Work around a retroactive conformance bug in Swift 6.2.

The Swift 6.2 compiler emits spurious warnings about retroactive conformances
to protocols that are inherited through a protocol that is written module
qualified in the inheritance clause (the Swift compiler bug is tracked by
swiftlang/swift#85153). Suppress the warnings by
making the inherited conformances explicit and module qualified.

Author: tshortli

CodeGeneration/Sources/generate-swift-syntax/templates/swiftsyntaxbuilder/SyntaxExpressibleByStringInterpolationConformancesFile.swift

@@ -36,6 +36,8 @@ let syntaxExpressibleByStringInterpolationConformancesFile = SourceFileSyntax(le
       """
       #if compiler(>=6)
       extension \(type): Swift.ExpressibleByStringInterpolation {}
+      // Work around https://github.com/swiftlang/swift/issues/85153 by restating the implicit conformances.
+      extension \(type): Swift.ExpressibleByStringLiteral, Swift.ExpressibleByExtendedGraphemeClusterLiteral, Swift.ExpressibleByUnicodeScalarLiteral {}
       #endif
       """
     )

Sources/SwiftSyntaxBuilder/Syntax+StringInterpolation.swift

@@ -467,6 +467,10 @@ extension TokenSyntax: SyntaxExpressibleByStringInterpolation {
 // Silence warning that TokenSyntax has a retroactive conformance to `ExpressibleByStringInterpolation` through
 // `SyntaxExpressibleByStringInterpolation`.
 extension TokenSyntax: Swift.ExpressibleByStringInterpolation {}
+// Work around https://github.com/swiftlang/swift/issues/85153 by restating the implicit conformances.
+extension TokenSyntax: Swift.ExpressibleByStringLiteral {}
+extension TokenSyntax: Swift.ExpressibleByExtendedGraphemeClusterLiteral {}
+extension TokenSyntax: Swift.ExpressibleByUnicodeScalarLiteral {}
 #endif
 
 // MARK: - Trivia expressible as string
@@ -515,7 +519,13 @@ extension Trivia {
 }
 
 #if compiler(>=6)
+// Silence warning that Trivia has a retroactive conformance to `ExpressibleByStringInterpolation` through
+// `SyntaxExpressibleByStringInterpolation`.
 extension Trivia: Swift.ExpressibleByStringInterpolation {}
+// Work around https://github.com/swiftlang/swift/issues/85153 by restating the implicit conformances.
+extension Trivia: Swift.ExpressibleByStringLiteral {}
+extension Trivia: Swift.ExpressibleByExtendedGraphemeClusterLiteral {}
+extension Trivia: Swift.ExpressibleByUnicodeScalarLiteral {}
 #else
 extension Trivia: ExpressibleByStringInterpolation {}
 #endif