Handle object literal's rewriting of the first argument label

The macro signature of the object literals is different from the
initializer that's used for the rewritten version. Account for this in
the macro's definition.

Author: DougGregor

Sources/_SwiftSyntaxMacros/MacroSystem+Builtin.swift

@@ -177,6 +177,19 @@ struct FunctionMacro: ExpressionMacro {
   }
 }
 
+/// Replace the label of the first element in the tuple with the given
+/// new label.
+private func replaceFirstLabel(
+  of tuple: TupleExprElementListSyntax, with newLabel: String
+) -> TupleExprElementListSyntax{
+  guard let firstElement = tuple.first else {
+    return tuple
+  }
+
+  return tuple.replacing(
+    childAt: 0, with: firstElement.withLabel(.identifier(newLabel)))
+}
+
 struct ColorLiteralMacro: ExpressionMacro {
   static var name: String { "colorLiteral" }
 
@@ -188,14 +201,17 @@ struct ColorLiteralMacro: ExpressionMacro {
   static var signature: TypeSyntax =
      """
      (
-      _colorLiteralRed red: Float, green: Float, blue: Float, alpha: Float
+      red: Float, green: Float, blue: Float, alpha: Float
      ) -> T
      """
 
   static func apply(
     _ macro: MacroExpansionExprSyntax, in context: MacroEvaluationContext
   ) -> MacroResult<ExprSyntax> {
-    let initSyntax: ExprSyntax = ".init(\(macro.argumentList))"
+    let argList = replaceFirstLabel(
+      of: macro.argumentList, with: "_colorLiteralRed"
+    )
+    let initSyntax: ExprSyntax = ".init(\(argList))"
     if let leadingTrivia = macro.leadingTrivia {
       return MacroResult(initSyntax.withLeadingTrivia(leadingTrivia))
     }
@@ -212,12 +228,15 @@ struct FileLiteralMacro: ExpressionMacro {
       """
 
   static var signature: TypeSyntax =
-      "(fileReferenceLiteralResourceName path: String) -> T"
+      "(resourceName path: String) -> T"
 
   static func apply(
     _ macro: MacroExpansionExprSyntax, in context: MacroEvaluationContext
   ) -> MacroResult<ExprSyntax> {
-    let initSyntax: ExprSyntax = ".init(\(macro.argumentList))"
+    let argList = replaceFirstLabel(
+      of: macro.argumentList, with: "fileReferenceLiteralResourceName"
+    )
+    let initSyntax: ExprSyntax = ".init(\(argList))"
     if let leadingTrivia = macro.leadingTrivia {
       return MacroResult(initSyntax.withLeadingTrivia(leadingTrivia))
     }
@@ -234,12 +253,15 @@ struct ImageLiteralMacro: ExpressionMacro {
       """
 
   static var signature: TypeSyntax =
-      "(imageLiteralResourceName path: String) -> T"
+      "(resourceName path: String) -> T"
 
   static func apply(
     _ macro: MacroExpansionExprSyntax, in context: MacroEvaluationContext
   ) -> MacroResult<ExprSyntax> {
-    let initSyntax: ExprSyntax = ".init(\(macro.argumentList))"
+    let argList = replaceFirstLabel(
+      of: macro.argumentList, with: "imageLiteralResourceName"
+    )
+    let initSyntax: ExprSyntax = ".init(\(argList))"
     if let leadingTrivia = macro.leadingTrivia {
       return MacroResult(initSyntax.withLeadingTrivia(leadingTrivia))
     }

Tests/SwiftSyntaxMacrosTest/MacroSystemTests.swift

@@ -39,7 +39,7 @@ final class MacroSystemTests: XCTestCase {
       1
       let a = (2)
       let b = (x + y, #"x + y"#)
-      .init(red: 0.5, green: 0.5, blue: 0.25, alpha: 1.0)
+      .init(_colorLiteralRed: 0.5, green: 0.5, blue: 0.25, alpha: 1.0)
       let c = 9
       """
     )