-swift -enable-experimental-feature AllowUnsafeAttribute -enable-experimental-feature WarnUnsafe -print-diagnostic-groups
+// RUN: %target-typecheck-verify-swift -strict-memory-safety -print-diagnostic-groups
+
+// The feature flag should be enabled.
+#if !hasFeature(StrictMemorySafety)
+#error("Strict memory safety is not enabled!")
+#endif
 
-// REQUIRES: swift_feature_AllowUnsafeAttribute
-// REQUIRES: swift_feature_WarnUnsafe
 
 @unsafe
 func unsafeFunction() { }

test/Unsafe/safe_argument_suppression.swift

@@ -1,7 +1,4 @@
-// RUN: %target-typecheck-verify-swift -enable-experimental-feature AllowUnsafeAttribute -enable-experimental-feature WarnUnsafe -print-diagnostic-groups
-
-// REQUIRES: swift_feature_AllowUnsafeAttribute
-// REQUIRES: swift_feature_WarnUnsafe
+// RUN: %target-typecheck-verify-swift -strict-memory-safety -print-diagnostic-groups
 
 @unsafe
 class NotSafe {

test/Unsafe/unsafe-suppression.swift

@@ -1,7 +1,4 @@
-// RUN: %target-typecheck-verify-swift -enable-experimental-feature AllowUnsafeAttribute -enable-experimental-feature WarnUnsafe -print-diagnostic-groups
-
-// REQUIRES: swift_feature_AllowUnsafeAttribute
-// REQUIRES: swift_feature_WarnUnsafe
+// RUN: %target-typecheck-verify-swift -strict-memory-safety -print-diagnostic-groups
 
 @unsafe
 func iAmUnsafe() { }

test/Unsafe/unsafe.swift

@@ -1,13 +1,10 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-swift-frontend -emit-module-path %t/unsafe_swift_decls.swiftmodule %S/Inputs/unsafe_swift_decls.swift -enable-experimental-feature AllowUnsafeAttribute
+// RUN: %target-swift-frontend -emit-module-path %t/unsafe_swift_decls.swiftmodule %S/Inputs/unsafe_swift_decls.swift
 
-// RUN: %target-typecheck-verify-swift -enable-experimental-feature AllowUnsafeAttribute -enable-experimental-feature WarnUnsafe -I %t -print-diagnostic-groups
+// RUN: %target-typecheck-verify-swift -strict-memory-safety -I %t -print-diagnostic-groups
 
 // Make sure everything compiles without error when unsafe code is allowed.
-// RUN: %target-swift-frontend -typecheck -enable-experimental-feature AllowUnsafeAttribute %s -I %t
-
-// REQUIRES: swift_feature_AllowUnsafeAttribute
-// REQUIRES: swift_feature_WarnUnsafe
+// RUN: %target-swift-frontend -typecheck %s -I %t
 
 import unsafe_swift_decls
 

test/Unsafe/unsafe_c_imports.swift

@@ -1,7 +1,4 @@
-// RUN: %target-typecheck-verify-swift -enable-experimental-feature AllowUnsafeAttribute -enable-experimental-feature WarnUnsafe -I %S/Inputs
-
-// REQUIRES: swift_feature_AllowUnsafeAttribute
-// REQUIRES: swift_feature_WarnUnsafe
+// RUN: %target-typecheck-verify-swift -strict-memory-safety -I %S/Inputs
 
 import unsafe_decls
 

test/Unsafe/unsafe_command_line.swift

@@ -1,6 +1,4 @@
-// RUN: %target-swift-frontend -typecheck -enable-experimental-feature WarnUnsafe -Ounchecked -disable-access-control %s 2>&1 | %FileCheck %s
-
-// REQUIRES: swift_feature_WarnUnsafe
+// RUN: %target-swift-frontend -typecheck -strict-memory-safety -Ounchecked -disable-access-control %s 2>&1 | %FileCheck %s
 
 // CHECK: warning: '-Ounchecked' is not memory-safe
 // CHECK: warning: '-disable-access-control' is not memory-safe

test/Unsafe/unsafe_concurrency.swift

@@ -1,12 +1,10 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-swift-frontend -emit-module-path %t/unsafe_swift_decls.swiftmodule %S/Inputs/unsafe_swift_decls.swift -enable-experimental-feature AllowUnsafeAttribute -enable-experimental-feature AllowUnsafeAttribute
+// RUN: %target-swift-frontend -emit-module-path %t/unsafe_swift_decls.swiftmodule %S/Inputs/unsafe_swift_decls.swift
 
-// RUN: %target-typecheck-verify-swift -enable-experimental-feature WarnUnsafe -enable-experimental-feature StrictConcurrency -enable-experimental-feature AllowUnsafeAttribute -I %t
+// RUN: %target-typecheck-verify-swift -strict-memory-safety -enable-experimental-feature StrictConcurrency -I %t
 
 // REQUIRES: concurrency
 // REQUIRES: swift_feature_StrictConcurrency
-// REQUIRES: swift_feature_WarnUnsafe
-// REQUIRES: swift_feature_AllowUnsafeAttribute
 
 @preconcurrency import unsafe_swift_decls // expected-warning{{@preconcurrency import is not memory-safe because it can silently introduce data races}}
 

test/Unsafe/unsafe_disallowed.swift

@@ -1,5 +0,0 @@
-// RUN: %target-typecheck-verify-swift
-
-@unsafe func f() { }
-// expected-error@-1{{attribute requires '-enable-experimental-feature AllowUnsafeAttribute'}}
-

test/Unsafe/unsafe_feature.swift

@@ -0,0 +1,19 @@
+// RUN: %target-typecheck-verify-swift
+
+
+// Can use @unsafe and @safe without strict memory safety being enabled.
+@unsafe func f() { }
+@safe func g(_: UnsafeRawPointer) { }
+
+protocol P {
+  func f()
+}
+
+struct X: @unsafe P {
+  @unsafe func f() { }
+}
+
+// The feature flag is not enabled, though.
+#if hasFeature(StrictMemorySafety)
+#error("Strict memory safety is not enabled!")
+#endif

test/Unsafe/unsafe_imports.swift

@@ -1,10 +1,7 @@
 // RUN: %empty-directory(%t)
-// RUN: %target-swift-frontend -emit-module-path %t/unsafe_swift_decls.swiftmodule %S/Inputs/unsafe_swift_decls.swift -enable-experimental-feature AllowUnsafeAttribute
+// RUN: %target-swift-frontend -emit-module-path %t/unsafe_swift_decls.swiftmodule %S/Inputs/unsafe_swift_decls.swift
 
-// RUN: %target-typecheck-verify-swift -enable-experimental-feature AllowUnsafeAttribute -enable-experimental-feature WarnUnsafe -I %S/Inputs -I %t
-
-// REQUIRES: swift_feature_AllowUnsafeAttribute
-// REQUIRES: swift_feature_WarnUnsafe
+// RUN: %target-typecheck-verify-swift -strict-memory-safety -I %S/Inputs -I %t
 
 import unsafe_decls
 import unsafe_swift_decls

test/Unsafe/unsafe_in_unsafe.swift

@@ -1,7 +1,4 @@
-// RUN: %target-typecheck-verify-swift -enable-experimental-feature AllowUnsafeAttribute -print-diagnostic-groups
-
-// REQUIRES: swift_feature_AllowUnsafeAttribute
-
+// RUN: %target-typecheck-verify-swift -print-diagnostic-groups
 
 protocol P { }
 

test/Unsafe/unsafe_stdlib.swift

@@ -1,10 +1,7 @@
-// RUN: %target-typecheck-verify-swift -enable-experimental-feature WarnUnsafe
+// RUN: %target-typecheck-verify-swift -strict-memory-safety
 
 // Make sure everything compiles without error when unsafe code is allowed.
-// RUN: %target-swift-frontend -typecheck -enable-experimental-feature AllowUnsafeAttribute -warnings-as-errors %s
-
-// REQUIRES: swift_feature_AllowUnsafeAttribute
-// REQUIRES: swift_feature_WarnUnsafe
+// RUN: %target-swift-frontend -typecheck -warnings-as-errors %s
 
 func test(
   x: OpaquePointer,