ASTGen: Accept @cdecl

Author: xymus

include/swift/AST/ASTBridging.h

@@ -970,11 +970,12 @@ BridgedBackDeployedAttr BridgedBackDeployedAttr_createParsed(
     BridgedSourceRange cRange, BridgedPlatformKind cPlatform,
     BridgedVersionTuple cVersion);
 
-SWIFT_NAME("BridgedCDeclAttr.createParsed(_:atLoc:range:name:)")
+SWIFT_NAME("BridgedCDeclAttr.createParsed(_:atLoc:range:name:underscored:)")
 BridgedCDeclAttr BridgedCDeclAttr_createParsed(BridgedASTContext cContext,
                                                BridgedSourceLoc cAtLoc,
                                                BridgedSourceRange cRange,
-                                               BridgedStringRef cName);
+                                               BridgedStringRef cName,
+                                               bool underscored);
 
 SWIFT_NAME(
     "BridgedCustomAttr.createParsed(_:atLoc:type:initContext:argumentList:)")

lib/AST/Bridging/DeclAttributeBridging.cpp

@@ -247,10 +247,11 @@ BridgedBackDeployedAttr BridgedBackDeployedAttr_createParsed(
 BridgedCDeclAttr BridgedCDeclAttr_createParsed(BridgedASTContext cContext,
                                                BridgedSourceLoc cAtLoc,
                                                BridgedSourceRange cRange,
-                                               BridgedStringRef cName) {
+                                               BridgedStringRef cName,
+                                               bool underscored) {
   return new (cContext.unbridged())
       CDeclAttr(cName.unbridged(), cAtLoc.unbridged(), cRange.unbridged(),
-                /*Implicit=*/false, /*Underscored*/true);
+                /*Implicit=*/false, /*Underscored*/underscored);
 }
 
 BridgedCustomAttr BridgedCustomAttr_createParsed(

lib/ASTGen/Sources/ASTGen/DeclAttrs.swift

@@ -535,20 +535,37 @@ extension ASTGenVisitor {
   /// E.g.:
   ///   ```
   ///   @_cdecl("c_function_name")
+  ///   @cdecl(c_function_name)
+  ///   @cdecl
   ///   ```
   func generateCDeclAttr(attribute node: AttributeSyntax) -> BridgedCDeclAttr? {
-    self.generateWithLabeledExprListArguments(attribute: node) { args in
-      guard let name = self.generateConsumingSimpleStringLiteralAttrOption(args: &args) else {
+    let attrName = node.attributeName.as(IdentifierTypeSyntax.self)?.name.text
+    let underscored = attrName?.hasPrefix("_") ?? false
+
+    var name: BridgedStringRef? = nil
+    if node.arguments != nil || underscored {
+      name = self.generateWithLabeledExprListArguments(attribute: node) {
+          args in
+        if underscored {
+          self.generateConsumingSimpleStringLiteralAttrOption(args: &args)
+        } else {
+           self.generateConsumingPlainIdentifierAttrOption(args: &args) {
+             return $0.rawText.bridged
+           }
+        }
+      }
+      guard name != nil else {
         return nil
       }
-
-      return .createParsed(
-        self.ctx,
-        atLoc: self.generateSourceLoc(node.atSign),
-        range: self.generateAttrSourceRange(node),
-        name: name
-      )
     }
+
+    return .createParsed(
+      self.ctx,
+      atLoc: self.generateSourceLoc(node.atSign),
+      range: self.generateAttrSourceRange(node),
+      name: name ?? "",
+      underscored: underscored
+    )
   }
 
   struct GeneratedDerivativeOriginalDecl {

test/ASTGen/attrs.swift

@@ -5,6 +5,7 @@
 // RUN:   -enable-experimental-feature LifetimeDependence \
 // RUN:   -enable-experimental-feature RawLayout \
 // RUN:   -enable-experimental-feature SymbolLinkageMarkers \
+// RUN:   -enable-experimental-feature CDecl \
 // RUN:   -enable-experimental-concurrency \
 // RUN:   -enable-experimental-move-only \
 // RUN:   -enable-experimental-feature ParserASTGen \
@@ -15,6 +16,7 @@
 // RUN:   -enable-experimental-feature LifetimeDependence \
 // RUN:   -enable-experimental-feature RawLayout \
 // RUN:   -enable-experimental-feature SymbolLinkageMarkers \
+// RUN:   -enable-experimental-feature CDecl \
 // RUN:   -enable-experimental-concurrency \
 // RUN:   -enable-experimental-move-only \
 // RUN:   | %sanitize-address > %t/cpp-parser.ast
@@ -28,6 +30,7 @@
 // RUN:   -enable-experimental-feature LifetimeDependence \
 // RUN:   -enable-experimental-feature RawLayout \
 // RUN:   -enable-experimental-feature SymbolLinkageMarkers \
+// RUN:   -enable-experimental-feature CDecl \
 // RUN:   -enable-experimental-concurrency \
 // RUN:   -enable-experimental-move-only
 
@@ -39,6 +42,7 @@
 // REQUIRES: swift_feature_LifetimeDependence
 // REQUIRES: swift_feature_RawLayout
 // REQUIRES: swift_feature_SymbolLinkageMarkers
+// REQUIRES: swift_feature_CDecl
 
 // rdar://116686158
 // UNSUPPORTED: asan
@@ -95,7 +99,9 @@ func fn(_: Int) {}
 
 @_disallowFeatureSuppression(NoncopyableGenerics) public struct LoudlyNC<T: ~Copyable> {}
 
-@_cdecl("c_function_name") func foo(x: Int) {}
+@_cdecl("c_function_name") func cdeclUnderscore(x: Int) {}
+@cdecl(c_function_name_official) func cdecl(x: Int) {}
+@cdecl func cdeclDefault() {}
 
 struct StaticProperties {
   dynamic var property: Int { return 1 }