Merge pull request #71637 from apple/ApolloZhu/SE-0422/accepted

Author: DougGregor

CHANGELOG.md

@@ -4,6 +4,33 @@
 > This is in reverse chronological order, so newer entries are added to the top.
 
 ## Swift 5.11
+* [SE-0422][]:
+  Non-built-in expression macros can now be used as default arguments that
+  expand at each call site. For example, a custom `#CurrentFile` macro used as
+  a default argument in 'Library.swift' won't be expanded to `"Library.swift"`:
+
+  ```swift
+  @freestanding(expression)
+  public macro CurrentFile() -> String = ...
+
+  public func currentFile(name: String = #CurrentFile) { name }
+  ```
+
+  Instead, it will be expanded at where the function is called:
+  
+  ```swift
+  print(currentFile())
+  // Prints "main.swift"
+  ```
+
+  The expanded code can also use declarations from the caller side context:
+
+  ```swift
+  var person = "client"
+  greetPerson(/* greeting: #informalGreeting */)
+  // Prints "Hi client" if macro expands to "Hi \(person)"
+  ```
+
 * [SE-0417][]:
   Tasks now gain the ability to respect Task Executor preference.
   This allows tasks executing default actors (which do not declare a custom executor),

include/swift/AST/DiagnosticsSema.def

@@ -7535,9 +7535,6 @@ ERROR(extension_macro_invalid_conformance,none,
 ERROR(macro_attached_to_invalid_decl,none,
       "'%0' macro cannot be attached to %1 (%base2)",
       (StringRef, DescriptiveDeclKind, const Decl *))
-ERROR(macro_as_default_argument, none,
-      "non-built-in macro cannot be used as default argument",
-      ())
 ERROR(conformance_macro,none,
       "conformance macros are replaced by extension macros",
       ())

include/swift/Basic/Features.def

@@ -123,6 +123,7 @@ SUPPRESSIBLE_LANGUAGE_FEATURE(RetroactiveAttribute, 364, "@retroactive")
 SUPPRESSIBLE_LANGUAGE_FEATURE(ExtensionMacroAttr, 0, "@attached(extension)")
 LANGUAGE_FEATURE(TypedThrows, 413, "Typed throws")
 SUPPRESSIBLE_LANGUAGE_FEATURE(Extern, 0, "@_extern")
+LANGUAGE_FEATURE(ExpressionMacroDefaultArguments, 422, "Expression macro as caller-side default argument")
 
 UPCOMING_FEATURE(ConciseMagicFile, 274, 6)
 UPCOMING_FEATURE(ForwardTrailingClosures, 286, 6)
@@ -144,7 +145,6 @@ EXPERIMENTAL_FEATURE(NamedOpaqueTypes, false)
 EXPERIMENTAL_FEATURE(FlowSensitiveConcurrencyCaptures, false)
 EXPERIMENTAL_FEATURE(CodeItemMacros, false)
 EXPERIMENTAL_FEATURE(BodyMacros, true)
-EXPERIMENTAL_FEATURE(ExpressionMacroDefaultArguments, false)
 EXPERIMENTAL_FEATURE(TupleConformances, false)
 
 // Whether to enable @_used and @_section attributes

lib/Sema/TypeCheckDeclPrimary.cpp

@@ -1027,13 +1027,6 @@ static bool checkExpressionMacroDefaultValueRestrictions(ParamDecl *param) {
   auto *initExpr = param->getStructuralDefaultExpr();
   assert(initExpr);
 
-  // Prohibit default argument that is a non-built-in macro to avoid confusion,
-  // unless the experimental feature flag is set.
-  if (!ctx.LangOpts.hasFeature(Feature::ExpressionMacroDefaultArguments)) {
-    ctx.Diags.diagnose(initExpr->getLoc(), diag::macro_as_default_argument);
-    return false;
-  }
-
 #if SWIFT_BUILD_SWIFT_SYNTAX
   auto *DC = param->getInnermostDeclContext();
   const SourceFile *SF = DC->getParentSourceFile();

test/Macros/macro_default_argument.swift

@@ -3,7 +3,7 @@
 // RUN: %empty-directory(%t)
 // RUN: %host-build-swift -swift-version 5 -emit-library -o %t/%target-library-name(MacroDefinition) -module-name=MacroDefinition %S/Inputs/syntax_macro_definitions.swift -g -no-toolchain-stdlib-rpath
 
-// RUN: %target-typecheck-verify-swift -swift-version 5 -load-plugin-library %t/%target-library-name(MacroDefinition) %s -enable-experimental-feature ExpressionMacroDefaultArguments
+// RUN: %target-typecheck-verify-swift -swift-version 5 -load-plugin-library %t/%target-library-name(MacroDefinition) %s
 
 public typealias Stringified<T> = (T, String)
 

test/Macros/macro_default_argument_access_level.swift

@@ -3,7 +3,7 @@
 // RUN: %empty-directory(%t)
 // RUN: %host-build-swift -swift-version 5 -emit-library -o %t/%target-library-name(MacroDefinition) -module-name=MacroDefinition %S/Inputs/syntax_macro_definitions.swift -g -no-toolchain-stdlib-rpath
 
-// RUN: %target-typecheck-verify-swift -swift-version 5 -load-plugin-library %t/%target-library-name(MacroDefinition) %s -enable-experimental-feature ExpressionMacroDefaultArguments -enable-bare-slash-regex
+// RUN: %target-typecheck-verify-swift -swift-version 5 -load-plugin-library %t/%target-library-name(MacroDefinition) %s -enable-bare-slash-regex
 
 public typealias Stringified<T> = (T, String)
 

test/Macros/macro_default_argument_diagnostics.swift

@@ -4,7 +4,7 @@
 
 // RUN: %host-build-swift -swift-version 5 -emit-library -o %t/%target-library-name(MacroDefinition) -module-name=MacroDefinition %S/Inputs/syntax_macro_definitions.swift -g -no-toolchain-stdlib-rpath
 
-// RUN: %target-swift-emit-module-interface(%t.swiftinterface) %s -module-name CheckInterface -load-plugin-library %t/%target-library-name(MacroDefinition) -enable-experimental-feature ExpressionMacroDefaultArguments -I %t
+// RUN: %target-swift-emit-module-interface(%t.swiftinterface) %s -module-name CheckInterface -load-plugin-library %t/%target-library-name(MacroDefinition) -I %t
 // RUN: %target-swift-typecheck-module-from-interface(%t.swiftinterface) -module-name CheckInterface -load-plugin-library %t/%target-library-name(MacroDefinition) -I %t
 
 // RUN: %FileCheck %s < %t.swiftinterface

test/Macros/macro_default_argument_library.swift

@@ -5,9 +5,9 @@
 
 // RUN: %host-build-swift -swift-version 5 -emit-library -o %t/%target-library-name(MacroDefinition) -module-name=MacroDefinition %S/Inputs/syntax_macro_definitions.swift -g -no-toolchain-stdlib-rpath
 
-// RUN: %target-build-swift-dylib(%t/%target-library-name(Serialized)) %S/macro_default_argument_library.swift -module-name Serialized -emit-module -emit-module-path %t/Serialized.swiftmodule -load-plugin-library %t/%target-library-name(MacroDefinition) -enable-experimental-feature ExpressionMacroDefaultArguments -I %t -swift-version 5
+// RUN: %target-build-swift-dylib(%t/%target-library-name(Serialized)) %S/macro_default_argument_library.swift -module-name Serialized -emit-module -emit-module-path %t/Serialized.swiftmodule -load-plugin-library %t/%target-library-name(MacroDefinition) -I %t -swift-version 5
 
-// RUN: %target-build-swift -enable-experimental-feature ExpressionMacroDefaultArguments -swift-version 5 -load-plugin-library %t/%target-library-name(MacroDefinition) %s -o %t/main -module-name MacroUser -emit-tbd -emit-tbd-path %t/MacroUser.tbd -I %t -L %t %target-rpath(%t) -lSerialized
+// RUN: %target-build-swift -swift-version 5 -load-plugin-library %t/%target-library-name(MacroDefinition) %s -o %t/main -module-name MacroUser -emit-tbd -emit-tbd-path %t/MacroUser.tbd -I %t -L %t %target-rpath(%t) -lSerialized
 // RUN: %target-codesign %t/main
 // RUN: %target-run %t/main | %FileCheck %s
 

test/Macros/macro_default_argument_serialized.swift

@@ -5,11 +5,11 @@
 
 // RUN: %host-build-swift -swift-version 5 -emit-library -o %t/%target-library-name(MacroDefinition) -module-name=MacroDefinition %S/Inputs/syntax_macro_definitions.swift -g -no-toolchain-stdlib-rpath
 
-// RUN: %target-build-swift-dylib(%t/%target-library-name(WithMacroDefaultArg)) %S/Inputs/with_macro_default_arg_module.swift -module-name WithMacroDefaultArg -emit-module -emit-module-path %t/WithMacroDefaultArg.swiftmodule -load-plugin-library %t/%target-library-name(MacroDefinition) -enable-experimental-feature ExpressionMacroDefaultArguments -I %t -swift-version 5
+// RUN: %target-build-swift-dylib(%t/%target-library-name(WithMacroDefaultArg)) %S/Inputs/with_macro_default_arg_module.swift -module-name WithMacroDefaultArg -emit-module -emit-module-path %t/WithMacroDefaultArg.swiftmodule -load-plugin-library %t/%target-library-name(MacroDefinition) -I %t -swift-version 5
 
-// RUN: %target-build-swift-dylib(%t/%target-library-name(WithMacroDefaultArgInterface)) %S/Inputs/with_macro_default_arg_interface.swift -module-name WithMacroDefaultArgInterface -enable-library-evolution -emit-module-interface-path %t/WithMacroDefaultArgInterface.swiftinterface -load-plugin-library %t/%target-library-name(MacroDefinition) -enable-experimental-feature ExpressionMacroDefaultArguments -I %t -swift-version 5
+// RUN: %target-build-swift-dylib(%t/%target-library-name(WithMacroDefaultArgInterface)) %S/Inputs/with_macro_default_arg_interface.swift -module-name WithMacroDefaultArgInterface -enable-library-evolution -emit-module-interface-path %t/WithMacroDefaultArgInterface.swiftinterface -load-plugin-library %t/%target-library-name(MacroDefinition) -I %t -swift-version 5
 
-// RUN: %target-build-swift -enable-experimental-feature ExpressionMacroDefaultArguments -swift-version 5 -load-plugin-library %t/%target-library-name(MacroDefinition) %S/Inputs/with_macro_default_arg_same_module.swift %s -o %t/main -module-name MacroUser -emit-tbd -emit-tbd-path %t/MacroUser.tbd -I %t -L %t %target-rpath(%t) -lWithMacroDefaultArg -lWithMacroDefaultArgInterface
+// RUN: %target-build-swift -swift-version 5 -load-plugin-library %t/%target-library-name(MacroDefinition) %S/Inputs/with_macro_default_arg_same_module.swift %s -o %t/main -module-name MacroUser -emit-tbd -emit-tbd-path %t/MacroUser.tbd -I %t -L %t %target-rpath(%t) -lWithMacroDefaultArg -lWithMacroDefaultArgInterface
 // RUN: %target-codesign %t/main
 // RUN: %target-run %t/main | %FileCheck %s