Sema: Implement adoption mode for ExistentialAny

Author: AnthonyLatsis

Diff for: lib/Sema/TypeCheckType.cpp

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2025 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -6497,7 +6497,15 @@ class ExistentialTypeSyntaxChecker : public ASTWalker {
                                       /*isAlias=*/isa<TypeAliasDecl>(decl)));
     }
 
-    diag->warnUntilSwiftVersion(7);
+    // If the feature is enabled in adoption mode, warn unconditionally.
+    // Otherwise, until Swift 7.
+    if (Ctx.LangOpts.getFeatureState(Feature::ExistentialAny)
+            .isEnabledForAdoption()) {
+      diag->limitBehavior(DiagnosticBehavior::Warning);
+    } else {
+      diag->warnUntilSwiftVersion(7);
+    }
+
     emitInsertAnyFixit(*diag, T);
   }
 

Diff for: test/type/explicit_existential.swift

@@ -1,7 +1,19 @@
-// 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-
+// RUN: %target-typecheck-verify-swift \
+// RUN:   -verify-additional-prefix default-swift-mode-
+
+// RUN: %target-typecheck-verify-swift -swift-version 6 \
+// RUN:   -verify-additional-prefix swift-6-
+
+// RUN: %target-typecheck-verify-swift -enable-upcoming-feature ExistentialAny \
+// RUN:   -verify-additional-prefix default-swift-mode- \
+// RUN:   -verify-additional-prefix explicit-any-
+
+// RUN: %target-typecheck-verify-swift -enable-upcoming-feature ExistentialAny:adoption \
+//        To verify that the message is not followed by
+//        "; this will be an error ...".
+// RUN:   -print-diagnostic-groups \
+// RUN:   -verify-additional-prefix default-swift-mode- \
+// RUN:   -verify-additional-prefix explicit-any-adopt-
 
 // REQUIRES: swift_feature_ExistentialAny
 
@@ -20,8 +32,10 @@ protocol Bar {
 class Bistro {
   convenience init(_: Bar){ self.init()}
   // expected-explicit-any-warning@-1 {{use of protocol 'Bar' as a type must be written 'any Bar'; this will be an error in a future Swift language mode}}{{23-26=any Bar}}
+  // expected-explicit-any-adopt-warning@-2 {{use of protocol 'Bar' as a type must be written 'any Bar' [ExistentialAny]}}{{23-26=any Bar}}
   class func returnBar() -> Bar {}
   // expected-explicit-any-warning@-1 {{use of protocol 'Bar' as a type must be written 'any Bar'; this will be an error in a future Swift language mode}}{{29-32=any Bar}}
+  // expected-explicit-any-adopt-warning@-2 {{use of protocol 'Bar' as a type must be written 'any Bar' [ExistentialAny]}}{{29-32=any Bar}}
 }
 
 func useBarAsType(_ x: any Bar) {}
@@ -221,6 +235,7 @@ enum E1: RawRepresentable {
 
   var rawValue: P1 {
     // expected-explicit-any-warning@-1 {{use of protocol 'P1' as a type must be written 'any P1'; this will be an error in a future Swift language mode}}{{17-19=any P1}}
+    // expected-explicit-any-adopt-warning@-2 {{use of protocol 'P1' as a type must be written 'any P1' [ExistentialAny]}}{{17-19=any P1}}
     return ConcreteComposition()
   }
 }
@@ -318,8 +333,10 @@ enum EE : Equatable, any Empty { // expected-error {{raw type 'any Empty' is not
 
 // Protocols from a serialized module (the standard library).
 do {
+  // expected-explicit-any-adopt-warning@+2 {{use of protocol 'Decodable' as a type must be written 'any Decodable' [ExistentialAny]}}
   // expected-explicit-any-warning@+1 {{use of protocol 'Decodable' as a type must be written 'any Decodable'; this will be an error in a future Swift language mode}}
   let _: Decodable
+  // expected-explicit-any-adopt-warning@+2 {{use of 'Codable' (aka 'Decodable & Encodable') as a type must be written 'any Codable' (aka 'any Decodable & Encodable') [ExistentialAny]}}
   // expected-explicit-any-warning@+1 {{use of 'Codable' (aka 'Decodable & Encodable') as a type must be written 'any Codable' (aka 'any Decodable & Encodable'); this will be an error in a future Swift language mode}}
   let _: Codable
 }
@@ -547,6 +564,7 @@ func testEnumAssociatedValue() {
     case c1((any HasAssoc) -> Void)
     // expected-warning@+1 {{use of protocol 'HasAssoc' as a type must be written 'any HasAssoc'}}
     case c2((HasAssoc) -> Void)
+    // expected-explicit-any-adopt-warning@+2 {{use of protocol 'P' as a type must be written 'any P' [ExistentialAny]}}
     // expected-explicit-any-warning@+1 {{use of protocol 'P' as a type must be written 'any P'; this will be an error in a future Swift language mode}}
     case c3((P) -> Void)
   }
@@ -574,5 +592,7 @@ func f(_ x: Objectlike) {}
 typealias Copy = Copyable
 func h(_ z1: Copy,
        // expected-explicit-any-warning@-1 {{use of 'Copy' (aka 'Copyable') as a type must be written 'any Copy' (aka 'any Copyable'); this will be an error in a future Swift language mode}}
+       // expected-explicit-any-adopt-warning@-2 {{use of 'Copy' (aka 'Copyable') as a type must be written 'any Copy' (aka 'any Copyable') [ExistentialAny]}}
        _ z2: Copyable) {}
        // expected-explicit-any-warning@-1 {{use of protocol 'Copyable' as a type must be written 'any Copyable'; this will be an error in a future Swift language mode}}
+       // expected-explicit-any-adopt-warning@-2 {{use of protocol 'Copyable' as a type must be written 'any Copyable' [ExistentialAny]}}