Add tailrec annotations wherever possible (#945)

IntelliJ has a button for adding `@tailrec` wherever needed.
So I clicked it. Let's see what happens now!

Author: jiribenes

effekt/jvm/src/main/scala/effekt/util/PathUtils.scala

@@ -44,7 +44,7 @@ object paths extends PathUtils {
   implicit def file(uri: URI): File = file(uri.getPath)
   implicit def file(filepath: String) =
     if (filepath.startsWith("file:"))
-      file(new URI(filepath).getPath)
+      file(new URI(filepath))
     else
       file(new JFile(filepath))
 }

effekt/shared/src/main/scala/effekt/Namer.scala

@@ -13,6 +13,7 @@ import effekt.util.messages.ErrorMessageReifier
 import effekt.symbols.scopes.*
 import effekt.source.FeatureFlag.supportedByFeatureFlags
 
+import scala.annotation.tailrec
 import scala.util.DynamicVariable
 
 /**
@@ -944,6 +945,7 @@ trait NamerOps extends ContextOps { Context: Context =>
    * 2) If the tighest scope contains blocks, then we will ignore all values
    *    and resolve to an overloaded target.
    */
+  @tailrec
   private def resolveFunctionCalltarget(id: IdRef, candidates: List[Set[TermSymbol]]): Either[TermSymbol, List[Set[BlockSymbol]]] =
 
     // Mutable variables are treated as values, not as blocks. Maybe we should change the representation.

effekt/shared/src/main/scala/effekt/core/optimizer/Normalizer.scala

@@ -125,6 +125,7 @@ object Normalizer { normal =>
    * A good testcase to look at for this is:
    *   examples/pos/capture/regions.effekt
    */
+  @tailrec
   private def active[R](b: Block)(using C: Context): NormalizedBlock =
     normalize(b) match {
       case b: Block.BlockLit   => NormalizedBlock.Known(b, None)

effekt/shared/src/main/scala/effekt/core/vm/VM.scala

@@ -205,6 +205,7 @@ class Interpreter(instrumentation: Instrumentation, runtime: Runtime) {
     stack match {
       case Stack.Empty => ???
       case Stack.Segment(frames, prompt, rest) =>
+        @tailrec
         def go(frames: List[Frame], acc: List[Frame]): Stack =
           frames match {
             case Nil =>

effekt/shared/src/main/scala/effekt/generator/llvm/Transformer.scala

@@ -7,6 +7,7 @@ import effekt.util.intercalate
 import effekt.util.messages.ErrorReporter
 import effekt.machine.analysis.*
 
+import scala.annotation.tailrec
 import scala.collection.mutable
 
 object Transformer {
@@ -633,6 +634,7 @@ object Transformer {
   }
 
   def shareValues(values: machine.Environment, freeInBody: Set[machine.Variable])(using FunctionContext, BlockContext): Unit = {
+    @tailrec
     def loop(values: machine.Environment): Unit = {
       values match {
         case Nil => ()

effekt/shared/src/main/scala/effekt/source/Tree.scala

@@ -4,6 +4,8 @@ package source
 import effekt.context.Context
 import effekt.symbols.Symbol
 
+import scala.annotation.tailrec
+
 /**
  * Data type representing source program trees.
  *
@@ -125,6 +127,7 @@ enum FeatureFlag extends Tree {
 }
 object FeatureFlag {
   extension (self: List[ExternBody]) {
+    @tailrec
     def supportedByFeatureFlags(names: List[String]): Boolean = names match {
       case Nil => false
       case name :: other =>

effekt/shared/src/main/scala/effekt/symbols/Scope.scala

@@ -4,6 +4,7 @@ package symbols
 import effekt.source.IdRef
 import effekt.util.messages.ErrorReporter
 
+import scala.annotation.tailrec
 import scala.collection.mutable
 
 /**
@@ -100,6 +101,7 @@ object scopes {
 
   case class Scoping(modulePath: List[String], var scope: Scope) {
     def importAs(imports: Bindings, path: List[String])(using E: ErrorReporter): Unit =
+      @tailrec
       def go(path: List[String], in: Namespace): Unit = path match {
         case pathSeg :: rest => go(rest, in.getNamespace(pathSeg))
         case Nil => in.importAll(imports)

effekt/shared/src/main/scala/effekt/util/Structural.scala

@@ -1,6 +1,7 @@
 package effekt
 package util
 
+import scala.annotation.tailrec
 import scala.quoted.*
 
 /**
@@ -128,6 +129,7 @@ class StructuralMacro[Self: Type, Q <: Quotes](debug: Boolean)(using val q: Q) {
   val self = TypeRepr.of[Self].typeSymbol
 
   val rewriteMethod =
+    @tailrec
     def findMethod(sym: Symbol): Symbol =
       if (sym.isDefDef && !sym.isAnonymousFunction) sym else findMethod(sym.owner)
 
@@ -145,6 +147,7 @@ class StructuralMacro[Self: Type, Q <: Quotes](debug: Boolean)(using val q: Q) {
   val rewrites: List[RewriteMethod] = self.methodMember(rewriteName).map { m =>
     TypeRepr.of[Self].memberType(m) match {
       case tpe: MethodType =>
+        @tailrec
         def findResult(tpe: TypeRepr): TypeRepr = tpe match {
           case tpe: LambdaType => findResult(tpe.resType)
           case _ => tpe