Provide compile-time-checkd fully-qualified classname class

src/core/codepoint.scala

@@ -18,6 +18,7 @@ package digression
 
 import rudiments.*
 import anticipation.*
+import fulminate.*
 
 import scala.quoted.*
 
@@ -29,10 +30,41 @@ object Codepoint:
 case class Codepoint(source: Text, line: Int):
   def text: Text = Text(s"${source.s.split("/").nn.last.nn}:$line")
 
+given Realm = realm"digression"
+
 object Digression:
   def location(using Quotes): Expr[Codepoint] =
     import quotes.*, reflect.*
     val path = Expr(Position.ofMacroExpansion.sourceFile.path)
     val line = Expr(Position.ofMacroExpansion.startLine + 1)
 
     '{Codepoint(Text($path), $line)}
+
+  private val javaKeywords: Set[String] =
+    Set
+     ("abstract", "continue", "for", "new", "switch", "assert", "default", "if", "package", "synchronized",
+      "boolean", "do", "goto", "private", "this", "break", "double", "implements", "protected", "throw",
+      "byte", "else", "import", "public", "throws", "case", "enum", "instanceof", "return", "transient",
+      "catch", "extends", "int", "short", "try", "char", "final", "interface", "static", "void", "class",
+      "finally", "long", "strictfp", "volatile", "const", "float", "native", "super", "while")
+
+  def fqcn(context: Expr[StringContext])(using Quotes): Expr[Fqcn] =
+    import quotes.reflect.*
+    val parts = IArray.from(context.valueOrAbort.parts.head.split("\\.").nn.map(_.nn))
+
+    parts.foreach: part =>
+      if part.length == 0 then fail(msg"a package name cannot be the empty string")
+      if javaKeywords.has(part) then fail(msg"a package cannot be named $part, because it is a Java keyword")
+
+      def valid(char: Char): Boolean =
+        char >= 'A' && char <= 'Z' || char >= 'a' && char <= 'z' || char >= '0' && char <= '9' || char == '_'
+
+      if !part.all(valid) then fail(msg"a package name may only contain the characters A-Z, a-z, 0-9 and _")
+
+      if part.head >= '0' && part.head <= '9' then fail(msg"a package name cannot start with a digit")
+
+
+    '{Fqcn(${Expr(parts.map(_.tt))})}
+
+extension (inline context: StringContext)
+  inline def fqcn(): Fqcn = ${Digression.fqcn('context)}

src/core/stacktrace.scala

@@ -25,6 +25,15 @@ import language.experimental.captureChecking
 
 extension (error: Throwable) def stackTrace: StackTrace = StackTrace(error)
 
+//case class FqcnError(name: Text) extends Error(msg"the class name $name is not valid")
+
+object Fqcn
+
+case class Fqcn(parts: IArray[Text]):
+  def text: Text = parts.mkString(".").tt
+  def className: Text = parts.last
+  def packageName: Text = parts.init.mkString(".").tt
+
 object StackTrace:
   case class Method(className: Text, method: Text)
   case class Frame(method: Method, file: Text, line: Optional[Int], native: Boolean)