swiftlang · artemcm · Apr 1, 2026
@@ -1,29 +1,29 @@
 # SwiftWarningControl
 
-A library to evaluate `@warn` diagnostic group controls within a Swift syntax tree.
+A library to evaluate `@diagnose` diagnostic group controls within a Swift syntax tree.
 
 ## Overview
 
-Swift provides a mechanism to control the behavior of specific diagnostic groups for a given declaration's lexical scope with the `@warn` attribute.
+Swift provides a mechanism to control the behavior of specific diagnostic groups for a given declaration's lexical scope with the `@diagnose` attribute (also accepts the old `@warn` spelling).
 
-The syntax tree and its parser do not reason about warning group controls. The syntax tree produced by the parser represents the `@warn` attribute in a generic fashion, as it would any other basic attribute on a declaration. The per-declaration nature of the attribute means that for any given lexical scope, the behavior of a given diagnostic group can be queried by checking for the presence of this attribute in its parent declaration scope.
+The syntax tree and its parser do not reason about warning group controls. The syntax tree produced by the parser represents the `@diagnose` attribute in a generic fashion, as it would any other basic attribute on a declaration. The per-declaration nature of the attribute means that for any given lexical scope, the behavior of a given diagnostic group can be queried by checking for the presence of this attribute in its parent declaration scope.
 
 ```swift
-@warn(Deprecate, as: error)
+@diagnose(Deprecate, as: error)
 func foo() {
   ...
-  @warn(Deprecate, as: warning)
+  @diagnose(Deprecate, as: warning)
   func bar() {
     ...
-    @warn("Deprecate", as: ignored, reason: "Foo")
+    @diagnose("Deprecate", as: ignored, reason: "Foo")
     func baz() {
       ...
     }
   }
 }
 ```
 
-The `SwiftWarningControl` library provides a utility to determine, for a given source location and diagnostic group identifier, whether or not its behavior is affected by an `@warn` attribute of any of its parent declaration scope.
+The `SwiftWarningControl` library provides a utility to determine, for a given source location and diagnostic group identifier, whether or not its behavior is affected by an `@diagnose` attribute of any of its parent declaration scope.
 
 * `SyntaxProtocol.getWarningGroupControl(for diagnosticGroupIdentifier:)` produces the behavior control specifier (`WarningGroupControl`: `error`, `warning`, `ignored`) which applies at this node.
 

@@ -23,7 +23,7 @@ extension SyntaxProtocol {
   ///   - globalControls: The global controls to consider, specified by the client (compiler)
   ///     representing module-wide diagnostic group emission configuration, for example
   ///     with `-Wwarning` and `-Werror` flags. These controls can be overriden at
-  ///     finer-grained scopes with the `@warn` attribute.
+  ///     finer-grained scopes with the `@diagnose` attribute.
   @_spi(ExperimentalLanguageFeatures)
   public func warningGroupControl(
     for diagnosticGroupIdentifier: DiagnosticGroupIdentifier,

@@ -14,8 +14,9 @@
 
 extension AttributeSyntax {
   var warningGroupControl: (DiagnosticGroupIdentifier, WarningGroupControl)? {
-    // `@warn` attributes
-    guard attributeName.as(IdentifierTypeSyntax.self)?.name.text == "warn"
+    // `@diagnose` attributes (also accepts the old `@warn` spelling)
+    guard let attrName = attributeName.as(IdentifierTypeSyntax.self)?.name.text,
+      attrName == "diagnose" || attrName == "warn"
     else {
       return nil
     }
@@ -51,7 +52,7 @@ extension AttributeSyntax {
 }
 
 extension WithAttributesSyntax {
-  /// Compute a dictionary of all `@warn` diagnostic group behavior controls
+  /// Compute a dictionary of all `@diagnose` diagnostic group behavior controls
   /// specified on this warning control declaration scope.
   var allWarningGroupControls: [(DiagnosticGroupIdentifier, WarningGroupControl)] {
     attributes.reduce(into: [(DiagnosticGroupIdentifier, WarningGroupControl)]()) { result, attr in

@@ -45,7 +45,7 @@ extension SyntaxProtocol {
   }
 }
 
-/// Add this warning control decl syntax node warning group controls (as specified with `@warn`)
+/// Add this warning control decl syntax node warning group controls (as specified with `@diagnose`)
 /// to the tree.
 extension WarningControlRegionTree {
   mutating func addWarningControlRegions(for syntax: some WithAttributesSyntax) {

@@ -43,27 +43,27 @@ public struct DiagnosticGroupIdentifier: Hashable, Sendable, ExpressibleByString
   public let identifier: String
 }
 
-/// Describes all of the `@warn` diagnostic group behavior controls within the
+/// Describes all of the `@diagnose` diagnostic group behavior controls within the
 /// given syntax node, indicating each group's active behavior at a given position.
 ///
 /// For example, given code like the following:
 ///
 /// ```
-///  1 |  @warn(Deprecate, as: error)
+///  1 |  @diagnose(Deprecate, as: error)
 ///  2 |  func foo() {
 ///  3 |     let a = dep
-///  4 |     @warn(Deprecate, as: warning)
+///  4 |     @diagnose(Deprecate, as: warning)
 ///  5 |     func bar() {
 ///  6 |         let b = dep
-///  7 |         @warn(Deprecate, as: ignored)
+///  7 |         @diagnose(Deprecate, as: ignored)
 ///  8 |         func baz() {
 ///  9 |           let c = dep
 /// 10 |        }
-/// 11 |        @warn(Deprecate, as: error)
-/// 12 |        @warn(OtherGroup, as: error)
+/// 11 |        @diagnose(Deprecate, as: error)
+/// 12 |        @diagnose(OtherGroup, as: error)
 /// 13 |        func qux() {
 /// 14 |            let d = dep
-/// 15 |             @warn(SomeOtherGroup, as: warning)
+/// 15 |             @diagnose(SomeOtherGroup, as: warning)
 /// 16 |            func corge() {
 /// 17 |              let e = dep
 /// 18 |            }
@@ -150,7 +150,7 @@ public struct WarningControlRegionTree {
   }
 
   /// Add warning control regions to the tree root node.
-  /// For example, controls corresponding to a top-level `using @warn()` statement.
+  /// For example, controls corresponding to a top-level `using @diagnose()` statement.
   mutating func addRootWarningGroupControls(controls: [(DiagnosticGroupIdentifier, WarningGroupControl)]) {
     addWarningGroupControls(range: rootRegionNode.range, controls: controls)
   }

@@ -3757,6 +3757,39 @@ final class UsingDeclarationTests: ParserTestCase {
       )
     )
 
+    assertParse(
+      "using @diagnose(DiagGroupID, as: error)",
+      substructure: UsingDeclSyntax(
+        usingKeyword: .keyword(.using),
+        specifier: .attribute(
+          AttributeSyntax(
+            attributeName: IdentifierTypeSyntax(
+              name: .identifier("diagnose")
+            ),
+            leftParen: .leftParenToken(),
+            arguments: .argumentList(
+              LabeledExprListSyntax([
+                LabeledExprSyntax(
+                  expression: DeclReferenceExprSyntax(
+                    baseName: .identifier("DiagGroupID")
+                  ),
+                  trailingComma: .commaToken()
+                ),
+                LabeledExprSyntax(
+                  label: .identifier("as"),
+                  colon: .colonToken(),
+                  expression: DeclReferenceExprSyntax(
+                    baseName: .identifier("error")
+                  )
+                ),
+              ])
+            ),
+            rightParen: .rightParenToken()
+          )
+        )
+      )
+    )
+
     assertParse(
       """
       nonisolated